DISTRIBUTION STATEMENT A: Approved for public release; distribution is unlimited.

NONRESIDENTTRAININGCOURSE

May 1990

ConstructionElectrician 1NAVEDTRA 14046

DISTRIBUTION STATEMENT A: Approved for public release; distribution is unlimited.

Although the words “he,” “him,” and“his” are used sparingly in this course toenhance communication, they are notintended to be gender driven or to affront ordiscriminate against anyone.

COMMANDING OFFICERNETPDTC

6490 SAUFLEY FIELD RDPENSACOLA, FL 32509-5237

ERRATA 13 Jun 2001

Specific Instructions and Errata forNonresident Training Course

CONSTRUCTION ELECTRICIAN 1, NAVEDTRA 14046

1. No attempt has been made to issue corrections for errors in typing,punctuation, etc., that do not affect your ability to answer the question orquestions.

2. Make the following changes:

a. Delete chapter 2 on “Airfield Lighting.” This chapter is deletedbecause airfield lighting is no longer covered by occupational standardsfor Construction Electricians.

b. Delete chapter 7 on “Alarm Systems.” This chapter is deleted becausefire alarms are no longer covered by occupational standards forConstruction Electricians.

3. Delete the following questions, and leave the corresponding spaces blank onthe answer sheets:

Questions

2-1 through 2-436-1 through 6-53

i

PREFACE

By enrolling in this self-study course, you have demonstrated a desire to improve yourself and the Navy.Remember, however, this self-study course is only one part of the total Navy training program. Practicalexperience, schools, selected reading, and your desire to succeed are also necessary to successfully roundout a fully meaningful training program.

THE COURSE: This self-study course is organized into subject matter areas, each containing learningobjectives to help you determine what you should learn along with text and illustrations to help youunderstand the information. The subject matter reflects day-to-day requirements and experiences ofpersonnel in the rating or skill area. It also reflects guidance provided by Enlisted Community Managers(ECMs) and other senior personnel, technical references, instructions, etc., and either the occupational ornaval standards, which are listed in the Manual of Navy Enlisted Manpower Personnel Classificationsand Occupational Standards, NAVPERS 18068.

THE QUESTIONS: The questions that appear in this course are designed to help you understand thematerial in the text.

VALUE: In completing this course, you will improve your military and professional knowledge.Importantly, it can also help you study for the Navy-wide advancement in rate examination. If you arestudying and discover a reference in the text to another publication for further information, look it up.

1990 Edition Prepared byCECS Billy F. Johnson

Published byNAVAL EDUCATION AND TRAINING

PROFESSIONAL DEVELOPMENTAND TECHNOLOGY CENTER

NAVSUP Logistics Tracking Number0504-LP-026-7220

ii

Sailor’s Creed

“I am a United States Sailor.

I will support and defend theConstitution of the United States ofAmerica and I will obey the ordersof those appointed over me.

I represent the fighting spirit of theNavy and those who have gonebefore me to defend freedom anddemocracy around the world.

I proudly serve my country’s Navycombat team with honor, courageand commitment.

I am committed to excellence andthe fair treatment of all.”

CONTENTS

CHAPTER

1. Area Lighting Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2. Airfield Lighting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3. Electrical Load Requirements . . . . . . . . . . . . . . . . . . . . . . .

4. Solid-State Devices and Circuits . . . . . . . . . . . . . . . . . . . . .

5. Power Generation and Distribution . . . . . . . . . . . . . . . . . .

6. Field Rigging and Hoisting Systems . . . . . . . . . . . . . . . . . .

7. Alarm Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

APPENDIX

I. Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

II. Formulas and Conversion Tables . . . . . . . . . . . . . . . . . . . .

III. Reference List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Page

1-1

2-1

3-1

4-1

5-1

6-1

7-1

AI-1

AII-1

AIII-1

INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . INDEX-1

iii

CREDITS

The illustrations listed below are included in this edition of ConstructionElectrician 1 through the courtesy of the designated sources. Permission touse these illustrations is gratefully acknowledged. Permission to reproduceillustrations and other materials in this publication must be obtained fromthe source.

SOURCE FIGURES

Basler Electric 4-7, 4-9, 4-10, 4-11,4-12, 4-29

GE Lighting Systems 1-10 and 1-12 through1-27, Table 1-2, Table1-3

National Fire ProtectionAssociation

Tables 3-1 through3-7, Table 5-3, Table5-4, Notes for Tables5-3 and 5-4

Sencore 4-22, 4-23, 4-25, 4-27,4-28, 4-30, 4-31, 4-32,4-33, and Table 4-1

iv

v

INSTRUCTIONS FOR TAKING THE COURSE

ASSIGNMENTS

The text pages that you are to study are listed atthe beginning of each assignment. Study thesepages carefully before attempting to answer thequestions. Pay close attention to tables andillustrations and read the learning objectives.The learning objectives state what you should beable to do after studying the material. Answeringthe questions correctly helps you accomplish theobjectives.

SELECTING YOUR ANSWERS

Read each question carefully, then select theBEST answer. You may refer freely to the text.The answers must be the result of your ownwork and decisions. You are prohibited fromreferring to or copying the answers of others andfrom giving answers to anyone else taking thecourse.

SUBMITTING YOUR ASSIGNMENTS

To have your assignments graded, you must beenrolled in the course with the NonresidentTraining Course Administration Branch at theNaval Education and Training ProfessionalDevelopment and Technology Center(NETPDTC). Following enrollment, there aretwo ways of having your assignments graded:(1) use the Internet to submit your assignmentsas you complete them, or (2) send all theassignments at one time by mail to NETPDTC.

Grading on the Internet: Advantages toInternet grading are:

• you may submit your answers as soon asyou complete an assignment, and

• you get your results faster; usually by thenext working day (approximately 24 hours).

In addition to receiving grade results for eachassignment, you will receive course completionconfirmation once you have completed all the

assignments. To submit your assignmentanswers via the Internet, go to:

https://courses.cnet.navy.mil

Grading by Mail: When you submit answersheets by mail, send all of your assignments atone time. Do NOT submit individual answersheets for grading. Mail all of your assignmentsin an envelope, which you either provideyourself or obtain from your nearest EducationalServices Officer (ESO). Submit answer sheetsto:

COMMANDING OFFICERNETPDTC N3316490 SAUFLEY FIELD ROADPENSACOLA FL 32559-5000

Answer Sheets: All courses include one“scannable” answer sheet for each assignment.These answer sheets are preprinted with yourSSN, name, assignment number, and coursenumber. Explanations for completing the answersheets are on the answer sheet.

Do not use answer sheet reproductions: Useonly the original answer sheets that weprovide— reproductions will not work with ourscanning equipment and cannot be processed.

Follow the instructions for marking youranswers on the answer sheet. Be sure that blocks1, 2, and 3 are filled in correctly. Thisinformation is necessary for your course to beproperly processed and for you to receive creditfor your work.

COMPLETION TIME

Courses must be completed within 12 monthsfrom the date of enrollment. This includes timerequired to resubmit failed assignments.

vi

PASS/FAIL ASSIGNMENT PROCEDURES

If your overall course score is 3.2 or higher, youwill pass the course and will not be required toresubmit assignments. Once your assignmentshave been graded you will receive coursecompletion confirmation.

If you receive less than a 3.2 on any assignmentand your overall course score is below 3.2, youwill be given the opportunity to resubmit failedassignments. You may resubmit failedassignments only once. Internet students willreceive notification when they have failed anassignment--they may then resubmit failedassignments on the web site. Internet studentsmay view and print results for failedassignments from the web site. Students whosubmit by mail will receive a failing result letterand a new answer sheet for resubmission of eachfailed assignment.

COMPLETION CONFIRMATION

After successfully completing this course, youwill receive a letter of completion.

ERRATA

Errata are used to correct minor errors or deleteobsolete information in a course. Errata mayalso be used to provide instructions to thestudent. If a course has an errata, it will beincluded as the first page(s) after the front cover.Errata for all courses can be accessed andviewed/downloaded at:

https://www.advancement.cnet.navy.mil

STUDENT FEEDBACK QUESTIONS

We value your suggestions, questions, andcriticisms on our courses. If you would like tocommunicate with us regarding this course, weencourage you, if possible, to use e-mail. If youwrite or fax, please use a copy of the StudentComment form that follows this page.

For subject matter questions:E-mail: n314.products@cnet.navy.milPhone: Comm: (850) 452-1001, Ext. 1826

DSN: 922-1001, Ext. 1826FAX: (850) 452-1370(Do not fax answer sheets.)

Address: COMMANDING OFFICERNETPDTC (CODE N314)6490 SAUFLEY FIELD ROADPENSACOLA FL 32509-5237

For enrollment, shipping, grading, orcompletion letter questionsE-mail: fleetservices@cnet.navy.milPhone: Toll Free: 877-264-8583

Comm: (850) 452-1511/1181/1859DSN: 922-1511/1181/1859FAX: (850) 452-1370(Do not fax answer sheets.)

Address: COMMANDING OFFICERNETPDTC (CODE N331)6490 SAUFLEY FIELD ROADPENSACOLA FL 32559-5000

NAVAL RESERVE RETIREMENT CREDIT

If you are a member of the Naval Reserve, youwill receive retirement points if you areauthorized to receive them under currentdirectives governing retirement of NavalReserve personnel. For Naval Reserveretirement, this course is evaluated at 10 points.(Refer to Administrative Procedures for NavalReservists on Inactive Duty, BUPERSINST1001.39, for more information about retirementpoints.)

COURSE OBJECTIVES

In completing this nonresident training course,you will demonstrate a knowledge of the subjectmatter by correctly answering questions on thefollowing: performing tasks involved in theinstallation, maintenance, and repair of arealighting systems, airfield lighting systems,power generation and distribution systems, andalarm systems; the rigging and erecting ofhoisting systems; the calculation of electricalsystems load requirements; and the use of solid-state testing devices.

vii

Student Comments

Course Title: Construction Electrician 1

NAVEDTRA: 14046 Date:

We need some information about you:

Rate/Rank and Name: SSN: Command/Unit

Street Address: City: State/FPO: Zip

Your comments, suggestions, etc.:

Privacy Act Statement: Under authority of Title 5, USC 301, information regarding your military status isrequested in processing your comments and in preparing a reply. This information will not be divulged withoutwritten authorization to anyone other than those within DOD for official use in determining performance.

NETPDTC 1550/41 (Rev 4-00)

CHAPTER 1

AREA LIGHTING SYSTEMS

Advancement brings both increased rewardsand increased responsibilities. The advantages areobvious-higher pay, greater prestige, moreinteresting and challenging assignments, and thesatisfaction of getting ahead in your chosencareer. As a Construction Electrician first classpetty officer, you will have many responsibilitiesadded to those you had as a second class pettyofficer. You have acquired a lot of valuableknowledge, and now it is your turn to pass on thetechnical know-how of your job to others.

In addition to supervising and training lowerrated personnel, you will be required to performvarious leadership and administrative duties. Thetype of activity to which you are assignedwill determine just how you carry out yourresponsibilities, but the ability to apply effectivetechniques of leadership and to get along withpeople will help you succeed in the Navy,regardless of your assignment.

These duties and responsibilities are coveredin the Naval Construction Force/Seabee FirstClass Petty Officer Training Manual, NAV-EDTRA 10601.

This chapter covers the streetlighting systems,the floodlighting systems, and the security lightingsystems that are required at all military installa-tions. When properly constructed and installed,these original basewide lighting systems willprovide years of trouble-free operation witha minimum of minor maintenance and bulbchanging required to keep the system fullyoperational.

Several factors can change the base require-ments for area lighting. These factors includesuch changes as facility usage, updating ofsystems, changes in the base mission, or expand-ing existing systems.

With the cost of energy rising daily, anysystem that can provide a higher level of efficiencyfor the energy used must be considered. In thisarea the use of the newer high-pressure dischargesystems for lighting seems to offer savingsboth in the lifespan of the bulbs and in the

lumens per watt of energy used. These systemsare replacing the older incandescent systems in anever-increasing pace. The higher initial cost ofthese systems is being offset by the efficiency ofthe energy used and savings of energy dollars.

OUTDOOR LIGHTING

There are a number of light systems in usetoday. They are streetlights, floodlights, andsecurity lights. These systems can be as simple asa few portable floodlights to help accomplish anafter-dark-rush job or a base streetlighting system.In this section, we will discuss the lighting systemrequirements and equipment that is common toall three systems.

LUMINAIRE TYPES AND FIXTURES

While most of us think of streetlights as usingincandescent bulbs, the first electrical streetlampsused arc lights. While the quantity of lightproduced was sufficient, the brightness, color,cost, and maintenance of the system presentedproblems that were unacceptable. With Edison’sinvention of the incandescent bulb, electricallighting became a practical way of life. While theincandescent bulbs are still in use and solved manyproblems, they have created some new problems.

Aging is one of the primary problems ofincandescent bulbs. Two factors are involved.Both of these factors concern the tungstenfilament. When the filament is heated, part of themetal is driven off by thermionic emission andis unable to return to the filament. This metalcollects on the inside of the glass bulb causing theglass to darken and reduce the light rays that canbe passed through the glass to provide light. Metalthat is lost from the filament reduces the size ofthe filament. This reduction in size increases theresistance and thereby reduces the light produced.Over the lifespan of an incandescent bulb, it maylose as much as 30 percent of its ability to deliverlight because of these two factors.

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Electric-Discharge Lighting

Efforts to improve the power efficiency andreduce the maintenance costs led to the develop-ment of a new family of lighting which has beengenerally categorized as the electric-dischargelamps. These lamps all have a negative resistancecharacteristic. This means that the resistancedecreases as the lamps heat up. This wouldnormally cause the current flow to increase. Eachlamp of this type must be equipped with a current-limiting device called a ballast. Lamp life andmore light per watt are two main advantages thatelectric-discharge lamps have over incandescentbulbs. The basic types of electric-discharge lampsused in area lighting are vapor, metal halide, andfluorescent lamps.

Figure 1-1 shows the basic configuration ofvapor and metal halide bulbs. In these lamps, amaterial, such as sodium, mercury, or metalhalide of thallium, sodium, or indium, in additionto mercury, is added to the arc tube. In design,the lamp has three electrodes, with one electrodebeing used only for starting. The arc tube containssmall amounts of pure argon gas to aid in starting.Free electrons are accelerated by the startingvoltage. In this state of acceleration, theseelectrons strike atoms and displace other electronsfrom their normal atomic positions. Once thedischarge begins, the enclosed arc becomes thelight source. The addition of the metal halides tothe arc tube results in a bulb with a 50-percenthigher efficiency and a better color quality thanthe mercury arc bulb. In the past, the maindrawback of sodium lights has been the poor colorquality of the light produced. The new high-pressure sodium light is smaller and has a bettercolor. This light has a higher light-producingefficiency than does any other commerciallyproduced white light source.

Commercial companies that produce theselight bulbs claim a 100-percent increase in lamplife over tungsten filament bulbs that produce thesame amount of light. The power in watts requiredto operate these lamps is less than one-half thatrequired for filament lamps. The initial cost ofthe components for lights is substantially greateras these lights will require ballasts; however, thiscost can be made up later by the savings of energycosts. The selection of lighting fixtures will dependon budgeted dollars for new installation projectsversus maintenance dollars.

Most discharge lighting fixtures are suppliedwith the required ballast installed in the fixture.

Figure 1-1.—Vapor and metal halide bulb configuration.

In some cases ballasts, usually called trans-formers, are externally installed.

High-Intensity Discharge (HID) Lighting

HID lighting systems are being used more andmore for two reasons: longer bulb life and greaterenergy efficiency. Longer bulb life results in lowermaintenance (relamping) costs. Greater energyefficiency, simply stated, means more light(lumens) per watt of energy. As a comparisonbetween incandescent bulbs and HID bulbs, anincandescent bulb that consumes 575 wattsprovides 10,000 lumens and has a lifespan of 1,200hours, while a metal halide lamp at 400 wattsprovides 32,000 lumens and has a lamp life of10,500 hours. A high-pressure sodium HID bulbof 400 watts consumption provides 42,000 lumenswith a life of 6,000 hours. As you can see fromthese examples, the HID lamps far surpass theolder incandescent lamps in light bulb life andefficiency. The economic life of the HID bulbsranges from 6,000 to 20,000 hours. Lamptemperatures should be maintained below 210°Fat the base and should not exceed 400°F outerbulb temperature. Specific voltages are requiredfor these lamps and should not vary more than5 percent above or below this specified rating.Low voltages will cause the lamps to go out.

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Normally they will not restart until the internalvapor pressure is reduced to a point at which thearc can be restarted. This time may vary from 4to 8 minutes. The existing conditions will governthis time. Where extremely cold conditions exist,such as in streetlight or floodlight systems inwinter temperatures, specially designed ballasts(transformers) are installed to provide a higheropen-circuit voltage to aid in starting the lamps.

You should remember that all HID lightsproduce a stroboscopic effect and, when possible,adjacent lamps should be powered from differentphases to reduce the results of this effect.

If a system is simply being upgraded bychanging out incandescents for HID lamps, thepresent wiring is probably adequate to handle thechange since the HID lamp requires less powerthan the older incandescent system. Either a seriesor a multiple wiring system may be used. In somecases, isolating transformers are used withthe lighting fixture on a series system. Onnew projects, either overhead or undergrounddistribution may be used. In recent years,underground distribution has become morepopular. This is especially true where hollow steelor aluminum standards or poles are to be used.Ballasts and/or isolating transformers can bemounted in the bases of the standards, makingaccess to these units easier for inspection andreplacement. Only the size of wire required to feedthe lamps on that particular standard must becarried up the pole to the fixture. This smaller wiresize makes fixture connections easier. Under-ground distribution offers more protection to thedistribution cables than do overhead systems.

CAUTION: Mercury-vapor and metal halidelamps are highly efficient, energy-saving lamps,but if broken they may give off dangerousultraviolet radiation. A number of publicationshave been published warning of this danger. Ifyou find yourself in the position of having to workwith or around these high-discharge lamps, it isadvisable to become aware of the informationcontained in the Occupational Safety and HealthAdministration (OSHA) standards, NAVSEA-INST 5100.3B, and NAVELEXINST 5100.7.

As mentioned, high-intensity mercury vaporand halide lamps can be dangerous if theycontinue to operate when the outer globe of thebulb is broken, punctured, or missing. A brokenouter globe allows the lamp to emit intenseultraviolet radiation. PERSONS EXPOSED TOEXCESSIVE AMOUNTS OF ULTRAVIOLET

Fluorescent lamps of high-pressure, hardglass are now being used to some extent forfloodlighting where a low-level, highly diffusedlight is desired. This would include club parkinglots, outside shopping areas, parks, or grass areas.This bulb is much the same in operation as themercury-vapor lamp with the exception thatthe fluorescent tube has an inside coating ofmaterial called phosphor that gives off light whenbombarded by electrons. In this case, the visiblelight is a secondary effect of current flow throughthe lamp. As with other electric-discharge lamps,the fluorescent lamp requires a ballast foroperation. The color produced by the lightdepends on the phosphor material used.

Luminaire Ballasts

1-3

Every electric-discharge lamp needs a ballastto operate. The ballast is simply a coil of insulatedwire wound on a frame, or a laminated iron core.

Ballasts may perform any or all of thefollowing functions:

Limit the current flow through the lampto the value for which the lamp is designed.

RADIATION CAN SUFFER SEVERE SKINBURNS, PAINFUL AND EVEN PERMANENTEYE DAMAGE, AND, IF THE EXPOSURE ISINTENSE OR REPEATED, PERHAPS EVENSKIN CANCER.

If plans require the installation of mercury-vapor or metal halide lighting in an area ordinarilyoccupied, care must be taken to prevent injuriesby following these simple instructions:

Use bulbs that have extinguishing devices.

Use totally enclosed lighting fixtures withprotective shields that protect the lamp fromdamage and absorb ultraviolet radiation.

As a special warning for underground seriescircuits using HID equipment, the system willrequire auxiliary equipment to provide protectionfrom high voltages caused by resonant powerconditions that occur during “hot restarts.”Failure to incorporate this equipment will causelamps to blow, sockets to flash, or ballasts to fail.The individual manufacturer of the particularequipment to be installed should be consulted asto what hot start preventer they provide orrecommend.

Fluorescent Lighting

Cause a drop in line voltage and providethe desired lamp voltage, which, in turn,determines the rated current in the lamp.

Provide power factor correction.

Provide radio interference suppression.

The ballast core is made of laminated trans-former steel wound with copper or aluminummagnet wire. The assembly is impregnated withinsulating material that provides electricalinsulation while aiding in heat dissipation and,with leads attached, is placed into a case. The caseis filled with a potting material containing a filler,such as silica. This compound completely fills thecase encapsulating the core, coil, and capacitor.

Average ballast life at a 50-percent duty cycleand at proper ballast operating temperature isnormally estimated at about 12 years. At higherballast temperature or longer duty cycle, shorterballast life will result.

According to the National Electrical Code®,(NEC®)1, Article 410-73e, it is mandatory thatall fluorescent lamp ballasts used indoors beinternally protected and that replacements forthese ballasts be integrally protected. Theseprotective measures were taken to preventmisapplication of the ballast as well as to protectagainst undesirable failure and conditions whichcan occur at the end of ballast life. The thermallyprotected Underwriters’ Laboratories approvedballast is known and marked, or labeled, as“Class P.”

The operating characteristics of the ballastmay result in a low- or high-power factor. Themeasured watts of a low-power-factor ballast areapproximately the same as the measured watts ofthe high-power-factor ballast when they areconnected to the same load. The low-power-factorballast draws more current from the powersupply, and therefore, larger supply conductorsmay be necessary. The high-power-factor ballastpermits greater loads to be carried by the existingwiring system.

Fixtures

There are fixture configurations to meetalmost any lighting requirement or design. Whilethe basic purpose of the fixture is to hold andprevent damage to the lamps and lamp sockets,

1 National Electrical Code® and NEC® are registered trade-marks of the National Fire Protection Association, Inc.,Quincy, MA.

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the fixture also helps direct the light beams intothe lighting patterns desired. The fixture, with itsreflector and lens, determines the quality of thelight being produced. Reflectors can either con-centrate or diffuse light rays, and the lens can passor refract light rays. Quite often, the lens may beused to do both from one light source; that is, partof the light rays are refracted to produce a soft,even spread of light in the outer part, while thelight rays are concentrated in other areas of thelens to produce a bright, hard light at a specificarea. Some streetlight fixtures are examples of this.The sides of the lenses produce a general diffusedlighting to prevent blinding automobile operatorswhile, at the same time, they produce a bright lightpattern below the lamp along the curb.

Flood or security lighting fixtures may beeither open or enclosed. The open fixtures providehigher maintained efficiency and more accuratebeam control. The open fixture will, under someconditions, require a “hard glass” bulb to preventbulb breakage caused by rain, snow, or insectsstriking the hot bulb.

Most fixtures will have provisions for mount-ing ballasts (transformers) within the fixture andwill provide protection for the ballast. In somecases, particularly in high bay lighting, the ballastsmay be mounted at some central location andnot mounted in the fixture. Figure 1-2 showsrepresentative samples of the styles of fixtures

Figure 1-2.—Fixture styles available.

available. In the pole-mounted group, the ballastsare located in the pole base. Several methods offixture attachment are possible and should beconsidered when fixtures for a particular job areordered. The location and job determine whetherthe fixture is suspended, bracket mounted, or armmounted. Most brackets can be attached eitherto wood or metal support structures. In eithercase, the fixture should be firmly attached to thestructure so that precise aiming for lightdistribution can be made.

LIGHT CIRCUITS

As we stated earlier, a number of light systemsare in use today, such as streetlights, floodlights,and security lights. These systems are either seriesor multiple (parallel), depending on how they areused and the equipment available.

The series circuit is supplied by a regulatingtransformer which gives a constant current, usuallyof 6.6 amperes, to the lighting circuit. If a higheramperage is required, *autotransformers are avail-able for stepping up the current to 15 or 20amperes. This higher amperage permits the use ofmore rugged lamp filaments, which give longerlife for lamps of equal candlepower and higherlamp efficiency.

The series circuit is easily controlled, but anybreak interrupts the entire circuit. The use offilm-disk cutouts (fig. 1-3) in the lamp socket

Figure 1-3.—Series lamp, socket, and film disk.

prevents lamp failure from interrupting thecircuit.

The multiple (parallel) circuit consists of anumber of streetlights supplied by a distributiontransformer delivering a constant low voltage toa circuit or secondary main which also suppliesother loads. However, running secondary con-ductors any great distance to supply a parallel-connected lamp or a group of lamps is impracticalbecause of the excessive voltage drop.

The cost of the multiple luminaire is lowcompared to the series type because the lowvoltage allows for the elimination of otherluminaire accessories. This saving is largely offset,however, by the increased requirement for controldevices and the copper wire cost. Lamp lifeand efficiency are comparatively low and theillumination is not as uniform as in the seriescircuit.

In choosing a system, here are a fewsuggestions which may aid in your selection.

If the total wattage of the circuit exceeds2 kilowatts or more than 15 lights, consider aseries lighting system.

When extending an existing system, use theexisting circuit.

If low-voltage capacity exists at theproposed location, use a multiple system eventhough the load exceeds 2 kilowatts.

When several small lights are to be spacedrather far apart and no low-voltage secondaryexists along the route, use the series systemregardless of the load size or the number of lights.

When estimates show that one type ofsystem will save money and time, use the moreeconomical system.

Series Circuits

Let’s consider a series streetlight system. Thepower for the circuit will be supplied from thebase primary distribution lines, through fusecutouts, to an oil switch, and from the oil switchto a constant-current regulator. The constant-current regulator will supply power to the seriesloops and, thus, to the individual lamps. Whilethe current (normally 6.6 amperes) remainsconstant, the voltage will vary with the appliedload.

1-5

A series circuit may be installed with its supplylead and the return lead on the same pole or theymay follow a different route. The type of routefollowed would be known as a closed loop whenthe leads are on the same pole, and as an openloop when the leads follow a different route. (Seefig. 1-4.) If the open-loop method is used, bringingthe two conductors to the same pole at severalpoints makes troubleshooting easier (the circuitmay be shunted at this point). An open-loopcircuit is less expensive initially, but trouble-shooting is difficult, time consuming, and costly.

Installing the series circuit on the samecrossarm as the primary-distribution conductoris usually the most economical. If two primarycrossarms are used, the streetlight wires shouldbe carried on the lower arm in the end-pinposition. If two separate single-conductor streetcircuits are on the same crossarm, they should notbe placed in adjacent pin positions because ofconfusion in troubleshooting.

Insulator sizes should be based on theopen-circuit voltage of the largest regulator usedand are usually the same size as those used forprimary distribution. White insulators should beused on a series street circuit to distinguish themfrom the primary distribution insulators and toassist in identifying the circuits for operating andmaintenance work. Small strain insulators shouldbe used for cutting in individual lamps or loopsof five lamps or fewer. Equivalent voltageinsulators with automatic line splices may also beused. If the loop consists of more than five lamps,a primary disk insulator is used. The insulator isusually cut in after the conductors have beenstrung.

Figure 1-4.—Diagrams of open and closed loops in seriescircuits.

The conductor size should be No. 6 mediumhard-drawn copper or its mechanical equivalent.Although No. 8 hard-drawn copper is usually tooweak for longer spans, the use of copperweld orsimilar conductors of high mechanical strengthovercomes the difficulty. Conductor sag shouldbe the same as for primary distribution.

Constant-current regulators should be pro-tected on overhead circuits by lightning arresterson both the primary and secondary sides.

Multiple Circuits

The multiple streetlight system uses a dis-tribution transformer of the proper size as serviceequipment. (See fig. 1-5.) Notice that thetransformer is fed directly through fuse cutoutsfrom the base primary distribution system. Thecontrol for the circuit is connected into one lineof the secondary side. The selection of outputvoltage of the transformer depends on the voltagerequired for the individual lamps that areinstalled. Depending on the types of lampsselected, this voltage may be from 120 volts to480 volts. You must know the type of lamp thatwill be used in the circuit before you can properlyselect the transformer to feed the streetlightsystem. While the multiple system is not asdangerous as the series system, it is dangerous,and caution must be exercised by those workingon the system.

COMPONENTS AND CONTROLS

There are many components required toconstruct an area lighting system. These includeconstant-current transformers, relays, controls,fixtures, wiring, and lamps. Controls can bemanual, automatic, or a combination.

Figure 1-5.—Multiple light circuit.

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Constant-Current Transformer

The constant-current transformer, usuallycalled a regulator, has a movable secondarywinding that automatically changes position toprovide constant current for any load within itsfull-load rating. The balance point between coilweight and magnetic force may be adjusted toprovide the desired output current.

A moving-coil regulator is recommendedbecause of the close regulation required forstreetlighting work. It consists of a fixed primarycoil and a movable secondary coil on a laminatedcore (fig. 1-6). Voltage applied to the primarywinding causes voltage to be induced in thesecondary winding. When the secondary circuit

is closed, the magnetic field in the secondary reactswith the primary-coil field to push the movablecoil up. The balance point between coil weight andmagnetic force is designed to provide the desiredsecondary current (usually 6.6 amperes).

Since as little as 1-percent overcurrent reduceslamp life by 20 to 25 percent, close adjustmentis necessary. This is obtained by a movable weighton the balancing lever. The primary currentremains constant for all loads, but the powerfactor varies with the load, thereby changing theprimary input. Since the secondary voltageincreases with the load, regulator size should berestricted to keep the secondary voltage withindesired limits.

Figure 1-6.—Moving-coil constant-current regulator.

1-7

On most existing installations, the constant-current regulator is of the outdoor type (fig. 1-7).Three main types of installation are used forthese regulators: two-pole platform, timber orsteel construction single-pole platform, and polemounted. Any regulator larger than 20 kilovoltamperes should be mounted on a platform.

Constant-current regulators should be loadedas near 100 percent as possible since bothefficiency and power factor are best at this load.Specifications of the American Institute ofElectrical Engineers (AIEE) require constant-current transformers to deliver the ratedsecondary current at 10-percent overload. A larger

size regulator should not be installed before thislo-percent overload is reached. When largerregulators must be installed and are not readilyavailable, a booster transformer may be used withits secondaries connected into the series streetcircuit and its primaries connected to the primaryfeeder supplying the regulator (fig. 1-8). Sincetransformers used for this purpose should havesecondary bushings insulated for the high voltageof the series street circuit, a special boostertransformer is preferred to an ordinary distri-bution transformer for use with constant-currentregulators of 10 kilowatts and larger. In using abooster transformer, the primary coil must be

Figure 1-7.—Pole-mounted regulator.

1-8

Figure 1-8.—Method of relieving slightly overloaded regulators with a distribution or booster transformer.

isolated from the secondary coil, which necessi-tates removing any internal lead connecting thetwo coils. The additional load handled by thisdevice equals the product of the street-circuitcurrent and the secondary voltage of the trans-former. Thus, if a 2,400/240-volt transformer isused, the additional load which the street circuitcan carry is 240 volts × 6.6 amperes or 1.584kilowatts.

Table 1-1 shows the maximum number ofseries lamps in the various sizes that may be usedfor full-load rating on a regulator. The averagenumber of watts of energy consumption for eachsize lamp may be computed since the regulatorratings are based on their output. In this manner,the load of a circuit consisting of different sizelamps may be computed.

Example: What size regulator would berequired to supply the following lamps?

25 1,000-lumen, 6.6-ampere, straight-serieslamps.

50 2,500-lumen, 6.6-ampere, straight-serieslamps.

10 6,000-lumen, 20-ampere lamps withisolating transformer.

Solution: Table 1-1 shows that the averageenergy consumption of a 1,000-lumen,6.6-ampere, straight-series lamp with film cutoutis 69 watts per lamp. In a similar manner, the

average energy consumption of a 2,500-lumenlamp is 167 watts, and a 6,000-lumen, 20-amperelamp with isolating transformer is 405 watts.Totaling the combined load shows the following:

25 × 69 = 1,725 watts50 × 167 = 8,350 watts10 × 405 = 4,050 watts

14,125 watts or 14.1 kilowatts

Therefore, a 15-kilowatt regulator would berequired.

NOTE: The table makes allowances for linelosses in the average series street circuits.

Control Circuits

There are several methods used to controlthe operation of area lighting systems. Forrecreational lighting, only a manual switch isrequired. On the other hand, streetlights andsecurity lights have more sophisticated controls.

Lights normally are on during the hours ofdarkness or when unusual weather conditionsindicate the need for artificial light. Althoughlights could be activated by assigning an individualto manually operate the controls, they are usuallyturned on and off by a combination of controls.

Most control circuits that you will encounterin the field use one of the following devices tocontrol the lighting system: photoelectric cell,cadmium sulphide cell, time clock, pilot wirerelay, or cascading relays. A detailed description

1-9

Table 1-1.—Approximate Lamp Capacity for Streetlighting Regulators

STRAIGHT-SERIES LAMPS WITH FILM CUTOUT

CIRCUIT RATING IN AMPERES

6.6 15 20

REGULATOR 600 800 1,000 2,500 4,000 6,000 4,000 4,000 6,000 10,000 15,000 25,000RATING LUMENS LUMENS LUMENS LUMENS LUMENS LUMENS LUMENS LUMENS LUMENS LUMENS LUMENS LUMENS

(kW)

1 21 17 14 6 4 2 4 3 32 42 34 28 12 8 5 8 7 6 3 2 13 64 51 43 18 12 8 12 11 9 5 3 25 107 86 72 30 20 13 20 19 13 9 6 37.5 161 129 108 45 30 20 30 29 21 12 9 5

10 214 172 144 60 40 26 40 39 28 16 11 715 321 258 216 90 60 40 60 58 47 25 16 1020 428 344 288 120 80 55 80 78 56 34 22 1325 535 430 360 150 100 66 100 97 70 42 28 1730 642 516 432 180 120 80 121 117 85 50 34 21

UNIT kW* .047 .058 .069 .167 .250 .375 .249 .256 .354 .600 .880 1.43

LAMPS WITH AUTOTRANSFORMERS AND LAMPS WITH ISOLATION TRANSFORMERS

CIRCUIT RATING IN AMPERES

15 20 6.6 15 20

EGULATOR 4,000 6,000 10,000 15,000 25,000 1,000 2,500 4,000 6,000 10,000 15,000 25,000RATING LUMENS LUMENS LUMENS LUMENS LUMENS LUMENS LUMENS LUMENS LUMENS LUMENS LUMENS LUMENS

(kW)

1 3 2 1 1 0 12 5 3 2 1 1 02 7 5 3 2 1 24 10 7 5 3 2 13 11 7 4 3 2 32 15 10 7 4 3 25 18 13 8 5 3 53 25 17 12 7 5 37.5 27 19 12 8 5 80 38 26 18 11 7 5

10 37 26 16 11 6 107 51 35 25 15 10 615 55 39 24 16 10 160 76 52 37 23 15 1020 74 52 32 22 12 215 102 70 50 30 20 1225 92 65 40 27 16 268 127 87 62 38 25 1630 110 78 48 32 20 322 152 104 74 46 30 20

UNIT kW* .273 .384 .625 .935 1.500 .093 .197 .288 .405 .650 1.000 1.500

HIGH-INTENSITY DISCHARGE LAMPS

LAMP CAPACITY OF REGULATORS IS LIMITED BY STARTING CURRENT. DETERMINE UNIT kW BY MULTIPLYING LAMP WATTAGEBY THE FOLLOWING FACTORS: 2.1 FOR AMBIENT TEMPERATURES NOT BELOW +35°F (+2°C)

2.5 FOR AMBIENT TEMPERATURES TO -30°F (-34°C)

THE PROPER SIZE REGULATOR TO SELECT IS THE SMALLEST RATING WHICH EXCEEDS THE SUM OF THE UNIT kW FOR ALL LAMPSON THE CIRCUIT, REGARDLESS OF TYPE.

*UNIT kW IS THE APPROXIMATE kW CAPACITY REQUIRED FOR A SPECIFIC LAMP AND ITS ASSOCIATED TRANSFORMER OR BALLASTAS APPLICABLE.

1-10

of each of these devices is contained in previous Table 1-2.—Roadway Illumination and Lamp Selectiontraining manuals. Guide

26.330.1X

STREETLIGHTING

Streetlighting at naval facilities usually neednot produce as high a level of illumination as thatrequired in many municipal areas. Because nightactivity by vehicles and pedestrians is low, onlyenough light is supplied to permit personnel toidentify streets and buildings and to furnishsufficient visibility for local security requirements.The streetlighting equipment used need not be asattractive as that frequently installed in municipalsystems. It should be functional and of goodquality. These factors permit economical street-lighting installations.

STREET AND AREA CLASSIFICATION

Streetlighting requirements generally consistof a minimum average maintained footcandlelevel and a maximum allowable uniformity ratiofor the installation. The authority for theserequirements is the American National StandardsInstitute (ANSI)/Illumination Engineering Society(IES) publication, Standard Practice for RoadwayLighting. Another publication which may provehelpful is Informational Guide for RoadwayLighting, published by the American Associationof State Highway and Transportation Officials.The only significant difference between the twopublications is that the latter allows a 4 to 1uniformity ratio instead of the 3 to 1 uniformityratio specified by IES. These uniformity ratios aredefined as the ratio of the average footcandlevalue divided by the minimum footcandle value.

Collector: The distributor and collectorroadways serving traffic between major and localroadways. These are roadways used mainly fortraffic movements within residential, commercial,and industrial areas.

LIGHTING INTENSITY

Local: Roadways used primarily for directaccess to residential, commercial, industrial, orother abutting property. They do not includeroadways carrying through traffic.

The illumination and uniformity requirementsare given in table 1-2. Note that the illuminationlevel is dependent upon the roadway classificationand the area classification, which are defined inthe following material.

The locality or area is also defined by threemajor categories: commercial, intermediate, andresidential.

Streets are classified into three major cate-gories: major, collector, and local.

Major: The part of the roadway systemthat serves as the principal network for throughtraffic flow. The routes connect areas of principaltraffic generation and important rural highwaysentering the city.

Commercial: That portion of a munici-pality in a business development where ordinarilythere are large numbers of pedestrians and a heavydemand for parking space during periods of peaktraffic or a sustained high pedestrian volume anda continuously heavy demand for off-streetparking during business hours.

Intermediate: That portion of a munici-pality which is outside of a downtown area butgenerally within the zone of influence of a business

1-11

or industrial development, characterized often bya moderately heavy nighttime pedestrian trafficand a somewhat lower parking turnover than isfound in a commercial area. This definitionincludes military installations, hospitals, andneighborhood recreational centers.

Residential: A residential development,or a mixture of residential and commercial

establishments,- characterized by few pedestriansand a lower parking demand or turnover at night.This definition includes areas with single familyhomes and apartments.

SELECTION OF LUMINAIRE

Luminaires are designed to provide lightingto fit many conditions. For street and arealighting, five basic patterns are available, as shown

Figure 1-9.—Light distribution patterns for roadway lighting.

1-12

in figure 1-9. While many luminaires can beadjusted to produce more than one pattern, noluminaire is suitable for all patterns. Care mustbe used, especially in repair and replacement, toinstall the proper luminaire for the desiredpattern, as specified in the manufacturer’sliterature. Even when the proper luminaire isinstalled, care must be used to ensure that alladjustments have been properly made to producethe desired results.

1. Type I (fig. 1-9a) is intended for narrowroadways with a width about equal to lampmounting height. The lamp should be near thecenter of the street. A variation of this (fig. 1-9b)is suitable for intersections of two such roadwayswith the lamp at the approximate center.

2. Type II (fig. 1-9c) produces more spreadthan does Type I. It is intended for roadways witha width of about 1.6 times the lamp mountingheight, with the lamp located near one side. Avariation (fig. 1-9d) is suitable for intersectionsof two such roadways, with the lamp not near thecenter of the intersection.

3. Type III (fig. 1-9e) is intended forluminaires located near the side of the roadway

with a width of not over 2.7 times the mountingheight.

4. Type IV (fig. 1-9f) is intended for side-of-road mounting on a roadway with a width of upto 3.7 times the mounting height.

5. Type V (fig. 1-9g) has circular distributionand is suitable for area lighting and wide roadwayintersections. Types III and IV can be staggeredon opposite sides of the roadway for betteruniformity in lighting level or for use on widerroadways.

MOUNTING HEIGHT AND SPACING

There are two criteria for determininga preferred luminaire mounting height: thedesirability of minimizing direct glare from theluminaire and the need for a reasonably uniformdistribution of illumination on the street surface.The higher the luminaire is mounted, the fartherit is above the normal line of vision and the lessglare it creates. Greater mounting heights mayoften be preferable, but heights less than 20 feetcannot be considered good practice.

26.338X

You must be somewhat familiar with theterminology relating to how fixtures are locateddown a roadway. Figure 1-10 shows these

Figure 1-10.—Luminaire arrangement and spacing.

1-13

relationships graphically. The followinginformation will be useful when determining themost appropriate mounting arrangements:

The transverse direction is defined as backand forth across the width of the road, and thelongitudinal direction is defined as up and downthe length of the road.

Modern roadway fixtures are designed tobe mounted in the vicinity of one of the curbs ofthe road. The overhang is defined as thedimension between the curb behind the fixture anda point directly beneath the fixture.

A luminaire overhang should not exceed25 percent of the mounting height.

No attempt should be made to light aroadway that is more than twice the width of thefixture mounting height. A roadway luminaireproduces a beam in both longitudinal directionsand is limited in its ability to light across thestreet.

There are three ways that a luminaire maybe positioned longitudinally down the roadway.(See fig. 1-10.) Note that the spacing is always thedimension from one fixture to the next fixturedown the street regardless of which side of thestreet that fixture is on.

A staggered arrangement generates betteruniformity and possibly greater spacing than aone-side arrangement. This is particularly truewhen the width of the road becomes significantlygreater than the mounting height. When the widthof the road starts approaching two mountingheights, an opposite arrangement should definitelybe considered. This would, in effect, extend thetwo-mounting-height width limitation out to fourmounting heights.

The classification of a road and the corre-sponding illumination levels desired influences thespacing between luminaires. On a residential roadit may be permissible to extend the spacing so thatthe light beams barely meet (fig. 1-11). For trafficon business roadways where uniformity ofillumination is more important, it may bedesirable to narrow the spacing to provide 50- to100-percent overlap.

Figure 1-11.—Pavement brightness.

MANUFACTURER’S LITERATURE

The performance specifications of each model,type, and size of luminaire are provided with thefixture or obtained from the manufacturer’sordering information. A working knowledge ofthis information will assist you in selecting andinstalling the correct luminaire to accomplish thejob. Figure 1-12 is the manufacturer’s literatureprovided with a General Electric, 250- or 400-watt,Lucalox® streetlight.

Utilization Curve

The utilization curve (fig. 1-12a), a measureof luminaire efficiency, shows the amount of lightthat falls on the roadway and adjacent areas. Theamount of light that is usable or actually falls onthe area to be lighted is plotted as a percentageof the total light generated within the luminairefor various ratios of transverse distance (acrossthe street from the luminaire on both the houseside and street side) to the mounting height

1-14

26.339XFigure 1-12.—Streetlight manufacturer’s literature.

1-15

(see fig. 1-13). The coefficient of utilization forany specific situation is obtained from this curve.The utilization curve will determine the amountof light that actually strikes the roadway surface.This percentage of light has an impact on thespacing distance of the luminaires.

Isofootcandle Curves

The isofootcandle diagram (fig. 1-12b) showsthe distribution of illumination on the roadsurface in the vicinity of the luminaire.

The lines on this diagram connect all pointshaving equal illumination, much as the contourlines on a topographical map indicate all pointshaving the same elevation. Thus at any point onthe diagram (or roadway) we know the magnitudeand direction, with respect to nearby points. Tomake this data more universal, both the tophorizontal and left vertical axes are given in termsof mounting-height ratios.

It is sometimes convenient for you to replotthe isofootcandle data to the same scale as thatused on a drawing containing a lighting layout.By superimposing this diagram, you can study thedistribution of light. Under the unity correctionfactor in the mounting-height table, one can findthe mounting height for which the data arecalculated.

The numbers beside each line represent theinitial footcandle values per 1,000 lamp lumens.For instance, the GE, 400-watt, Lucalox® lampproduces 50,000 lumens. Each footcandle valuemust be multiplied by 50 to obtain the correctfootcandle value on the isofootcandle diagram.This ratio of actual lamp lumens divided by1,000 is known as the lamp factor (LF). Note thatthis allows a curve to represent the distributionfrom more than one lamp wattage; for example,from 250- and 400-watt Lucalox® lamps.

26.330.2XFigure 1-13.—Luminaire utilization.

1-16

Maintenance Factor

Lighting efficiency is seriously impaired byblackened lamps, by lamp life, and by dirton the reflecting surfaces of the luminaire. Tocompensate for the gradual loss of illumination,a maintenance factor (MF) must be applied to thelighting calculations.

Normally, each luminaire manufacturer cansupply you with the maintenance factor for yourlamp model. However, when the manufacturer’sinformation is not available, a 0.70 maintenancefactor is widely used in the industry.

LIGHTING INTENSITYCALCULATIONS

Achieving the most satisfactory solution forany given lighting problem requires soundjudgment in making necessary compromises of allfactors involved.

Selection of the luminaire can be influencedby budget constraints, present stock levels in theFederal Supply System, and availability. Once theluminaire is selected, it is important that you usethe manufacturer’s literature to determine thenumber of luminaires, mounting height, andspacing required to produce the desiredillumination intensity.

Using the manufacturer’s literature suppliedin figure 1-12, let’s solve this sample problem:

Find:

1. One-sided spacing required to providespecified illumination

2. Uniformity of illumination

Given: (See fig. 1-14.)

Street width, 50 feet

Mounting height, 40 feet

Pole setback from curb, 2 feet

Bracket length, 12 feet

Required average maintained level ofillumination, 2 footcandles

GE, 400-watt, Lucalox® luminaire (50,000lamp lumens)

26.330.3XFigure 1-14.—Streetlight sample problem.

Solution:

1. Spacing. The equation to determine correctspacing is

Spacing (S) =(LL) (MF) (CU)

(fc) (W)

Where:

LL = rated initial lamp lumens

MF = maintenance factor

CU = coefficient of utilization

fc = illumination in footcandles

W = street width, curb to curb

The values are given for LL (50,000), MF(assume 0.70), W (50), and fc (2). After a valuefor CU is determined, you can solve the equationfor average spacing.

To determine the coefficient of utilization, itis necessary to calculate the amount of wastedlight on the street side (SS) and the house side (HS)where:

Ratio of House Side (HS) = Transverse Distance =Mounting Height

1040 = 0.25

Ratio of Street Side (SS) = Transverse Distance =Mounting Height

50 - 10 4040 = 40 = 1.0

From the utilization curve in figure 1-15, theratio of 1.0, street side, corresponds to 40 percent,and the ratio of 0.25, house side, corresponds to3 percent, for a total of 43 percent CU.

Spacing can be determined as

S = (50,000) (0.70) (0.43)(2) (50)

= 150 feet

2. Uniformity.

The uniformity of illumination is expressed interms of a ratio of

Average fcMinimum fc

It has been determined that one-side spacingof 150 feet will produce an average of 2footcandles on the roadway surface. The pointof minimum illumination can now be determinedfrom the isofootcandle diagram.

The minimum value of the illumination canbe found by studying the isofootcandle diagramand taking into account all luminaires that arecontributing significant amounts of light.Generally, the minimum value will be found alonga line halfway between two consecutively spacedluminaires. This can be determined by checking

26.340X

Figure 1-15.—Utilization curve.

1-17

26.330.4XFigure 1-16.—Streetlight layout.

26.340.1XFigure 1-17.—Isofootcandle curve.

1-18

the minimum footcandle values at points P1, P2,and P3, as shown in figure 1-16.

The roadway surface can be plotted on theisofootcandle curve by observing the 40-footmounting height to longitudinal and transversedistance ratios. (See fig. 1-17.) Since P1 is locatedoutside the 0.02 footcandle line, it is the lowesttotal footcandle value. This value would be0.03 fc (0.015 footcandle from each luminaire).

Figure 1-18 shows a perspective view of thetwo isofootcandle lines that are considered whendetermining the illumination value at P1.

The following factors are now applied to this“raw” footcandle value as shown in the formula:

fc min = (fc) (LF) (MF) (CF)

Where:

fc min = minimum point footcandles

fc = raw footcandle from isofootcandlediagram

LF = lamp factor

MF = maintenance factor

CF = mounting height correction factor

earlier as 50 for the GE, 400-watt, Lucalox® lamp.The CF factor can be determined from thecorrection chart below the isofootcandle curve infigure 1-12. ‘The CF for a 40-foot mounting heightis 0.56.

The minimum point footcandles are

fc min= (0.03) (50) (0.70) (0.56) = 0.58

Therefore, the average-to-minimum ratio ofuniformity would be

2 fc0.58 fc = 3.4

A uniformity ratio of 3.4 meets the ANSVIESrecommended roadway illumination levels (table1-2) for a major, commercial roadway.

There are a number of charts and illustrationstogether with typical examples dealing withroadway complexities that require special con-siderations, such as intersections, interchanges,curves, hills, underpasses, railroad crossings, andmany others. Helpful information in this area maybe obtained from the IES Lighting Handbook.

FLOODLIGHTS

The values are given for fc (0.03) and MF(assume 0.70). The value for LF was determined

Streetlighting systems usually give lightingintensity from .01 to 0.5 footcandle; however, thisvalue is too low for any night activity requiring

26.330.5XFigure 1-18.—Roadway perspective view.

1-19

Table 1-3.—Recommended Intensities for Specific Night Activities

26.341X

1-20

good visibility. Table 1-3 gives recommendedillumination intensities for specific night activities.The following suggestions should be followed toimprove the efficiency of floodlighting systems:

• Select floodlight locations so beams strikethe surface to be illuminated as nearly perpen-dicular as possible.

2. Class GP (General Purpose)—Enclosedwith a one-piece housing with the inner surfaceserving as a reflector and the outer surface beingexposed to the elements.

3. Class O (Open)—One-piece housing with-out cover glass.

4. Class OI—Same as Class O except with anauxiliary inner reflector to modify the beam.

• When lighting irregular surfaces, use two The suffix letter B should be added to theor more floodlights to reduce sharp shadows above class designations to indicate an integralcaused by surface contour. ballast when required.

• For lighting extended horizontal surfaces, Example: A heavy-duty floodlight with ansuch as work areas, mount floodlights high integral ballast would be designated as a Classenough to minimize glare. HDB floodlight.

• For lighting extended vertical surfaces,such as smoke stacks or towers, mount floodlightsso distance between floodlights or groups does notexceed twice the distance from the floodlight tothe illuminated surface.

• Use a smaller number of large floodlightsinstead of a larger number of smaller floodlights.

The beam spread can be described in degreesor by NEMA types (fig. 1-19). The beam spreadis based on the angle to either side of the aimingpoint where the candlepower drops to 10 percentof its maximum value. The lamp and floodlightNEMA type is given in the upper left-hand cornerof each isofootcandle diagram.

SELECTION OF LUMINAIRE

The National Electrical Manufacturer’s Asso-ciation (NEMA) has classified floodlighting lumi-naires into four classes according to construction:

1. Class HD (Heavy Duty)—Enclosed with anouter housing into which is placed a separate andremovable reflector, or an enclosure in which a Vseparate housing is placed over the reflector.

The NEMA type should only be used as areference. It does not describe the shape of thelight pattern the floodlight produces or the peakillumination level (footcandles). Symmetricalfloodlights have the same horizontal and verticalbeam spread and are classified with one NEMAnumber. Asymmetrical beam spreads have ahorizontal (H) and a vertical (V) designation. Thehorizontal value is always given first.

Example: NEMA TYPEH7

×6

Beam NEMASpread TypeDegrees Designation

10 up to 18 1 —18 up to 29 229 up to 46 346 up to 70 470 up to 100 5

100 up to 130 6130 and up

BeamDescription

very narrownarrowmedium narrowmediummedium widewide

7 very wide

High-IntensityDischarge

Min. Beam Efficiency, Percent

Incandescentand

TungstenHalogen

3840 3046 3450 3854 4256 4660 50

26.341.1XFigure 1-19.—Luminaire designations.

1-21

MOUNTING HEIGHT AND SPACING

The size of the area to be illuminated has adirect effect on determining the number andspacing of the poles. The suggested area that canbe covered by a single pole is four times themounting height. This is known as the “2X-4X”rule.

Areas lighted from interior poles or othercentral locations (fig. 1-20a) can be moreeconomical, but perimeter locations are alsodesirable to provide needed visibility at entrancesand exits. In the case of perimeter poles (fig.1-20b), if corner locations are not used, thedistance from any side location to the edge of thearea should not exceed twice the mounting height.

limited to only one side of the area to be lighted(fig. 1-20c), the system will be effective for adistance of only two mounting heights unless glareis not a determining factor.

According to the 2X-4X rule, the spacing isdetermined to be, from the corner to the first pole,two times the mounting height (X). The next poleis set four times this mounting height (X), andthe CE will continue in this manner until reachingthe last pole, which also is to be set two times themounting height from the far corner. This rulecan be used to calculate the minimum number ofpoles. For long, narrow areas, it is better to chooseseveral short poles than one tall one, especiallysince pole costs increase substantially above 40feet. It is wise to consider several alternatives,however, to determine the system with the lowest

If building-mounted luminaire locations are cost.

26.342XFigure 1-20.—2X-4X mounting height rule.

1-22

If the pole is located inside the area to belighted, there should be at least three floodlightsor two streetlights per pole. For one side perimetermounting, there should be two floodlights or onestreetlight per pole.

FLOODING AIMING

When a fixture is aimed at the surfaceat an angle other than perpendicular, themaximum lighting level will always occur behindthe aiming point, or point of maximum candela.This is important to know when the fixturesare placed close to the base of a tall structure.In this case the highest lighting level willoccur at the base even though the fixture is aimedat the top.

For vertical aiming, the aiming point shouldbe two-thirds to three-fourths the distance acrossthe area or twice the mounting height, whicheveris the lowest value. Higher aiming angles will notimprove utilization and uniformity. (See fig.1-21.)

The highest light level (vertical and horizontal)a floodlight can produce at a distance from thepole occurs when the maximum intensity orcandlepower is aimed to form approximately a 3,4, 5 triangle. (See fig. 1-22.) This is useful whendetermining pole height for area lighting orsetback for building floodlighting.

Floodlights with NEMA 6 or 7 horizontalbeams will effectively light an area 45° to eitherside of the aiming line. In figure 1-23, theperimeter pole needs at least two floodlights tocover the area in all directions. Narrower beamfloodlights require less separation to achieveuniform lighting.

Figure 1-21.—Vertical aiming.26.342.1X

26.342.2XFigure 1-22.—Maximum candlepower of illumination.

Select lighting fixtures with a beam spreadgreater than the area being lighted. Where severalunits are required, good lighting overlap occurswhen the edge of the beam of one fixture coincideswith the aiming point of the adjacent fixture.

By examining the shape (beam spread) of thelighting pattern emitted by the fixture, you canbegin the process of selecting the NEMA typefloodlight best suited for the application.

Horizontal and vertical lumen distribution isstated on each photometric test. Generally, themore concentrated the luminous intensity(candela), the tighter the beam spread. Forinstance, the NEMA Type 2 Power Spot® flood-light has a beam spread of 22° horizontal by21° vertical, whereas a NEMA Type 5 hasa beam spread of 77° horizontal by 77°vertical. The isofootcandle diagrams shown in

26.343XFigure 1-23.—Horizontal aiming.

1-23

figure 1-24 compare 1,000-watt metal halidePower Spot® luminaires of NEMA Type 2 andType 5 when each luminaire is aimed out adistance of twice its mounting height.

The initial footcandle level at the aiming pointof different NEMA Types varies a great deal. Forexample, assume that each luminaire is mounted

at a 50-foot mounting height and aimed 100 feet(2 x MH) directly in front of its location. If youare using a NEMA Type 2 distribution, theapproximate initial footcandle level at that pointwould be 20; however, if you are using a NEMAType 5 distribution, the initial footcandle levelwould be approximately 1.5.

26.343.1XFigure 1-24.—Isofootcandle diagrams.

1-24

By understanding the intensity of the lightingpattern, we can now appreciate the need for arange of distribution patterns.

MANUFACTURER’S LITERATURE

The performance specifications of each model,type, and size of luminaire are provided with thefixture or obtained from the manufacturer’sordering catalog. A working knowledge of thisinformation will assist you in selecting andinstalling the correct floodlight to accomplish thejob. Figure 1-25 shows the manufacturer’sliterature provided with a General Electric,250- to 1,000-watt, Lucalox®, HLX Power-flood® luminaire.

ISOFOOTCANDLE DIAGRAMS

The isofootcandle diagrams show what thelight level will be at any given point. The

dimensions for the diagram are based on themounting height (MH) of the floodlight. Theaiming point ( ) is also based on the mountingheight. Figure 1-25 provides a diagram formounting heights of MH × 0.5, MH × 1, andMH × 2.

The grid pattern is also based on the mountingheight. The grid line values left and right give thedistance to either side of the floodlight. The valuesup the side show the distance in line with theaiming direction of the floodlight. The number3, for instance, represents 3 × 40, or 120, feetfrom a 40-foot mounting height.

Each isofootcandle line shows where thefootcandle level is the same. These lines areidentified by a letter, which is used with the initialfootcandle (fc) table. The footcandle valuesbetween isofootcandle lines do not change morethan 2 to 1. This makes it possible to approximatethe level between lines.

The initial footcandle table gives the foot-candle value for each isofootcandle curve at aspecific mounting height. The values for each

26.343.2X

Figure 1-25.—Floodlight manufacturer’s literature.

1-25

letter are the same on each set of curves. Thismakes it possible to compare diagrams directlyand interpolate between curves for differentaiming distances.

The mounting heights given in the table arerepresentative of the wattage and beam patternassociated with the floodlight. To convert to othermounting heights, use the following formula:

OLD NEW(FROM CHART) (FROM CALCULATION)

(fc)(MH2)=

(fc)(MH2)

For example, a 5-footcandle level at 50 feet(isofootcandle curve F) would have a value of 4.13at a 55-foot mounting height.

fc =(N)(LL)(CU)

AREA

(5)(502) = (fc)(552) fc = 4.13

In figure 1-25 (aiming point MH × 2), thefloodlight is aimed a distance of two mountingheights away from a point on the ground directlybelow the floodlight. This would be 80 feet fora 40-foot mounting height.

UTILIZATION GRAPH

The luminaire utilization graph gives thepercentage of the initial lamp lumens that fall intothe area being lighted. Knowing this, you caneasily determine the average lumens per squarefoot, or footcandles.

The number beside each curve identifies theaiming point so that the utilization curve can beidentified with the associated isofootcandlediagrams. In the example, for instance, thefloodlight aimed two mounting heights away fromthe pole would have a utilization of 35 percentif it were lighting an area three mounting heightswide. The same floodlight aimed at one mountingheight away from the pole would have a utilizationof 45 percent for the same area.

MAINTENANCE FACTOR

Lighting efficiency in floodlighting, as instreetlighting, is seriously impaired by blackenedlamps, by lamp life, and by dirt on the reflectingsurfaces of the luminaire. A maintenance factor(MF) must be applied in the lighting calculationsto compensate for the gradual losses of illumina-tion on the lighted area.

The following maintenance factors have beenwidely used in industry when manufacturer’sinformation is not available:

Enclosed floodlamps, 0.76

Open floodlamps, 0.65

LIGHT INTENSITY CALCULATIONS

There are a number of ways by which todetermine luminaire requirements. Since mostmethods would require an engineering back-ground, we will only discuss the basic area lightingdesign considerations that you, as a ConstructionElectrician, can perform in the field if engineeringassistance is not available. To better understandhow the calculations are performed, solve thissample problem:

Determine the average initial light levelin a 160-foot × 160-foot material storage yardusing two NEMA 6 × 5 HLX 1,000-wattLucalox® floodlights.

Solution:

1. Apply the 2X-4X rule (see fig. 1-26) todetermine spacing and mounting height. A 40-footmounting height provides MH x 2 or an80-foot aiming distance.

2. The formula used to calculate the averageinitial light level (fc) is as follows:

26.343.3XFigure 1-26.—Material yard sample problem.

1-26

where:

N = number of floodlights

LL = initial lamp lumens

CU = utilization of the floodlights

From the utilization data (fig. 1-25), you canfind that the utilization for the HLX luminaireaimed at two mounting heights across an area 160feet or four mounting heights wide is 38 percent.The initial lumens for the 1,000 watt lamp is140,000 lumens, obtained from the manufac-turer’s literature. Substituting in the formula,

fc = (2)(140,000)(0.38)(160)(160) = 4.2 fc

The maintained light level is obtained bymultiplying the initial light level by the mainte-nance factor.

fc = (4.2)(0.75) = 3.15 fc

Using the isofootcandle diagram, we obtainpoint by point footcandle values. For example,the center of the area occurs just inside isofoot-candle line E. From the initial footcandle table,the 1,000-watt Lucalox® HLX at 40 feet produces3.1 footcandles at line E and 7.8 at line F. Sincethe point is approximately one-fourth of thedistance between the two isofootcandle lines, thevalue will be about 4.0 foot-candles. With the twofloodlights contributing, the value in the centerwill be 8.0 footcandles. Note that the corners ofthe area will have very little light. This is why twoor more floodlights are recommended at perimeterlocations.

Another design method that will yieldsufficient accuracy is the quick selector designmethod. The general layout considerations shownin figure 1-26 should be followed. The watts persquare foot obtained from the graph in figure 1-27produce an average lighting level accurate to

26.344XFigure 1-27.—Lamp watts per square foot chart.

1-27

within 20 percent of desired value. This is closeenough since the difference between the luminairerequirement obtained from the graph and thenumber that will actually be needed to satisfy thephysical requirements of the job involveadjustments greater than 20 percent. It is notunusual, for instance, to need two poles insteadof one or to require three luminaires per poleinstead of two. This calculation method shouldnot be used for sports lighting or where the polesare set back from the area to be lighted.

Before determining the number of luminaires,you should work out the size of the lighted arealocation of the luminaires. Also, you shoulddetermine the maintained illumination level. Thefollowing rules of thumb provide some guidelinesto help in these decisions.

Approximate required lamp watts/squarefoot.

1. From table 1-3, you find that the minimumaverage footcandles recommended for industrialyard/material handling is 5.

2. Read up the left side of the graph infigure 1-27 until you come to 5.0. Follow this lineacross until you intersect the dark diagonal linerepresenting Lucalox®.

3. By reading straight down from thisintersection to the value at the bottom of thechart, you find 0.095 lamp watts/square foot ofthe area is required to light the yard to 5footcandles.

4. Area to be lighted is (160)(160) = 25,600square feet.

5. Multiply 25,600 by 0.095 = 2,432 lampwatts.

2,432 is more than two 1,000-wattLucalox® lamps

2,432 is approximately equal to six400-watt Lucalox® lamps

2,432 is approximately equal to ten250-watt Lucalox® lamps

6. By using the general layout considerations,you will find that the most economical floodlightinstallation will use the 400-watt Lucalox® lamps,mounted on 40-foot poles as shown below.

2X + 2X = 4X = 160 feet

X 160 feet= 4 = 40 feet MH

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SECURITY LIGHTING

Requirements for security lighting at activitieswill depend upon the situation and the area to beprotected. Each situation requires careful studyto provide the best visibility that is practical forsuch guard duties as identifying personnel andvehicles, preventing illegal entry, detectingintruders, and investigating unusual or suspiciouscircumstances.

The type of security lighting may be either thecontinuous or the standby type. The continuoustype, as the name implies, is on all the timeduring the hours of darkness. The standby typeis activated either manually or automaticallywhen suspicious activity is detected.

SECURITY AREA CLASSIFICATION

The installation of security lighting is set forthin OPNAVINST 5530.14A, United States NavyPhysical Security Manual. It providesspecifications on searchlights and minimumfootcandle requirements under given situations.The illumination of boundaries, entrances,structures, and areas must be according to thesecurity manual.

LIGHTING CONTROL

Each security lighting system is designed tomeet a particular activity’s needs. The design issuch that it provides the security required atmaximum economy.

Multiple circuits may be used to advantagehere. The circuits are so arranged that the failureof any one lamp will not darken a long sectionof the area. The protective lighting system shouldbe independent of other lighting systems andprotected from interruption in case of fire.

The switches and controls of the system shouldbe locked, and/or guarded at all times. The mosteffective means is to have them located in a keyguard station or central station similar to thesystem used in intrusion alarm central stationinstallations.

ALTERNATE POWER SOURCES

In general, any security area provided withprotective lighting should have an emergencypower source located within that security area.The emergency power source should be adequateto sustain all security requirements and otheressential service required within the security area.

Provisions should be made to ensure the plans must provide for responsible personnel toimmediate availability of the emergency power in respond immediately in times of emergency. Inthe event of power failure. Security force addition, battery-powered lights and essentialpersonnel should be capable of operating thepower unit. If technical knowledge prevents this,

communications should be available at all timesat key locations within the secure area.

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CHAPTER 2

AIRFIELD LIGHTING

As a Construction Electrician, first class pettyofficer, you may be responsible for supervisingthe installation of expeditionary airfield lightingand any repairs or maintenance required to thatinstallation as well as to permanent advanced baselaunch and landing facilities.

Since the SEABEES’ existence is based onbeing used in contingency operation, you, as anelectrician, should know the equipment andcomponents of such a contingency lightingsystem; the “expedient airfields assembly, 30300,”as taken from the advanced base functionalcomponent kit listings, is such a package. If theworld situation should develop to a point wherethe SEABEES are alerted and tactical air supportis required, such a kit, plus portable generators,must accompany you to the forward area. Forcontingency operations, the types of airfields usedmay be any of the following:

1. Vertical takeoff and landing (VTOL)airfields

2. Vertical short takeoff and landing(VSTOL) airfields (600 and 1,800 feet)

3. Strategic Expeditionary Landing Field(SELF)

4. Expeditionary airfield (EAF)

The scope of this chapter is not so much toprovide details on the electrical systems used ateach of the above-mentioned airfields, but toacquaint you with the systems’ components andtheir functions for both expeditionary and thepermanent type of airfields. Normally, the VTOLairfield is an installation made of aluminummatting and is used as a forward landing field byeither helicopters or harrier type of aircraft,whereas the VSTOL airfield, also an aluminum-matted installation, is usually used as a forwardoperational facility. The SELF is used by

high-performance aircraft, such as the F4Phantom, the A4 Skyhawk, or the F14 Tomcat,and is also used as a forward air facility. The EAFis similar to the SELF, only with a longer runway.

AIRFIELD LIGHTING SYSTEMS

Airfield lighting systems are designed to aidthe pilots during launch, recovery, and taxioperations. These systems date back to thesmudge pots and the burning of brush piles to helpguide pilots into safe landings. Through the years,the methods of lighting airfields have becomemore sophisticated. The lighting systems todaymust have the light properly distributed, have lightcontrols, and also have the ability to define certainareas by means of different colored lenses andfilters inside of the lighting fixtures.

The patterns and colors of the lights, as wellas the markings, at each airfield must be uniformto enable the pilots to interpret what is seen and,then, to react almost automatically. To ensure thatthese airfield lighting standards are met, theFederal Aviation Administration (FAA) has beentasked with making these standards and with thepolicing authority within the United States; inaddition, the FAA’s standards are used in airfieldsconstructed by the military overseas.

The design of airfield lighting systems mustprovide for locating an obstructional warningsystem, runway and approach markings, andtaxiway and parking facility markings.

AIRFIELD LAYOUT

The VTOL forward operating site is a portableairfield of minimum size designed for operationsdependent upon logistic or tactical support byhelicopters and other vertical takeoff or landingaircraft. The field consists of a surface pad 72 feet

2-1

square, as shown in figure 2-1, view A, withoutlighting, communications, or recovery systems.

A VSTOL facility is a portable airfield capableof providing support to VSTOL fixed-wingaircraft as well as helicopters. The field consistsof a surfaced runway 900 feet long and 72 feetwide and turnoff, parking, and maintenanceareas. The nature of the aircraft to be servicedprecludes the necessity for arresting gear;however, a field lighting system and a communica-tions system are supplied to provide suitableaircraft recovery capability. A VSTOL facility canreadily be converted to a VSTOL air base.

A VSTOL air base is a portable airfieldcapable of providing support for VSTOL fixed-wing aircraft as well as helicopters. The fieldconsists of a surfaced runway 1,800 feet long and72 feet wide and turnoff, maintenance, andparking areas to accommodate up to twelveaircraft. From the VSTOL air base assets,plans are provided from which three VSTOLFACILITIES can be constructed. The VSTOL airbase can support at least one squadron oflight VSTOL attack aircraft and a number ofhelicopters. The nature of the aircraft serviced bythe VSTOL air base precludes the necessity forarresting gear; however, a field lighting system,a Fresnel lens optical landing system (FLOLS),and a communications system are incorporatedto provide suitable aircraft support. A VSTOLair base may readily be converted to an expedi-tionary airfield (EAF).

The EAF is a portable airfield that providesa surfaced runway 5,200 feet long and 96 feetwide, as shown in figure 2-1, view D, and parkingand maintenance areas for up to six squadronsof light-to-medium fighter/attack aircraft, inaddition to a complement of reconnaissanceaircraft and helicopters. The field includes twoM-21 aircraft recovery systems, two FLOLS, andfield lighting and communications systems. AnEAF may readily be converted to a strategicexpeditionary landing field (SELF).

The SELF is a portable airfield that providesa surfaced runway 8,000 feet long and 96 feetwide, as shown in figure 2-1, view E. The SELFis a pre-positioned war reserve (PWR) setup.The airfield provides turnoff, maintenance,and parking areas to accommodate up to sixsquadrons of light-to-medium fighter/attackaircraft, a detachment of KC-130 tanker aircraft,and various transient logistic support aircraft. TheSELF configuration includes two M-21 aircraftrecovery systems as well as two FLOLS and fieldlighting and communications systems.

AIRFIELD LIGHTING VAULT

The beginning of the airfield lighting systemis the airfield lighting vault. The primary powerfeeder enters the vault and supplies power to allof the major components. These components, inturn, control and operate the airfield lights. Thevault houses the high-voltage power cables, thecurrent regulators, the relay cabinets, and thecontrol panels.

The control cables are installed between thevault and the control tower or other controlpoints. The high-voltage cables are connected tothe regulators and run out to the lights. Thelighting control panels are used to give local/remote control of the system. The same type ofremote control panel that is in the vault shouldalso be installed in the control tower.

The airfield lighting vault should be about3,000 feet from the runway. This distance ensuresthat no interference will occur with the airfield’soperations, and still it is not so far away thatvoltage drops might cause a problem. The lengthsof the control circuits between the controltower and the vault are limited by operationalcharacteristics; for example, size of field,obstructions, and so forth. The minimum distanceis 350 feet; this is to prevent the equipment in thevault from causing radio interference. If thecontrol cable leads terminate into actuating coilsof relays in the pilot relay cabinet, the maximumdistance is 7,350 feet.

Safety

The airfield lighting vault should have certainitems of safety equipment on hand and affixedto a board. This board should be in open displayand easily accessible. It should be a minimum of1/2 inch thick and 4 by 4 feet in width and length.The color should be dark green with white lettersand borders.

On this board, some of the safety items youshould have are as follows:

1. Operating instructions for the equipmentin the vault

2. Resuscitation instructions3. A phone and a list of emergency phone

numbers4. A first-aid kit5. A switch stick with a minimum length of

5 feet, and a 300-pound pull ability6. A hemp rope, 1/2 inch thick, with a

minimum length of 15 feet

2-2

Figure 2-1.—Field arrangement direct installation.

2-3

7. Insulated fuse pullers (for secondary

8. A nonmetallic-encased flashlight marked

9. A shorting stick10. Rubber gloves

cartridge fuses)

with luminescent tape to aid in itslocation in the dark

For the safety of personnel, the airfieldlighting vault must be grounded. This may beaccomplished by using two 1/2-inch-diameter,8-foot-long, copper-plated electrodes, driven intothe ground about 8 feet apart and connected ina loop with the vault or ground cable part of theground grid. This typical connection is shown infigure 2-2.

Power Supply

In many cases, the power supply will not beall high or low voltage; in fact, in manyexpeditionary airfields, the system may be acombination of high and low voltage. However,if you are assigned to a naval air station, chancesare that you may be required to maintainhigh-voltage airfield lighting systems. Basically,

Figure 2-2.—Vault grounding arrangement.

the systems are identical, but because of safetyrequirements, the high-voltage systems will havea few variables. As an example, take the isolationtransformer (IT) in the high-voltage system; itserves to step the voltage down, but its primarypurpose is to prevent an opening in the primaryseries loop when a lamp failure occurs. In alow-voltage system, the transformer is usually a2:1 or 1:1 ratio unit that serves to maintain aclosed loop, the same function as the one in thehigh-voltage system. Even though we will betalking primarily about high-voltage systems mostof the time, the functions of the components willapply to either system.

In the 2,400/4,160-volt system, the four-wirewye primary source is usually from the baseelectrical system by means of either an overheador an underground line. Inside the vault, the linesare connected to a suitable switch, then to a bussystem consisting of heavy metal bars that aresupported on insulators. This bus system may bemounted on either the wall or the ceiling.

The bus is divided into a high-voltage(2,400-volt) bus and a low-voltage (120/240-volt)bus for service as follows: The 2,400-volt bussupplies all of the 2,400-volt regulators and oneor more distribution type of transformers. Thedistribution transformers supply 240 volts to thelow-voltage bus that is connected to the regulatorsoperating from this lower voltage as well as forlight and power inside the lighting vault.

Where an emergency power supply is availablefor airfield lighting, a changeover switch makesthe primary connection to the bus. This change-over switch in its normal position connects the busto the base power source. Changing the switch tothe emergency operation position connects the busto the emergency power and, at the same time,disconnects the base power source.

Emergency power can be supplied by acompletely automatic engine-driven generator.For example, failure of the base power causes theengine to start. In a matter of seconds, thechangeover switch automatically shifts to theemergency position, connecting the generator tothe airfield lighting bus.

At many advance bases, this automatic featuremay not exist. Then, you become its replacement.The generator should have a kilowatt (kW) ratingcapable of handling the airfield lighting systems,runway edge lights, threshold lights, approachlights, distance markers, optical launching system(OLS), and other circuits that may be used. Thegenerator is three phase; its voltage output variesfrom 120/240 volts delta or 120/208 volts wye to

2-4

2,400/4,160 volts, and it has to be capable ofbeing operated at frequencies of 50 or 60 hertz(Hz).

Constant-Current Regulator

Runway lighting systems are supplied fromseries circuits served by constant-currentregulators (CCRs). Each lighting circuit on theairfield has a separate regulator. The CCRsmaintain the output current throughout its ratedoutput value, depending on the load. Some of theregulators are equipped with brightness controls.These brightness controls adjust the brightness ofthe lamps in the lighting system to compensatefor visibility conditions.

The CCR uses solid-state devices to maintaina constant-current level in its respective lightingsystem. The regulators are silicon-controlledrectifiers (SCRs) in a feedback circuit to obtaina constant-current output instead of resonantcircuits, moving transformer elements, orsaturable reactors. The SCRs are controlled tovary the part of a cycle during which the current

is permitted to flow into the load circuit. In theload circuit, the current is maintained constantat any value preset with the brightness control bymeans of a feedback circuit as the load resistanceis varied from maximum to zero. The blockdiagram (fig. 2-3) shows the elements constitutingthe regulator. Load current is measured by thecurrent transformer and the Hall unit or multiplierunit, which has an output voltage proportionalto the square of the load current. The Hall ormultiplier output is filtered and fed into the inputof an amplifier and compared with an input froma brightness control potentiometer. The outputvoltage is a function of the difference between thetwo inputs. The output voltage is applied to theinput of the gate pulse generator that determinesthe condition angle of the SCRs and changes itto bring the system to equilibrium. Transientoverload protection is provided for the semi-conductor element of the Hall unit. Open-circuitprotection is provided when no current is drawnby the load and the brightness potentiometeroutput voltage is any value other than zero. Underthese conditions, the SCRs will be prevented from

Figure 2-3.—Block diagram of constant-current regulator.

2-5

conducting, and the output voltage to the loadwill be zero.

Remote Control

The airfield lighting systems may be operatedcompletely by the remote control panel assembly.The only operation required at the electricaldistribution vault is to ensure that all circuitbreakers are engaged, the regulators are setfor remote operation, and the load switchesare in the ON position. As the electrician, ensurethat the unit is installed properly and that thedifferent levels of light intensity desired can beachieved. Figure 2-4 is a typical view of a remotecontrol unit that you may encounter in theinstallation of a contingency airfield lightingsystem.

The unit uses 120 volts as the control voltagewith low-burden pilot relays to compensate forthe voltage drop caused by the long distancesusually found between the control tower and thevault. In this type of control system, the switcheson the control panel actuate low-burden relays;these, in turn, actuate the power switches,contactors, and the relays controlling theregulators that supply the airfield lightingcircuits.

Both the tower and vault control panels are

cabinet” located in the vault. This is shown infigure 2-5 with a single line representing thecontrol cable. The transfer-relay can connecteither control panel to the pilot-relay cabinet. Itcan switch the system control from the tower tothe vault or from the vault to the tower. Thetransfer relay has an eight-pole, double-throw,transfer-relay assembly unit. This unit is actuatedby a toggle switch.

The low-burden pilot relay is designed tooperate at a wide range of voltages lowerthan the designed 120-volt ac rating. The pilotrelay can be actuated at voltages from 50 to 90volts ac.

The standard control cable is a seven-conductor, 600-volt, Buna-insulated, polychloro-prene-sheathed cable. One conductor (black) isa No. 12 American wire gauge (AWG), and theremaining conductors are No. 16 AWG. The No.12 conductor is the hot lead, and the No. 16s, the“switch legs.”

LIGHTING CIRCUITS

Several different lighting circuits are used onairfields: runway edge lighting circuits, taxiwaylighting circuits, approach lighting circuits,obstruction lighting circuits, beacon lightingcircuits, and the condenser discharge circuits,

wired into a double-throw “transfer-relay which will be covered separately.

Figure 2-4.—Typical remote control panel operating controls.

2-6

Runway Edge Lights

Runway edge lighting is designed to show thewidth and length of the usable landing area; thereare two rows of lights, one row on each side, thatrun the length of the runway. The light they

give off is aviation white (clear). The edge lightsare installed not more than 10 feet from the edgeof the full-strength runway paving. Both lines oflights will be the same distance from the runwaycenter line. It is best if the lines of lights arelocated as close to the runway as the base

Figure 2-5.—Airfield lighting control system.

2-7

mounting for the lights allows. The lights areequally spaced along the runway at distances notto exceed 200 feet. (See fig. 2-6.)

The runway lighting controls are set up so thatthe lights on intersecting runways cannot be onat the same time. Also, the controls must turn allthe light systems of one runway on at the sametime. The runway edge lights are controlled so allthe lights are the same brightness. In a high-intensity system, threshold lights are one stephigher than the runway edge lights, except whenthe runway edge lights are at full brightness. Atthis time, the runway edge lights and the thresholdlights are at full brightness. In a medium-intensityrunway lighting system, all lights (runway edgelights and threshold lights) are the samebrightness.

In some instances, it is a good practice to userunway edge light fixtures and lamps for thethreshold lights, so that the difference is noticeablewhen the threshold lighting configuration has tobe stepped up one brightness higher than therunway edge lights. To determine the number ofcircuits required for runway edge lights, you needto determine the length of the runway. Youdetermine the number of lights on one circuit byconsidering not only the number of lightsconnected to the circuit but also the volt/ampereloss for the circuit cables and the feeder cablesfrom the vault to the runway. If this distance islong, you may need to adjust the number of lightsin the circuit.

Do not load the regulator less than one-half ofits rated kW output. If more than one regulator isrequired, each regulator should be equally loaded.

Each light circuit will be fed by a series loop.The current leaves one terminal of the CCR, goesthrough the circuit to each light unit, and returnsto the other terminal of the regulator.

Taxiway Lights

Taxiway lights are used to show the pilot thewidth and direction of the “taxiing route.” Thelights are aviation blue in color. They are basicallythe same as runway lighting circuits.

Approach Lights

Runway approach light systems are used onhigh-intensity-equipped runways. The systemstarts at the threshold and extends outward for3,000 feet. Where the full length of the land

cannot be used, the greatest length possible isused. Condenser discharge (strobe) lights that putout a high-intensity, bluish white light start at the3,000-foot mark and flash in sequence toward thethreshold. The system is used to help the pilotsland under low-visibility conditions. (This isdiscussed in more detail later in this chapter.)

The lights of the approach system are locatedon an imaginary line that extends from the runwaycenter line. Each light bar is centered on thisimaginary line and spaced the same distance apartfor the entire 3,000 feet.

The supply and control circuits of theapproach lighting systems are installed under-ground and are usually in conduit. However, insome cases, the last 2,000 feet of the approachlights can be above ground. In some cases, thesupply cable from the series circuit can be directburial. The direct burial method of cable installa-tion will be discussed in another chapter.

Aboveground circuits may be used forapproach lighting when the cables do not presenta hazard to vehicular traffic or are not accessibleto unauthorized personnel and animals. The cablemust be installed, normally, a minimum of 22 feetabove ground. Where the area is completely closedoff (fenced), a lower ground clearance is accepta-ble. Control circuits may use a small-size con-ductor when it is supported by a messengercable. DO NOT USE ALUMINUM CONDUC-TORS. Use standard overhead constructionpractices for series circuits. Use lightning arresterswhen the cables go from underground to over-head. Connect the ends of the circuits to ITs thesame way as underground cables.

Besides the basic runway light configurations,there are other airfield lighting aids to help thepilot in landing and takeoff operations. Four suchaids for landing and taking off are the visualapproach slope indicators (VASI), the FLOLS,the runway distance markers, and the thresholdlights.

VISUAL APPROACH SLOPE INDICA-TORS (VASI).—The VASI system helps the pilotto make a visual glide slope landing approach.When there is an electronic glide slope system, theVASI system must be set up to give the sameindication.

The VASI system consists of twelve light boxeswith three lights in each box. There is onecomplete system for each end of the runway.There are two pairs of bars, one bar on each sideof the runway. Each wing bar is composed of

2-8

Figure 2-6.—Typical airfield lighting layout.

2-9

three light boxes. (See fig. 2-7.) The pair of barsnearest the threshold is called the downwind bars,and the other pair, the upwind bars. Each lightbox projects a beam of light that is white (clear)in its upper part and red in its lower part. Thelights are so arranged that the pilot of an airplane,during the approach, sees all of the wing bar lightsas red when below the glide slope. When on theglide slope, the pilot sees the downwind bar lightas white, the upwind bar as red. When above theglide slope, the pilot sees all the wing bar lightsas white.

FRESNEL LENS OPTICAL LANDINGSYSTEM (FLOLS).—Another system designedfor continuous automatic operation is the FLOLS.(See fig. 2-8.) It also provides optical landingassistance by indicating the correct glide slopeangle to the pilot of an approaching aircraft. Thissystem contains two groups of horizontal datumlights set perpendicular to the approach path, twovertical bars of wave off lights, two double-typecut lights, and a source light indicator assembly,consisting of five vertical cell assemblies. Each cellassembly contains source lights, a Fresnel lens,and a lenticular lens. The arrangement of these

lenses gives the pilot the glide slope. The unitshould be set up on the left side of the runwaywith respect to the approaching plane, about 10feet from the edge of the pavement and 750 feetfrom the runway threshold.

Power for the system is provided by aninstalled field lighting supply or by an auxiliarypower unit capable of 20 kW, 60 Hz, three-phase,120 volts phase to neutral.

RUNWAY DISTANCE MARKER.—Withthe use of high-speed aircraft, the runway distancemarker system is needed to tell the pilots howmuch runway is left to take off or to land. Thedistance information, in thousands of feet, isgiven by numbers on the side of the marker. Thenumbers are on two sides of the signs, so that thedistance left can be shown for both directions.There is one row of signs on each side of therunway. Each row is the same distance from therunway center line. They are spaced 1,000 feetapart. The signs have painted numbers that arelit so they can be seen at night and during periodsof restricted visibility.

Figure 2-7.—Visual approach slope indicators (VASI).

2-10

Figure 2-8.—Fresnel lens optical landing system.

The power supply should be from a separateseries circuit for serving the runway distancemarkers. Do not have the markers supplied fromcircuits feeding either the runway, threshold, orthe approach lighting circuits, since these circuitsare operated at various brightness steps, and thesigns are operated at their full brightness at alltimes. Also, do not connect them to taxiway cir-cuits because of the intermittent operation require-ments. The cable used for the circuit is a singleconductor, No. 8 AWG, stranded, 5,000 volts.

THRESHOLD LIGHTS.—The thresholdlights are a part of the approach light system. Four

sets of light systems are used in the threshold lightconfiguration. These lights are as follows: inboardthreshold lights, winged-out threshold lights, pre-threshold wing bars, and a terminating bar. Thesefour sets of lights are installed on both ends ofthe runway and are used to mark the beginningof the runway.

Inboard Threshold Lights.—Inboardthreshold lights are installed in the area at the endof the runway between the two runway edge lightlines. This line of lights will be at a right angleto the runway center line. They are as close to thefull-strength paving as possible but not more than

2-11

10 feet from it. The lights are spaced 10 feet apart.Their color is aviation green. (See fig. 2-6.)

Winged-Out Threshold Lights.—The winged-out threshold light bar is on the same light lineas the inboard lights. These lights extend out fromthe end of each side of the inboard light bar. Eachbar is 40 feet long and has nine lights spaced 5feet apart. The first light location is at theintersection of the runway edge light line and thethreshold light line. The color of these lights isalso aviation green. (See fig. 2-6.)

Pre-threshold Wing Bars.—A pre-thresholdwing bar is located on each side of the extendedrunway center line 100 feet out from thethreshold. The innermost light of the bar is 75 feetfrom the center line. Each bar (14 feet long) hasfive aviation red lights spaced 3 1/2 feet apart.(See fig. 2-6.)

Terminating Bar.—The terminating bar islocated in the overrun area. The light bar is at aright angle to the runway center line and 200 feetout from the runway threshold (100 feet out fromthe pre-threshold lights). There are 11 aviation redlights in the bar. The bar is 50 feet long and isarranged so that one-half of the bar is on eachside of the center line. The lights are arranged inthree groups: five lights spaced 3 1/2 feet aparton a 14-foot bar in the middle and, on each side,one lo-foot bar of three lights spaced 5 feet apart.(See fig. 2-6.)

Obstruction Lights

The obstruction lighting is a system of redlights used to show the height and width of naturalor man-made objects that are hazardous to airflight. These lights are for the safety of aircraftin flight. The lights must be seen from alldirections and are aviation red in color.

The obstruction lights are turned on duringall hours of darkness and during periods ofrestricted visibility. They are placed on all objectswith an overall height of more than 150 feet aboveground or water within the airspace.

At least two lights (or one light fixture withtwo lamps) are located at the top of theobstruction. When the top of an obstruction ismore than 150 feet above the level of thesurrounding ground, an intermediate light, orlights, is provided for each 150 feet. These lightsare equally spaced from the top to the bottom.

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Where obstructions cover an extensivehorizontal plane, the top lights will be put on thepoint or edge of the obstruction highest in relationto the obstruction-marking surface. The lightsshould not be spaced more than 150 feet apart.This spacing indicates the general extent of theobstruction. Double lights are used at thehorizontal limits of the obstruction, and singlelights are used for intermediate lights. If two ormore edges are of the same height, the edgenearest the airfield is lit.

On overhead wires, obstruction lights areplaced at intervals not exceeding 150 feet and ata level not below that of the highest wire at eachlight location.

Obstruction lighting systems are served byeither a series or a multiple circuit. The type ofcircuit used depends on the location of theobstruction and the type of lighting equipmentinstalled. The six most common types of circuitsthat may be used for the obstruction lights areas follows:

1. Low-voltage multiple service from the vaultwhen the length of the circuit is less than 800 feet

2. Series circuit when the load is less than 4kW from a taxiway type of regulator in the vault

3. 2,400-volt service from the vault to adistribution transformer to serve a multiple circuit

4. 2,400-volt service from the vault to a CCRthat serves a series circuit

5. Control circuit from the vault whichoperates any of the previously listed circuits bymeans of a relay

6. Time clock or a photocell with a series ormultiple circuit for the lights

Obstruction lights on objects that are morethan 150 feet above ground or water must be onall the time or controlled by a photocell.

Beacon Lights

The landing facility location is provided by theaeronautical beacon. The beacon is a highcandlepower flashing light visible throughout360°. It provides the pilot a visual signal to locateand identify airfields during night operations orduring periods of restricted visibility, day or night.

There are three functional types of beaconsthat we will discuss: the airport beacon, theidentification or code beacon, and the hazard orobstruction beacon.

The airport beacon is normally located within5,000 feet of the airfield. The rotatable unit will

display alternate double-peaked white flashes anda single green flash to identify the airfield as amilitary facility. The size of the unit is about 24inches, a rigid drum duplex type with a cleardouble-flasher spread-light lens on one end anda plain green lens on the other. There is anautomatic built-in lamp change in case of lampburnout. An illustration of a typical airportbeacon is shown in figure 2-9. Beacon lights maybe manually controlled from the tower or fromthe lighting vault. If the facility is not operatedon a 24-hour basis, an automatic control ispossible with a photoelectric control that turns theunit on or off automatically.

The identification beacon or code beaconidentifies an airfield where the airport beacon ismore than 5,000 feet away from the airfield orwhere two or more airfields are close enough touse the same airport beacon. This nonrotatableunit can be seen from all directions and isequipped with a flasher switch operating at 40flashes per minute with a range adjustment. Thebeacon has white lenses with green filters and ismanually controlled from the tower but may becontrolled automatically.

The third beacon, the hazard or obstructionbeacon, furnishes visual identification of naturalfeatures or structures which are 150 feet aboveairfield elevation for on-station or off-stationhazards; that is, tanks, towers, stacks, and soforth. The beacon uses white lenses with red filtersand is manually controlled from the tower. Whenautomatic controls are desirable, a photoelectriccontrol system may be used. Since the beacon doesnot rotate, a flashing system is used, flashing 26times per minute. The beacon lamps and motorrequire 120 volts for operation. Most of the time,this unit is fed by a 120/240-volt or 120/208-volt,three-wire service. You can use a 120-volt, two-wire service, but it is not recommended. Whenthe lighting vault is less than 800 feet away fromthe beacon, a low-voltage service can be used.When the vault is more than 800 feet away, highvoltage (2,400 volts) from the lighting vault is usedto supply a distribution transformer at the baseof the beacon. You can also run a control wirefrom the vault to the beacon to operate a relaythat, in turn, switches on the power from a localsource near the beacon. The last method worksbest when the beacon is at a remote location fromthe airfield.

Figure 2-9.—Beacon with one door open and base pan dropped.

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1. Electrical distribution vault.2. Remote control assembly.3. 4-kW constant-current regulator.4. 15-kW constant-current regulator.5. Center-line light.6. Runway light.7. Threshold light.8. Taxiway light.

9. Approach light.10. Strobe light.11. Extended line-up light.12. Strobe timer.13. Strobe power supply.14. Obstruction light.15. Circling guidance light.16. Rotating beacon light.

17. Status light.18. 500-W floodlight.19. 200-W floodlight.20. Wind cone assembly.21. Rotation light.22. Transformer - runway and approach.23. Transformer - taxiway.24. Transformer - work area.

*Will be furnished until supply is exhausted.

Figure 2-10.—Airfield lighting components.

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Table 2-1.—Airfield Lighting Equipment Required

ComponentNAEC Quantity Per Field

PartNumber VSTOL VSTOL EAF SELF

900´ 1,800´ 5,200´ 8,000´

Approach Light AssemblyCenter-line Light AssemblyCircling Guidance Light Assembly –Electrical Distribution VaultFloodlight Assembly 500WFloodlight Assembly 200W

Obstruction Light AssemblyRegulator Constant Current 4kWRegulator Constant Current 15kWRemote Control AssemblyRotating Beacon Assembly –Rotating Light Assembly – –Runway Light AssemblyStatus Light Assembly –

–Strobe Light AssemblyStrobe Power SupplyStrobe Timer AssemblyTaxiway Light AssemblyThreshold Light Assembly – –

– –Wind Cone Assembly

505954-1613593-1508233-1615220-1615902615506-1

or616324-1505956-1

*616040-1*614384-1

614896-1609990-1505954-2615911-1409823-1409823-2506208-1610361-1610036-1615910-1505954-3505954-4506054-1

10 20 20 2017 34 86 51

8 16 161 1 1 1

26 54 125 12512 12 24 12

10 10 20 201 2 2 46 7 11 111 1 1 1

1 1 14 4

18 32 64 662 2 22 2 2

10 10 10 1010 10 10 102 2 2 2

37 92 122 2288 8

4 41 2 2 2

**Lamp Holder 413021-1 10 – – –**Adapter Bracket 423041-1 10 – – –**Lamp MS24348-5 10 – – –

*616040-1 and 614384 replaced with 618650 and 616360, respectively when supply is exhausted.**Components of extended line-up light.

Because of the extreme hazard to life, an used to give off the right kind of light. Aalternate low-voltage source near the beacon isusually required.

TYPES OF FIXTURES AND LAMPS

To meet different system requirements,different intensities of lighting are required. Alongwith these systems, you need different kinds offixtures to meet the needs of designated locations.In each fixture, a certain type of lamp must be

runway light fixture, in a series loop system,requires an insolation transformer (IT). Thesetransformers must be matched to each lampaccording to amperage and watts. Figure 2-10provides you a pictorial view of the lightingfixtures used in contingency airfield opera-tion; table 2-1 provides the Naval Air SystemCommand part number of each fixture plus thenumber of fixtures required per given type of fieldinstallation.

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Several different types of lights are used. Theexact type used depends on the system. Not onlyare there different fixtures for different widths ofrunways, but there are different intensities. Inmost cases, high-intensity lighting systems areused for high-speed aircraft. Also, high-intensitylighting systems are required during low-visibilityconditions.

CONDENSER DISCHARGELIGHTING SYSTEM

The condenser discharge lights are added tomake the approach system complete. Because thelamps flash on and off to give a stroboscopiceffect, the term strobe is used for these lights.From here on out, the term strobe will be usedwhen referring to condenser discharge lights.

The transformer and the master sequencetimer cabinet are located in a small vault or padnear the center of the approach system. The vaultor pad should be secured so neither animals norunauthorized personnel can enter.

The major components of the condenserdischarge lighting system are the elevated andsemiflush strobe light units, the master sequencetimer cabinet (containing the local/remote controlunit, the monitor and control chassis, and the

master sequence timer), and the tower controlunit.

Strobe Light System

The strobe lights are installed on each center-line light bar starting 300 feet from the runwaythreshold and extending outward for the lengthof the system. The strobe light will be located onthe center-line light bar, midway between thecenter light and the next light on either the leftor right side. They can be placed in front of thelight bar but not more than 10 feet. No matterwhere they are placed, they must be in the sameposition on each light bar throughout the entireapproach system.

In the overrun area, the strobe lights areinstalled as flush lights. Starting with the1,000-foot bar (decision bar) and going out, anelevated type of strobe light is used. An elevatedapproach light bar looks like the one shown infigure 2-11.

The strobe lights are controlled from theremote control panel. They can be turned on andoff independently or so triggered that they comeon when the approach light switch is in eitherthe third, fourth, or fifth brightness position.

Figure 2-11.—Elevated approach light bar.

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The brightness of the strobe lights cannot be knowledge of one will give you an understandingcontrolled. of the others.

The strobe lights put out a high beam of light Strobe lights are either flush mounted orthat peaks at 30 million candlepower. DO NOT elevated. Since the components are easier to seeLOOK INTO THE BEAM OF LIGHT WHEN on an elevated unit, we will illustrate ourYOU ARE NEAR ONE OF THE LAMPS OR discussion with an elevated unit, as shown inYOUR EYES COULD BE DAMAGED. The figure 2-12. The operation of the flush light issystem we discuss here is one of several different exactly the same as that of the elevated light unit.types manufactured. The operation is the same The main difference between the units is the wayno matter who manufactures them. Your in which the components are arranged.

1. Cabinet light (240 V).2. Light switch and fuse.3. Safety interlock switches.4. Flash capacitor.5. Capacitor bleeder relay.6. Fuse and switch, 240-volt power.7. Connector receptacle.

8. Monitor relay.9. Trigger relay.

10. Four-pin connector.11. Tracks.12. Flashtube socket.13. Rectifier tubes.

14. Plate caps.15. Transformer.16. Reflector.17. Glass.18. Door stop and bracket.19. Lightning arresters.

26.310Figure 2-12.—Condenser discharge light.

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Each strobe light has four inputs from the restof the system: (1) 240 volts ac, (2) ground, (3) 120volts ac timing pulses at the rate of two persecond, and (4) a dc voltage connection to themonitor system. These inputs are plugged into acable through a four-pin connector (No. 10). Theunit steps up the 240 volt ac input voltage to 1,460volts ac with a transformer (No. 15) and passesthis voltage through a full-wave rectifier circuitof vacuum tubes (No. 13). The resultant 2,000volts dc is applied to the electrodes of a flashtubeand across the flash capacitor (No. 4).

The xenon-filled flashtube will fire only whenionization is initiated by a trigger pulse of about5,000 volts applied to its third electrode. Thispulse is supplied by a trigger coil. At the same timethat the flash capacitor is storing its charge, thetrigger capacitor is also being charged by theprimary of the trigger coil, which is an auto-transformer and cuts the bleeder resistors in seriesout of the circuit. When the 120 volt ac timingsignal arrives, it is applied to the coil of thetrigger relay (No. 9), thus closing the relaycontacts, allowing the trigger capacitor todischarge through the primary of the trigger coil.This generates the necessary trigger pulse in thesecondary of the trigger coil, the flashtubefires, and the flash capacitor discharges acrossthe flashtube electrodes. The flash capacitordischarges down to the deionization potential ofthe flashtube, at which point the tube becomesa nonconductor. The light-producing arc ceases,and the charge cycle begins again.

The charge stored in the flash capacitor is apotential safety hazard. To make sure that thecapacitor is discharged when the light unit is shutoff, provide a discharge circuit by a series ofbleeder relays. The bleeder relay (No. 5) closesthis discharge circuit when the power to thetransformer is turned off.

The current that charges the flash capacitorcreates a pulse voltage in a surge resistor twiceeach second. A part of this voltage is applied toa silicon rectifier through a tap-off of the surgeresistor. The rectified voltage is then filtered andapplied to the monitor relay. The value of thisvoltage is sufficient to keep the monitor relayenergized when the unit is flashing normally.When the unit stops operating because of acomponent failure in the unit, the absence of thepulse voltage at the surge resistor will allow thecontacts of the monitor relay to close. This actioncompletes a circuit from the monitor connectionthrough a monitor resistor of 22 kilohms to

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ground. The monitor and control chassis react tothe ground by warning the operator.

Master Sequence Timer Cabinet

The master sequence timer cabinet has all ofthe controls for the strobe light system except thetower control unit. The cabinet is supplied froma 240-volt, phase-to-ground circuit. Our dis-cussion of how the system operates is keyed tothe numbers in figure 2-13.

LOCAL/REMOTE CONTROL UNIT.—Thelocal/remote control unit (No. 1) gives you a wayto turn the system on locally or give control tothe tower. In the center of this unit is a controlknob with three positions: REMOTE/OFF/LOCAL-ON. There are two red indicator lightsabove the control knob and two green lights belowit. When the control knob is in the LOCAL-ONposition, the system is turned on, and red lightswill glow to indicate that the system is onLOCAL CONTROL. The green monitor lightsshould burn unless there is a fault in the system;in which case, they will go out. When the controlknob is placed in the REMOTE position, thesystem can be turned on and off at the towercontrol unit. The red indicator lights will go out,but the monitor lights will continue to work asbefore. You should remember that the tower hasno control except when the switch is in REMOTE.

MONITOR AND CONTROL CHASSIS.—The monitor and control chassis has severalfunctions. They are as follows:

1. It de-energizes the monitor lights in bothcontrol units when a set number of lights stopworking.

2. It has a step-down transformer to supplythe voltages needed for control and indication.

3. It has a diode rectifier that supplies directcurrent for relay operation.

4. It has the fuses that protect the mastersequence timer, the indicator circuits, and othercomponents.

The main power transformer in the monitorand control chassis is energized all the time froma local 240 volt ac supply. The secondary voltagefrom this transformer energizes the indicator lamptransformer and the transformer of the dc circuit.The indicator lamp transformer supplies 12 voltsac to the indicator lights in the local/remotecontrol unit. The transformer for the dc power

.

1. Local/remote control. 6. DC power supply.2. Elapsed time meter. 7. DC regulator tube.3. Main relay and switch. 8. Fuses.4. Sensitivity rheostat. 9. 12-volt transformer.5. Sensitivity selector switch. 10. Terminal blocks.

11. Lightning.12. Timer motor.13. Timer switches.14. Cabinet light (240 volts).15. Fuse and light switch.

Figure 2-13.—Master sequence timer and controls.26.311

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will supply 95 volts ac to a bridge rectifier whichsupplies 120 volts dc to the dc monitor circuit.

As long as the master control switch is on,power is fed to the tower control unit no matterwhat position the local/remote control unit switchis in. When the flasher control switch in the vaultcontrol unit is closed, the dc power interlock relaycloses and energizes the monitor lights in the towercontrol unit. The unit responds in the same wayas if the system were in full operation and workingwell. For this reason, the tower personnel mustbe notified when the switch in the local/remotecontrol unit is in the OFF position. When theflasher control switch on the local/remote controlunit is in the OFF or LOCAL-ON position, thered indicator lights tell you that the tower controlunit is not in full operation.

There is a monitor-sensing relay to monitorthe operation of the strobe lights. When all thelight units are working correctly, there will notbe enough current through the coil of the monitor-sensing relay to actuate the relay. A variableadjustable resistor can be adjusted so that therewill be 7,333 ohms of resistance between themonitor-sensing relay and ground. A resistanceof 7,333 ohms equals three 22-kilohm resistors inparallel. The monitoring circuit in each light unithas a 22-kilohm resistor. So, if you take the three22-kilohm resistors out of the monitor controlunit, the monitor-sensing relay actuates when atleast three light units have ceased to work andtheir monitoring circuits are grounded, asdescribed earlier.

The sensitivity selector switch lets you reducethe number of malfunctioning lights needed toactuate the monitor-sensing relay by increasingthe current flowing through its coil. There arethree 22-kilohm resistors in the monitor controlunit. Each of these three resistors simulates theeffect of a grounded monitor connection to oneof the lights.

If the monitor-sensing relay is tripped, themonitor lights on the local/remote control unitwill go out. At the same time, the monitor lightsin the tower control unit go out and a buzzersounds.

The adjustment for the sensitivity of themonitor system is made at the monitor and controlchassis in the master sequence timer cabinet.

With all of the strobe lights operating and thesensitivity selector switch in the No. 1 UNITposition, the green monitor lamps should be on.If you turn the strobe light units on and themonitor lights do not come on, you need to adjustthe sensitivity of the variable resistor (sensitivity

rheostat). You need a small screwdriver to fit theslot in the rheostat shaft (No. 4). Turn the shaftclockwise as far as it will go (about half a turn).The green lamps should now be lit. Now, turn therheostat counterclockwise slowly until the greenlamps go out. Then turn the rheostat backclockwise slowly and stop as soon as the greenlamps light. Check this setting by slipping a pieceof paper between the contacts of one of the timerswitches. The monitor lamps should go out.Remove the paper and turn the control switch toOFF for a few seconds and then to ON. The greenlamps should now stay lit. Repeat this fordifferent lamps and shift the rheostat slightly ifyou need to until you find a setting which willoperate for any of the approach lights.

Change the sensitivity selector switch to theNo. 2 UNIT position and repeat the procedurewhile blocking two of the switches with pieces ofpaper. This is like having two strobe light unitsout and should have the same results as before.Restore the monitor lights the same as before.Repeat the procedure with the sensitivity switchin the No. 3 UNIT position while you block threeof the timer switches. Now, check the operationof the monitor circuit with number 1, 2, and 3strobe lights out.

When you find the correct setting of therheostat, no further adjustments should beneeded. When your base requires the selectorswitch to be on the No. 1 UNIT position, then,in proper operation, if one strobe light fails, thealarm is stilled by just moving the selector switchto the No. 2 UNIT position. The switch is left inthis position until the bad strobe light is fixed.At that time, the selector is returned to the No.1 UNIT position.

MASTER SEQUENCE TIMER.—Themaster sequence timer controls the order and rateof the triggering impulses to the light units. Thetimer has two camshafts driven by a motor(No. 12) through a reduction gear. The camsactuate 30 contacts (No. 13), one for each lightunit, staggered on the shafts so that the contactsare closed in rapid succession as the shafts turn.Note that although there are 30 contacts, only28 are used. Each of the 28 contacts is electricallyconnected to one of the light units. Thus,when the motor is energized, the contacts aremomentarily closed in a predetermined sequencetwice each second. This provides a series of120-volt ac pulses to the trigger relays in the lights.These pulses are known as the timing circuit.Power for the 120-volt motor and the 120-volt

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timing pulses comes from the monitor and controlchassis. An elapsed time meter (No. 2) is mountednext to the timer to show the total time theequipment has been in use; thus it serves as a guidefor maintenance. Forty-five lightning arresters(No. 11) are installed in the lower part of thecabinet to protect the equipment from voltagesurges on any of the lines.

Tower Control Unit

The control switch on the tower control unitworks only when the local/remote control unit inthe timer cabinet is in the REMOTE position. Theaudible and visible monitoring alarms, however,are operable whenever the system is in use, evenif the local/remote unit is at the LOCAL-ONposition. Adjustments are provided on the panelfor regulating the brightness of the two greenmonitor lights and the loudness of the buzzer.A push-button switch is used to test the operationof the buzzer.

MAINTENANCE OF AIRFIELDLIGHTING SYSTEMS

Regardless of the design of an airfieldsystem, maintenance is highly recommended toensure the operational dependency of the field.Routine scheduled downtime is much better thanunscheduled downtime in the midst of an opera-tion. Simple visual inspection plus periodicresistance readings of circuit devices, components,and cables reveal probable trouble areas.

Do not get caught in the “jury-rigged trap.”This tendency to patch, bypass, piece together,or otherwise rig a system to work “just for alittle while” can be as dangerous as a coiledrattlesnake. That “temporary fix” is just sittingthere waiting to catch some uninformed individualsent out to work on the system. This section coversroutine maintenance for airfield lighting andunderground systems, troubleshooting cablesystems, and cable splicing and repair.

ROUTINE MAINTENANCE

Routine maintenance includes, but is notlimited to, cleaning, adjusting, lubricating, paint-ing, and treating for corrosion. Components andconnections must be checked for condition andsecurity. The insulation of the conductors shouldbe checked for good condition and burns, scrapes,breaks, cracks, or evidence of overheating.

Visual Inspection

During your visual inspection of an airfieldlighting wiring system, you should check theconstant-current regulator (CCR) for chipped orcracked porcelain bushings, correct connections,proper fuses and switches, and relays for freedomof movement. Only relay panel covers should beremoved. It is not necessary to open the mainregulator tank. All covers that are removed shouldbe cleaned and then reinstalled tightly. Cable andIT connectors require close visual inspections forcuts, bruises, or other mishandling; theseconditions could cause premature failure to thesystem. The mating surfaces of these molded-rubber connectors must be clean and dry whenthey are plugged together. Either dirt or moistureprevents the mating surfaces from makingcomplete surface contact and causes a failure atthe connector. When connectors are pluggedtogether, trapped air can cause them to partiallydisengage. Wait a few seconds and push themtogether again. Apply two or three turns of tapeto hold them in place. When the connectors areclean, dry, and properly taped, the connection isequal or superior to a high-voltage splice.

Check light fixture connections andcounterpoise connections for tightness. Look forcable bends that are too sharp; sharp bends cancause insulation breakdown or connector failure.

Operational Check

Once all components of the system have beenvisually inspected for damage and the cable systemhas been checked with a megger and hi-pot, makean operational check of the entire airfield lightingsystem.

1. Working from the control tower with anobserver in the vault, operate each switch of theairport and taxiway panel, so that each positionis reached at least twice. You must have radio ortelephone communication with the observer in thevault during this operation. The observer in thevault determines that each switch properlycontrols its corresponding circuit.

2. Repeat this operation from the vault(alternate control panel) in the same manner,assuring that each switch position is reachedtwice.

3. Now, repeat the test by using the localcontrol switches on the regulator.

4. Operate each lighting circuit at maximumbrightness for 6 continuous hours. Make a visual

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inspection of all lights, both at the beginning andat the end of this test to assure that the propernumber of lights are operating at full brightness.Measure lamp terminal voltage on at least onelamp in each multiple circuit to assure that thisvoltage is within ±5 of the rated lamp voltage.Dimming of some or all of the lights in a circuitindicates grounded cables.

Condenser Discharge Light System

Periodic maintenance of this system is fairlysimple. Remember, however, that high voltagesexist in the components of the system and youmust be extra careful. One such area is the flashcapacitor. This capacitor may contain as muchas 2,000 volts. Anyone working on the lightfixture should make sure that this capacitor isdischarged before working on the light unit. Thecapacitor should bleed down through its resistornetwork in 5 seconds; however, the capacitorshould be shorted out before any work being doneinside the unit. In a flush unit, short betweenterminals 7 and 10 of the terminal board with ashorting stick. In the elevated light, short the twocontacts on the left side of the flashtube socket.This must be done before any work is done insidethe light unit, such as changing a flashtube orcleaning the reflector.

Since these are sealed units, cleaning thereflectors should rarely be required. When suchcleaning is required, be sure to use a nonabrasivecleaner. The lenses in both the elevated and flushunits should be cleaned periodically, dependingon the local conditions.

Inspect the timer contacts to see that they areclean and making good contact. If not, thestationary timer contacts can be adjusted. Thetimer gears of the master sequence timer requireperiodic lubrication. Match the grease to theambient temperatures expected in your particulararea. NEVER use a graphite-based grease, asgraphite is electrically conductive.

Check to see that both pairs of green indicatorlights will light. When only one lamp is lit oneither unit, the other bulb has burned out. Toreplace one of these bulbs, remove the front panel,pull off the colored lens, push out the old bulb,and insert the new bulb from the front of thepanel. Replace the lens and panel.

Underground Distribution Systems

Normally speaking, underground systems thatare properly installed require little maintenance

of the routine type. Since both the equipment andthe cable are well protected from man and theelements, the system normally is not subjectto the same problems that overhead systemsexperience.

In some areas, groundwater or dampness maycreate some problems for underground systemsby increasing rust or corrosion. Racks and spliceboxes may require more painting and other rustor corrosion maintenance. Look especially forrusted nuts on boxes and rack hangers. Theyshould be cleaned and painted. The manholes andvaults should be cleaned. These areas should notbe used for storage nor should trash be allowedto collect in them.

Check the manhole walls for evidence ofcracks, breaks, or other evidence of water seepageor leakage. Check empty ducts for plugs andevidence of water seepage.

You will find manholes with enough water inthem to hamper or prohibit work operations. Insuch cases, bail the water out with a bucket andrope or pump it out with a manhole pump.Sometimes sump holes are built into the floor ofmanholes, and these provide places to bail fromor to pump from the lowest places in the manhole.When water runs into a manhole from unoccupiedducts, hard rubber plugs are provided to stop orslow the water. When the manhole pump is used,place it in a position so the flow of water will beaway from the manhole. This would be on thedownhill side. Place the pump at least 10 feet fromthe manhole opening. The pump has a hose tobe inserted in the manhole and an outlet hose tocarry the water away from the manhole. Checkcables for proper racking, making sure that theyare trained in the proper direction and positionedso an ample cable radius is left for bends andexpansion/contraction. This radius is basically 5to 12 times the cable diameter, depending on thesheath type and the number of conductors. Makesure that 6 inches of straight cable exists forracking on each side of the splice. Check splicesfor evidence of leakage or tracking. Look forscrapes, burns, cracks, corrosion, or any otherevidence of cable insulation deterioration. See thatall cables are properly tagged for identification.

Check potheads and terminations that areattached to risers for leakage, tracking, andevidence of overheating or an overvoltage. Alsocheck the security of the mounting of the potheadand conduit.

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TROUBLESHOOTING CIRCUITS

Troubleshooting of cable systems is much thesame as any other type of electrical trouble-shooting. You need a thorough knowledge of thesystem as well as the ability to analyze troubles.A review of the history of the system providesclues to present or future troubles. Simply usingyour eyes and head is sometimes the most effectivemethod of locating the trouble. A knowledge oftest equipment, an ability to read drawings orschematics, and an understanding of electricityare the key factors in locating electrical troubles.

Types of Trouble

The same basic types of trouble can occur inthe airfield lighting cable system whether thatsystem is in series or in multiple; however, theresults of these circuit troubles can cause dramaticdifferences. For instance, a short circuit acrossthe terminals of a distribution transformersupplying a multiple system is a dangerousoverload; while the same short circuit across theoutput terminals of a CCR and series transformeris a no-load condition. An open in the outputcircuit of a CCR, on the other hand, creates adangerous overload. Burned-out lamps in thesecondary of a series IT will not damage thetransformer, but the secondary voltage will riseabove normal and distort the wave shape of theprimary current. When enough lamps burn out,the primary current may rise high enough toshorten lamp life and possibly damage theregulator. These critical factors should tell youwhy you need to know the circuit.

In the discussion above, all types of electricaltrouble were mentioned. They are opens, shorts,grounds, and improper power.

OPENS.—An open circuit is an incompletecircuit. Somewhere the circuit has a break;therefore, there is not a complete path for currentflow throughout the circuit. Because there is nocurrent flow, the circuit cannot operate. Inanalyzing circuit trouble, if the lights are notburning, the motor is not running, and so forth,you know that you will be looking for a breakin the circuit. Usually this break will be at theunit(s) of resistance (burned-out lamp, brokenresistor, motor burned out), but sometimes thebreak will happen in the cable. When the cablebreaks, this break is most likely to happen at asplice or connection. Other cable breaks may becaused by digging operations being done in the

wrong place. This occurs when base mapsare not kept up and when unauthorized diggingoperations take place. It is an excellent reason forinstalling and maintaining direct burial cablemarkers.

Improper installation of cables can cause themto fail. Cables may be damaged by kinking,bruised by rocks, crushed by wheels, or cut byshovels when proper care is not exercised duringhandling and installation. While the damage maynot be great enough at the time it occurs to takethe cable out of service, it may be the startingpoint for a cable failure at a later date. This failuremay be either in the form of a broken cable(open), cross type of short (two cables touching),or a short to ground (cable in contact with earthground). Any of these troubles can render thecircuit inoperative. The indication of the type oftrouble that you have in the circuit and the pointin the circuit where this indication appearsshould assist you in locating and repairing thecircuit.

With an open circuit, that portion of thelighting system being supplied by the affectedcable will not operate. A string of lamps that donot light, then, would indicate an open cable.

SHORTS.—If lamps are lit when they are notsupposed to be or if a circuit is affected by anothercircuit, you most likely have a cross type of shortbetween the two circuits. The logical point to startlooking for this trouble is where the two cablescross or where they are close to each other.

GROUNDS.—When a string of lights burnsdim or when fuses blow on a circuit, you havea short to ground. The insulation on the supplycable is damaged. This defect lets current passdirectly from the conductor to the earth andprevents the lamps from receiving enough powerto operate correctly; that is, some of the resistanceof the circuit is being bypassed. The amount ofresistance being bypassed in the circuit governsthe effect of the short to ground. If enoughresistance is removed (bypassed), then the currentrises to a point that is sufficient to blow the fusesand thus disconnect the circuit.

IMPROPER POWER.—Improper power canresult when regulators or distribution trans-formers are not connected properly. If the incor-rect input voltage is connected or if the regulatorhas been purposely connected for an unusual loadrequirement, improper power can be applied tothe system and serious damage may result.

2-23

Underground Lighting Problems

As stated earlier in this chapter, the care andcraftsmanship of the original installation will, toa large extent, determine the life of the system.Still, no system lasts forever. Even the bestinstallation and the most conscientious inspectionand maintenance program cannot prevent theaging and gradual breakdown of a system. Inalmost all cases when an underground cablebreaks down, it goes to ground. Where more thanone conductor is enclosed in one sheath, theinsulation within the sheath may deteriorate sothat a cross type of short occurs. This contactalmost always creates enough heat and pressureto rupture the sheath and put the conductors incontact with ground.

Moisture is one of the most common causesof an underground system breakdown. Impuritiesin the water helps set up corrosion cells, breaksdown neoprene, and rots rubber. Only a trace ofmoisture, when superheated by the electricalpower of the circuit and converted to steam, cancause an explosion that will rip the cable to shreds.Groundwater contains enough minerals to providean excellent conductor to all other parts of thesystem. Some underground cables are bondedtogether. The usual way to find out that an

underground power cable has a problem is tocheck when the circuit opens.

In ducted systems, the maximum runs betweenmanholes are 600 feet. The normal method ofrepair is to replace the cable. In direct burial cablesystems, the cable runs may be quite long, andit would be impractical to replace the entire run.In this case, cable fault locators are used to locatethe fault. Before starting to work, make sure thatall power is off on the circuits in the trench;this must be done before you start digging orrepairing the cable.

This chapter will not discuss circuit trouble-shooting in more detail, because each system isdifferent. When you are in charge of installationor maintenance of an airfield, reference material,such as the components’ manuals, should beacquired. If unattainable, NAVFAC P-272,Definitive Designs for Naval Shore Facilities;DM 23.1, Navigational and Traffic Aids;NAVAIR 51-50AAA-2, Visual Landing AidsDesign Standards; and NAVAIR 51-40ABA-7,Lighting and Marking Systems for Expedi-tionary Airfields are recommended as references.Problems, such as improper power connections,component connections, safety grounding, cablesplices, cable terminations, and cable installations,are discussed in detail in these publications.

2-24

CHAPTER 3

ELECTRICAL LOAD REQUIREMENTS

As a Construction Electrician first class, youmay be required to provide electrical service tovarious types of facilities. The material presentedin this chapter is based on the 1990 NationalElectrical Code® (NEC®)1 and addresses require-ments in the installation of an industrial feedersystem for dwelling units and industrial areas, thefunction and the correct steps for operation andinstallation of ground fault interrupter circuitbreakers, and restrictions placed on electricalsystems installed in hazardous locations. Uponcompletion of this chapter, you will be able to (1)compute electrical load requirements and (2)provide safe electrical service to the load.

SINGLE-FAMILY DWELLING

Performing the calculations to provide elec-trical power to a dwelling can be divided into twophases. Phase I is determining the number andsize of branch circuits required to serve the load.Phase II is calculating the size of the service-entrance conductor and the size of the neutralconductor.

TYPES OF DWELLING UNIT LOAD

The total load of a dwelling unit can be dividedinto three categories: general lighting load, smallappliance and laundry load, and special applianceload.

General Lighting Load

The NEC® states that receptacle outlets ratedat 20 amps or less may be used for generallighting. These receptacles may be included in thecalculations for general lighting load.

1 National Electrical Code® and NEC® are registered trade-marks of the National Fire Protection Association, Inc.,Quincy, MA 02269.

The easiest method to determine the generallighting load is to multiply the square footage ofa dwelling by the volt-amperes (VA) per squarefoot listed in table 3-1 (NEC®, table 220-3(b)).Do not include garages, carports, patios, or openporches in the square footage calculations.Multiply the outside length times the outside widthtimes the number of floors to determine the totalarea. Multiply this number times 3 VA todetermine the general lighting load. Use thefollowing formulas to find the general lightingload:

Total area = outside length × outside width× number of floors

General lighting load = total area × VA

Small Appliance and Laundry Load

In addition to the number of branch circuitsdetermined by the general lighting loadcalculations, at least two 20-amp, 1,500-VA smallappliance circuits must be installed in the kitchen,pantry, breakfast room, and dining room only.The load on these circuits must be distributedequally across the phases to minimize unbalancedload on the neutral.

At least one additional 20-amp, 1,500-VAbranch circuit must be provided to supply thelaundry load. Do not install any other receptacleoutlets on this branch circuit.

The 1,500-VA rating of each branch circuit isapplied to the calculations for the service-entranceconductor size. The 20-amp branch circuit ratingis used to supply the small appliance and laundryloads.

The small appliance and laundry loads maybe totaled and added to the general lighting loadprovided they meet the demand factors discussedlater in this chapter.

3-1

Table 3-1.—General Lighting Loads by Occupancies

Type of OccupancyUnit Load per

Sq. Ft. (Volt-Amperes)

Armories and Auditoriums 1

Banks 3 1/2**

Barber Shops and Beauty Parlors 3

Churches 1

Clubs 2

Court Rooms 2

*Dwelling Units 3

Garages—Commercial (storage) 1/2

Hospitals 2

*Hotels and Motels, including apartment houses without provisionsfor cooking by tenants 2

Industrial Commercial (Loft) Buildings 2

Lodge Rooms 1 1/2

Office Buildings 3 1/2**

Restaurants 2

Schools 3

Stores 3

Warehouses (storage) 1/4

In any of the above occupancies except one-family dwellings andindividual dwelling units of two-family and multifamily dwellings:

Assembly Halls and AuditoriumsHalls, Corridors, Closets, StairwaysStorage Spaces

1l/2l / 4

For SI units: one square foot = 0.093 square meter.*All general use receptacle outlets of 20-ampere or less rating in one-family, two-family and

multifamily dwellings and in guest rooms of hotels and motels [except those connected to the receptaclecircuits specified in Sections 220-4(b) and (c)] shall be considered as outlets for general illumination,and no additional load calculations shall be required for such outlets.

**In addition a unit load of 1 volt-ampere per square foot shall be included for general purposereceptacle outlets when the actual number of general purpose receptacle outlets is unknown.

Reprinted with permission from NPFA 70-1990, the National Electrical Code®, Copyright©1989, National Fire Protection Association, Quincy, MA02269. This reprinted material is not the complete and official position of the National Fire Protection Association, on the referenced subject which is

represented only by the standard in its entirety.

26.X

3-2

Special Appliance Load

Any additional electrical appliances, such asranges, hot-water heaters, air conditioners, dryers,dishwashers, and garbage disposals, must besupplied by individual branch circuits. Do notconnect these appliances to the general lightingcircuits. If the appliances were connected to thegeneral lighting circuits, a fault in the appliance(s)could de-energize the lighting, creating a serioussafety hazard.

DEMAND FACTORS

All the loads in a dwelling are not used atthe same time, especially for any extended

period of time. The NEC® allows you toapply demand factors to appliances and generallighting loads to compensate for this fact. As aresult of these reduced-demand loads, service-entrance conductors can be sized smaller, allowingthe use of smaller branch circuit conductors andcircuit breakers. This results in lower materialcosts.

General Lighting andReceptacle Loads

A demand factor may be applied to generallighting and receptacle loads following table 3-2(NEC®, table 220-11). The following example

Table 3-2.—Lighting Load Feeder Demand Factors

Portion of Lighting Load DemandType of to Which Demand Factor

Occupancy Factor Applies (volt-amperes) Percent

Dwelling Units First 3000 or less at . . . . . . . . . . . . . . . . . . . 100From 3001 to 120,000 at . . . . . . . . . . . . . . . 35Remainder over 120,000 at . . . . . . . . . . . . . 25

*Hospitals First 50,000 or less at. . . . . . . . . . . . . . . . . . 40Remainder over 50,000 at . . . . . . . . . . . . . . 20

*Hotels and Motels — Including First 20,000 or less at. . . . . . . . . . . . . . . . . . 50Apartment Houses without Provision From 20,001 to 100,000 at . . . . . . . . . . . . . 40for Cooking by Tenants Remainder over 100,000 at . . . . . . . . . . . . . 30

Warehouses First 12,500 or less at. . . . . . . . . . . . . . . . . . 100(Storage) Remainder over 12,500 at . . . . . . . . . . . . . . 50

All Others Total Volt-amperes . . . . . . . . . . . . . . . . . . . . 100

*The demand factors of this table shall not apply to the computed load of feeders to areas inhospitals, hotels, and motels where the entire lighting is likely to be used at one time, as in operatingrooms, ballrooms, or dining rooms.

Reprinted with permission from NPFA 70-1990, the National Electrical Code®, Copyright©1989, National Fire Protection Association, Quincy, MA02269. This reprinted material is not the complete and official position of the National Fire Protection Association, on the referenced subject which is

represented only by the standard in its entirety.

26.X

3-3

shows how the general lighting and receptacle Table 3-3.—Demand Factors for Household Electric Clothesdemand loads can be determined. Dryers

Given:

2,000-sq-ft dwelling with 120-/240-V,single-phase service

Two appliance circuits and one laundrycircuit

Number of Demand FactorDryers Percent

Solution:

2,000 sq ft × 3 VA = 6,000 VA

1,500 VA × 2 circuits = 3,000 VA

1,500 VA × 1 circuit = 1,500 VA

10,500 VA

1 . . . . . . . . . . . . . . . . . . . . . . . . 1002 . . . . . . . . . . . . . . . . . . . . . . . . 1003 . . . . . . . . . . . . . . . . . . . . . . . . 1004 . . . . . . . . . . . . . . . . . . . . . . . . 1005 . . . . . . . . . . . . . . . . . . . . . . . . 806 . . . . . . . . . . . . . . . . . . . . . . . . 707 . . . . . . . . . . . . . . . . . . . . . . . . 658 . . . . . . . . . . . . . . . . . . . . . . . . 609 . . . . . . . . . . . . . . . . . . . . . . . . 55

10 . . . . . . . . . . . . . . . . . . . . . . .11-13

50. . . . . . . . . . . . . . . . . . . . . 45

14-19 . . . . . . . . . . . . . . . . . . . . . 4020-24 . . . . . . . . . . . . . . . . . . . . . 3525-29 . . . . . . . . . . . . . . . . . . . . . 32.530-34 . . . . . . . . . . . . . . . . . . . . . 3035-39 . . . . . . . . . . . . . . . . . . . . . 27.540 & over . . . . . . . . . . . . . . . . . . 25

First 3,000 VA of total connected load

3,000 VA × 100 percent = 3,000 VA

Remaining total connected load

7,500 VA × 35 percent = 2,625 VA

5,625 VA

Reprinted with permission from NPFA 70-1990, the National ElectricalCode®, Copyright©1989, National Fire Protection Association,Quincy, MA 02269. This reprinted material is not the complete andofficial position of the National Fire Protection Association, on thereferenced subject which is represented only by the standard in

its entirety.This demand factor can be applied only when youare performing the calculations for the service-entrance conductor size.

26.X

Fixed Appliance Loads

A 75-percent demand factor may be appliedif there are four or more fixed appliances on abranch circuit. The wattage or VA rating takenfrom the appliance nameplate must be used whenthis calculation is made. The nameplate full-loadrating must be used if three or fewer appliancesare connected to a branch circuit.

whichever is larger. All dryers rated less than 5kilowatts must be figured at 5 kilowatts. It is rarethat a dwelling will have more than four clothesdryers, so a loo-percent demand factor is used inmost cases.

Electric Range Load

NOTE: This demand factor does not applyto ranges, clothes dryers, air conditioners, orspace-heating units. The demand loads for theseappliances are calculated individually.

Electric Clothes Dryer Load

Table 3-3 (NEC@, table 220-18) shows thedemand factors that may be applied to electricclothes dryers. For the wattage of the dryer, usethe rating given on the nameplate or 5,000 watts,

3-4

The demand load for electric ranges, wall-mounted ovens, and counter-mounted cookingunits is defined in table 3-4 (NEC®, table 220-19).You must know the nameplate rating (in kilo-watts) before you can determine the demandfactor. Use column A of table 3-4 for applianceratings of 9 to 12 kilowatts. The demand factorhas already been calculated for you and isexpressed in kilowatts, depending on the numberof appliances on a branch circuit. Column B isused for appliances rated less than 3 1/2 kilowatts,and column C is for appliances rated 3 1/2kilowatts to 8 3/4 kilowatts. Both columns are

Table 3-4.—Demand Loads for Household Electric Ranges, Wall-Mounted Ovens, Counter-Mounted Cooking Units, andOther Household Cooking Appliances Over 1 3/4 kW Rating

(Column A to be used in all cases except as otherwise permitted in Note 3 below.)

NUMBER OFAPPLIANCES

Maximum Demand FactorsDemand Percent

(See Notes) (See Note 3)

COLUMN A COLUMN B COLUMN C(Not over 12 (Less than 3 l/2 (3 l/2 kW to 8 3/4kW Rating) kW Rating) kW Rating)

1 8 kW 80% 80%2 11 kW 75% 65%3 14 kW 70% 55%4 17 kW 66% 50%5 20 kW 62% 45%6 21 kW 59% 43%7 22 kW 56% 40%8 23 kW 53% 36%9 24 kW 51% 35%

10 25 kW 49% 34%11 26 kW 47% 32%12 27 kW 45% 32%13 28 kW 43% 32%14 29 kW 41% 32%15 30 kW 40% 32%16 31 kW 39% 28%17 32 kW 38% 28%18 33 kW 37% 28%19 34 kW 36% 28%20 35 kW 35% 28%21 36 kW 34% 26%22 37 kW 33% 26%23 38 kW 32% 26%24 39 kW 31% 26%25 40 kW 30% 26%

26-30 15 kW plus 1 kW 30% 24%31-40 for each range 30% 22%41-50 25 kW plus 3/4 30% 20%51-60 kW for each 30% 18%61 & over range 30% 16%

Note 1. Over 12 kW through 27 kW ranges all of same rating. For ranges individually rated more than 12 kW but notmore than 27 kW, the maximum demand in Column A shall be increased 5 percent for each additional kW of rating ormajor fraction thereof by which the rating of individual ranges exceeds 12 kW.

Note 2. Over 8 3/4 kW through 27 kW ranges of unequal ratings. For ranges individually rated more than 8 3/4 kWand of different ratings but none exceeding 27 kW, an average value of rating shall be computed by adding together theratings of all ranges to obtain the total connected load (using 12 kW for any range rated less than 12 kW) and dividing’ bythe total number of ranges; and then the maximum demand in Column A shall be increased 5 percent for each kW or majorfraction thereof by which this average value exceeds 12 kW.

Note 3. Over 1 3/4 kW through 8 3/4 kW. In lieu of the method provided in Column A, it shall be permissible to addthe nameplate ratings of all ranges rated more than 1 3/4 kW but not more than 8 3/4 kW and multiply the sum by thedemand factors specified in Column B or C for the given number of appliances.

Note 4. Branch-Circuit Load. It shall be permissible to compute the branch-circuit load for one range in accordance withTable 220-19 in the National Electrical Code®. The branch-circuit load for one wall-mounted oven or one counter-mountedcooking unit shall be the nameplate rating of the appliance. The branch-circuit load for a counter-mounted cooking unitand not more than two wall-mounted ovens, all supplied from a single branch circuit and located in the same room, shallbe computed by adding the nameplate rating of the individual appliances and treating this total as equivalent to one range.

Note 5. This table also applies to household cooking appliances rated over 1 3/4 kW and used in instructional programs.Reprinted with permission from NPFA 70-1990, the National Electrical Code ®, Copyright©1989, National Fire Protection Association, Quincy, MA02269. This reprinted material is not the complete and official position of the National Fire Protection Association, on the referenced subject which is

represented only by the standard in its entirety.

26.X

3-5

expressed as a percentage of nameplate rating,depending on the number of appliances on abranch circuit.

Heating and Air-Conditioning Loads

Where it is unlikely that two loads will be inuse at the same time, the NEC® allows the smallerof the two loads to be omitted. Since the electricheating load is usually larger than the air-conditioning load, the air-conditioning load isdropped when the service-entrance conductor sizeis figured.

In determining branch circuit conductor sizefor heating equipment, use 125-percent demandfactor. Also, figure the fan motor load, ifapplicable, at 125-percent nameplate rating.

Water Heater Load

In determining the size of the service-entranceconductor, apply the nameplate full-load currentrating (100 percent) of all fixed-storage type ofwater heaters rated for 120 gallons or less.

The branch circuit conductors supplying waterheaters are required to be large enough to carry125 percent of the nameplate full-load rating. Solution:

Motor Loads

Motors are classified as continuous duty, andthe branch circuit conductors supplying motorshave to be sized to carry 125 percent of thefull-load current rating. Conductors that arefeeding a group of motors have to be large enoughto carry 125 percent of all rated current of thelargest motor plus the sum of the full-load runningcurrent of the remaining motors.

Branch circuit conductors supplying a com-bination of motor loads and lighting or applianceloads have to have an ampacity of 125 percentof the largest motor plus the sum of the otherloads.

DETERMINATION OF NUMBER ANDSIZE OF BRANCH CIRCUITS

Determining the number of branch circuitsrequired to serve a dwelling unit is a relatively easyprocess after you identify the number and typeof appliances that will be installed. You candetermine the general lighting and receptacle loadby multiplying the area of the dwelling by 3 VA.The size of the branch circuits supplying theremaining loads is based on the nameplate rating

of the device and is computed by using theapplicable demand factors. Solving this sampleproblem will assist you in determining the size andnumber of branch circuits for a dwelling unit.

Given:

1,600-sq-ft dwelling with 120-/240-V,single-phase service

Two small appliance circuits and onelaundry circuit

Special appliance circuits

One 12-kVA range

One 1.2-kVA dishwasher

One 0.8-kVA compactor

One 6.0-kVA water heater

One 10-kVA central heater

General lighting and receptacle load

1,600 sq ft × 3 VA = 4,800 VA

120 V × 15 amps (circuit breaker capacity)= 1,800 VA

The number of 15-amp circuits is deter-mined as follows:

4,800 VA1,800 VA = three 15-amp circuits

Small appliance and laundry circuits

Three 20-amp circuits are required.

12-kVA range

The demand factor (table 3-4) for a12-kVA range is 8kVA.

8,000 VA240 V = 33.33 amps

One 35-amp circuit is required.

3-6

1.2-kVA dishwasher

1,200 VA120 v = 10 amps

One 15-amp circuit is required.

0.8-kVA compactor

800 VA120 v = 6.6 amps

One 15-amp circuit is required.

6.0-kVA water heater

The demand factor for a water heater is125 percent.

6,000 VA × 125 percent240 V = 31 amps

One 35-amp circuit is required.

10-kVA central heater

The demand factor for space heating is 125percent.

10,000 VA × 125 percent240 V = 52 amps

One 60-amp circuit is required.

The total number and size of branch circuitsrequired to serve the sample dwelling are asfollows:

Five 15-amp circuits

Three 20-amp circuits

Two 35-amp circuits

One 60-amp circuit

SIZING OF SERVICE-ENTRANCECONDUCTORS

The most important point to remember whenyou are determining the size of service-entranceconductors is to ensure they are large enough tocarry the load. A conductor that is too small maybecome overheated and create a fire hazard. Onthe other hand, sizing the conductors far too

large to supply the load can be expensive andunnecessary.

The NEC® (Section 230-42(b)) has establishedthe minimum size for service-entrance conductorsas the following:

1. 100-ampere for a three-wire service to asingle-family dwelling with six or more two-wirebranch circuits.

2. 100-ampere for a three-wire service to asingle-family dwelling when the total load hasbeen determined to be 10 kVA or more.

3. 60-ampere service for other loads.

Determine the size of the service-entranceconductors in the following example.

Given:

1,600-sq-ft dwelling with 120-/240-V,single-phase service

Two small appliance loads and onelaundry load

Special appliance loads

12-kVA range

6.0-kVA dryer

15-kVA central heater

9.0-kVA air conditioner

4.8-kVA water heater

1.2-kVA dishwasher

0.8-kVA disposal

1.6-kVA attic fan

0.4-kVA vent fan

Solution:

General lighting and receptacle loads

1,600 sq ft × 3 VA = 4,800 VA

Small appliance loads

1,500 VA × 3 circuits = 4,500 VA

Total = 9,300 VA

3-7

The demand factor (table 3-2) for general lightingand small appliance loads is as follows:

First 3,000 VA × 100 percent = 3,000 VA

Remaining 6,300 VA × 35 percent = 2,205 VA

Total demand load = 5,205 VA

12-kVA range

The demand factor (table 3-4) for a12-kVA range is 8 kVA.

Total demand load = 8,000 VA

6.0-kVA dryer

The demand factor (table 3-3) for one6-kVA dryer is 100 percent.

Total demand load = 6,000 VA

Heating and air conditioning

The smallest load (air conditioning) can bedisregarded. The demand factor forheating load is 100 percent.

Total demand load = 15,000 VA

• Fixed appliances

The demand factor for four or more fixedappliances is 75 percent.

Water heater = 4,800 VA

Dishwasher = 1,200 VA

Disposal = 800 VA

Attic fan = 1,600 VA

Vent fan = 400 VA

Total = 8,800 VA

8,800 VA × 75 percent of demand factor= total demand load of 6,600 VA

Largest motor load

The demand factor for largest motor loadis an additional 25 percent.

1,600 VA × 25 percent = total demandload of 400 VA

3-8

Total connected load for phases A and B

General lighting 5,205 VA

Range 8,000 VA

Dryer

Heating

Fixed appliances

Motor

6,000 VA

15,000 VA

6,600 VA

400 VA

Total = 41,205 VA

41,205 VA240 V = 171.7 amps

Refer to table 3-5 (NEC® table 310-16), column2, to determine the size of the entrance conductor.Two 2/0 THW copper conductors are required.

SIZING OF NEUTRAL CONDUCTORS

The neutral conductor is required to be largeenough to carry the maximum unbalanced loadbetween the neutral conductor and any phaseconductor. For example, if phase A on a 240-volt,single-phase service carried a 75-amp, 120-voltload and phase B carried a 50-amp, 120-volt load,the neutral would have to carry the difference,or 25 amps. However, the largest load betweenany phase and neutral is 75 amps, so the neutralconductor must be rated to that ampacity.

Since the neutral conductor has to carry onlyphase-to-neutral loads (120 volts), all single-phaseor three-phase, 208-volt or 240-volt loads can beomitted. There is one exception to this rule,however. For a feeder supplying householdelectric ranges, wall-mounted ovens, counter-mounted cooking units, and electric dryers, themaximum unbalanced load must be computed at70 percent of the demand load. Electric rangesand dryers cannot be considered phase-to-phaseloads because they may have 120-volt heatingelements or 120-volt motors.

As a sample problem, let’s determine the sizeof the neutral conductor in the previous example.

General lighting and receptacle demandload = 5,205 VA

Table 3-5.—Ampacities of Insulated Conductors Rated 0-2000 Volts, 60° to 90°C (140° to 194°F) Not More ThanThree Conductors in Raceway or Cable or Earth (Directly Buried), Based on Ambient Temperature of 30°C(86°F)

†Unless otherwise specifically permitted elsewhere in this Code, the overcurrent protection for conductor types marked with anobelisk (†) shall not exceed 15 amperes for 14 AWG, 20 amperes for 12 AWG, and 30 amperes for 10 AWG copper; or 15 amperes for12 AWG and 25 amperes for 10 AWG aluminum and copper-clad aluminum after any correction factors for ambient temperature and numberof conductors have been applied.

Reprinted with permission from NPFA 70-1990, the National Electrical Code®, Copyright©1989, National Fire Protection Association, Quincy, MA02269. This reprinted material is not the complete and official position of the National Fire Protection Association, on the referenced subject which is

represented only by the standard in its entirety.

26.X

3-9

Fixed appliances (phase to neutral)

Dishwasher = 1,200 VA

Disposal = 800 VA

Attic fan = 1,600 VA

V e n t = 4 0 0 V A

4,000 VA

4,000 VA × 75 percentdemand factor = 3,000 VA

Range load

8,000 VA × 70 percent = 5,600 VA

Dryer load

6,000 VA × 70 percent = 4,200 VA

Largest motor load

1,600 VA × 25 percent = 400 VA

Total neutral load

General lighting 5,205 VA

Fixed appliances 3,000 VA

Range

Dryer

Largest motor

5,600 VA

4,200 VA

400 VA

18,405 VA

18,405 VA240 V = 76.7 amps

Refer to table 3-5, column 2, to determine the sizeof the neutral conductor.

One No. 4 THW copper conductor isrequired.

NOTE: The NEC® states that the size of theneutral conductor (grounded conductor) shall notbe less than the size of the grounding electrodeconductor.

Table 3-6 (NEC®, table 250-94) shows theminimum grounding electrode conductor size

based on the size of the service-entranceconductor. In the previous example we determinedthat a No. 4 THW copper conductor was neededto carry the neutral current. Refer to table 3-6 todetermine the neutral conductor size required fora 2/0 service-entrance conductor. A No.4 THWcopper conductor is the correct size in this examplebut not in every case. Always consult table 3-6after making the neutral conductor load calcu-l a t i o n s .

INDUSTRIAL BUILDINGSAND SHOPS

Determining electrical service requirements forindustrial buildings and shops is quite differentfrom determining dwelling unit services. Branchcircuits supplying lighting loads may serve lightingloads only. Receptacle circuits may supplyreceptacle outlets only. Individual appliances andequipment are identified as special appliance loadsor motor loads. The branch circuits supplyingthese devices are determined by nameplate ratings.

TYPES OF INDUSTRIAL LOAD

All industrial loads are categorized ascontinuous or noncontinuous duty, depending ontheir uses. A load is considered continuous dutyif the appliance or motor operates 3 hours ormore. Conductors supplying continuous dutyloads are required to have an ampacity equalto 125 percent of the total connected load.Conductors for noncontinuous duty loads haveto be large enough to supply 100 percent of thetotal connected load.

Industrial loads can be divided into fourgroups: general lighting loads, general-purposereceptacle loads, special appliance loads, andmotor loads.

General Lighting Loads

Lighting loads for industrial buildings may becomputed using the VA-per-square-foot ratiolisted in table 3-1. Receptacle loads may not beincluded in the lighting load calculations. Ifelectric-discharge lighting is used, either theVA-per-square-foot ratio or the sum of all ballastsis used, whichever is larger. Remember, anylighting loads identified as continuous duty is tobe computed at 125 percent of the total connectedload. The total connected load divided by thecircuit breaker rating determines the number of

3-10

Size of Largest Service-Entrance Size of GroundingConductor or Equivalent Area for Electrode

Parallel Conductors Conductor

Copper

2 or smaller1 or 1/02/0 or 3/0Over 3/0 thru

350 kcmilOver 350 kcmil

thru 600 kcmilOver 600 kcmil

thru 1100 kcmilOver 1100 kcmil

Aluminum orCopper-CladAluminum

1/0 or smaller2/0 or 3/04/0 or 250 kcmilOver 250 kcmil

thru 500 kcmilOver 500 kcmil

thru 900 kcmilOver 900 kcmil

thru 1750 kcmilOver 1750 kcmil

Copper

1/0

2/0

3/0

*Aluminum orCopper-CladAluminum

6421/0

3/0

4/0

250 kcmil

Table 3-6.—Grounding Electrode Conductor for AC Systems

Where multiple sets of service-entrance conductors are used as permitted in Section 230-40, ExceptionNo. 2, the equivalent size of the largest service-entrance conductor shall be determined by the largestsum of the areas of the corresponding conductors of each set.

Where there are no service-entrance conductors, the grounding electrode conductor size shall bedetermined by the equivalent size of the largest service-entrance conductor required for the load tobe served.

*See installation restrictions in Section 250-92(a).(FPN): See Section 250-23 (b).

Exception No. 1: Grounded Systems.a. Where connected to made electrodes as in Section 250-83(c) or (d), that portion of the grounding

electrode conductor which is the sole connection to the grounding electrode shall not be required tobe larger than No. 6 copper wire or No. 4 aluminum wire.

b. Where connected to a concrete-encased electrode as in Section 250-81(c), that portion of thegrounding electrode conductor which is the sole connection to the grounding electrode shall not berequired to be larger than No. 4 copper wire.

c. Where connected to a ground ring as in Section 250-81(d), that portion of the grounding electrodeconductor which is the sole connection to the grounding electrode shall not be required to be largerthan the conductor used for the ground ring.

Exception No. 2: Ungrounded Systems.a. Where connected to made electrodes as in Section 250-83(c) or (d), that portion of the grounding

electrode conductor which is the sole connection to the grounding electrode shall not be required tobe larger than No. 6 copper wire or No. 4 aluminum wire.

b. Where connected to a concrete-encased electrode as in Section 250-81(c), that portion of thegrouding electrode conductor which is the sole connection to the grounding electrode shall not be requiredto be larger than No. 4 copper wire.

c. Where connected to a ground ring as in Section 250-81(d), that portion of the grounding electrodeconductor which is the sole connection to the grounding electrode shall not be required to be largerthan the conductor used for the ground ring.

Reprinted with permission from NPFA 70-1990, the National Electrical Code®, Copyright©1989, National Fire Protection Association, Quincy, MA02269. This reprinted material is not the complete and official position of the National Fire Protection Association, on the referenced subject which is

represented only by the standard in its entirety.

26.X

3-11

branch circuits required to supply the lightingload.

The NEC® permits the use of a demand factorfor lighting loads installed in the industrial andcommercial buildings listed in table 3-2.

General-Purpose Receptacle Loads Motor Loads

All receptacles used in industrial areas have As we discussed in the dwelling units sectionto be computed at 180 VA per outlet. One of this chapter, all motors are classified asexception to this rule involves the use of multi- continuous duty. The branch circuit conductorsoutlet assemblies (prefabricated, wall-mounted supplying one motor must be sized to carry 125outlet strips). The load for outlet strips is to be percent of the full-load current rating. Ifcomputed at 180 VA for every 5 feet of assembly. conductors are feeding a group of motors, theyIf the outlet strip will be heavily loaded with are required to be large enough to carry 125portable tools, such as bench grinders, drill percent of the full-load current of the largestpresses, soldering irons, and so forth, a load of motor plus the sum of the full-load current of the180 VA per foot is to be computed. remaining motors.

All receptacles identified as continuous dutyare required to be computed at 180 VA times 125percent to obtain the total load rating. TheNEC® allows the use of a demand factor to allnoncontinuous duty receptacles. Table 3-7 statesthat the first 10 kVA has to be figured at 100percent and the remaining VA at 50 percent. Thisreduction of load is based on the concept that notall receptacles in a building are used at the sametime.

Branch circuit conductors supplying a com-bination of motor loads and appliance or lightingloads are required to have an ampacity of 125percent of the largest motor plus the sum of theother loads.

VOLTAGE DROP CALCULATION

Voltage drop becomes important in industrialareas in which long runs of conductors aresupplying large (ampacity) loads. Excessivevoltage drop can cause overheating of breakers,conductors, and appliances, creating a safetyhazard.

Special Appliance Loads

The branch circuit rating to supply specialappliances is computed using the nameplate ratingof the appliance. The NEC® permits the use of

Table 3-7.—Demand Factors for Nondwelling ReceptacleLoads

Portion of Receptacle Load towhich demand factor applies

(volt-amperes)

DemandFactorPercent

First 10 kVA or lessRemainder over 10 kVA at

10050

Reprinted with permission from NPFA 70-1990, the National ElectricalCode®, Copyright©1989, National Fire Protection Association,Quincy, MA 02269. This reprinted material is not the complete andofficial position of the National Fire Protection Association, on thereferenced subject which is represented only by the standard in

its entirety.

demand factors for appliances, such as galleyequipment and arc welders. To determine thecorrect demand factor for each application,consult the NEC®.

Conductors for a branch circuit should besized to prevent a voltage drop exceeding 3 percentat the farthest outlet of power, heating, or lightingload. Conductors supplying a feeder circuit shouldalso be sized to prevent a voltage drop exceeding3 percent at the farthest outlet.

Total voltage drop consists of the voltage dropin the feeder plus the voltage drop in thebranch circuit. The maximum voltage drop of acombination feeder/branch circuit should notexceed 5 percent. The conductors of the feedershould be sized to prevent a voltage drop of morethan 2 percent, and the conductors of the branchcircuit should be sized to prevent a voltage dropexceeding 3 percent.

The basic formula for determining voltagedrop in a circuit is as follows:

26.XVD = 2 × r × L × I

C M

3-12

where:

VD = voltage drop

r = resistivity for conductor material:

Aluminum = 18 ohms per CM-ft

Copper = 12 ohms per CM-ft

L = one-way length of circuit conductor infeet

I = current in conductor in amperes

CM = conductor area in circular mils (Seetable 8 in chapter 9 of the NEC® )

Sample problem: Determine the voltage dropin a 230-volt, two-wire heating circuit. Theload is 50 amps. The conductor size is No. 6AWG THW copper, and the one-way circuitlength is 150 feet.

VD = 2 × 12 × 150 ft × 50 180,00026,240

=26,240 = 6.86 V

The maximum voltage drop is 5 percent of240 volts, or 12 volts. A 6.86-volt drop iswithin the acceptable percentage. If the voltagedrop had exceeded 5 percent, a larger sizeconductor would have to be used or the circuitlength shortened.

SIZING OF SERVICE-ENTRANCECONDUCTORS

The process of calculating the size of theservice-entrance conductors supplying anindustrial building is similar to the processwe performed for a single-dwelling unit.The industrial load is divided into threegroups:

1. General lighting loads

2. General-purpose receptacle loads

3. Special or equipment loads

Apply the appropriate demand factors andperform the standard calculations to determinethe total load. Use table 3-5 to determine thecorrect service-entrance conductor size.

GROUND FAULT INTERRUPTERS

Ground fault interrupters (GFIs) are designedto provide reliable protection from line-to-ground faults, while other types of over-current protection may see the ground faultonly as a load current. GFIs detect a groundfault by using a current transformer with theline and neutral conductors passing throughthe center of the transformer (fig. 3-1). Aground fault on any one of the conductorscauses an unbalance in the circuit. The currenttransformer senses this unbalance and trips thecircuit breaker quickly. All GFIs manufacturedafter 1 January 1976 are required to trip openautomatically when the fault current reaches 5milliamps.

The NEC® requires all receptacles installedin bathrooms, garages, and outside areas tobe protected by GFI circuit breakers or GFIreceptacles. An exception to this rule appliesto receptacles installed in garages to supplypower to dedicated appliances, such as re-frigerators, freezers, or gas dryers. Also,receptacles that are not readily accessibleare not required to have GFI protection; forexample, the receptacle for an overhead garagedoor motor.

GFI-protected receptacles are required for all120-volt, single-phase, 15-amp and 20-ampcircuits used by personnel on construction sites.This requirement can be fulfilled by installing GFIbreakers on all receptacle circuits or by installingGFI receptacles at the jobsite.

Figure 3-1.—GFI circuit breaker.

3-13

ELECTRICAL INSTALLATIONS INHAZARDOUS LOCATIONS

The material in this section is presented todevelop your awareness of the special conditionsto consider when you are installing and maintain-ing electrical equipment in hazardous locations.The requirements for each particular hazardouslocation project is beyond the scope of thischapter. Always consult the NEC®, engineeringdepartment, or local authority when you areplanning or constructing a project in a hazardouslocation.

CLASSIFICATION OF HAZARDOUSLOCATIONS

A “hazardous location” is defined as anylocation where fire or explosion hazards may existbecause of flammable gases or vapors, flammableliquids, combustible dust, or ignitible fibers.Articles 501, 502, and 503 of the NEC® classifythese hazardous locations and specify the electricalcomponents that are required to be installed insuch locations to ensure safe operation.

The NEC® divides hazardous locations intothree classes: Classes I, II, and III and twodivisions: Divisions 1 and 2.

Class I locations are those in which flammablegases or vapors are or may be present in quantitiessufficient to cause explosions or fires. Class Ilocations include such facilities as fuel farms,flammable storage lockers, and paint spraybooths. Class II locations are those where thereis a potential for explosion or fire becausecombustible dust is present. Class III locations areignitible-fiber locations.

Each hazardous class has two divisions. InDivision 1 under each class, the particular hazardexists at any or all times of normal operation.Division 2 applies to locations where a hazardwould exist if an accident, equipment failure, orunusual condition occurred. For example, ClassI, Division 1 locations are areas where flammablegases or vapors are present during normaloperating conditions, such as a paint spray booth.A flammable storage locker is considered a ClassI, Division 2 location, and the hazard would existonly if the storage containers were accidentallyruptured or a spill occurred.

WIRING METHODS INHAZARDOUS LOCATIONS

The NEC® recommends that whereverpossible electrical equipment supplying hazardouslocations be installed in less hazardous areas. Italso suggests that by adequate ventilation, the

hazardous condition may be reduced or elimi-nated. The installation of dust-collecting systemsmay greatly reduce the hazards in a Class IIlocation.

Equipment and Fittings

When you are installing or repairingequipment in hazardous locations, first be sureyou know exactly how the location is classified.Always select equipment that is specificallydesigned for that classification. Table 3-8 indicatessome of the equipment that should be used inhazardous locations. The table does not includeall electrical equipment; nor does it cover specificapplications within each class of hazardouslocation.

As you can see by reviewing table 3-8, ClassI locations are considered the most hazardouslocations. Rigid metal conduit, intermediate metalconduit (IMC), or type MI (mineral-insulated)cable must be used in most locations. All fixturesand fillings must be explosion proof and threaded.

Sealing and Bonding

The NEC® requires that seals be installed inconduit systems in a majority of Class I, Division1 and 2 locations. The purpose of the seal is toprevent an explosion in an enclosure fromtraveling through the conduit to other enclosures.Seals are required in conduits as follows:

1. In each conduit run entering an enclosurewhere sparks, arcs, or high temperature could bepresent. Seals must be placed as close aspracticable but not more than 18 inches from theenclosure.

2. In each conduit run of 2-inch size or largerentering an enclosure that houses terminals,splices, or taps.

3. In each conduit run passing from a Class Ihazardous location into a nonhazardous location.The seal may be installed at any convenient pointin the run on either side of the boundary.

If there is a possibility that liquid or othercondensed vapor may build up in an enclosure orconduit run, a drainage system has to be installedto prevent accumulation in the system.

Grounding

Grounding requirements in hazardous loca-tions are more stringent than in nonhazardousareas. The use of double locknuts or locknut andbushing grounding methods is not allowed in haz-ardous locations. Bonding jumpers with approvedfittings must be installed to assure groundingcontinuity in Class I, II, and III locations.

3-14

Table 3-8.—Equipment Requirements in Hazardous Locations

CLASS I CLASS II CLASS IIIMATERIAL

DIVISION 1 DIVISION 2 DIVISION 1 DIVISION 2 DIVISION 1 DIVISION 2

CONDUIT

RIGID

IMC

EMT

PVC

FLEXIBLE CONDUIT

EXPLOSION PROOF

LIQUID TIGHT

EXTRA-HARD USAGE CORD

BOXES AND FITTINGS

THREADED

EXPLOSION PROOF

DUST-IGNITION PROOF

DUST TIGHT

SWITCHES

EXPLOSION PROOF

GENERAL PURPOSE-HERM. SEALED

GENERAL PURPOSE-OIL IMMERSED

DUST-IGNITION PROOF

DUST TIGHT

NOTE: MI CABLE IS APPROVED FOR ALL HAZARDOUS LOCATIONS.

3-15

CHAPTER 4

SOLID-STATE DEVICES AND CIRCUITS

Since the invention of the transistor, solid-statedevices have been developed and improved at anunbelievable rate. Great strides have been madein the manufacturing techniques, and there is noforeseeable limit to the future of these devices.Solid-state devices made from semiconductormaterials offer compactness, efficiency, rugged-ness, and versatility. Consequently, these deviceshave invaded virtually every field of science andindustry.

As the applications of solid-state devicesmount, the need for knowledge about thesedevices become increasingly important. You, asa Construction Electrician first class, will have tounderstand solid-state devices if you are to becomeproficient in the repair and maintenance ofelectronic equipment. In this chapter, we willdefine the common semiconductor componentsand describe some of their applications in fieldequipment. We will also discuss the use ofelectronic test equipment required to performtroubleshooting in the field.

This chapter will not, repeat, will not providesolid-state theory of semiconductor devices. Theintroduction to solid-state devices and powersupplies is explained in the Navy Electricity andElectronics Training Series (NEETS), Module 7,NAVEDTRA 172-07-00-82. It is highly recom-mended that you complete Module 7 beforestarting this chapter.

SEMICONDUCTOR DEVICESAND SYMBOLS

There are many different types of semicon-ductors. The specific devices commonly used arerectifier diodes, zener diodes, silicon controlledrectifiers (SCRs), transistors, unijunctiontransistors (UJTs), and integrated circuits (ICs).

To clarify the purpose of each of these devicesin the circuit, we will describe each of these devicesand its function.

RECTIFIER DIODE

The rectifier is a device that will allow currentto flow through it in only one direction. Itspurpose is to convert alternating current (ac) todirect current (dc), and it is used extensively inbattery chargers, fire alarm systems, and voltageregulators. The schematic symbol and physicalpackage are shown in figure 4-1. The current flowsfrom the bottom (cathode) of the rectifier to thetop (anode). This is known as a forward polarityrectifier. Other rectifiers are manufactured with

Figure 4-1.—Rectifier diode.

4-1

Figure 4-2.—Rectifier diode polarity.

reverse polarity (fig. 4-2), and the flow of currentis then in the opposite direction (top [cathode] tobottom [anode]). This type of reverse polarityrectifier is easily identified by the letter R stampedon the case or by the arrow pointed in the oppositedirection on the case. Whenever it is necessary tochange a rectifier, it is important to observe thesepolarity marks to ensure that the rectifier used asa replacement has exactly the same polarity withthe arrow pointed in the same direction.

ZENER DIODE

A zener diode (fig. 4-3) is designed to allowa current to flow through it in a direction that isreverse to the normal flow of current that wouldoccur if it were used as a rectifier. Current canflow through a zener diode in both directions. Inthe forward direction, current will flow at a lowvoltage, usually about 1 volt. In the reversedirection, no current will flow until the voltageimpressed across it is equal to the zener voltage.At this point, a current will flow and an extremelysmall increase in voltage will cause a large increase

in current. Most importantly, it should be notedthat the current flow through the zener diode is inthe reverse direction to that of a normal rectifier.

When the zener diode is connected to a sourceof direct current through a resistor of the correctvalue, the voltage drop across it can be made tobe relatively constant or remain at the same valuewith wide variations or changes in the voltage ofthe direct current source. With care in selectionof the zener diode and the series resistor, thevoltage drop across the diode will remain the sameregardless of changes in the source voltage andtemperature.

The purpose of the zener diode is to providea voltage reference.

SILICON CONTROLLED RECTIFIER

Figure 4-4 shows the physical outline and theschematic symbol of the silicon controlled rectifier(SCR). The SCR looks much like an ordinaryrectifier and has many of its characteristics.Current will flow through the SCR in only onedirection, from the cathode to the anode. Unlikethe rectifier, the SCR must be electrically turnedon before any current will flow through it.

A current from an external source must flowfrom the cathode to the gate to turn it on. Whenthe SCR is turned on by this method, it is saidto be “fired.” Circuits that supply this firingcurrent are called firing circuits.

Another characteristic of the SCR is its abilityto stay turned on or fired without the need of acontinuous current or signal supplied to the gate.It will remain turned on even if the gate signalis cut off until the current flow of the alternatingcurrent main supply reverses its direction ofcurrent flow. Because the SCR cannot conductin the opposite direction, no current will flow and

Figure 4-3.—Zener diode.

4-2

Figure 4-4.—Silicon controlled rectifier.

it is said to be cut off. It will not conduct againregardless of the current direction from the sourceuntil the gate signal is again applied and the SCRis fired. It will conduct only when fired by the gatesignal and when the alternating current flow is inthe correct direction (cathode to anode).

The ability of the SCR to stay turned on afterit is fired allows it to be fired with short burstsor pulses of current applied to its gate circuit.These pulses must be timed so that they will occurwhen the alternating current flow is in the correctdirection; otherwise, no current will flow. Thisis known as pulse firing and is the method usedto fire the SCRs in voltage regulators.

TRANSISTOR

Transistors are frequently used as amplifiers.Some transistor circuits are current amplifiers witha small load resistance; other circuits are designedfor voltage amplification and have a high loadresistance; others amplify power.

Transistors, like rectifiers, are made in twopolarity designs. Figure 4-5 shows the polarityinherent in an NPN transistor. In the NPNtransistor, the current flows into the transistorthrough the emitter and emerges through thecollector. There should be no confusion in findingthe correct type of transistor to use when makinga replacement, as each transistor must be replaced

Figure 4-5.—NPN transistor.

4-3

with the exact type number (for instance,2N1475), which automatically guarantees thecorrect polarity.

In a transistor of the opposite polarity, calleda PNP transistor, the current enters the collectorand emerges from the emitter.

With a direct current of the correct polarityfor the NPN transistor, negative on the emitterand positive connected to the collector, currentflows through the transistor if a current signal(known as base current) is applied between thebase and the emitter. This transistor conductscurrent from the emitter to the collector. Thestronger the base current, the greater the flow ofcurrent through the emitter-collector circuit. Thisfeature of its operation gives the transistor itsamplification characteristics.

Relatively small base currents (microamperes)and voltage (1 volt is typical) cause relatively largecurrents (several milliamperes) to flow in theemitter circuit.

UNIJUNCTION TRANSISTOR

Another type of transistor is the unijunction.The unijunction transistor (UJT) operates in anentirely different manner from other transistors.It is used in voltage regulators to generate thecurrent pulses that fire the SCRs.

The UJT (fig. 4-6) is a three-terminal semi-conductor device that has electrical charac-teristics quite different from the conventional

two-junction transistor. Physically, this transistorconsists of two ohmic contacts, called base 1 andbase 2, on opposite ends of a bar of silicon. Asingle rectifying junction is located on base 2.

In normal operation, a positive voltage isapplied to base 2, and base 1 is grounded withno emitter current flowing. The device acts likea simple high-resistance voltage divider. Whensufficient positive voltage is applied to the emitter,with respect to base 2, emitter current will flow.The net result is a decrease in the resistancebetween the emitter and base 1, so that as theemitter current increases, the emitter voltagedecreases, and a negative resistance characteristicis obtained. The output can be used as atemperature-stable firing circuit for an SCRcontrol circuit.

INTEGRATED CIRCUIT

An integrated circuit (IC) is a device thatintegrates (combines) both active components(such as transistors and diodes) and passivecomponents (such as resistors and capacitors) ofa complete electronic circuit in a single chip (a tinyslice or wafer of semiconductor crystal orinsulator).

ICs have almost eliminated the use ofindividual components as the building blocks ofelectronic prints. Instead, tiny chips have beendeveloped, the functions of which are not that ofa single component, but of dozens of transistors,

Figure 4-6.—Unijunction transistor.

4-4

26.356X

Figure 4-7.—Integrated circuit packages.

resistors, capacitors, and other electronicelements, all interconnected to perform the taskof a complex circuit.

These chips are packaged to protect them andhelp dissipate the heat generated in the device. Oneof these packages may contain one or severalstages and often has several hundred components.Some of the most common package styles areshown in figure 4-7.

ICs are composed of parts so closelyassociated with one another that repair becomesalmost impossible. In case of failure, the entireIC package is replaced as a single component.

APPLICATIONS OFSOLID-STATE DEVICES

The application of solid-state devices isvirtually unlimited. Because of the rugged

construction and small size of these devices, youmay encounter them in every facet of your job.The scope of solid-state device application rangesfrom devices as simple as room thermostats to themore complicated ICs in fire alarm systems andvoltage regulators. The following paragraphs arejust a few examples of the ways in which solid-state devices are being used in NCF equipment.

DIRECT CURRENT POWER SUPPLIES

Diodes are solid-state devices used chiefly asrectifiers, converting alternating current (ac) todirect current (dc). Diode rectifiers are used in firealarm power supplies, battery chargers, andvoltage regulators. A typical power supply circuitthat uses a diode bridge or full-wave bridge isshown in figure 4-8.

Figure 4-8.—Typical bridge rectifier circuit.

4-5

When the ac input is applied across the second-ary winding of Tl, it will forward-bias diodes CR1and CR3, or CR2 and CR4. When the top of thetransformer is positive with respect to the bottom,as shown in figure 4-8 by the designation number1, both CR1 and CR2 will feel this positive voltage.CR1 will have a positive voltage on its cathode,a reverse-bias condition; and CR2 will have apositive voltage on its anode, a forward-biascondition. At this same time, the bottom of thesecondary winding will be negative with respectto the top; that is, CR4 will be in a forward-biascondition and CR3, in a reverse-bias condition.

During the half cycle of the input designatedby the number 1 in figure 4-8, we find that CR2and CR4 are forward biased and will thereforeconduct heavily. The conducting path is shownby the solid arrows from the source (the secondarywinding of T1) through CR4 to ground, upthrough RL, making the top of RL positive withrespect to the grounded end, to the junction ofCR2 and CR3. CR2, being forward biased, offersthe path of least resistance to current flow, andthis is the path current will take to get back tothe source.

During the alternation designated by thenumber 2 in figure 4-8, shown by the dashedarrows, the top of the secondary winding is goingnegative while the bottom is going positive. Thenegative voltage at the top is felt by both CR1 andCR2, forward-biasing CR1 and reverse-biasingCR2. The positive voltage on the bottom of theT1 secondary is felt by CR3 and CR4, forward-biasing CR3 and reverse-biasing CR4. Currentflow-starting at the source (T1 secondarywinding)-is through CR1 to ground, up throughRL (this is the same direction as it was when CR2and CR4 were conducting, making the top of RLpositive with respect to its grounded end), to thejunction of CR2 and CR3. This time CR3 isforward biased and offers the least opposition tocurrent flow, and current takes this path to returnto its source.

As can be seen, the diodes in the bridge circuitoperate in pairs; first one pair—CR1 andCR3—conducts heavily, and then the otherpair—CR2 and CR4—conducts heavily. Asshown in the output waveform, we get one pulseout for every half cycle of the input-or twopulses out for every cycle in.

The bridge circuit will also indicate amalfunction in one of two ways-it has no outputor a low output. If any one of the diodes opens,the circuit will act as a half-wave rectifier witha resultant lower output voltage.

VOLTAGE REGULATORS

A voltage regulator consists essentially of avoltage-sensitive element and associatedmechanical or electrical means to produce thechanges necessary to maintain a predetermined,constant generator voltage.

An introduction to or explanation of the manydifferent types and styles of voltage regulatorsmanufactured today surpasses the scope of thischapter. All regulators accomplish the same job,but different solid-state devices and circuits maybe used to arrive at the end result-voltageregulation. Two typical voltage regulators usedin NCF generating equipment are the SCR voltageregulator and the transistor voltage regulator.

Silicon Controlled Rectifier Regulator

The SCR regulator precisely controls theoutput voltage of an ac electrical generatingsystem by controlling the amount of currentsupplied to the exciter (or generator) field. Thisregulator may be used with brushless rotaryexciters, brush type of rotary exciters, or directexcitation machines.

The SCR regulator (fig. 4-9) senses thegenerator voltage, compares a rectified sample ofthat voltage with a reference diode (zener) voltage,

26.357.1XFigure 4-9.—SCR voltage regulator block diagram.

4-6

and supplies the field current required to maintain through CR6, capacitors C1 and C2, and filterthe predetermined ratio between the generator choke L1 (fig. 4-10). The sensing circuit will sensevoltage and the reference voltage. The SCR the generator voltage, rectify and filter this volt-regulator consists of five basic circuits. These are age, and apply the resultant dc signal to the errora sensing circuit, an error detector, an error detector and error amplifier. Transformer T1amplifier, a power controller, and a stability (terminals E1 and E2) is used on single-phase appli-network. The regulator also has an automatic cation, and transformer T2 (terminals E1, E2, andvoltage buildup circuit. E3) is added to supply three-phase sensing.

SENSING CIRCUIT.—This circuit consists ERROR DETECTOR.—The detector consistsof sensing transformer(s) T1 (T2), diodes CR1 of reference (zener) diode VR1 and a voltage

Figure 4-10.—SCR voltage regulator schematic diagram.26.357X

4-7

divider network, consisting of resistors R1, R2,R3, and R5. This network provides a dc signalthat is proportional to the generator voltage. Thevoltage at the junction of R3 and R5 is comparedto the voltage of VR1 to develop the error signal,which is applied to the error amplifier.

ERROR AMPLIFIER.—The amplifierconsists of two-stage transistor amplifier Q1 andQ2, unijunction transistor 43, emitter follower44, and their associated components. The errorsignal drives Q1, which, in turn, controls 42.Transistor Q2 controls the charging time ofcapacitor C4 in the emitter circuit of 43, thusproviding phase angle control of the firing signalapplied to the SCRs in the power, controller.Transistor 44 provides the correct voltage to base2 of 43 to maintain uniform SCR firing.

POWER CONTROLLER.—The power con-troller consists of SCRs CR11 and CR12 anddiodes CR13 and CR14 in a bridge rectifier circuit.The amount of output current depends upon theconduction time of the SCRs and the exciter fieldresistance. This circuit can be compared to avariable rectifier placed between the power souce(terminals 3 and 4) and the exciter field (terminalsF+ and F-).

INPUT POWER.—The voltage applied to theregulator input power stage (terminals 3 and 4)must be 120 volts for single-phase regulators andeither 208 or 240 volts for three-phase sensingregulators. The input power may be taken fromany generator phase that provides the correctvoltage (line to line or line to neutral). The phaserelationship of this input voltage in relationto other circuits is not important. When thegenerator output voltage is greater than thepreceding values, a power transformer must. beused to match the generator voltage to theregulator input.

STABILITY NETWORK.—This circuitprovides stable operation under all operatingconditions. It consists of capacitors C6 and C7;resistors R27, R28, R29; and variable resistor R4.This resistance-capacitance (RC) network injectsa stabilizing signal from the power stage to theerror amplifier to prevent oscillations (hunting).R4 determines the amount of stability applied tothe error amplifier.

AUTOMATIC VOLTAGE BUILDUP.—Relay K1 provides automatic voltage buildup

4-8

from generator residual voltage. Normally closedcontacts (relay de-energized) provide a currentpath around the control rectifiers (CR11 andCR12) to allow the generator residual voltage tobe converted to dc by diodes CR13, CR14, CR15,and CR16 and applied to the exciter field. Whenthe generator voltage reaches approximately 75percent of rated voltage, the relay pulls in,removing the rectifier diodes, thereby allowing theSCRs to take control. A minimum of 3 percentgenerator residual is required for automaticvoltage buildup. If less than 3 percent exists,external field flashing may be required.

PARALLEL COMPENSATION (REAC-TIVE DROOP).—When parallel operation isrequired, additional components are required inthe regulating system. These are resistor R25,transformer T3, and current transformer CT1.Two of the components are included in a parallel-equipped voltage regulator. These are R25 and T3.Current transformer CT1 is a separate item andmust be interconnected, as shown in figure 4-11.

These components allow the paralleled genera-tors to share the reactive load and reducecirculating reactive currents between them. Thisis accomplished in the following manner.

A current transformer CT1 is installed inphase B of each generator. It develops a signalthat is proportional in amplitude and phase to theline current. This current signal develops a voltageacross resistor R25 (fig. 4-10). A slider on R25supplies a part of this voltage to the primary oftransformer T3. The secondaries of T3 areconnected in series with the leads from thesecondary of sensing transformer T1 and thesensing rectifiers located on the printed circuitboard. The ac voltage applied to the sensingrectifier bridge is the vector sum of the stepped-down sensing voltage (terminals El and E3) andthe parallel CT signal supplied through T3(terminals 1 and 2). The regulator input sensingvoltage (terminals E1 and E3) and the parallelcompensation signal (terminals 1 and 2) must beconnected to the generator system so as to providethe correct phase and polarity relationship.

Regulators with single-phase sensing provideabout 8 percent maximum droop while three-phase-sensing regulators provide 6 percent droop.When generators are paralleled to the same busand have different types of sensing, care must betaken to compensate for these differences usingthe slide wire adjustment on droop resistor R25.

When a resistive load (unity power factor) isapplied to the generator, the voltage that appears’

26.385XFigure 4-11.—Parallel compensation interconnection diagram.

across R25 (and T3 windings) leads the sensing the two voltages result in a larger voltage beingvoltage by 90 degrees, and the vector sum of the applied to the sensing rectifiers. Since the actiontwo voltages is nearly the same as the original of the regulator is to maintain a constant voltagesensing voltage; consequently, almost no change at the sensing rectifiers, the regulator reacts byoccurs in generator output voltage. decreasing the generator output voltage.

When an inductive load (lagging power factor) When a leading power factor (capacitive) loadis applied to the generator, the voltage that is applied to the generator, the voltage across R25appears across R25 becomes more in phase with becomes out of phase with the sensing voltage.the sensing voltage, and the combined vectors of The combined vectors of the two voltages result

4-9

4-10

REACTIVE DIFFERENTIAL COMPENSA-TION (CROSSCURRENT).—Reactive dif-ferential compensation allows two or moreparalleled generators to share inductive reactiveloads with no decrease or droop in the generatorsystem output voltage. This is accomplished bythe action and circuitry described previously forreactive droop compensation and by the additionof cross-connecting leads between the parallel CTsecondaries, as shown in figure 4-12. When thefinish of one parallel CT is connected to the startof another, a closed series loop is formed. Thisloop interconnects the CTs of all generators tobe paralleled. The signals from the interconnectedCTs cancel each other when the line currents areproportional and in phase. No system voltagedecrease occurs. These regulators provide thenecessary circuit isolation so that parallel reactivedifferential compensation can be used. THEREACTIVE DIFFERENTIAL CIRCUIT CANBE USED ONLY WHEN ALL THE GEN-ERATORS CONNECTED IN PARALLELHAVE IDENTICAL PARALLELINGCIRCUITS INCLUDED IN THE LOOP.REACTIVE DIFFERENTIAL COMPEN-SATION CANNOT BE USED WHENPARALLELED WITH THE UTILITY OROTHER INFINITE (UTILITY) BUS.

in a smaller voltage being applied to the sensingrectifiers. Then the regulator reacts by increasingthe generator voltage.

When two generators are operating in parallel,if the field excitation on one generator shouldbecome excessive and cause a circulating currentto flow between generators, this current willappear as a lagging power factor (inductive load)to the generator with excessive field current anda leading power factor (capacitive load) to theother. The parallel compensation circuit will causethe voltage regulator to decrease the fieldexcitation on the generator with the lagging powerfactor and increase the field excitation on thegenerator with the leading power factor so as tominimize the circulating currents between thegenerators.

This action and circuitry is called reac-tive droop compensation (droop). It allowstwo or more paralleled generators to shareinductive loads proportionally by causing adecrease or droop in the generator systemvoltage.

26.359XFigure 4-12.—Crosscurrent compensation interconnection

diagram.

Transistor Voltage Regulator

The transistor voltage regulator uses transistoramplifiers to control a saturable core transformerthat regulates field excitation. The circuitry alsoincludes a power supply, error detection andamplifier circuit, stability circuit, crosscurrentcompensation circuit, and a field flash circuit. Atransistor voltage regulator circuit is shown infigure 4-13. The assembly operates as follows:

1. The regulated exciter field voltage atterminals S and R is obtained by saturablecore transformer T1. The inductance of thistransformer can be varied with the controlwinding 5-7 so that the voltage ratio betweenwindings 1-2 and 3-4 may be increased ordecreased in proportion to the direct currentflowing in winding 5-7. When the magnitude of

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4-13

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the control current increases, the inductancedecreases, and there is a lowered magneticcoupling between the windings that carry thealternating currents, hence a lowered voltageoutput. The reverse occurs when the controlcurrent is decreased.

2. The power input at terminals J and K issupplied by current transformers at CT4, CT5,and CT6 on the three generator load phases. Thevoltage at terminals L and M is supplied fromphase C of the generator. The two inputs arecombined by transformer T1 under the controlof winding 5-7, then rectified by diodes CR1through CR4 and supplied to the exciter fieldthrough terminals S and R. In the event of a shortcircuit, the voltage at L-M can drop to zero, butthere is a high voltage at J-K from the currenttransformers so that the exciter provides sufficientfield current for the generator output to actuatethe protective devices to shut down the set.

3. The voltage at terminals S and R iscompared to the reference voltage at transistor Q1and zener diode VR1 of differential amplifier41-42. Any difference or error signal at thecollector of 42 is amplified by transistors QS-Q6and 43-44 and then fed to control winding 5-7of saturable core transformer T1. The transformerwill increase or decrease the exciter currentto reduce the error signal to zero, therebymaintaining the output of the generator set withinthe range as preset by resistor R33. NetworksR31-C1 and R32-C3 are used for phase shiftcompensation. If hunting is present, adjustmentof R32 will provide the proper amount offeedback to eliminate the hunting. Adjustment ofR31 will smooth and improve the transientresponse.

4. The voltage at terminals A and B issupplied by phase C of the generator through theoperator’s voltage adjust rheostat and from thecrosscurrent compensation network when two ormore generators are connected in parallel. Thisvoltage is stepped down by transformer T5,rectified by diodes CR12-CR15, filtered by R16,R2, C2, C5, and fed to the reference side ofdifferential amplifier 41-42.

5. The generator output voltage is determinedby the level of the reference voltage and iscontrolled by the setting of R33, which adjuststhe range voltage and operator’s rheostat, whichsets the actual output. During parallel operation,the reference voltage is dependent on the cross-current compensation network. For example, ifone generator draws more current, the networkincreases the magnitude of the reference voltage.

4-12

This causes the voltage regulator to sense morevoltage, thereby decreasing the current to theexciter field stator winding. This provides paralleloperations with droop.

6. Power for the transistor amplifiers and thecontrol winding (5-7 of T1) is obtained fromterminals L and M through step-down trans-former T4 and diodes CR8 through CR11. DiodeCR17 and resistor R21 provide feedback to theamplifiers to enhance the gain.

7. When the start switch of the generator setis actuated, 24 volts dc from the battery bank isapplied to the exciter field (terminals S and R)from terminals C and D through limiting resistorR17 and isolation diode CR16. The purpose is tobuild up the magnetic field in the main rotorwindings quickly to produce an immediate outputfrom the generator. This field flashing voltage isthen removed automatically by relay K5.

SOLID-STATE PROTECTIVE RELAYS

A protective relay is a device that whenenergized by suitable inputs responds to theseinputs in a prescribed manner to indicate or isolatean abnormal operating condition. The inputs tothese protective devices are usually electrical butmay be mechanical, thermal, or a combinationof these quantities. This discussion will beconcerned with solid-state relays having electricalinputs.

Overvoltage Protective Relay

The overvoltage relay (fig. 4-14) is a solid-statedevice that functions to protect the load in theevent that generator voltage exceeds preset limits.It actuates after a predetermined time delay whenthe generator voltage rises to approximately 125percent of the rated output voltage. Uponactuation, contacts within the overvoltage relayclose (K1, 7-8) to display the fault condition atthe annunciator and open (K1, 3-4) to secure thegenerator set.

1. The ac input voltage (terminals 1 and 2) isrectified by diode CR1 and applied to a voltagedivider network consisting of resistors R2, R3, andR5. Zener diode CR4 conducts when the voltageat the wiper of R5 exceeds its zener breakdownvoltage. The point at which the ac input voltagecauses the zener breakdown of CR2 can beadjusted by R5.

2. When an overvoltage condition occurs,zener diode CR4 conducts and triggers SCR1 forconduction. This energizes relay K1 and causes

Undervoltage Protective Relay

The undervoltage relay (fig. 4-15) functionsto protect the load in the event the generatordecreases below preset limits. It actuates after apredetermined time delay when generator voltagedecreases to approximately 75 percent of the ratedoutput voltage. Upon actuation, contacts withinthe undervoltage relay close to signal theannunicator and open to de-energize the generatorbreaker (contactor), resulting in a display of thefault condition and removal of the load from thegenerator.

1. The single-phase input voltage is rectifiedby diode CR2 and applied to a sampling networkconsisting of resistors R1, R2, and R3. The dcvoltage sampled at the wiper of potentiometer R2is filtered by capacitor C4. Transistor Q1compares the sample voltage on capacitor C4 toa reference voltage obtained by zener diode CR3.

2. When the input voltage is above the trippoint, transistor Q1 conducts. This causes zenerdiode CR1 to limit the voltage across capacitorsC1, C2, and C3 to 15 volts. This voltage forward-biases transistors 42 and 43 for conduction.Transistors 42 and 43 function as a switch toenergize a relay contained in the encapsulatedbase.

Figure 4-14.—Solid-state overvoltage protective relay.

its contacts to transfer. Resistor R1 limits thecurrent to the relay while the voltage to the relayis limited to a peak value of 30 volts by zenerdiodes CR2 and CR3.

3. Resistor R4 and capacitor C3 preventtransients from triggering silicon controlled switchSCR1 into conduction.

Figure 4-15.—Solid-state undervoltage protective relay.

4-13

3. When the input voltage is below the trippoint or approximately the zener breakdownvoltage of CR3, transistor Q1 will turn off. Whenthis happens, the capacitors discharge throughresistors R6 and R8 and zener diode CR6. Whenthe voltage across these capacitors falls below thezener breakdown voltage of CR6, transistors Q2and Q3 will turn off. This de-energizes the relay.

4. Diodes CR7 through CR10 are used as afull-wave bridge to rectify the input voltage to adc level for the detector circuit and the relay.Capacitor C5 reduces the ripple of the rectifiedvoltage to prevent relay chatter.

Underfrequency Protective Relay

The underfrequency relay (fig. 4-16) is a solid-state device that functions to protect the load inthe event generator frequency decreases belowpreset limits. It actuates when the frequencydecreases to 55 hertz for 60-hertz operation and46 hertz for 50-hertz operation. Upon actuation,contacts within the relay close to signal theannunicator and open to de-energize the generatorbreaker (contactor), resulting in a display of thefault condition and removal of the load from thegenerator.

Frequency sensing is accomplished by a tunedcircuit consisting of capacitors C1 and C2 andcomponents in the encapsulated base. Zener

diodes CR1, CR2, and CR3 limit the peak voltageto the tuned circuit. The ac output of the tunedcircuit is rectified by diode CR4 and applied toa voltage divider consisting of resistors R1, R2,R3, and R4. Transistor Q1 compares the voltageat the wiper of potentiometer R3 with thereference voltage established by zener diode CR7.When transistor Q1 conducts, transistor 42operates as a switch to control the coil voltage ona relay contained in the encapsulated base. Bothtransistors Q1 and Q2 and the relay in theencapsulated base are energized when thefrequency of the input voltage to terminals 1 and2 is normal frequency (50 to 60 hertz). When anunderfrequency condition occurs, the voltage atthe base of transistor Q1 is not sufficientfor conduction. This causes the relay to bede-energized and its contacts to switch. Theunderfrequency trip point is adjusted by potenti-ometer R3.

Reverse-Power Protective Relay

The reverse-power relay (fig. 4-17) is asolid-state device that functions to protectthe generator in the event of a reverse-poweroperating condition during parallel operation. Itoperates in conjunction with the load measure-ment unit. This unit produces a dc output voltagewhose polarity and magnitude are functions of

Figure 4-16.—Solid-state underfrequency protective relay.,

4-14

Figure 4-17.—Solid-state reverse-power protective relay.

the total load on the generator set regardless ofphase or power factor. When the reverse-powerflow into the generator exceeds 20 percent of ratedload, the load measurement unit output hassufficient magnitude and correct polarity to causethe reverse-power relay to activate. Uponactuation, contacts within the reverse-power relayclose to signal the annunicator and open tode-energize the generator breaker (contactor).This results in a display of the fault condition andremoval of the load from the generator.

1. During normal operation with powerpassing from the generator set to the load, theload measurement unit impresses a dc signalacross terminals 1 and 2 of the reverse-powerrelay, with terminal 1 negative and terminal 2positive. This reverse-biases transistor Q1 off,causing Q2 and Q3 to be off and relay coil K1to be de-energized. Thus, under all conditions offorward power by the generator set, relay K1 isde-energized, terminals 5 and 6 remain open, andterminals 7 and 8 are shorted.

2. Reverse-power trip-level-control potenti-omenter R2 is factory adjusted to cause relay coilK1 to be energized when dc voltage of 2 volts isimpressed across terminals 1 and 2, with terminal1 positive and terminal 2 negative.

3. When the system reverse power reaches 20percent, the dc voltage across the wiper of R2 andterminal 2 has sufficient magnitude to turn Q1on. The superimposed ac voltage on the dc inputto terminals 1 and 2 is then impressed across the

anode of CR2 and terminal 4. Diode CR3 rectifiesthis ac signal and capacitor C2 smooths it. Theresultant dc voltage forward-biases Q2 and Q3 on,causing relay coil K1 to become energized.

Overload Protective Relay

The overload (overcurrent) relay (fig. 4-18) isa solid-state device whose function is to protectthe load in the event of an overload condition.An “overload condition” is defined as the statein which generator output current in any phaseexceeds 110 percent of rated value. The overloadrelay is a current-sensing device and operates onan inverse-time principle as the current in anyphase (coil A, B, or C) exceeds the overload state.At the point just above 130 percent of ratedcurrent, the overload relay will actuate inapproximately 10 minutes. Upon actuation,contacts within the overload relay close to signalthe annunicator and open to de-energize thegenerator breaker (contactor). This results in thedisplay of the fault condition and the removal ofthe load from the generator.

TESTING SOLID-STATE DEVICES

After electrical generating plants, distributionsystems, communications systems, and other

Figure 4-18.—Solid-state overload protective relay.

4-15

electrical apparatus and equipment have beenconstructed and put into operation, they must betested, inspected, and maintained.

To do this, you must know how to operatethe various testing and measuring instruments totest for grounds, opens, and shorts and be ableto measure current, voltage, power, resistance,frequency, and so forth,

The theory of operation for basic typesof testing and measuring devices, such asmegohmmeters, voltmeters, ammeters, andohmmeters, is explained in the ConstructionElectrician 3 & 2 training manual. Moresophisticated types of test equipment presentlybeing distributed to the battalions and shorefacilities will be discussed in this chapter. Theseinclude the transistor tester, waveform analyzer(oscilloscope), and the capacitor-inductoranalyzer. You undoubtedly recognize theimportance of becoming familiar with any testequipment capable of performing tests on thesenewer components and the advantages each ofthese specialized instruments has. Knowledge onthe use of these instruments will enable you toplace equipment into operation status quickly andsafely. As you increase your capabilities, youshould find it easier to advance in rate.

Solid-state devices, although generally morerugged mechanically than vacuum tubes, aresusceptible to damage by excessive heat andelectrical overload. The following precautionshave to be taken in servicing transistorizedequipment:

Check equipment and soldering irons tomake certain that there is no leakage current fromthe power source. If leakage current is detected,use isolation transformers.

Do not use ohmmeter ranges that requirea current of more than 1 milliampere in the testcircuit for testing transistors.

Do not use battery eliminators to furnishpower for transistor test equipment because thesedevices have poor voltage regulation and possiblyhigh ripple voltage.

When soldered connections are required,keep the heat applied to a transistor to a minimumby using a low-wattage soldering iron and heatshunts, such as long-nose pliers, on the transistorleads.

Check all associated circuits for defectsbefore rejecting a transistor.

Remove all power from the equipmentbefore you replace a transistor or other circuitpart.

On equipment with closely spaced parts,the placement of conventional test probes is oftenthe cause of accidental short circuits betweenadjacent terminals. Momentary short circuits,which rarely cause damage to a vacuum tube, mayruin a transistor. To avoid accidental shorts, youcan cover test probes with insulation for all buta short length of the tip.

RECTIFIER DIODE TESTING

A convenient test for a rectifier diode requiresonly an ohmmeter. The forward-and-backresistance can be measured at a voltagedetermined by the battery potential of theohmmeter and the resistance range at which themeter is set. When the test leads of the ohmmeterare connected to the diode, a resistance will bemeasured that is different from the resistanceindicated if the leads are reversed. The smallervalue is called the FORWARD resistance, and thelarger value is called the BACK resistance. If theratio of back-to-forward resistance is greater than10:1, the diode should be capable of functioningas a rectifier. This is a limited test and does nottake into account the action of the diode atvoltages of different magnitudes and frequencies.

Another test that may be performed on adiode is the front-to-back current leakage. Thistest will be discussed in the “Transistor Testing”portion of this chapter.

ZENER DIODE TESTING

The testing of zener diodes requires a variabledc power supply. A typical test circuit can beconstructed, as shown in figure 4-19. In thiscircuit, the variable power supply is used to adjustthe input voltage to a suitable value for the zenerdiode being tested. Resistor R1 limits the currentthrough the diode. With the zener diode connectedas shown in figure 4-19, no current will flow untilthe voltage across the diode is equal to the zenervoltage. If the diode is connected in the oppositedirection, current will flow at a low voltage,usually less than 1 volt. Current flow at a lowvoltage in both directions indicates that the zenerdiode is defective.

4-16

Figure 4-19.—Testing a zener diode.

SILICON CONTROLLEDRECTIFIER TESTING

To test an SCR, connect an ohmmeter betweenthe anode and cathode, as shown in figure 4-20.Start the test at R × 10,000 and reduce the valuegradually. The SCR under test should show a highresistance regardless of the ohmmeter polarity.The anode, which is connected to the positive leadto the ohmmeter, is now to be shorted to the gate.This will cause the SCR to conduct, giving a lowresistance reading on the ohmmeter. Removingthe anode-to-gate short will not stop the SCRfrom conducting. Removal of either of theohmmeter leads will cause the SCR to stopconducting, and the resistance reading will then

Figure 4-20.—Testing an SCR with an ohmmeter.

return to its previous high value. Some SCRs willnot operate when connected to an ohmmeter. Thereason for this is that the ohmmeter does notsupply enough current. However, most of theSCRs in Navy equipment can be tested by theohmmeter method. If an SCR is sensitive, theR × 1 scale may supply too much current to thedevice and damage it. It is advisable to try testingsensitive SCRs on the higher resistance scales.

An SCR can also be tested for switching actionand leakage, as discussed in the “TransistorTesting” section of this chapter.

UNIJUNCTION TRANSISTOR TESTING

Testing a unijunction transistor (UJT) is arelatively easy task if you view the UJT as beinga diode connected to the junction of two resistors,as shown in figure 4-21. With an ohmmeter,measure the resistance between base 1 and base2; then reverse the ohmmeter leads and takeanother reading. Both readings should show thesame high resistance regardless of the meter leadpolarity. Connect the ohmmeter’s negative leadto the UJT’s emitter. Using the positive lead,measure the resistance from the emitter to base1, and then from the emitter to base 2. Bothreadings should indicate high resistancesapproximately equal to each other. Disconnect thenegative lead from the emitter and connect thepositive lead to it. Using the negative lead,measure the resistance from the emitter to base1, then from emitter to base 2. Both readings

Figure 4-21.—Unijunction transistor equivalent circuit.

4-17

should indicate low resistances approximatelyequal to each other.

TRANSISTOR TESTING

Most transistors that fail do so completely.These transistors can be detected by using thetransistor gain test. Two exceptions are transistorsthat are just starting to fail and transistors incritical bias circuits. The quality of thesetransistors can be checked by using the transistorleakage test. An accurate, easy-to-use transistortester (fig. 4-22) that allows both in- and out-of-circuit testing can make you more efficient introubleshooting solid-state circuits.

The transistor tester can also test diodes,SCRs, and field effect transistors (FETs). An FETis a device that combines the high input impedanceof the vacuum tube with all the advantages of thetransistor. For detailed testing information onFETs, consult the transistor tester operator’smanual.

If a transistor checks BAD in circuit andGOOD out of circuit (including leakage), thereis probably something wrong in the circuit.

Transistor Leakage

4-18

26.361XFigure 4-22.—Sencore TF46 transistor and FET tester.

Leakage in a transistor can shunt signals orchange bias voltages and upset circuit operationeven though the transistor has gain. Transistorleakage should be checked whenever circuittroubleshooting indicates improper bias voltageseven though the transistor has gain.

Transistor Gain

The transistor gain test provides a safe andreliable method of determining if a transistor hasgain. The gain test is a Go/No-Go test providinga test tone and meter indication that indicates gainis present. No technical information is needed fortesting for transistor gain. The same procedureis used for testing a transistor in or out of circuit.

WARNING

Be sure power to the transistor has beenremoved and filter capacitors dischargedbefore connecting the test leads.

To test for transistor gain:

1. Connect the three test leads to the threeleads of the transistor in any order.

NOTE: The position (up or depressed) of thePARAMETER SELECTOR buttons (to the leftof the PERMUTATOR SWITCH) has no effecton the test.

2. Rotate the PERMUTATOR SWITCH onecomplete turn while watching the meter and/orlistening for the test tone. If the transistorhasgain, the meter will read in the GOOD portionof the GAIN scale in either one or twoPERMUTATOR SWITCH positions.

3. If the transistor tests BAD in circuit, checkthe schematic of the transistor being tested to seeif there is a low-impedance shunt path around thetransistor (between any two elements).

It is recommended that transistors that checkBAD in circuit be removed from the circuit andtested again to eliminate the possibility of external’loading. If the transistor now checks GOOD,perform the out-of-circuit leakage check.

There are six possible leakage paths in atransistor (fig. 4-23). Collector/base (ICBO) andemitter/base (IEBO) leakage paths are the two keyleakage paths that most often upset circuitoperation. The tester will read all six paths if yourotate the PERMUTATOR SWITCH through allsix positions indicated for the polarity of thedevice under the test.

KEY LEAKAGE TEST

Leakage tests should be done out of circuit,since the associated components of the circuit maycause false leakage readings.

To test for key leakage:

1. Perform the transistor gain test as describedpreviously. Note the two positions that indicateGOOD gain on this test.

2. Depress the LEAKAGE push button withthe PERMUTATOR SWITCH in either of thetransistor gain positions and read the leakage onthe lower (ICBO/IGSS) scale of the meter.

3. Switch the PERMUTATOR SWITCH tothe other position that gave the transistor gaintest. Again depress the leakage button and readthe leakage on the meter. Refer to table 4-1 fortypical leakage limits.

Rectifier Diode Testing

The transistor tester can check the front-to-back current leakage of a diode. Since theresulting readings are given in microamperes, theresults may be compared to a specification (spec)sheet to determine if the diode is within specs. The

26.361.1XFigure 4-23.—Leakage paths for a PNP transistor.

Table 4-1.—Transistor Leakage Chart

MAXIMUM LEAKAGEFOR “GOOD” TRANSISTORS

DEVICE KEY LEAKAGE

Small Si. Trans. 0.1µALarge Si, Small Ge. Trans. 1-50µALarge Ge. Trans. 10-2500µAJFET 0µAMOSFET 0µA

26.X

test will also determine the polarity of anunknown diode. The test should be done out ofcircuit since current paths through externalcomponents in a circuit may cause false leakagereadings.

To test a diode:

1. Connect the RED and GREEN test leadsto the diode leads in either order.

2. Move the PERMUTATOR SWITCH toeither of the two positions marked “DIODE.”

3. Press the LEAKAGE (DIODE) switch andnote the amount of leakage current on theLEAKAGE scale of the meter.

4. Repeat Step 3 in the other positionof the PERMUTATOR SWITCH marked“DIODE.”

a. A good diode will show one high andone low leakage reading.

b. A shorted diode will show high leakagein both positions.

c. An open diode will show no leakage ineither position.

5. To determine the polarity of the diodeunder test:

a. If the highest reading was obtained inthe YGR position, connect the cathode to theRED lead.

b. If the highest reading was obtained inthe YRG position, connect the cathode to theGREEN lead.

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Silicon Controlled Rectifier Testing

Although the transistor tester is not specificallydesigned to test SCRs, it will test many types. TheSCR specification that determines whether or notit can be tested is the gate trigger voltage orcurrent.

Two tests are available for SCR testing:switching action (gain) and leakage.

To test for SCR switching action:

1. Connect the three leads of the tester to theSCR as if it were a transistor.

2. Perform the transistor gain test.3. An SCR that is being triggered by the tester

and switching properly will show one position asa good PNP transistor and one as a good NPNtransistor.

4. If no good readings are obtained, use acomparison test by testing a replacement SCR ofthe same type. If the replacement SCR testsproperly, use the results of Step 3 as the. testresults.

5. If the replacement SCR does not test, thetrigger characteristics are beyond the test signallevels supplied by the tester. Proceed with the SCRleakage test.

Testing for SCR leakage:

1. Connect the RED and GREEN leads of thetester to the anode and cathode leads of the SCRunder test.

2. Perform the diode test.3. If the SCR is shorted, both positions of the

test will show high leakage.4. If the SCR is not leaky, NEITHER position

will show high leakage.5. An open SCR will not be detected unless

it is one that can be tested using the transistor gaintest.

TESTING INTEGRATED CIRCUITS

Digital ICs are relatively easy to troubleshootand test because of the limited numbers ofinput/output combinations involved. Anyparticular IC can be tested by simply comparingit to a known good one. A device that can be ofgreat value in troubleshooting integrated circuitsis the logic probe shown in figure 4-24.

Use of a suitable logic probe can greatlysimplify the troubleshooting of logic levelsthrough integrated circuitry. It can show youimmediately whether a specific point in the circuitis low, high, open, or pulsing. Some probes havea feature that detects and displays high-speedtransient pulses as small as 10 nanoseconds wide.

Figure 4-24.—Typical logic probe.

These probes are usually connected directly to thepower supply of the device being tested, althougha few also have internal batteries. Since most ICfailures show up as a point in the circuit stuckeither at a high or low level, these probes providea quick, inexpensive way of locating the fault.They can also display that single short-durationpulse that is hard to catch on an oscilloscope.

Testing ICs uses an approach somewhatdifferent from that used in testing transistors. Thephysical construction of ICs is the prime reasonfor this different approach. The most frequentlyused ICs are manufactured with either fourteenor sixteen pins, all of which are soldered directlyinto the circuit. It can be quite a job to unsolderall of these pins, even with the special toolsdesigned for this purpose. After unsoldering allof the pins, you then have the tedious job ofcleaning and straightening them. Although thereare a few IC testers on the market, theirapplications are highly limited. Just as thetransistor must be removed from the circuit forchecking on a tester, the IC must be removed topermit testing. When ICs are used in conjunctionwith external components, these components

4-20

should first be checked for proper operation. Thisis particularly important in linear applications,where a change in the feedback of a circuit canadversely affect the component’s entire operatingcharacteristics. Any linear (analog) IC is sensitiveto its supply voltage. This is especially the caseamong those that use bias and control voltagesin addition to a supply voltage. If a linear IC issuspected of being defective, it is important tocheck all voltages coming to the IC against thecircuit diagram of the equipment manufacturerfor any special notes on voltages. Themanufacturer’s handbook will also giverecommended voltages for any particular IC.When troubleshooting ICs (either digital orlinear), a technician cannot be concerned withwhat is going on inside the IC. He cannot takemeasurements or conduct repairs inside the IC.He can therefore consider the IC as a “black box”that performs a certain function. The IC can bechecked, however, to see that it can perform itsdesign characteristics. After checking staticvoltages and external components associated withthe IC, check it for dynamic operation. If the ICis intended to function as an amplifier, then

measure and evaluate its input and output. If itis to function as a logic gate or combination ofgates, it is relatively easy to determine what inputsare required to achieve a desired high or lowoutput.

WAVEFORM ANALYSIS OFSOLID-STATE DEVICES

Waveform analysis can be made by observingdisplays of voltage and current variations withrespect to time or by harmonic analysis ofcomplex signals. Waveform displays are particu-larly valuable for adjusting and testing pulse-generating, pulse-forming, and pulse-amplifyingcircuits. The waveform visual display is also usefulfor determining signal distortion, phase shift,modulation factor, frequency, and peak-to-peakvoltage. In this section, we will briefly discuss theinstrument used to provide you with these visualinterpretations of waveforms, the oscilloscope.

DUAL-TRACE OSCILLOSCOPE

The cathode-ray tube (CRT) oscilloscope(fig. 4-25) is commonly used for the analysis of

Figure 4-25.—Sencore SC61 waveform analyzer.26.363X

4-21

waveforms generated by electronic equipment.Several types of cathode-ray oscilloscopes areavailable for making waveform analysis. Theoscilloscope required for a particular test isdetermined by such characteristics as input-frequency response, input impedance, sensitivity,sweep rate, and the methods of sweep control.

The display observed on a cathode-rayoscilloscope is ordinarily one similar to thoseshown in figure 4-26. Views A and B show theinstantaneous voltage of the wave plotted againsttime. Elapsed time is indicated by horizontaldistance from left to right across the etched grid(graticule) placed over the face of the tube. Theamplitude of the wave is measured vertically onthe graph.

The oscilloscope is also used to picture changesin quantities other than simply the voltages inelectric circuits. For example, if you need to seethe changes in waveform of electric current, youmust first send the current through a smallresistor. You can then use the oscilloscope to viewthe voltage wave across the resistor. Otherquantities, such as temperatures, pressures,speeds, and accelerations, can be translated intovoltages by means of suitable transducers and thenviewed on the oscilloscope.

The oscilloscope shown in figure 4-25 also hasthe capability to provide a digital readout of the

Figure 4-26.—Typical waveform displays.

signal displayed on the CRT. This featureeliminates the need to count the grids on the screenand perform the mathematical calculationsrequired to determine the magnitude of thewaveform.

There are two types of digital measurementsmade through the same probe used for the CRTdisplay. The first three functions for each channelare called the Auto-Tracking™ tests. “Auto-Tracking™” means the microcomputer auto-matically tracks the CRT display at all times. Thethree Auto-Tracking™ functions are measuringdc volts, peak-to-peak volts, and frequency. Allthree functions measure the entire waveform.

The second group of digital tests are the deltatests, which let you measure part of a waveform.These tests measure the peak-to-peak amplitude,time, or frequency of any part of the waveformshown on the CRT.

Both types of digital tests are unaffected bythe vertical or horizontal verniers or positioncontrols, allowing the CRT display to be any sizeyou want without affecting the accuracy of thedigital readout. All tests are automatically rangedor directly interfaced to the input attenuators fordirect readings.

One final test allows the frequency of thesignal applied to channel A to be compared to thefrequency of the signal applied to channel B. Thedigital display shows the ratio of the twofrequencies to troubleshoot divider or multiplierstages.

Front Panel Controls

The fastest way to become familiar with theoscilloscope is to use the same procedure to setup every waveform. The front panel has all of thecontrols grouped by function to allow you tomove clockwise around the panel as you apply thesignals, adjust the trigger circuits, and then adjustthe horizontal sweep circuits. Always start fromthe same point when you apply a new signal orexperience difficulty in locking the waveform.

Use the following procedures as a checklistto follow as you learn how to operate theoscilloscope. Each of these simplified proceduresis covered in detail in the operator’s manual. Besure to read your manual to understand fully theeffect each control has on the waveform. To setup any waveform, refer to figure 4-27 andperform the following steps:

1. Select the desired CRT display button toproduce a single-trace, dual-trace, or vectordisplay.

4-22

Fig

ure

4-27

.—F

ront

pan

el c

ontr

ols.

2. Apply the signal(s) to the vertical input(s).a. Make sure the INPUT COUPLING

switch is not set to the “ground” position. Itshould be in the AC position for mostmeasurements.

b. Set the VOLTS/DIVISION switch to aposition that is one-half to one-eighth. theamplitude of the input signal.

NOTE: Remember the VOLTS/DIVISIONswitches are calibrated to read directly when thesupplied low capacity probes are used; it is notnecessary to multiply times 10.

3. Adjust the four TRIGGER controls to lockthe signal.

a. Set the TRIGGER SOURCE switch tothe signal you want to use as your reference. CHA will trigger on a sample of the signal appliedto the channel A input, CH B will trigger on asample of the channel B input, AC LINE willtrigger on a sample of the ac line, and EXT willtrigger on the signal applied to the EXT TRIGINPUT jack.

b. Set the TRIGGER MODE switch to thedesired position. AUTO will be used for mostsignals, TV is used for composite video signals,and NORM is used for special triggeringconditions.

c. Set the TRIGGER POLARITY switchfor the desired starting point. The polarity is oftenunimportant. When using the TV position of theTRIGGER MODE switch, however, you must setthe TRIGGER POLARITY switch to the polarityof the sync pulses.

d. Adjust the TRIGGER LEVEL controluntil the trace is properly locked on the CRT.

4. Adjust the TIMEBASE-FREQ switch forthe desired number of waveforms across the CRT.Remember to use the frequency markings on theoutside ring as a guide when the frequency of thesignal is known. Use the position with a markedfrequency that is lower than the frequency of theapplied signal.

5. Adjust the VERTICAL POSITION,HORIZ POSITION, FOCUS, and INTENSITYcontrols as desired for the best waveform.

Process of Locating the Trace

You may occasionally lose the trace becauseone or more of the CRT controls is improperlyadjusted. Pressing the BEAM FINDER button(fig. 4-25) overrides several internal circuits toforce the trace back onto the screen. Adjust the

vertical position control and/or the horizontalposition control to position the trace on the CRT.Adjust the FOCUS and INTENSITY control toobtain a sharp, bright trace.

Test Probe Frequency Compensation

Each test probe has a special compensationcapacitor built into the BNC connector body. Thiscapacitor matches the capacity of the probe andconnecting cable to the input of the oscilloscopefor flat frequency response. An uncompensatedprobe may result in waveform distortion orincorrect amplitude readings. The compensationaffects both the CRT display and the digital peak-to-peak funct ion . Check the probe’scompensation by connecting it to the PROBECOMP jack on the front panel. The resultingCRT display (fig. 4-28) should have a flat top andbottom with square corners (view A). Overshoot(view B) or rounding (view C) indicates thecapacitor in the probe needs adjustment. Performthis adjustment as specified in the operator’smanual.

26.363.2XFigure 4-28.—Probe compensation display.

4-24

Test Probe Ground Connections

Each test probe comes with two ground leadsand a ground clip. It is important that you usethe shortest possible ground connector whenworking in high-frequency circuits or circuits thatproduce square-wave signals with fast rise time.The inductance of extra ground lead length causesdistortion in these signals. The long (12-inch)ground lead is to be used only when measuringlow-frequency signals.

It is always necessary to ground each probeto prevent interference or other waveformdistortion on high-frequency signals. The groundconnection should be made as close to the testpoint as possible because the extra inductance ofa printed circuit board or chassis wiring will havethe same effect on the displayed signal as thelonger ground leads-waveform distortion.

You should use the small ground clip whenmaking tests in digital stages. The small size isdesigned for easy connection when the spring-loaded tip is removed. The clip is made of springsteel to allow connections to the closely spacedpins of an IC. And, above all, the length of theclip is the smallest possible to prevent signaldistortion on fast rise-time signals.

USING THE OSCILLOSCOPE

The oscilloscope may be used to test solid-statedevices; however, this may require theconstruction of special test circuits. This shouldpose no problem if you have access to a testlaboratory. There is usually a multimeter,transistor tester, or similar piece of test equipmentavailable to test components out of the circuit.The oscilloscope is particularly useful in theprocess of analyzing electronic circuits duringoperating conditions.

To analyze waveform displays effectively, youhave to know the correct wave shape. Themaintenance manual for each piece of equipmentshows what waveforms you should observe at thevarious test points throughout the equipment.Waveforms that will be observed at any oneselected test point will differ; each waveform willdepend on whether the operation of the equipmentis normal or abnormal.

Figure 4-29 represents a typical schematicdiagram with oscilloscope waveforms. Byattaching the oscilloscope test probe to point Ain the circuit, you can compare the CRT displayto the waveform shown in view A. You cantroubleshoot the entire circuit by comparing the

4-25

waveforms at test points A, B, C, and D with thatof your scope.

TESTING CAPACITORSAND INDUCTORS

The use of capacitors in electronics hasdramatically increased in the past few years andthe forecast is for an even greater usage. Thetransistor has given way to the IC, but becauseof the nature and construction of the capacitorand the inductor, these are not replaced with ICs.The more ICs we use, the more capacitors andinductors we will use. The need to measurecapacity value, leakage of the capacitor, inductorvalue, and quality of the inductor has becomemore important than ever before. Without a goodmeasure of these important parameters, propercircuit operation becomes more difficult. With acapacitor-inductor analyzer, capacitors can bechecked for value and for leakage at the ratedworking voltage on a digital readout. Inductorscan be checked for inductance and for qualitywhen a meter,, such as the one shown in figure4-30, is used.

TESTING CAPACITORS

A capacitor is nothing more than two metalplates separated by an insulator called thedielectric. The common causes of capacitorfailures are excessive dielectric leakage, change incapacity value, and an increase in dielectricabsorption (battery action). All capacitors shouldbe removed from the circuit before testing.Impedances found in the circuit will result in falsemeter readings.

Capacitor Value

All types of capacitors change in value withage. A reliable value test is important when yoususpect that a capacitor may have changed valueor is the wrong value when new. To checkcapacitors for capacity value, perform thefollowing steps:

1. Connect the test leads to the capacitor tobe tested. Polarity of the test leads is importantonly if you are checking a polarized capacitor.When checking polarized capacitors, be sure toconnect the red test lead to the positive capacitorterminal.

26.364XFigure 4-29.—Typical schematic diagram with oscilloscope waveforms.

2. Depress the CAPACITOR VALUE pushbutton.

3. Read the value of the capacitor on thedisplay. The value. of capacity will be inmicrofarads if the LED in front of the µF

indicator is lit, or in picofarads if the LED in frontof the pF indicator is lit.

NOTE: Most capacitor values are displayedquickly, but extremely large electrolytic capacitors

4-26

Figure 4-30.—Sencore LC75 capacitor-inductor analyzer.26.365X

(over 50,000 µF) may take a few seconds to displaya reading. For example, a 50,000-µF capacitor willtake about 5 seconds before a reading is seen onthe digital readout, and a 100,000 µF electrolyticcapacitor may take 10 seconds. If the value doesnot appear in the time listed above, the capacitoris either shorted or quite leaky. In either case, itis probably defective.

Capacitor Leakage

Capacitors will often read the correct 2. Select the desired current range with thevalue but exhibit leakage that may affect LEAKAGE RANGE switch. Use the ALLtheir operation in the circuit. Any type of OTHER CAPACITORS (100 µA max) range forcapacitor may develop excessive leakage if most small electrolytics and for paper, mica, film,the capacitor is subjected to excessive applied and ceramic capacitors. Use the LARGE ALUM.voltage or high-voltage spikes. These types ELECTROLYTICS (10K µA max) range for largeof overloads may actually puncture the dielectric electrolytics. Consult the leakage charts on the

material and produce a short circuit or high-resistance leakage path. Leakage often shows uponly when the capacitor is charged to its normaloperating voltage and may not show up under alow-voltage check such as you might make withan ohmmeter. To check a capacitor for leakage,perform the following steps:

1. Connect the capacitor to be tested to thetest leads. If the capacitor is polarized, connectthe positive capacitor terminal to the red test leadand the negative terminal to the black test lead.

4-27

pullout tab under the analyzer (figs. 4-31 and 4-32) to the other range. You can switch ranges of theto determine which range should be used. LEAKAGE RANGE switch while holding theStart with the highest range (LARGE ALUM. LEAKAGE button in.ELECTROLYTICS) if you are not sure which 3. Select the normal dc working voltage of therange to use. If the display shows “000,” switch capacitor with the LEAKAGE VOLTAGE

Figure 4-31.—Capacitor leakage chart for dipped solid tantalum capacitors.26.X

4-28

Figure 4-32.—Capacitor leakage chart for standard aluminum electrolytic capacitors.26.X

4-29

switch. If the capacitor’s normal working voltagefalls between switch ranges, select the next lowerrange. For example, if the capacitor’s workingvoltage is 35 volts, select the 25-volt position ofthe LEAKAGE VOLTAGE switch.

4. Depress the LEAKAGE button and readthe amount of leakage current in microampereson the display. Capacitors take a certain amountof time to charge before a reading of the leakagecurrent is displayed. Consult the leakage chartson the pullout tab under the analyzer (figs. 4-31and 4-32) to determine which range should beused.

Ceramic, paper, film, and mica capacitorsshould not show any leakage at all. The maximumallowable leakage is below the sensitivity of themeasuring circuit. If any of these capacitorsexhibit leakage, they are defective.

Leakage measurements on nonpolarized elec-trolytics must be made in both directions. Simplymake the leakage test, note the leakage current,and then reverse the leads and make the leakagetest again. If both ends of the nonpolarizedelectrolytic are insulated from the case, themaximum allowable leakage is the same as listedin the leakage chart. If one end is connected tothe case, the allowable leakage is doubled.

Capacitor Dielectric Absorption

Dielectric absorption is the inability of acapacitor to discharge completely to zero. Thisis sometimes called battery action or capacitormemory and occurs because the dielectric of thecapacitor retains a charge. All capacitors havesome dielectric absorption, but electrolyticcapacitors have the highest amount, and it willoften affect circuit operation if it becomesexcessive. You can check electrolytics for dielectricabsorption during the normal test for capacitorvalue and leakage by simply rechecking the valueof the capacitor after the leakage test in thefollowing manner:

1. Connect the capacitor to the test leads andtest for the capacitor value in the normal manner.Note the value of the capacitor.

2. Test the capacitor for leakage at the ratedworking voltage of the capacitor. Allow theleakage current shown on the display to drop tothe maximum allowable leakage or below, asshown on the leakage chart in figures 4-31 or 4-32,depending on the type of capacitor.

4-30

3. Release the LEAKAGE button and allowthe display to drop to 000. Then immediatelydepress the VALUE button and note the capacitorreading.

a. If the capacity reading is within 5percent of the original value and the readingincreases slowly upward toward the original value,or if there is no difference in the readings, thecapacitor has little dielectric absorption and isgood.

b. If the value reading difference is greaterthan 5 percent but less than 15 percent, thecapacitor may require reforming as describedlater. Some of the dielectric oxide hasdeteriorated, and reforming the electrolytic maybring it back to a useful life. Recheck for dielectricabsorption after attempting to reform thecapacitor.

c. If the value reading difference is greaterthan 15 percent and the reading changes upwardrapidly toward the original value, the capacitorhas excessive dielectric absorption. Electrolyticcapacitors exhibiting this much dielectric absorp-tion may be reformed in some cases. If thecapacitor exhibits similar dielectric absorptionafter reforming has been attempted, it should bereplaced; otherwise, it will give trouble in thecircuit.

NOTE: If a mica or film type of capacitorshows any dielectric absorption, it can beconsidered bad and should be replaced.

Reforming of Electrolytic Capacitors

Aluminum electrolytics will often show lowvalue or high leakage if they have been sitting ona shelf for a long period of time. Generally, anyaluminum electrolytic capacitor sitting on the shelffor over 1 year will show one or both of thesecharacteristics. This is caused by a loss of someof the oxide coating that forms the dielectric ofthe capacitor. In many cases, the oxide coatingmay be reformed with the application of a dcvoltage for a period of time. The capacitor-inductor analyzer can reform the dielectricmaterial by using the same dc power supply thatis used for leakage testing. Reforming mayrequire more than an hour before the capacitorreturns to its normal condition. A TESTBUTTON HOLD-DOWN ROD is included with

the analyzer to hold the LEAKAGE button downfor reforming electrolytics.

1. Connect the electrolytic to be reformed tothe test leads observing polarity.

2. Select the proper voltage with theAPPLIED VOLTAGE switch.

3. Depress the LEAKAGE button and, whileholding the button in, place the hold-down rodon the button. Bring the meter carrying handleto the front of the meter and wedge the hold-downrod between the handle and the LEAKAGEbutton so that the rod holds the button depressed(fig. 4-33).

CAUTION

This method of holding the LEAKAGEbutton in provides a greater degree ofsafety than a “latching” type of switch.Always observe extreme caution when yousee the handle in front of the switches, asthis will tell you voltage is being appliedto the test leads and capacitor. Neverattempt to operate any other function pushbuttons when the hold-down rod is beingused.

4. After the capacitor has been reformed forat least 1 hour, let it discharge and sit for about30 minutes. Then recheck the value and theleakage to see if the reforming process hasimproved the capacitor.

26.366XFigure 4-33.—Application of the hold-down rod.

These are just a few of the tests that can beperformed with a capacitor analyzer. Consult theoperator’s manual for the ‘test equipment that youare operating for additional information.

TESTING INDUCTORS

An inductor is a device consisting of one ormore windings of wire with or without a magneticcore. Frequent causes of inductor coil failures areshorted turns, open turns, and changes in inductorvalue. Small power supply transformers aresimilar in construction to inductors and can betested with the capacitor-inductor analyzer shownin figure 4-30.

Inductors may be tested in the circuit, but thecircuit impedance will have some effect on thereadings. It is recommended that you remove theinductor or transformer from the circuit beforeyou perform any tests.

Inductor Value

Inductor coils can change in value. This maybe caused by overstressing the wire in the windingprocess. The wire may then relax after a periodof time. This changes its position and shape. Youmay also find coils that have been altered ininductance by a previous technician who spreador compressed the windings in an attempt tocorrect a faulty circuit.

Inductance value can be checked by perform-ing the following steps:

1. Balance out the inductance of the test leadsaccording to the operator’s manual instructions.

2. Connect the test leads to the coil ortransformer to be tested.

3. Depress the INDUCTORS VALUEbutton.

4. Read the value of inductance of the coil ortransformer on the digital display. The LED willlight in front of the µH if the value is inmicrohenrys or in front of the mH if the valueis in millihenrys.

NOTE: A reading of flashing 888 with asteady 0 indicates an open circuit. Recheck yourlead connections to ensure proper terminations.

Inductor Opens

Coils frequently open up. Occasionally, toomuch stress is put on the coil when it is wound.This may cause the wire to break. At other times,

4-31

the coil is stressed when it is placed in the circuit orremoved for testing. Coils can also open if a screw-driver or some other object accidently falls ormakes contact with the windings. Finally, the coilmay open if excessive current burns the wire open.

Open windings in coils are easily spottedwith the inductor analyzer. Just hook up theinstrument to check the inductance value. If thedisplay shows flashing 888 with a stationary 0,then the coil is open. Check the lead connectionsto the coil to be sure. If the coil is a small wiretype, be sure to check the fine wires that go tothe solder lugs on the coil form. The fine wire canbe broken easily from tension or extreme heat andcold variations.

On large transformers that have several taps orwindings in series, simply check them from top tobottom for an open. The actual open can be iso-lated by moving one lead down the series of tapsuntil the instrument gives an inductance reading.The tap above this point has the open winding.

Some coils above 10 µH may not show 10 ormore rings because of the nature of theconstruction or core material used in the coil.These may show eight or nine rings and still begood. The quality of these coils may be confirmedby adding a “shorted turn” and rechecking theringing of the coil. If the coil is bad, the numberof rings will not change or will change little,indicating the coil already has a shorted turn. Ifthe number of rings drops off drastically, thenthe coil is good. A good shorted turn can be madefrom a piece of solder wrapped around the coiltightly and twisted together at the ends. Smalldiameter wire or stranded wire does not give thesame effect and could give misleading results. Besure to use solder or a heavy-gauge solid wire forthe shorted turn.

To test the quality of a coil with the ringingtest:

1. Connect the test leads to the inductor tobe tested.

Inductor Ringing

The most common coil defect is a shorted turnor group of shorted turns. Shorted turns aregenerally caused by weak insulation that breaksdown under voltage. A circuit malfunction thatcauses excessive voltage across the coil can alsolead to shorted turns.

2. Depress the RINGING TEST button. Holdthe button down and rotate the IMPEDANCEMATCH switch through all six positions forregular inductors or through the last fourpositions for TV yokes and flybacks.

The ringing test allows you to determine if acoil (without an iron core) is good or bad withan accurate but easy-to-perform test of the qualityof Q factor. A good coil should show a readingof 10 rings or more on the digital display. A badcoil will show less than 10 ringing cycles.

3. If a reading of 10 or more appears on thedisplay in one or more positions of theIMPEDANCE MATCH switch, the inductor isgood. If a reading of less than 10 is displayed onall positions of the switch, the inductor isdefective.

The ringing test measures the Q factor byapplying a reference pulse to the coil and thendigitally counting the number of ringing cyclesproduced until the signal is damped to a presetlevel. A shorted turn in a coil will lower its Q andcause the ringing to dampen faster than in a goodcoil. An open coil will show no ringing.

If a continuously changing reading occurs,move the coil being tested to a location away fromthe source of ac radiation, and check theconnections to the coil. If you suspect that thecoil may be open or the leads may not beconnected properly, merely recheck the inductancevalue. If the readout shows a flashing 888 witha stationary 0, the coil is open or the leads arenot connected properly.

The ringing test should not be used on coilsand transformers having laminated iron cores,such as power transformers, audio outputtransformers, and filter chokes. The iron core inthese types of transformers and coils absorbs theringing energy of the coil and results in lowreadings that are unreliable.

Good coils below 10 µH in value may not ring10 cycles. The low inductance of these coilsgenerally allows only about two to four cycles.A comparison test should be made on a knowngood coil to see if the Q factor results are correct.

Coils and transformers that are shielded witha metal shield may not give a reading of good onthe ringing test. The metal shield may absorb theringing energy, depending on how close the shieldis to the coil. You should consider a shielded coilgood if it shows 10 or more rings. If the coil showsless than 10 rings in all positions of theIMPEDANCE MATCH switch, you should eitherremove the shield and repeat the test or make acomparison test on a known good shielded coil.For accurate results, be sure the coil is identicalto the one in the circuit being tested.

4-32

CHAPTER 5

POWER GENERATION AND DISTRIBUTION

As a Construction Electrician first class, youmay have the responsibility of supervising theinstallation, maintenance, and repair of mobileelectrical power (MEP) equipment. This equip-ment is portable and ranges. in size from 5kilowatts to 100 kilowatts. In time of war ornational emergency, advanced base functionalcomponents (ABFC) will normally be used attemporary overseas bases. Even in peacetime,MEP equipment may be used at remote bases.

At large, more permanent activities, you mayhave duties associated with the installation andoperation of large electrical power systems.

A power distribution system includes all partsof an electrical system between the power sourceand the customer’s service entrance. The powersource may be either a local generating plant ora high-voltage transmission line feeding asubstation that reduces the high voltage to avoltage suitable for local distribution. At mostadvanced bases, the source of power will begenerators connected directly to the load.

This chapter gives the correct procedures forthe operation and maintenance of power plantsand distribution systems and presents technicalinformation for the selection and installation ofpower-generating plants.

POWER GENERATION

The characteristics built into naval electricalinstallations are simplicity, ruggedness, reliability,and flexibility to permit continued service aftera part of the equipment has been damaged. It isthe function of those who operate these plants tomake full use of their inherent capabilities andto maintain, as far as possible, uninterruptedavailability of electrical power where it is needed.

To be able to do this, operating personnelshould possess the following:

• A thorough knowledge of how to operateand maintain the components of the electricalplant

5-1

A complete familiarity with the electricalplant as a whole

A comprehensive understanding of systemoperation

The ability to apply general electrical andelectronic principles to specific installations

A knowledge of a few simple rules ofsystem operation that are applicable to all navalinstallations

When you have finished studying this chapter,see if your capabilities for performing the abovefunctions haven’t improved.

GENERATOR SELECTION

When an overseas base is first established,electrical power is needed in a hurry; you will nothave time to set up a centrally located generatingstation. Instead, you will spot a portable plant ateach important location requiring power. Table 5-1

Table 5-1.—Types of Portable Generators

Frequency

Voltage 120 120/208

Phase 1 l & 3 3WiresFuelkW Rating

510153060

100200

Alternating current60-hertz

X

2G D

4*G

XXX

D

XXXXXX

120/208240/416

G4

D

X

XXXX

G-Gasoline driven. D-Diesel driven.*-Panel connections permit, at rated kW output: 120/208V

3-phase 4-wire, 120V 3-phase 3-wire, 120V single-phase2-wire, 120/240V single-phase 3-wire.

lists some of the standard alternating current (ac)generators available. These standard generatorsare capable of meeting the power requirementsof advanced bases. Representative 30-kilowatt and200-kilowatt generators are shown in figures 5-1and 5-2.

The electrical loads to be supplied-power,voltage, phase, frequency, and duty cyclerequirements-govern the selection of generatingequipment. Probable load deviation, probable lifeof the installation, availability of fuels, andavailability of skilled personnel are otherimportant factors.

Electrical plants at advanced bases serve avaried load of lighting, heating, and powerequipment, most of which demand power day andnight. The annual load factor (the ratio of averagepower to peak power) of a well-operated activebase should be 50 percent or more with a powerfactor (explained later in this chapter) of 80percent or higher. If the load is more than a fewhundred feet from the power source, a high-voltage distribution system is required.

If several generators are to serve primarydistribution systems, they should generate thesame voltage to avoid the need for voltagetransformation. The number of phases requiredby the load may differ from that produced by thegenerator. As loads can usually be divided andbalanced between phases, most generators ofappreciable size are wound for three-phaseoperation.

Figure 5-1.—30-kW portable generator.

Power and Voltage Requirements

The selection of voltage is affected by the size,character, and distribution of the load; length,capacity, and type of transmission and distribu-tion circuits; and size, location; and connectionof generators. Practically all general-purposelighting in the United States and at United Statesoverseas bases is 120 volts. The lighting voltagemay be obtained from a three-wire, 120/240-volt,single-phase circuit or a 120/208-volt, three-phase,four-wire circuit. Some small motors can besupplied by direct current (dc) or single-phase acat nominally 120 volts. Large three-phase, acmotors above 5 horsepower generally operatesatisfactorily at any voltage between 200 and 240.The general use of combined light and powercircuits increases the use of 240 and 208 volts forgeneral power application.

Computation of the Load

As mentioned earlier in this chapter, thereare various factors that must be taken intoconsideration in the selection of the requiredgenerating equipment. The following technicaldata will help you in computing the load.

Before any part of the system can be designed,the amount of power to be transmitted, or theelectrical load, must be determined. Electricalloads are generally measured in terms of amperes,kilowatts, or kilovolt-amperes. In general,electrical loads are seldom constant for anyappreciable time but fluctuate constantly. Incalculating the electrical load, you must determinethe connected load first. The connected load isthe sum of the rated capacities of all electricalappliances, lamps, motors, and so on, connectedto the wiring of the system. The maximumdemand load is the greatest value of all connectedloads that are in operation over a specified periodof time. Knowledge of the maximum demand ofgroups of loads is of great importance becauseit is the group maximum demand that determinesthe sizes of conductors and apparatus throughoutthe electrical system.

The ratio between the actual maximumdemand and the connected load is called theDEMAND FACTOR. If a group of loads wereall connected to the supply source and drew theirrated loads at the same time, the demand factorwould be 1.00. There are two main reasons whythe demand factor is usually less than 1.00. First,all load devices are seldom in use at the same timeand, even if they are, they will seldom reach

5-2

Figure 5-2.—200.kW portable generator.

maximum demand at the same time. Second,some load devices are usually slightly larger thanthe minimum size needed and normally draw lessthan their rated load. Since the maximum demandis one of the factors determining the size ofconductors, it is important that the demand factorbe established as closely as possible.

The demand factor varies considerably fordifferent types of loads and services. Demandfactors for military structures are given intable 5-2.

Example: A machine shop has a total con-nected load of 50.3 kilowatts. The demand factorfor this type of structure is taken at 0.70.The maximum demand is 50.3 × 0.70 = 35.21kilowatts.

Table 5-2.—Demand Factor

Structure Demand Factor

Housing . . . . . . . . . . . . . . . . . . . . . . . . . 0.9Aircraft maintenance facilities . . . . . . .7Operation facilities . . . . . . . . . . . . . . . . .8Administrative facilities . . . . . . . . . . . .8Shops . . . . . . . . . . . . . . . . . . . . . . . . . . . .7Warehouses . . . . . . . . . . . . . . . . . . . . . . .5Medical facilities . . . . . . . . . . . . . . . . . .8Theaters . . . . . . . . . . . . . . . . . . . . . . . . . .5NAV aids . . . . . . . . . . . . . . . . . . . . . . . . .7Laundry, ice plants, and bakeries. .. 1.0All others. . . . . . . . . . . . . . . . . . . . . . . . .9

5-3

The application of the demand factor indesigning electrical facilities is a major item inreducing initial costs. Knowing the demandfactors for various types of buildings andinstallations is also beneficial when existingfacilities are rearranged because increased servingcapacity is often not required, even though theconnected load is greatly increased. Similarly,increasing the size of feeder conductors becauseof a major load addition to the circuit may notbe required.

GENERATOR INSTALLATION

Generators are not permitted to be closer than25 feet to a load; however, in setting up thegenerator, try to place the equipment near pointsof large demand to reduce the size of wirerequired, to hold the line losses to a minimum,and to afford adequate voltage control at theremote ends of the lines.

Moving the generator may be accomplishedby lifting or pulling. The generator set comesequipped with a lifting sling usually stowed in theskid on the side of the unit opposite the operator’scontrol panel.

Site Selection

If you are to select the site upon which thegenerator is to be set up, study a plot or chart ofthe area on which the individual buildings andfacilities (demand) have been plotted. The site youselect should be large enough to meet present andanticipated needs. It should be level, dry, and welldrained. If this type of site is not available, placethe generator set on a suitable foundation and boltit down to minimize any unnecessary vibration.

Sheltering of Generators

Although advanced base portable generatorsare designed to be operated outdoors, prolongedexposure to wind, rain, and other adverseconditions will definitely shorten their lives. If thegenerators are to remain on the site for anyextended period of time, they should be mountedon solid concrete foundations and installed undersome type of shelter.

There are no predrawn plans for shelters fora small advanced base generating station. Theshelter will be an on-the-spot affair, the

construction of which is determined by theequipment and material on hand plus youringenuity, common sense, and ability to cooperatewith men in other ratings. Before a Builder canget started on the shelter, you will have to informhim of such things as the number of generatorsto be sheltered, the dimensions of the generators,the method of running the generator load cablesfrom the generator to the distribution systemoutside the building, and the arrangement of theexhaust system, radiator discharge, and coolingair.

Installation specifications are available inthe manufacturer’s instruction manual thataccompanies each unit. Be sure to use them.Appropriate consultation with the Builderregarding these specifications may help minimizevarious installation and piping problems andcosts.

The following hints and suggestions will alsobe helpful:

1. Ventilation is an important factor toconsider when you are installing the units insidea building. Every internal combustion engine isa HEAT engine. Although heat does the work,excess amounts of it must be removed if the engineis to function properly. This can be accomplishedby setting the radiator grill of the engine near anopening in the wall and providing another openingdirectly opposite the unit. In this manner, coolair can be drawn in and the hot air directedoutdoors. These openings can be shielded withadjustable louvers to prevent the entrance of rainor snow. In addition, when the engine is operatingin extremely cold weather, the temperature in theroom can be controlled by simply closing aportion of the discharge opening. Additionaldoors or windows should be provided in theshelter if the plants are installed in localities wherethe summer temperatures exceed 80°F at any time.

2. Working space is another consideration. Besure to provide sufficient space around each unitfor repairs or disassembly and for easy access tothe generator control panels.

3. The carbon monoxide gas present in theexhaust of the engine is extremely poisonous.Under no circumstances should it be allowed tocollect in a closed room. Therefore, means haveto be provided to discharge the exhaust of theengine to the outdoors. This is done by extendingthe exhaust pipe through the wall or roof of thebuilding. Support the exhaust pipe and makecertain that there is no obstruction and that there

5-4

are not too many right-angle bends. Also,whenever possible, arrange the exhaust system sothat the piping slopes away from the engine. Inthis way, condensation will not drain back intothe cylinders. If the exhaust pipe should have tobe installed so that loops or traps are necessary,a drain cock should be placed at the lowest pointof the system. All joints have to be perfectly tight,and where the exhaust pipe passes through thewall, you have to take care to prevent thedischarged gas from returning along the outsideof the pipe back into the building. Exhaust pipinginside the building has to be covered withinsulation capable of withstanding a temperatureof 1500°F.

After the generating units have been set inplace and bolted down, Builders can proceed toerect the building, using the necessary informationthey have been given.

Generator Set Inspection

After setting up a portable generator, yourcrew must do some preliminary work beforeplacing the generator in operation. First, theyshould make a visual overall inspection of thegenerator. Have them look for broken or looseelectrical connections, bolts, and cap screws, andsee that the ground plate is properly grounded.Check the wiring diagrams in the instructionmanual furnished with the generator to see if anywire connection is suspected of being improperlyconnected. If you find any faults, you shouldcorrect them immediately.

PRIME MOVER INSPECTION.—Servicingthe prime mover is the next step in the processof placing the generator in operation. Be sure thatthe crankcase is filled with the proper grade oflubricant. A lubrication chart in the instructionmanual furnished with each generator will showthe proper grade of oil to use according to theoperating temperature. If the plant is to beoperated in freezing temperatures, be sure touse an antifreeze solution in the proportionsrecommended in the instruction manual for thegenerator. The fuel tank should be filled withclean fuel oil, strained if necessary.

Some of the prime movers of advanced baseelectrical power generators are started by startingunits that obtain their power from batteries. Ifthe prime mover that you are installing is equipped

5-5

with a battery (or batteries), your crew has anotherservicing job to do. Batteries are usually shippedwithout the electrolyte but with the plates in adry-charged condition. Thus, it is necessary tofill the battery with electrolyte. Usually, theelectrolyte is shipped with the generator and is ofthe correct specific gravity. Because specificgravity of the electrolyte depends on the type ofbattery furnished with the generator, use thespecific gravity value recommended by themanufacturer’s instruction manual.

On large generators, you should check the areaventilation; the fan cover has to be opened andlatched in that position. Be sure there is no coveror obstruction over the radiator section. Thebypass shutters or doors may be closed to shortenthe warming-up period, and roof hatches and sidelouvers may be opened for additional ventilation,if required.

ALTERNATOR INSPECTION.—Just asimportant as the preparation of the prime moverare the inspection and servicing of the alternator.Generally, you should take the following steps:

1. Check all the electrical connections byreferring to the connection diagrams of thegenerator.

2. Megger the generator stator windings,generator rotor windings, exciter field windings,and exciter armature.

CAUTION

Do not exceed 500 volts dc for low-voltage generating sets.

3. Check all electrical connections fortightness.

4. Check that the collector rings are clean andhave a polished surface.

5. Check collector brushes to make sure theyhave no tendency to stick in the brush holders,that they are properly located, and that the pigtailswill not interfere with the brush rigging.

6. Check the collector brush pressure to seeif it agrees with the figure recommended in themanufacturer’s instruction manual. If technical

manuals are not available, a pressure of 2 to2 1/2 psi of brush contact surface is recommendedfor integral horsepower and integral kilowattmachines, and about twice that pressure forfractional horsepower and fractional kilowattmachines.

Generator Connections

When you install a power plant that has adual-voltage alternator unit, make certain that thestator coil leads are properly connected to producethe voltage required by the equipment.

Proper grounding is also a necessity forpersonnel safety and for prevention of unstable,fluctuating generator output.

INTERNAL LEADS.—Generators previouslyused for advanced base power requirementsrequired you to make reconnections in theammeter and voltmeter circuits when thegenerator output voltage was changed. Themajority of manufacturers have made provisionsthat simplify the changeover from one voltage

output to another. A newer type of changeoverboard is shown in figure 5-3.

The voltage changeover board permits recon-nection of the generator phase windings to giveall specified output voltages. One end of each coilof each phase winding runs from the generatorthrough an instrumentation and a static excitercurrent transformer to the reconnection panel.This assures current sensing in each phaseregardless of voltage connection at the recon-nection board assembly. The changeover boardassembly is equipped with a voltage change boardto facilitate conversion to 120/208 or 240/416generator output voltage. Positioning of thevoltage change board connects two coils of eachphase in series or in parallel. In parallel, theoutput is 120/208; in series, the output is 240/416volts ac. The terminals on the changeover boardassembly for connection to the generator loadsare numbered according to the particular coil endof each phase of the generator to ensure properconnections.

Remember that you are responsible forthe proper operation of the generating unit.

Figure 5-3.—Changeover panel.

5-6

Therefore, proceed with caution on any recon-nection job. Study the wiring diagrams of theplant and follow the manufacturer’s instructionsto the letter. Before you start the plant upand close the circuit breaker, double-check allconnections.

GROUNDING.—It is imperative that yousolidly ground all electrical generators operatingat 600 volts or less. The ground can be, in orderof preference, an underground metallic waterpiping system, a driven metal rod, or a buriedmetal plate. A ground rod has to have a minimumdiameter of 5/8 inch if solid and 3/4 inch if pipe,and it has to be driven to a minimum of 8 feet.A ground plate has to have a minimum of 2square feet and be buried at a minimum depthof 2 1/2 feet. For the ground lead, use No. 6AWG copper wire and bolt or clamp it to the rod,plate, or piping system. Connect the other end ofthe ground lead to the generator set ground stud.

The National Electric Code® states that asingle electrode consisting of a rod, pipe, or platethat does not have a resistance to ground of 25ohms or less shall be augmented by additionalelectrodes. Where multiple rod, pipe, or plateelectrodes are installed to meet the requirements,they are required to be not less than 6 feet apart.

It is recommended that you perform an earthresistance test with a Vibroground® Test Setbefore you connect the generator to ground. Thistest will determine the number of ground rodsrequired to meet the requirements, or it may benecessary to construct a ground grid.

Feeder Cable Connections

While the electric generator is being installedand serviced, a part of your crew can connect itto the load. Essentially, this consists of runningwire or cable from the generator to the load. Atthe load end, the cable is connected to thesubstation or to the distribution center. At thegenerator end, the cable is connected either to theoutput terminals of a main circuit breaker or aload terminal board. Before the wires are run andconnections are made, it will be up to you to dothe following:

1. Determine the correct size of wire or cableto use.

2. Decide whether the wire or cable will beburied or carried overhead on poles.

3. Check the generator lead connections of theplant to see that they are arranged for the propervoltage output.

The information contained in the followingparagraphs will help you in these tasks.

CABLE SELECTION.—If the wrong sizeconductor is used in the load cable, varioustroubles may occur. If the conductor is too smallto carry the current demanded by the load, it willheat up and possibly cause a fire or a break inthe circuit. Even though the conductor is largeenough to carry the load current safely, its lengthmight result in a lumped resistance that producesan excessive voltage drop. An excessive voltagedrop results in a reduced voltage at the load end.This reduced voltage is incapable of operating theequipment safely. In this respect, it might be wellto point out the voltage drop should not exceed3 percent for power loads and 3 percent forlighting loads or 3 percent for combined powerand lighting loads.

Select a feeder conductor capable of carrying150 percent of rated generator amperes toeliminate overloading and voltage drop problems.Refer to tables 5-3 and 5-4 to select the propercable to carry the computed capacity accordingto insulation class.

CABLE INSTALLATION.—The load cablemay be installed overhead or underground. In anemergency installation, time is the importantfactor. It may be necessary to use trees, pilings,four-by-fours or other temporary line supportsto complete the installation. Such measures aretemporary; eventually, you will have to erect polesand string the wire on crossarms or bury itunderground. If the installation is near an airfield,it may be necessary to place the wires undergroundat the beginning. Wire placed underground shouldbe direct-burial, rubber-jacketed cable; otherwise,it will not last long.

Direct burying of cable for permanentinstallation calls for a few simple precautions toensure uninterrupted service. They are as follows:

1. Dig the trench deep enough so that thecable can be buried at least 18 inches (24 inchesin traffic areas and under roadways) below thesurface of the ground to prevent disturbance ofthe cable by frost or subsequent surface digging.

5-7

Tab

le 5

-4.—

Am

paci

ties

of

Insu

late

d C

ondu

ctor

s F

ree

Air

Tab

le 5

-3.—

Am

paci

ties

of

Insu

late

d C

ondu

ctor

s

Rep

rint

ed w

ith

perm

issi

on f

rom

NP

FA

70-

1990

, th

e N

atio

nal

Ele

ctri

cal

Cod

e®R

epri

nted

wit

h pe

rmis

sion

fro

m N

PF

A 7

0-19

90, t

he N

atio

nal

Ele

ctri

cal

Cod

e®,

Cop

yrig

ht©19

89,

Nat

iona

l F

ire

Pro

tect

ion

Ass

ocia

tion,

Qui

ncy,

MA

022

69.

This

Cop

yrig

ht©19

89,

Nat

iona

l F

ire

Pro

tect

ion

Ass

ocia

tion,

Qui

ncy,

MA

022

69.

This

repr

inte

d m

ater

ial

is n

ot t

he c

ompl

ete

and

offi

cial

pos

itio

n of

the

Nat

iona

l F

ire

repr

inte

d m

ater

ial

is n

ot t

he c

ompl

ete

and

offi

cial

pos

itio

n of

the

Nat

iona

l F

ire

Pro

tect

ion

Ass

ocia

tion,

on

the

refe

renc

ed s

ubje

ct w

hich

is

repr

esen

ted

only

by

the

Pro

tect

ion

Ass

ocia

tion,

on

the

refe

renc

ed s

ubje

ct w

hich

is

repr

esen

ted

only

by

the

stan

dard

in it

s en

tiret

y.st

anda

rd in

its

entir

ety.

26.X

26.X

Not

es t

o T

able

s 5-

3 an

d 5-

41.

Exp

lana

tion

of

Tab

les.

For

exp

lana

tion

of

Typ

e L

ette

rs,

and

for

reco

gniz

ed s

ize

ofco

nduc

tors

fo

r th

e va

riou

s co

nduc

tor

insu

lati

ons,

se

e S

ecti

on

310-

13.

for

inst

alla

tion

requ

irem

ents

, se

e S

ecti

ons

310-

1 th

roug

h 31

0-10

, an

d th

e va

riou

s ar

ticl

es o

f th

is C

ode.

For

flex

ible

cor

ds,

see

Tab

les

400-

4, 4

00-5

(A),

and

400

-5(B

).3.

120

/240

Vol

ts,

3-W

ire,

Sin

gle-

Pha

se D

wel

ling

Serv

ices

. In

dw

elli

ng u

nits

, co

nduc

tors

,as

lis

ted

belo

w,

shal

l be

per

mit

ted

to b

e ut

iliz

ed a

s 12

0/24

0-vo

lt,

3-w

ire,

sin

gle-

phas

e se

rvic

e-en

tran

ce c

ondu

ctor

s an

d fe

eder

con

duct

ors

in r

acew

ay o

r ca

ble

wit

h or

wit

hout

an

equi

pmen

tgr

ound

ing

cond

ucto

r. T

he g

roun

ded

cond

ucto

r sh

all

be p

erm

itte

d to

be

not

mor

e th

an t

wo

AW

G s

izes

sm

alle

r th

an t

he u

ngro

unde

d co

nduc

tors

for

app

lica

tion

of

this

not

e, p

rovi

ded

the

requ

irem

ents

of

Sec

tion

s 21

5-2,

220

-22,

and

230

-42

are

met

.

Con

duct

or T

ypes

and

Siz

esR

H-R

HH

-RH

W-T

HH

W-T

HW

-TH

WN

-TH

HN

-XH

HW

-USE

Con

ner

Alu

min

um a

ndSe

rvic

eC

onne

r-C

lad

AL

Rat

ing

in A

mps

AW

G4 3 2 1 1/0

2/0

3/0

4/0

250

kcm

il35

0 kc

mil

400

kcm

il

AW

G2 1 1/0

2/0

3/0

4/0

250

kcm

il30

0 kc

mil

350

kcm

il50

0 kc

mil

600

kcm

il

100

110

125

150

175

200

225

250

300

350

400

5. B

are

Con

duct

ors.

Whe

re b

are

cond

ucto

rs a

re u

sed

wit

h in

sula

ted

cond

ucto

rs,

thei

ral

low

able

am

paci

ties

sha

ll b

e li

mit

ed t

o th

at p

erm

itte

d fo

r th

e ad

jace

nt i

nsul

ated

con

duct

ors.

6. M

iner

al-I

nsul

ated

, M

etal

-She

athe

d C

able

. T

he t

empe

ratu

re l

imit

atio

n on

whi

ch t

heam

paci

ties

of

min

eral

-ins

ulat

ed,

met

al-s

heat

hed

cabl

e ar

e ba

sed

is d

eter

min

ed b

y th

e in

sula

ting

mat

eria

ls

used

in

th

e en

d se

al.

Ter

min

atio

n fi

ttin

gs

inco

rpor

atin

g un

impr

egna

ted,

or

gani

c,in

sula

ting

m

ater

ials

ar

e li

mit

ed

to

90°C

(1

94°F

) op

erat

ion.

7. T

ype

MT

W M

achi

ne T

ool

Wir

e.(F

PN

): F

or t

he a

mpa

citi

es o

f T

ype

MT

W w

ire,

see

Tab

le 1

3-5(

a) i

n th

e E

lect

rica

l S

tand

ard

for

Indu

stri

al

Mac

hine

ry,

NF

PA

79

-198

7.8.

Am

paci

ty A

djus

tmen

t F

acto

rs.

(a)

Mor

e th

an T

hree

Con

duct

ors

in a

Rac

eway

or

Cab

le.

Whe

re t

he n

umbe

r of

cond

ucto

rs i

n a

race

way

or

cabl

e ex

ceed

s th

ree,

the

am

paci

ties

sha

ll b

e re

duce

d as

sho

wn

inth

e fo

llow

ing

tabl

e:

Num

ber

ofC

ondu

ctor

s4

thro

ugh

67

thro

ugh

910

thr

ough

24*

25 t

hrou

gh 4

2*43

and

abo

ve*

Col

umn

AP

erce

nt o

f V

alue

s in

Tab

les

as A

djus

ted

for

Am

bien

t T

empe

ratu

reif

Nec

essa

ry80 70 70 60 50

Num

ber

ofC

ondu

ctor

s4

thro

ugh

67

thro

ugh

910

thr

ough

20

21 t

hrou

gh 3

031

thr

ough

40

41 t

hrou

gh 6

0

Col

umn

B**

Per

cent

of

Val

ues

inT

able

s as

Adj

uste

d fo

rA

mbi

ent

Tem

pera

ture

if N

eces

sary

80 70 50 45 40 35*T

hese

fac

tors

incl

ude

the

effe

cts

of a

load

div

ersi

ty o

f 50

per

cent

.**

No

dive

rsity

.

(FP

N):

Col

umn

A i

s ba

sed

on t

he f

ollo

win

g fo

rmul

a:

A2

=√

0.5

N×

(A

1) w

here

EA

1 =

Tab

le a

mpa

city

mul

tipl

ied

by f

acto

r fr

om N

ote

8(a)

N =

Tot

al n

umbe

r of

con

duct

ors

used

to

obta

in f

acto

r fr

om N

ote

8(a)

E =

Des

ired

num

ber

of e

nerg

ized

con

duct

ors

A2

=

Am

paci

ty

lim

it

for

ener

gize

d co

nduc

tors

Whe

re s

ingl

e co

nduc

tors

or

mul

tico

nduc

tor

cabl

es a

re s

tack

ed o

r bu

ndle

d lo

nger

tha

n 24

inch

es (

610

mm

) w

itho

ut m

aint

aini

ng s

paci

ng a

nd a

re n

ot i

nsta

lled

in

race

way

s, t

he a

mpa

city

of e

ach

cond

ucto

r sh

all

be r

educ

ed a

s sh

own

in t

he a

bove

tab

le.

Exc

epti

on N

o. 1

: W

hen

cond

ucto

rs o

f di

ffer

ent

syst

ems,

as

prov

ided

in

Sect

ion

300-

3,ar

e in

stal

led

in a

com

mon

rac

eway

or

cabl

e th

e de

rati

ng f

acto

rs s

how

n ab

ove

shal

l ap

ply

toth

e nu

mbe

r of

pow

er a

nd l

ight

ing

(Art

icle

s 21

0, 2

15,

220,

and

230

) co

nduc

tors

onl

y.E

xcep

tion

No.

2:

For

con

duct

ors

inst

alle

d in

cab

le t

rays

, th

e pr

ovis

ions

of

Sect

ion

318-

11sh

all

appl

y.E

xcep

tion

No.

3:

Der

atin

g fa

ctor

s ah

all

not

appl

y to

con

duct

ors

in n

ippl

es h

avin

g a

leng

thno

t ex

ceed

ing

24 i

nche

s (6

10 m

m).

Exc

epti

on

No.

4:

D

erat

ing

fact

ors

shal

l no

t ap

ply

to

unde

rgro

und

cond

ucto

rs

ente

ring

or l

eavi

ng a

n ou

tdoo

r tr

ench

if

thos

e co

nduc

tors

hav

e ph

ysic

al p

rote

ctio

n in

the

for

m o

f ri

gid

met

al c

ondu

it,

inte

rmed

iate

met

al c

ondu

it o

r ri

gid

nonm

etal

lic

cond

uit

havi

ng a

len

gth

not

exce

edin

g 10

fee

t (3

.05

m)

abov

e gr

ade

and

the

num

ber

of c

ondu

ctor

s do

es n

ot e

xcee

d 4.

(b)

Mor

e th

an O

ne C

ondu

it,

Tub

e, o

r R

acew

ay.

Spa

cing

bet

wee

n co

ndui

ts,

tubi

ng,

or r

acew

ays

shal

l be

mai

ntai

ned.

9. O

verc

urre

nt P

rote

ctio

n. W

here

the

sta

ndar

d ra

ting

s an

d se

ttin

gs o

f ov

ercu

rren

t de

vice

sdo

not

cor

resp

ond

wit

h th

e ra

ting

s an

d se

ttin

gs a

llow

ed f

or c

ondu

ctor

s, t

he n

ext

high

er s

tand

ard

rati

ng

and

sett

ing

shal

l be

pe

rmit

ted.

Exc

epti

on:

As

lim

ited

in

Se

ctio

n 24

0-3.

10.

Neu

tral

Con

duct

or.

(a)

A n

eutr

al c

ondu

ctor

whi

ch c

arri

es o

nly

the

unba

lanc

ed c

urre

nt f

rom

oth

erco

nduc

tors

, as

in

the

case

of

norm

ally

bal

ance

d ci

rcui

ts o

f th

ree

or m

ore

cond

ucto

rs,

shal

lno

t be

cou

nted

whe

n ap

plyi

ng t

he p

rovi

sion

s of

Not

e 8.

(b)

In a

3-w

ire

circ

uit

cons

isti

ng o

f 2-

phas

e w

ires

and

the

neu

tral

of

a 4-

wir

e, 3

-pha

sew

ye-c

onne

cted

sys

tem

, a

com

mon

con

duct

or c

arri

es a

ppro

xim

atel

y th

e sa

me

curr

ent

as t

heot

her

cond

ucto

rs a

nd s

hall

be

coun

ted

whe

n ap

plyi

ng t

he p

rovi

sion

s of

Not

e 8.

(c)

On

a 4-

wir

e, 3

-pha

se w

ye c

ircu

it w

here

the

maj

or p

orti

on o

f th

e lo

ad c

onsi

sts

of e

lect

ric-

disc

harg

e li

ghti

ng,

data

pro

cess

ing,

or

sim

ilar

equ

ipm

ent,

ther

e ar

e ha

rmon

ic c

urre

nts

pres

ent

in t

he n

eutr

al c

ondu

ctor

and

the

neu

tral

sha

ll b

e co

nsid

ered

to

be a

cur

rent

-car

ryin

gco

nduc

tor.

11.

Gro

undi

ng o

r B

ondi

ng C

ondu

ctor

. A

gro

undi

ng o

r bo

ndin

g co

nduc

tor

shal

l no

t be

coun

ted

whe

n ap

plyi

ng t

he p

rovi

sion

s of

Not

e 8.

†Unl

ess

othe

rwis

e sp

ecif

ical

ly p

erm

itte

d el

sew

here

in

this

Cod

e, t

he o

verc

urre

nt p

rote

ctio

nfo

r co

nduc

tor

type

s m

arke

d w

ith

an o

beli

sk (

†) s

hall

not

exc

eed

15 a

mpe

res

for

14 A

WG

.20

am

pere

s fo

r 12

AW

G,

and

30 a

mpe

res

for

10 A

WG

cop

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2. Lay the cable over a sand cushion (fig. 5-4).If this is impractical, loosen the trench base soit is cleared of rocks and stones.

3. Space the cables on 6-inch centers forfurther mechanical and electrical protection.

4. After laying the cable and before back-filling, cover it with earth free from stones, rocks,and so forth. This will prevent the cable frombeing damaged in the event the surrounding earthis disturbed by flooding or frost heaving.

GENERATING PLANT OPERATIONS

When you are in charge of a generatingstation, you will be responsible for schedulingaround-the-clock watches to ensure a continuousand adequate amount of electrical power.Depending on the number of operating personnelavailable, the watches are evenly divided over the24-hour period. It is common practice to schedule6-hour watches, or they may be stretched to8-hour watches without working undue hardshipon the part of the crew members. Watchesexceeding 8 hours, however, should be avoidedunless emergency conditions dictate their use.

The duties assigned to the personnel ongenerator watches can be grouped into threemain categories: (1) operating the equipment,(2) maintaining the equipment, and (3) keepingthe daily operating log. Operating and maintain-ing the generating equipment will be covered inthe succeeding sections of this chapter, so for thepresent you can concentrate on the importanceof the third duty of the station operator-keepinga daily operating log.

Figure 5-4.—Direct burial of cable.

The number of operating hours are recordedin the generating station log. The log serves as abasis for determining when a particular piece ofelectrical equipment is ready for inspection andmaintenance. The station log can be used inconjunction with previous logs to spot gradualchanges in equipment condition that ordinarilyare difficult to detect in day-to-day operation. Itis particularly important that you impress uponyour watch standers the necessity for takingaccurate readings at periods specified by localoperating conditions.

Ensure that watch standers keep theirspaces clean and orderly. Impress on themthe importance of keeping tools and auxiliaryequipment in their proper places when not in use.Store clean waste and oily waste in separatecontainers. OILY WASTE CONTAINERS AREREQUIRED TO BE KEPT COVERED. Emptyoily waste containers at least once a day to reducefire hazards. Care given the station floor will begoverned by its composition. Generally, it shouldbe swept down each watch. Any oil or grease thatis tracked around the floor should be removed atonce.

Plant Equipment

Setting up a power generator is only one phaseof your job. After the plant is set up and readyto go, you will be expected to supervise theactivities of the operating personnel of thegenerating station. In this respect, your super-vision should be directed toward one ultimategoal-to maintain a continuous and adequateflow of electrical power to meet the demand. Thiscan be accomplished if you have a thoroughknowledge of how to operate and maintain theequipment and a complete understanding of thestation’s electrical systems as a whole. Obviously,a thorough knowledge of how to operate andmaintain the specific equipment found in thegenerating station to which you are assignedcannot be covered here. However, generalinformation can be given. It will be up to you tosupplement this information with the specificinstructions given in the manufacturer’s instruc-tion manuals furnished with each piece ofequipment.

Figure 5-5 is a diagram of the auxiliaryequipment required by a diesel engine. It showsthe fuel oil system; the lube oil system piping,cooling, and centrifuge; the cooling water system;and the air-starting system piping.

5-10

Figure 5-5.—Piping diagram of diesel engine generator and equipment.

Similarly, familiarity with the station’selectrical system as a whole can be gained onlyby a study of information relating specifically tothat installation. This information can be foundto some extent in the manufacturer’s instructionmanuals. You can obtain the greater part of itfrom the station’s electrical plans and wiringdiagrams. Remember, however, to supplementyour study of the electrical plans and diagramswith an actual study of the generating station’ssystem. In that way, the generators, switchgear,cables, and other electrical equipment are notmerely symbols on a plan but physical objectswhose location is definitely known and whosefunctions and relation to the rest of the systemare thoroughly understood.

Single Plant Operation

Connecting an electric plant to a de-energizedbus involves two general phases: (1) starting thediesel engine and bringing it up to rated speedunder control of the governor and (2) operating

the switchboard controls to bring the power ofthe generator onto the bus.

Different manufacturers of generating plantsrequire the operator to perform a multitude ofsteps before starting the prime mover. Forexample, if a diesel engine is started bycompressed air, the operator would have to alignthe compressed air system. This would not benecessary if the engine is of the electric-start type.It’s important that you, as the plant supervisor,establish a prestart checklist for each generatingplant. The prestart checklist provides a methodicalprocedure for confirming the operational con-figuration of the generating plant; following thisprocedure assures that all systems and controlsare properly aligned for operation.

The checklist should include, but is not limitedto, the following:

1. Align ventilation louvers.2. Check lube oil, fuel oil, and cooling water

levels.

5-11

3. Ensure battery bank is fully charged.4. Align electrical breakers and switches for

proper operation of auxiliary equipment.5. Check control panel and engine controls.6. Select the proper operating position for the

following controls for single plant operation.

Voltage regulator switch to UNIT orSINGLE position.

Governor switch to ISOCHRONOUSor SINGLE position. NOTE: Adjusthydraulic governor droop position to 0.

Voltage regulator control switch toAUTO position.

The prestart checklist should be completedin sequence before you attempt to start thegenerating plant.

Start the generating plant and adjust enginerpm to synchronous speed. Adjust the voltageregulator to obtain the correct operating voltage.Set the synchronizing switch to the ON positionand close the main circuit breaker. Adjust thefrequency to 60 hertz with the governor controlswitch. Perform hourly operational checks todetect abnormal conditions and to ensure thegenerating set is operating at the correct voltageand frequency.

Parallel Plant Operation

If the load of a single generator becomes solarge that its rating is exceeded, it becomesnecessary to add another generator in parallel toincrease the power available for the generat-ing station. Before two ac generators can beparalleled, the following conditions have to befulfilled:

1. Their terminal voltages have to be equal.2. Their frequencies have to be equal.3. Their voltages have to be in phase.

When two generators are operating so that therequirements are satisfied, they are said tobe in synchronism. The operation of getting themachines into synchronism is called synchro-nizing.

Generating plants may be operated in parallelon an isolated bus (two or more generatorssupplying camp or base load) or on an infinitebus (one or more generators paralleled to a utilitygrid).

One of the primary considerations inparalleling generator sets is achieving the properdivision of load. This can be accomplished byproviding the governor of the generator withspeed droop. This would result in a regulation ofthe system. The relationship of REGULATIONto LOAD DIVISION is best explained byreferring to a speed versus load curve of thegovernor. For simplicity, we will refer to thenormal speed as 100 percent speed and full loadas 100 percent load. In the controlled system, wewill be concerned with two types of governoroperations: isochronous and speed droop.

The operation of the isochronous governor(0 percent speed droop) can be explained bycomparing speed versus load, as shown in figure5-6. If the governor were set to maintain the speedrepresented by line A and connected to anincreasing isolated load, the speed would remainconstant. The isochronous governor will maintainthe desired output frequency regardless of loadchanges if the capacity of the engine is notexceeded.

The speed droop governor (100 percent speeddroop) has a similar set of curves, but they areslanted, as shown in figure 5-7. If a speed droopgovernor were connected to an increasing isolatedload, the speed would drop (line A, fig. 5-7) untilmaximum engine capacity is reached.

Now let’s imagine that we connect the speeddroop governor (slave machine) to a utility busso large that our engine cannot change the busfrequency (an infinite bus). Remember that thespeed of the engine is no longer determined bythe speed setting but by the frequency of the

5-12

Figure 5-6.—Isochronous governor curve.

Figure 5-7.—Speed droop governor curve.

infinite bus. In this case, if we should change thespeed setting, we would cause a change in load,not in speed. To parallel the generator set, weare required to have a speed setting on line A(fig. 5-7), at which the no-load speed is equal tothe bus frequency. Once the set is paralleled, ifwe increase the speed setting to line B, we do notchange the speed, but we pick up approximatelya half-load. Another increase in speed setting toline C will fully load the engine. If the generatorset is fully loaded and the main breaker is opened,the no-load speed would be 4 percent abovesynchronous speed. This governor would bedefined as having 4 percent speed droop.

Paralleling an isochronous governor to aninfinite bus would be impractical because anydifference in speed setting would cause thegenerator load to change constantly. A speedsetting slightly higher than the bus frequencywould cause the engine to go to full-load position.Similarly, if the speed setting were slightlybelow synchronous speed, the engine would goto no-load position.

Setting speed droop on hydraulic governorsis accomplished by adjusting the speed droopknob located on the governor body. Setting theknob to position No. 5 does not mean 5 percentdroop. Each of the settings on the knob representsa percentage of the total governor droop. If thegovernor has a maximum of 4 percent droop, theNo. 5 position would be 50 percent of 4 percentdroop. Setting speed droops on solid-stateelectronic governors is accomplished by placing

the UNIT-PARALLEL switch in the PARALLELposition. The governor speed droop is factory set,and no further adjustments are necessary.

ISOLATED BUS OPERATION.—In thefollowing discussion, assume that one generator,called the master machine, is operating and thata second generator, called the slave machine, isbeing synchronized to the master machine.Governor controls on the master generator shouldbe set to the ISOCHRONOUS or UNIT position.The governor setting on the slave generator mustbe set to the PARALLEL position.

NOTE: The hydraulic governor droop settingis an approximate value. Setting the knob toposition No. 5 will allow you to parallel and loadthe generator set. Minor adjustments may benecessary to prevent load swings after the unit isoperational.

When paralleling in the droop mode withother generator sets, the governor of only one setmay be in the isochronous position; all others arein the droop position. The isochronous set (usuallythe largest capacity set) controls system frequencyand immediately responds to system load changes.The droop generator sets carry only the loadplaced on them by the setting of their individualspeed controls. Both voltage regulators should beset for parallel and automatic operation.

The slave machine is brought up to the desiredfrequency by operating the governor controls. Itis preferable to have the frequency of the slavemachine slightly higher than that of the mastermachine to assure that the slave machine willassume a small amount of load when the maincircuit breaker is closed. Adjust the voltagecontrols on the slave machine until the voltage isidentical to that of the master machine. Thus, twoof the requirements for synchronizing have beenmet: frequencies are equal and terminal voltagesare equal.

There are several methods to check generatorphase sequence. Some generator sets are equippedwith phase sequence indicator lights and a selectorswitch labeled “GEN” and “BUS.” Set thePHASE SEQUENCE SELECTOR SWITCH inthe BUS position, and the “1-2-3” phase sequenceindicating light should light. (The same light mustlight in either GEN or BUS position.) If “3-2-1”phase sequence is indicated, the slave machine hasto be shut down, the load cables isolated, and twoof the load cables interchanged at their connectionto the load terminals.

5-13

Another method to verify correct phasesequence is by using the synchronizing lights.When the synchronizing switch is turned on, thesynchronizing lights will start blinking. If thesynchronizing lights blink on simultaneously andoff simultaneously, the voltage sequences of thetwo machines are in phase. The frequency atwhich the synchronizing lights blink on and offtogether indicates the different frequency outputbetween the two machines. Raise or lower thespeed of the slave machine until the lights blinkon together and off together at the slowestpossible rate. If the synchronizing lights arealternately blinking (one on while the other is off),the voltage sequence of the two machines is notin phase. Correct this condition by interchangingany two of the three load cables connected to theslave machine.

Some of the portable generators being placedin the NMCB TOA are equipped with a permissiveparalleling relay. This relay, wired into the mainbreaker control circuit, prevents the operator fromparalleling the generator until all three conditionshave been met.

Now that all three paralleling requirementshave been met, the slave machine can be paralleledand loaded.

If a synchroscope is used, adjust the frequencyof the slave machine until the synchroscopepointer rotates clockwise slowly through the zeroposition (twelve o’clock). Close the main circuitbreaker just before the pointer passes through thezero position. To parallel using sychronizinglights, wait until the lamps are dark; then, whilethe lamps are still dark, close the main circuitbreaker and turn off the synchronizing switch.

After the main breaker has been closed, checkand adjust the load distribution by adjusting thegovernor speed control. Maintain approximatelyone-half load on the master machine by manuallyadding or removing the load from the slavemachine(s). The master machine will absorb allload changes and maintain correct frequencyunless it becomes overloaded or until its load isreduced to zero.

The operator must also ensure that allgenerating sets operate at approximately the samepower factor (PF). PF is a ratio, or percentage,relationship between watts (true power) of a loadand the product of volts and amperes (apparentpower) necessary to supply the load. PF is usuallyexpressed as a percentage of 100. Inductivereactance in a circuit lowers the PF by causingthe current to lag behind the voltage. Low PFscan be corrected by adding capacitor banks to the

circuit. This procedure will be discussed in the“Power Distribution” section of this chapter.

Since the inductive reactance cannot bechanged at this point, the voltage control rheostathas to be adjusted on each generator to share thereactive load. This adjustment has a direct impacton the generator current, thus reducing thepossibility of overheating the generator windings.

PF adjustment was not discussed in the“Single Plant Operation” section because a singlegenerator has to supply any true power and/orreactive load that may be in the circuit. The singlegenerator must supply the correct voltage andfrequency regardless of the power factor.

INFINITE BUS OPERATION.—Parallelinggenerator sets to an infinite bus is similar to theisolated bus procedure with the exception that allsets will be slave machines. The infinite busestablishes the grid frequency; therefore, thegovernor of each slave machine has to have speeddroop to prevent constant load changes.

Emergency Shutdown

In the event of engine overspeed, high jacketwater temperature, or low lubricating oil pressure,the engine may be shut down automatically anddisconnected from the main load by tripping themain circuit breaker. In addition, an indicatormay light or an alarm may sound to indicate thecause of shutdown. After an emergency shutdownand before the engine is returned to operation,the cause of shutdown should be investigated andcorrected.

NOTE: It is important to check the safetycontrols at regular intervals to determine that theyare in good working order.

Basic Operating Precautions

The order that you post in the station for theguidance of the watch standers should include ageneral list of operating rules and electrical safetyprecautions. BE SURE YOU ENFORCE THEM!

The important operating rules are relativelyfew and simple. They are as follows:

1. Watch the switchboard instruments. Theyshow how the system is operating and reveal

5-14

overloads, improper division of kilowatt load orof reactive current between generators operatingin parallel, and other abnormal operatingconditions.

2. Keep the frequency and voltage at theircorrect values. A variation from either will affect,to some extent at least, the operation of theelectrical equipment of the base. This is’ especiallytrue of such equipment as teletypewriters orelectrical clocks. An electrical clock and anaccurate mechanical clock should be installedtogether at the generating station so that theoperators can keep the generators on frequency.

3. USE GOOD JUDGMENT WHEN RE-CLOSING CIRCUIT BREAKERS AFTERTHEY HAVE TRIPPED AUTOMATICALLY.For example, generally the cause should beinvestigated if the circuit breaker trips immediatelyafter the first reclosure. However, reclosing of thebreaker the second time may be warranted ifimmediate restoration of power is necessary andthere was no excessive interrupting disturbancewhen the breaker tripped. It should be kept inmind, however, that repeated closing and trippingmay damage the circuit breaker and thus increasethe repair or replacement work.

4. Don’t start a plant unless all its switchesand breakers are open and all external resistanceis in the exciter field circuit.

5. Don’t operate generators at continuousoverload. Record the magnitude and duration ofthe overload in the log; record any unusualconditions or temperatures observed.

6. Don’t continue to operate a machine inwhich there is vibration until the cause is foundand corrected. Record the cause in the log.

The electrical safety precautions that shouldbe observed by the station personnel are asfollows:

1. Treat every circuit, including those as lowas 24 volts, as a potential source of danger.

2. Except in cases of emergency, never allowwork on an energized circuit. Take every care toinsulate the person performing the work fromground. This may be done by covering anyadjacent grounded metal with insulating rubberblankets. In addition, provide ample illumination;

cover working metal tools with insulating rubber;station men at appropriate circuit breakersor switches so that the switchboard can bede-energized immediately in case of emergency;and make available a person qualified to renderfirst aid for electric shock.

POWER PLANT MAINTENANCE

Inspection and servicing procedures coveredin this chapter are rather general. In most cases,they can be applied to any electrical powergenerator that you install. You realize, of course,that there are other special installation detailswhich pertain only to the particular generator youhappen to be working on. Because of the manydifferent types of generators, certain instructionsare applicable only to specific types of generators.Therefore, you should consult the manufacturer’sinstruction manuals for these details.

Power plant maintenance can be divided intotwo general categories: operator maintenance andpreventive maintenance.

Operator Maintenance

Operator maintenance includes the hourly,daily, and weekly maintenance requirementsrecommended in the manufacturer’s literature.Some operator maintenance and routine checksinclude the following:

Bring oil level to the high mark on the dipstick.

Free movement of ventilation louvers.

Drain water and sediment from strainers andfilters.

Maintain level of coolant.

Check radiator and coolant hoses for leaks.

Check battery electrolyte level.

Check all switches for proper operation.

Drain water from fuel tank.

Fill fuel tank as required with appropriatediesel fuel.

5-15

Check fuel tank for leaks.

Log all operator maintenance in the operationslog book when it is completed.

Preventive Maintenance

Preventive maintenance includes the monthly,quarterly, semiannual, and annual maintenancechecks recommended in the manufacturer’sliterature. The maintenance supervisor is responsi-ble for establishing a maintenance schedule toensure the preventive maintenance is performed.A maintenance log book should be established foreach generator plant and all maintenance checksrecorded. The operations log book should bereviewed periodically to ensure that all preventivemaintenance recommended by engine operatinghours is scheduled. For example, the schedule ofengine lube oil and filter replacement is normallybased on hours of operation.

POWER DISTRIBUTION

A power distribution system includes all of thegenerating plants, transmission lines, substations,feeders, primary mains, distribution transformers,and secondary mains necessary to supply powerfrom the generating plant to the load. Figure 5-8shows the basic components of a distributionsystem and the relationship of one component toanother.

A power distribution system may be either anoverhead distribution line or an undergroundcable system. In most Navy installations, theoverhead system is used, but in the vicinity ofairports or landing strips, it may be necessary toinstall an underground system. This chapter willdiscuss mainly the overhead distribution system.

An overhead distribution system can usuallybe installed and maintained more cheaply thanan underground system. Also, for equivalentconductor size, an overhead system has highercurrent capacity and offers greater flexibility withregard to changes in circuits and taps than anunderground system. Overhead distributionshould normally be used unless climatic orunusual conditions dictate otherwise.

SUBSTATIONS

The purpose of a substation is to switchcircuits on and off and to change the generated

Figure 5-8.—Elements of a power distribution system.

power to the proper voltage and frequencynecessary for transmission. Usually, a substationis used to connect the generating plant to thetransmission lines. The substation transforms thegenerated voltage to transmission voltage andprotects the generating plant against any faultson the transmission lines. Another substation isused to transform the transmission voltage to thatof the distribution voltage. The distributionsubstation protects the substation and trans-mission lines against any faults occurring on thedistribution feeders. At many advanced bases, thesource of the power will be generators connecteddirectly to distribution centers, thus eliminatingthe need for substations.

PRIMARY FEEDERS

Primary feeders are those conductors in adistribution system that are connected from the

5-16

substations and that transfer the power to thedistribution centers (fig. 5-8). They may bearranged as radial, loop, or network systems andmay be overhead or underground.

Radial Distribution System

A representative schematic of a radial distri-bution system is shown in figure 5-9. You will notethe branching out of the independent feeders toseveral distribution centers without intermediateconnections between feeders.

The most frequently used system is the radialdistribution system because it is the simplest andleast expensive system to build. It is not as reliableas most systems, however, because a fault in themain feeder may result in an outage on all loadsserved by the feeder.

Service on this type of feeder can be improvedby installing automatic circuit breakers that willreclose the service at predetermined intervals. Ifthe fault continues after a predetermined numberof closures, the breaker will be locked out untilthe fault is cleared and service is restored by handreset.

Loop, or Ring, Distribution System

The loop (or ring) system of distribution startsat the substation and is connected to or encirclesan area serving one or more distribution trans-formers or load centers; the conductors of thesystem return to the same substation.

Figure 5-9.—Radial distribution system.

The loop system (fig. 5-10) is more ex-pensive to build than the radial type, butit is more reliable. It may be justified inan area where continuity of service is of con-siderable importance—at a medical center, forexample.

In the loop system, circuit breakers sec-tionalize the loop on both sides of each distribu-tion transformer connected to the loop. The twoprimary feeder breakers and the sectionalizingbreakers associated with the loop feeder areordinarily controlled by pilot wire relaying ordirectional overcurrent relays. Pilot wire relayingis used when there are too many secondarysubstations to obtain selective timing withdirectional overcurrent relays.

A fault in the primary loop is cleared by thebreakers in the loop nearest the fault, and poweris supplied the other way around the loop withoutinterruption to most of the connected loads. Ifa fault occurs in a section adjacent to thedistribution substation, the entire load may haveto be fed from one direction over one side of theloop until repairs are made. Sufficient conductorcapacity must be provided in the loop to permitoperation without excessive voltage drop oroverheating of the feeder when either side of theloop is out of service. If a fault occurs in thedistribution transformer, it is cleared by thebreaker in the primary leads, and the loop remainsintact.

Network Distribution System

The network and radial systems differ withrespect to the transformer secondaries. In the

Figure 5-10.—Loop, or ring, distribution system.

5-17

network system (fig. 5-11), transformer sec-ondaries are paralleled; in a radial system, theyare not.

The network is the most flexible type ofprimary feeder system; it provides the bestservice reliability to the distribution transformersor load centers particularly when the systemis supplied from two or more distributionsubstations. Power can flow from any substationto any distribution transformer or load centerin the network system. The network systemis more flexible with regard to load growththan the radial or loop system and is adaptableto any rate of load growth. Service can readilybe extended to additional points of usagewith relatively small amounts of new construc-tion. The network system, however, requireslarge quantities of equipment and extensiverelaying; therefore, it is more expensive thanthe radial system. From the standpoint ofeconomy, the network system is suitable onlyin heavy-load-density areas where the load centerunits range from 1,000 to 4,000 kilovolt-amperes(BVA).

Primary Selective System

In some instances, a higher degree of reliabilitycan be attained with a primary selective system.In such a system, two feeders supply a single loadcenter with switching arranged for selection ofeither feeder. This selection may be ‘mademanually or automatically.

In laying out a distribution system for a base,you should divide the base into a number ofsections. These sections should be chosen so thatthe loads in each section are close to one of thedistribution centers. You do this to keep the lengthof the mains as short as possible and to keep thevoltage drop low between the distribution and theloads. The distribution or load centers should belocated as near as possible to the center of the areaof the connected load.

DISTRIBUTION CENTERS

The distribution center (fig. 5-12) is thelocation at which the primary main is connected

Figure 5-11.—Network distribution system.

5-18

Figure 5-12.—Overhead distribution center.

to the feeder circuit. The fused cutout switch forthe control and protection of the primary mainis usually mounted on the buck arm below theprimary main at the distribution center. Thevoltage at the distribution center should bemaintained practically constant from no load tofull load. Constant voltage can be maintained bya feeder voltage regulator at the substation.The voltage can then be held constant at thedistribution center by varying the voltage at the

substation. Figure 5-13 shows the distributioncenter used in advanced base construction.Portable generators are connected directly to thedistribution center using the load cables provided.

PRIMARY MAINS

The primary mains are connected to the feederat the distribution load center. They are alwayslocated below the feeder on a pole. The primary

Figure 5-13.—Advanced base distribution center.

5-19

mains operate at the same voltage as the feeder.The distribution transformers are connected to theprimary mains through fused or automaticcutouts. Figure 5-14 shows the primary main towhich the transformer is tapped. The cutouts, oneon each primary line, contain the fuses thatprotect the transformer against overload and shortcircuits. The primary mains are strung across theupper crossarm and usually lie in a horizontal

DISTRIBUTION TRANSFORMERS

Most electrical equipment in the Navy uses120/208 volts. The primary voltage distributed onNavy shore installations, however, is usually2,400/4,160 volts. A distribution transformer(step-down) is therefore required to reduce thehigh primary voltage to the utilization voltage of120/208 volts. The various types of transformerinstallations are discussed later in this chapter.Regardless of the type of installation orarrangement, transformers must be protected bycutout fuses or circuit breakers, and lightningarresters should be installed between the high-voltage line and the fused cutouts.

There are three general types of single-phasedistribution transformers. The conventional type

Figure 5-14.—Pole-mounted primary mains.

requires a lightning arrester and fused cutout onthe primary phase conductor feeding it. Theself-protected (SP) type has a built-in lightningprotector; the completely self-protected (CSP)type has the lightning arrester and current-overload devices connected to the transformer andrequires no separate protective devices.

Transformer Installation

If a blueprint of a particular transformerinstallation is available to you, your job will becomparatively easy. All the construction andelectrical specifications will be worked out for youbeforehand and all you have to do is convert thisinformation to the finished job. However, in someinstances, a blueprint will not be available. Then,it will be up to you to determine the location andsize of the transformer and install the transformeraccording to the latest specifications. You shouldbe familiar with the rules and requirements of themost current electrical codes. Be sure to study anyapplicable code requirements carefully beforeinstalling a transformer.

DETERMINATION OF TRANSFORMERSIZE.—Let’s suppose you are given the job ofinstalling a single-phase transformer in a certainarea of the advanced base. This area contains 10barracks that receive power from a 2,400-voltoverhead primary main. The electrical equipmentin the barracks consists of single-phase lights ormotors operating at either 110 or 220 volts. Athree-wire overhead secondary main distributesthe secondary voltage alongside the barracks.Service leads complete the connection between thesecondary main and each building.

The first thing you should do is make a roughdrawing of the area. When you are finished, itshould look like figure 5-15. The location of eachpole as well as the barracks is noted. Linesrepresenting the service leads are drawn betweenthe poles and the building.

Your next step is to determine the totalconnected load of each service. It soundscomplicated, but what it actually amounts to issumming up the power required by the lights andmotors in each barracks. This power demand isnoted in each square representing a barracks(fig. 5-15).

Next, figure out the kVA load per pole. In thisparticular example, each pole serves two barracks.Therefore, the kVA load of a pole will be the sumof the total connected loads of the two barracksserved by that pole.

5-20

Figure 5-15.—Transformer size calculations.

Now, calculate the total maximum connectedload on the transformer. As you can see fromfigure 5-15, the total connected load is the sumof the kVA loads per pole. It amounts to 25.85kVA. But don’t jump to conclusions. You won’tneed a 37.5-kVA transformer to take care of thetotal load. The amount 25.85 kVA represents theamount of power that the transformer would haveto supply if all the lights and motors were turnedon at the same time. Although that possibilityexists, the time interval would be small comparedto the length of time that only a portion of thetotal load would be on. Therefore, it is necessaryto calculate only the maximum demand load andthen use this figure as a basis for determiningtransformer size.

An approximation of the maximum demandload can be computed by multiplying the totalmaximum connected load by the demand factorlisted in table 5-2. In this example, the maximumdemand is 23.26 kVA (25.85 × 0.9). Thetransformer capacity required to meet thisdemand will be 25 kVA, since a 25-kVAtransformer is the next larger standard size.

DETERMINATION OF TRANSFORMERLOCATION.—Your next problem is to find themost suitable location for the transformer. Thatdoesn’t mean finding the strongest pole but the

Some of the particularly important trans-former installation rules are listed below.

1. One or more transformers may be hung ona single pole if the total weight does not exceed

5-21

one that is nearest to the ELECTRICALCENTER of the area.

The electrical center is the point where abalance is obtained between the total kVA spansto the north and south of the location of thetransformer. The kVA span is the product of thenumber of spans times the kVA load of the pole.

To begin with, assume that you are going toplace the transformer on pole K (fig. 5-15). Thenfigure the total kVA spans to the north and southof this location. A chart will simplify yourcalculations.

kVA spans north of kVA spans south ofpole K pole K

1 × 4.0 = 4.0 1 × 6.9 = 6.9

2 × .8 = 1.6 2 × 12.0 = 24.0

5.6 30.9

Total kVA spans north Total kVA spans southof pole K = 5.6 of pole K = 30.9

You can see that if you placed the transformeron pole K, it would be at an imbalanced electricalcenter; that is, it would be too far away from theheaviest loads.. So pick another pole. This timechoose pole L and make another chart.

kVA spans north of kVA spans south ofpole L pole L

1 × 2.15 = 2.15 1 × 12.0 = 12.0

2 × 4.0 = 8.0 12.0

3 × .8 = 2.4

12.55

Total kVA spans north Total kVA spans southof pole L = 12.55 of pole L = 12.0

Pole L is nearest to the electrical center of thearea. That is the pole, then, on which you willmount the transformer.

Transformer Installation Rules

the safe strength of the pole or of the crossarmsand bolts supporting them.

2. When more than one transformer isinstalled on crossarms, the weight should bedistributed equally on the two sides of the pole.

3. Single-phase distribution transformers of100 kVA or smaller are usually placed ABOVEthe secondary mains if conditions permit. Thoselarger than 100 kVA are usually platform or padmounted.

4. Lightning arresters and fused cutouts haveto be installed on the primary side of alldistribution transformers except the self-protectedtype.

5. Ground wires are required to be coveredwith plastic or wood molding to a point 8 feetabove the base of the pole.

GUYING OF POLES

A guy is a brace or cable that is anchored insome fashion to the ground and secured to a pointon the pole at the other end. Correctly selectedand installed, the guy will protect the pole linefrom damage caused by the strain of the lineconductors and pole-mounted equipment. Theguy will also minimize the damage to the pole linecaused by severe weather.

Basic guying information, such as types,locations, and anchors, is covered in ConstructionElectrician training manuals of lower rates. In thissection, we’ll be concerned with calculating the“line conductor load” for various line angles anddead ends, the effects that the lead-to-height ratioshave on guy tensioning, and methods used toselect the size and type of guy wire and anchorscorrectly.

The first step in determining the guy type andtension requirement is to determine the lineconductor tension. Table 5-5 lists the most

Table 5-5.—Breaking Strength of Line Conductors

Wire Size, AWG Breaking Strength(Copper, Hard Drawn) Lb

No. 8 830No. 6 1,280No. 4 1,970No. 2 3,045No. 0 4,750No. 00 5,927No. 0000 9,617

common size of line conductors (hard-drawncopper) that you will encounter in the field. Todetermine the conductor tension under maximumloading conditions, take 50 percent or one-halfof the breaking strength of the conductor. Thisallows for the safety factor of two required bythe National Electric Safety Code.

Example:

Line tension = 50 percent of breaking strength

For No. 6 copper = 50 percent of 1,280 = 640 lb

Next, we must determine the angle of change inthe line. Any change in the direction of the lineincreases the line conductor tension and, leftuncorrected, tends to pull the pole out ofalignment. Table 5-6 lists the most common lineangles in degrees and the constant by which theline tension must be multiplied to determine theside pull.

Example: For No. 6 copper conductor, for a30-degree angle,

640 × 0.517 = 330 lb

The total side pull can now be determined bymultiplying the side pull of one conductor by thenumber of conductors.

Example: On the basis of four conductors,the total side pull is as follows:

330 × 4 = 1,320 lb

The next step required to determine the correctguy tension is to find the multiplying factor forthe lead-to-height ratio. The lead-to-height ratiois the relationship of the lead (L) (distance betweenthe base of the pole and the anchor rod) to theheight (H) of the guy attachment on the pole, asshown in figure 5-16. This ratio will vary becausethe terrain of obstructions will restrict the locationof the anchor. A guy ratio of 1 to 1 is preferred.Shortening L increases the tension in the guy,causing increased stresses on the pole especiallyat dead ends and acute angles.

Using our previous example of four No. 6AWG copper conductors at a 30-degree angle,let’s determine the total guy tension using a 1-to-1ratio, assuming that H = 30 feet and L = 30 feet(refer to table 5-7). Locate the height of the guyattachment (30 ft) in the left-hand column. Move

5-22

Table 5-6.—Angle Constant Based on Line Angle

Line Angle, Deg102030405060708090 or dead end

Angle Constant0.1740.3470.5170.6840.8451.0001.151.291.41

HeightH of guy

attachmenton pole, ft

151617181920212223242526272829303132333435

Figure 5-16.—Methods of measuring height and lead dimensions.

Table 5-7.—Height and Distance Ratio Multiplier

5 6 7 8 10 12 14 16 18 20 25 30 35

3.16 2.69 2.36 2.12 1.80 1.60 1.46 1.37 1.30 1.25 1.16 1.12 1.093.35 2.85 2.47 2.24 1.89 1.67 1.52 1.41 1.34 1.28 1.19 1.13 1.103.54 3.00 2.63 2.35 1.97 1.73 1.57 1.46 1.37 1.31 1.21 1.15 1.113.73 3.16 2.76 2.46 2.06 1.79 1.63 1.50 1.41 1.35 1.23 1.17 1.123.93 3.32 2.89 2.58 2.15 1.87 1.68 1.55 1.45 1.38 1.26 1.19 1.144.12 3.48 3.03 2.69 2.24 1.94 1.74 1.60 1.49 1.41 1.28 1.20 1.154.32 3.64 3.17 2.81 2.33 2.01 1.80 1.65 1.54 1.45 1.31 1.22 1.174.51 3.80 3.30 2.93 2.42 2.09 1.86 1.70 1.58 1.49 1.33 1.24 1.184.71 3.96 3.44 3.04 2.51 2.16 1.92 1.75 1.62 1.52 1.36 1.26 1.204.90 4.12 3.57 3.16 2.60 2.24 1.98 1.80 1.67 1.56 1.39 1.28 1.215.10 4.28 3.71 3.28 2.69 2.31 2.04 1.85 1.71 1.60 1.41 1.30 1.235.29 4.45 3.84 3.40 2.79 2.39 2.11 1.91 1.76 1.64 1.44 1.32 1.255.51 4.62 3.99 3.52 2.88 2.46 2.17 1.96 1.80 1.68 1.47 1.34 1.265.69 4.78 4.13 3.64 2.97 2.54 2.24 2.01 1.85 1.72 1.50 1.37 1.285.89 4.94 4.27 3.76 3.07 2.61 2.30 2.06 1.90 1.76 1.53 1.39 1.306.08 5.09 4.41 3.88 3.16 2.68 2.36 2.12 1.95 1.80 1.56 1.41 1.326.28 5.26 4.54 4.04 3.26 2.77 2.42 2.18 1.99 1.84 1.59 1.44 1.336.48 5.42 4.68 4.13 3.36 2.85 2.49 2.24 2.04 1.89 1.62 1.46 1.356.68 5.59 4.82 4.24 3.45 2.93 2.56 2.29 2.09 1.93 1.65 1.48 1.376.88 5.75 4.96 4.36 3.54 3.01 2.62 2.34 2.14 1.97 1.69 1.51 1.397.08 5.92 5.10 4.48 3.64 3.08 2.69 2.40 2.19 2.02 1.72 1.53 1.41

Distance D from center of pole to guy rod, ft

5-23

to the right until you reach the column under 30,the number of feet the anchor is away from thepole. The figure shown (1.41) is the guy ratiomultiplier. Now let’s compute the guy tensioningvalue.

Example: Total side pull × guy ratiomultiplier

1,320 × 1.41 = 1,861 lb

The guy wire and anchor for this example mustbe rated to hold at least 1,861 foot-pounds ofload.

We now know the guy wire must have a breakingstrength of at least 3,722 pounds. Referring againto table 5-8, locate the breaking strength column;then move down this column until a value thatis at least 3,722 pounds is found. Our examplerequires a breaking strength of 3,722 pounds.Based on this value, a 3/8-inch common gradewould be sufficient.

Guy wire comes in various sizes and grades The final step needed to ensure a safe andfrom 1/4 to 1/2 inch. Table 5-8 lists the grades adequate guy is the selection of a guy anchor ofand sizes in the left-hand column with the sufficient holding power. The holding power ofbreaking and allowable tension strengths in the an anchor depends upon the area of the anchorright columns. To determine the correct grade and plate, the depth setting, and the type of soil. Thesize of guy wire, first multiply the calculated guy greater each of these is, the greater the volumetension by the safety factor of 2. Continuing with of earth required to hold it in place. Table 5-9 listsour example, solve for maximum breaking the most commonly used manufactured anchors.strength. To use this chart, determine the type of soil and

Example:

Maximum breakingstrength required = guy tension × 2

= 1,861 lb × 2 = 3,722 lb

Table 5-8.—Guy Wire Breaking Strength

Grade

Common . . . . . . . . . . . . . . . . . . . . . . . . . . .Siemens Martin . . . . . . . . . . . . . . . . . . . . .Utilities . . . . . . . . . . . . . . . . . . . . . . . . . . . .Siemens Martin high strength . . . . . . . . .Common . . . . . . . . . . . . . . . . . . . . . . . . . . .Siemens Martin . . . . . . . . . . . . . . . . . . . . .Specification. . . . . . . . . . . . . . . . . . . . . . . .Utilities . . . . . . . . . . . . . . . . . . . . . . . . . . . .Siemens Martin high strength . . . . . . . . .Common. . . . . . . . . . . . . . . . . . . . . . . . . . .Siemens Martin . . . . . . . . . . . . . . . . . . . . .Utilities . . . . . . . . . . . . . . . . . . . . . . . . . . . .Siemens Martin high strength . . . . . . . . .Specification. . . . . . . . . . . . . . . . . . . . . . . .Common. . . . . . . . . . . . . . . . . . . . . . . . . . .Siemens Martin . . . . . . . . . . . . . . . . . . . . .Siemens Martin high strength . . . . . . . . .Specification. . . . . . . . . . . . . . . . . . . . . . . .

Size,in.

1/4 1,900 9501/4 3,150 1,5751/4 4,500 2,2501/4 4,750 2,375

5/16 3,200 1,6005/16 5,350 2,6755/16 6,000 3,0005/16 6,500 3,2505/16 8,000 4,0003/8 4,250 2,1253/8 6,950 3,4753/8 8,500 4,2503/8 10,800 5,4003/8 11,500 5,7501/2 7,400 3,7001/2 12,100 6,0501/2 18,800 9,4001/2 25,000 12,500

Breakingstrength, lb

Allowabletension, lb

5-24

total guy tensioning amount. Move down thecorrect holding strength column until a value ofat least the required amount is found. In theexample just given, the guy tension allowed foris 3,722 pounds. Using table 5-9, we see that eitheran 8-inch expansion or screw would provideadequate holding power. The type selected wouldbe based on material available, cost, and ease ofinstallation. By following this five-step processclosely, you can quickly determine the correct guyrequirements for any situation.

PROTECTIVE DEVICES

Overcurrent protection and personnel safetyrequirements are provided for in a powerdistribution system by the use of air-breakswitches and fused cutouts. Pole-mounted oilswitches may also be used. Lightning arrestersprotect the primary lines from overvoltage causedby lightning.

Switches and Fused Cutouts

The air-break switch has both blade andstationary contact equipped with arcing horns, asshown in figure 5-17. These horns are pieces of Figure 5-17.—Three-phase ganged air switch.

Table 5-9.—Holding Power for Commonly Used Anchors

ANCHOR HOLDING STRENGTH, LB

TYPE SIZE IN POOR SOIL AVERAGE SOIL

Expansion 8 10,000 17,000

Expansion 10 12,000 21,000

Expansion 12 16,000 26,500

Screw or Helix* 8 6,000 15,000

Screw or Helix 11 5/16 9,500 15,000

Screw or Helix 32 10,000 23,000

Screw or Helix 34 15,500 27,000

Never-Creep 21,000 34,000

Cross Plate 18,000 30,000

*Screw or Helix anchors power installed.

5-25

metal between which an arc forms when a circuitcarrying current is opened. As the switch opens,the arcing horns are spread farther and fartherapart, lengthening the arc until it finally breaks.Air-break switches are usually mounted onsubstation structures or on poles and are used toisolate primary feeders.

The fused cutout provides fuse protection inaddition to isolating the line. Fused cutouts mustbe installed on the primary side of all distributiontransformers and capacitor banks.

The rating (size) of the fuse link used in aprimary cutout is important. The chart intable 5-10 will help you select the correct fuse size.As an example, suppose you have installed asingle-phase 75-kVA transformer that operatesfrom a 2,400-volt primary. Using the chart, firstfind the transformer capacity (75) on the left sideof the chart. Then proceed to the right until youintersect the primary voltage column (2,400 volts).The chart lists the full-load current as 31.3amperes and the recommended fuse size as 50

Table 5-10.—Fuse Size for Transformer Installations

SystemNominalVoltage

2,400 4,160 7,200 12,000 13,800

Trans-formerkVARating

Full- Fuse Full- Fuse Full- Fuse Full- Fuse Full- FuseLoad Ampere Load Ampere Load Ampere Load Ampere Load AmpereCurrent Rating Current Rating Current Rating Current Rating Current Rating

SINGLE-PHASE TRANSFORMERS

5 2.1 3 1.2 3 0 7 3 0 410 4.2 7 2.4 5 1.4 3 0.8

3 0.40.7

33 3

15 6.310.4

10 3.6 5 2.1 3 1.3 3 1.1 325 15 6.0 10 3 5 5 2.1 3 1.8 337.5 15.6 25 9.050 20.8 30 12.0

15 5.2 10 3 1 5 2.7 520 7.0 10 4.2 7 3 6 5

75 31.3 50 18.0 25 10.4 15 6.3 10 5.4 10100 41.7 65 24.0 40 13.9 20 8.3 15 7.2 10167 69.6 100 40.1 65 23.2 40 13.9 20 12.1 20250 104.2 150 60.1 100 34.8 50 20.8 30 18.1 25

THREE-PHASE TRANSFORMERS

9 2.2 3 1.3 3 0.7 3 0.4 3 0.4 315 3 6

7.25 2.1 3 1.2 3 0.7 3 0.6 3

30 10 4.2 7 2.4 5 1.4 3 1.3 345 10.8 15 6 3

10.410 3.6 5 2.2 3 1.9 3

75 18.1 25 15 6.0 10 3 6 5 3.1112.5 27.1 40 15.6 25 9 0

1 215 5.4 10 4.7

57

150 36.1 50 20.8 30 20 7.2 10 6.3 10225 54.2 80 31.3 50 18 25 10.8 15 9.4 15300 72.3 100 41.7 65 24 40 14.5 20 12.6 20500 120 200 69.5 100 40 65 24.1 40 21.0 30

Note: To compute the full-load current for transformers not listed on this table, use the formulas in appendix II.

5-26

amperes. Therefore, for this particular installationyou should use a 50-ampere fuse.

The protective requirements of a three-phasetransformer installation are the same as those fora single-phase service. The size of the fuse, again,is determined by the total capacity of thetransformer bank and the value of the primaryvoltage. The chart in table 5-10 will assist you inselecting the proper size fuse.

The questions you should now be askingyourself are, How much capacity do I add to thecircuit? and How do I go about computing therequired capacity with the information I now haveavailable to me? Perhaps the following illustrationwill help.

Lightning Arresters

The purpose of a lightning arrester installedon primary lines is twofold: first, to provide apoint in the circuit at which the lightning impulsecan pass to earth without injuring line insulators,transformers, or other connected equipment; andsecond, to prevent any follow-up power currentfrom flowing to ground. Lightning arresters mustbe installed on the primary side of all substations,distribution centers, distribution transformers,and capacitor banks.

Ground Wire

A ground wire on an overhead line may bea galvanized steel, copper-covered steel, oraluminum-covered steel cable. It is strung alongthe transmission line but is mounted above theother conductors. The ground wire is not a partof any electrical circuit, but is, instead, connectedto earth ground at frequent intervals (usually everyfifth pole) on pole lines. The ground or earthpotential is brought above the transmission lines,therefore reducing the stress placed on thelines and insulators caused by lightning. Theeffectiveness of a ground wire depends on lowground resistance. Good ground connectionsshould be made at frequent intervals along theline;

CAPACITOR BANKS

Capacitors are an important part of thedistribution system. They provide a convenientand practical means of improving the powerfactor by neutralizing the effect of lagging powerfactor loads. This action reduces the line currentand line losses and improves the line voltageregulation. Capacitors can be installed in relativelysmall banks and placed in the circuit near thesource of the reactive load or on the primaryfeeders. Be sure to use high-voltage capacitorswhen you place capacitors between the trans-former and the high-voltage primary lines.Typical capacitor bank connections are shown infigure 5-18. Figure 5-18.—Typical capacitor bank connections.

5-27

Assume you have a 100-kilowatt supply. Youhave determined by various measurements thatit is operating at 70-percent power factor (PF).You would like to improve the PF to 85 percent.How much capacity should you add? Refer tofigure 5-19 and the following calculations.

Given:

cos A = .70 = present PF

cos B = .85 = desired PF

From the cosines given above and trigonometrictables, you can determine the following angles andtangents:

Angle A = 45.6°; therefore, tan 45.6° = 1.0212

Angle B = 31.8°; therefore, tan 31.8° = .6200

and tan A - tan B = C = .4012

Multiply by 100-kW availability = 40 kVA

Angle C (fig. 5-19) is the amount of leadingcapacitive reactance you need to add to the circuitto reduce the lagging reactive component.Attempts to improve the PF above 90 percent bymeans of capacitors are seldom economical.

Listed below are a few rules to help yousupervise the installation of capacitors.

Use lightning arresters of the line type onthe capacitor banks of the sizes normally used.

Use primary cutouts in the majority ofinstallations to connect and disconnect thecapacitor bank. A liberal margin between normalcurrent ratings and fuse rating is necessary toavoid unnecessary operation on current transients.

Install capacitors at load centers toimprove lagging power factor.

Install capacitors at the end of the line forvoltage improvement.

WARNING

A disconnected capacitor retains itselectrical charge for some time and mayhave full line voltage across its terminals.When capacitors are removed from servicefor any purpose, consider them to be at fullvoltage until the terminals have beenshort-circuited and grounded. DO NOTSHORT-CIRCUIT TERMINALS UNTILCAPACITORS HAVE BEEN DE-ENERGIZED FOR AT LEAST 5MINUTES.

DISTRIBUTION SYSTEMMAINTENANCE

Inspection and maintenance of all distributionsystem components should be scheduled andconducted as outlined in NAVFAC P-322,Inspection for Maintenance of Public Works andPublic Utilities, Volume I, and Inspection Guides-Electrical, Volume II. Maintenance and testingof transformers are covered in NAVFACMO-200, Facilities Engineering Electrical ExteriorFacilities. Any inspection and maintenance of, orclose to, electrical wiring, equipment, orapparatus, are dangerous. It is vital that allpersonnel who make such inspections or performsuch maintenance know and observe all theprescribed safety precautions. Electrical accidents,like other types of accidents, do not just happenbut are the direct result of carelessness or failureto observe safety precautions.

ADVANCED BASE PLANNING

You, as a First Class Construction Electricianwithin the NCF, may be called upon to assist inthe planning and construction of an advancedbase. In this section we will discuss the layout ofa facility within a component of the AdvancedBase Functional Component (ABFC) System andhow it fits in with the overall structure of anadvanced base. For a more detailed breakdownof Facilities Planning Guide, NAVFAC P-437,and the Advanced Base Functional Component(ABFC) System, refer to NCF First Class PettyOfficer, NAVEDTRA 10601. Your primary taskas a First Class Construction Electrician will beto install and maintain the electrical system neededby your command to complete its assignedmission.

In Facilities Planning Guide, NAVFAC-437,Volume I, Part 2, you will find facility drawings,indexed by facility number and a DoD categorycode. Each drawing is a detailed constructiondrawing that describes and quantifies the facilityrequired to complete it. These predesignedfacilities give the planner alternatives for satisfyingcontingency requirements when a call out of acomplete component is not desired. Rememberthat a “component” is defined as a grouping ofpersonnel and material that has a specific functionor mission at an advanced base, whether locatedoverseas or in CONUS, and a component issupported by facilities, which, in turn, are

5-28

Fig

ure

5-19

.—C

alcu

lati

ng c

apac

itor

ban

k si

ze.

Fig

ure

5-20

.—A

BF

C c

ompo

nent

M8E

pri

nt.

supported by assemblies. Figure 5-20 shows theelectrical plan for a 60-bed mobile hospital,component M8E. Within this component, thereare several facilities. Figure 5-21 shows all thefacilities you will need to construct componentM8E (Hospital 60 Bed Mobile). When you areassigned the task of constructing an advanced baseusing the ABFC system, your ability to read printsand use logic is basically the only requirementother than the components, facilities, andassemblies you will need. The prints give you abasic idea of how this particular advanced base

component is to be layed out. Figure 5-22 showsfacilities 811 10AU, 811 10AV, 811 10AW, and811 10P, but, according to figure 5-21, the onlyfacility drawing that you will need for thisparticular component is 811 10AU. Figure 5-23shows one assembly (32601), which, along withsix others, makes up facility 811 10AU.

NCF First Class Petty Officer, NAVEDTRA10601, describes how assemblies can be brokendown even further by NSN numbers; as shownin figure 5-24.

Figure 5-21.—Comuonent M8E.

5-31

Fig

ure

5-22

.—F

acili

ties

pri

nt.

Figure 5-23.—Assembly.

5-33

Figure 5-24.—Assembly 32601.

5-34

FIELD RIGGING AND HOISTING SYSTEMS

CHAPTER 6

This chapter presents information on how torig and erect field hoisting systems used withinthe Naval Construction Force (NCF).

Formulas are given on how to determine orfind the safe working load (SWL) of fiber/synthetic line and wire rope. These formulas areimportant when constructing a field hoistingsystem and also when lifting by any other means.In addition, the breaking strengths of fiber lineand wire rope are covered.

FIELD-ERECTED HOISTINGDEVICES

The term FIELD-ERECTED HOISTINGDEVICE refers to a device, generally of atemporary nature, that is constructed in the field,using locally available material, for the purposeof hoisting and moving heavy loads. Basically, itconsists of a block-and-tackle system arranged onsome form of skeleton structure consisting ofwooden poles or steel beams. The tackle systemrequires some form of machine power or workforce to do the actual hoisting. The skeletonstructure with attached tackle is held in place andsupported by means of guy lines anchored toholdfasts in the ground.

HOLDFASTS

Gin poles, shear legs, and other rigging devicesare held in place by means of guy lines anchoredto HOLDFASTS. In fieldwork, the most desirableand economical holdfasts are natural objects, suchas trees, stumps, and rocks. When naturalholdfasts of sufficient strength are not available,proper anchorage can be provided throughthe use of man-made holdfasts. These includesingle-picket, combination-picket, combination-log-picket, and log deadman holdfasts.

Natural Types

When using trees or stumps as holdfasts,always attach the guys near ground level. Ofcourse, the strength of the tree or stump is alsoan important factor in determining its suitabilityas a holdfast. With this thought in mind, NEVERuse a dead tree or a rotten stump for this purpose.Such holdfasts are unsafe because they are likelyto snap suddenly when a strain is placed on theguy. Make it a practice to lash the first tree orstump to a second one (fig. 6-1). This will provideadded support for the guy.

Single-Picket Holdfast

Pickets used in the construction of picketholdfasts may be made of wood or steel. A woodpicket should be at least 3 inches (76.2 millimeters)in diameter and 5 feet (1.5 meters) long. ASINGLE-PICKET holdfast can be provided bydriving a picket 3 to 4 feet (0.9 to 1.2 meters) intothe ground, slanting it at an angle of 15° oppositeto the pull. In securing a single guy line to a picket,take two turns around the picket and then havepart of the crew haul in on the guy as you takeup the slack. When you have the guy taut, secureit with two half hitches. In undisturbed loam soil,

Figure 6-1.—Use of trees as natural holdfasts.

6-1

the single picket is strong enough to stand a pullof about 700 pounds (317.5 kilograms).

Combination-Picket Holdfast

A COMBINATION-PICKET holdfast con-sists of two or more pickets. Figure 6-2 gives youan idea of how to arrange pickets in constructinga 1-1-1 and a 3-2-1 combination-picket holdfast.

In constructing the 1-1-1 combination, drivethree single pickets about 3 feet (0.9 meter) intothe ground, 3 to 6 feet (0.9 to 1.8 meters) apart,and in line with the guy. For a 3-2-1 combination,drive a group of three pickets into the ground,lashing them together before you secure the guyto them. The group of two lashed pickets followsthe first group, 3 to 6 feet (0.9 to 1.8 meters) apart,and is followed by a single picket. The 1-1-1combination can stand a pull of about 1,800pounds (810 kilograms), while the 3-2-1 com-bination can stand as much as 4,000 pounds (1,800kilograms).

The combination of the pickets grouped andlashed together and the small stuff secured ontoevery pair of pickets makes the combination-picket holdfasts much stronger than the single-picket holdfasts.

The reason for grouping and lashing the firstcluster of pickets together is to reinforce the pointwhere the pull is the greatest. The small stuff linkseach picket to the next, thereby dividing the forceof pull so that the first picket will not have tostand all of the strain. Using 12- to 15-thread smallstuff, clove hitch it to the top of the first picket.Then, take about four to six turns around the first

and second pickets, going from the bottom of thesecond to the top of the first picket. Repeat thiswith more small stuff from the second to the thirdpicket, and so on, until the last picket has beensecured. After this, pass a stake between the turnsof small stuff, between EACH pair of pickets, andthen make the small stuff taut by twisting it withthe stake. Now, drive the stake into the ground.

If you are going to use a picket holdfast forseveral days, it is best to use galvanized guy wirein place of the small stuff. Rain will not affectgalvanized guy wire, but it will cause small stuffto shrink. If the small stuff is already taut, it couldbreak from overstrain. If you HAVE TO usesmall stuff, be sure to slack it off before leavingit overnight. You do this by pulling the stake up,untwisting the small stuff once, and then replacingthe stake.

Combination-Log-Picket Holdfast

For heavy loads or in soft- or wet-earth areas,a COMBINATION-LOG-PICKET holdfast isfrequently used. With this type, the guys areanchored to a log or timber supported against fouror six combination-picket holdfasts. (See fig. 6-3.)The timber serves as a beam and has to be placedso that it bears evenly against the front row ofthe pickets. Since the holding power of this setupdepends on the strength of the timber and anchorline as well as the holdfast, be sure to use a timberbig enough and an anchor line strong enough tostand the pull.

Rock Holdfast

ROCK holdfasts are made by inserting pipes,crowbars, or steel pickets in holes drilled in solid

Figure 6-2.—Combination-picket holdfast: A. 1-1-1combination, B. 3-2-1 combination. Figure 6-3.—Combination-log-picket holdfast.

6-2

rock. Using a star drill, drill holes in the rock1 1/2 to 3 feet (75 to 90 centimeters) apart,keeping them in line with the guy. Remember todrill the holes at a slight angle so that the picketswill lean away from the direction of pull. Makethe front hole about 1 1/2 to 3 feet (75 to 90centimeters) deep and the rear hole 2 feet (60centimeters) deep (fig. 6-4). After driving picketsinto the holes, secure the guy to the front picket.Then, lash the pickets together with chain or wirerope to transmit the load.

Deadman Holdfast

A DEADMAN provides the best form ofanchorage for heavy loads. It consists of a log,a steel beam, a steel pipe, or a similar objectburied in the ground with the guy connected toit at its center. (See fig. 6-5.) Because it is buried,the deadman is suitable for use as a permanentanchorage. When installing a permanent deadmananchorage, you should put a turnbuckle in the guynear the ground to permit slackening or tighteningthe guy when necessary.

In digging the hole in which to bury thedeadman, make sure it is deep enough for goodbearing on solid ground. The less earth youdisturb in digging, the better the bearing surfacewill be. As shown in figure 6-5, you shouldundercut the bank in the direction toward the guyat an angle of about 15° from the vertical. Toincrease the bearing surface, drive stakes into thebank at several points over the deadman.

A narrow, inclined trench for the guy has tobe cut through the bank and should lead to thecenter of the deadman. At the outlet of the trench,place a short beam or log on the ground underthe guy (fig. 6-5). In securing the guy to the centerof the deadman, see that the standing part (thepart on which the pull occurs) leads from thebottom of the log deadman. Thus, if the wire ropeclips slip under strain, the standing part will rotatethe log in a counterclockwise direction, causingthe log to dig into the trench rather than roll up

Figure 6-5.—Log deadman.

and out. See that the running end of the guy issecured properly to the standing part.

Steel-Picket Holdfast

The STEEL-PICKET holdfast shown in figure6-6 consists of steel box plates with nine holesdrilled through each and a steel eye welded on theend for attaching the guy. When installing thisholdfast, it is important that you drive steelpickets through the holes in such a manner thatwill cause them to clinch in the ground. You willfind the steel-picket holdfast especially useful foranchoring horizontal lines, such as the anchorcable on a pontoon bridge. The use of two ormore of the units in combination will provide astronger anchorage than a single unit.

Figure 6-4.—Rock holdfast. Figure 6-6.—Steel-picket holdfast.

6-3

GIN POLE

The GIN POLE is a rig constructed from asingle pole, square timber, or steel beam. It standsalmost vertically and is supported by guys. Loadsof medium weight can be lifted from 10 to 50 feet(3 to 16 meters) by a block and tackle supportedon the gin pole. The hauling part of the tackleleads through a snatch block at the base of thepole to the source of power.

The timber gin pole should not be longer than60 times its minimum thickness because of thetendency to buckle under compression. If the poleis too short and you have to splice two together,place the sections so that the end of one touchesthe end of the other. This is called BUTTSPLICING. Join the sections together by boltingwooden scabs or metal plates onto them. Some-times large spikes are used to fasten the woodenscabs. When there is a tendency on the part ofa spliced pole to buckle, fasten an additional setof guys at the splice.

Guy lines, incidentally, may be either wire ropeor fiber line, although wire rope is usuallypreferred because of its strength and resistanceto corrosion and weathering. Generally, four guysare considered a minimum with 90° anglesbetween guys. If the pole or spar supported bythe guys is long and slender, it may be advisableto provide support at several points on the polein a tiered effect.

Guy lines should be anchored a considerabledistance from the base of the gin pole. Therecommended minimum distance from the baseof the gin pole to the anchorage of the guy lineis twice the height of the pole.

The angle of the pole is especially importantin the matter of stress. For instance, if the poleis vertical, the stress on each after guy is practicallyzero. But, when the angle between the guy andthe ground is 45°, the stress on each guy is almostone half of the total load. That is why you haveto use a guy that will stand stress of at least onehalf of the load.

The weakest point in the gin pole assembly ismost likely to be the after guy. If you studyfigure 6-7, you will see that as the gin pole isslacked outward, distance (b) becomes less anddistance (a) becomes greater. After the pole hasreached a certain angle, (a) becomes greater than(b), and from then on, the guy has a strain onit greater than the weight. This increases so rapidlyas the pole approaches the horizontal that theamount of strain is theoretically almost infinitewhen the pole is lying nearly flat. Obviously, then,

Figure 6-7.—Stress on after guy and gin pole.

the nearer the gin pole is to the vertical, the lessthe stress on the after guy, and the pole cannotbe lowered far off the perpendicular withoutsetting up dangerous stresses.

The formula for finding the thrust on the poleitself is rather complicated and involves a valuethat is difficult to determine without the use oftrigonometry. You can easily see that in thevertical position, the pole would be supporting athrust equal to, but no greater than, the weight.As the pole is slacked outward, the thrust on it,like the stress on the guy, increases, reachingfantastic proportions when the pole gets beyonda certain angle.

About the best thing you can do, then, is toremember that a gin pole cannot be slacked tomore than a few degrees off the vertical beforeit begins to take a heavy strain.

Rigging

The basic steps in the procedure for rigginga gin pole are given below. Learn each step listed,and study carefully figure 6-8, which shows youhow a gin pole is erected and the details of thelashings.

1. Place the pole so that the base is at the spotwhere it is to be erected.

2. Make a tight lashing of eight or nine turnsof fiber line about 1 foot (30 centimeters) fromthe top of the pole with two or more of the centerturns engaging the hook of the upper block of thetackle. Secure the ends of the lashing with a squareknot, and attach cleats to the pole flush with thelower and upper sides of the lashing to preventthe lashing from slipping.

6-4

Figure 6-8.—The gin pole.

3. Lay out guy lines, each one about fourtimes as long as the pole. Each line makes twoguys if you make a clove hitch in the center andthen pass it over the top of the pole above thetackle lashing. The guys lead from the pole,opposite each other, to block-and-tackle arrange-ments, which are attached to an anchorage. Thus,the length of the guy from the pole to theanchorage is approximately twice the length of thepole

4. Make another tight lashing (as above)about 2 or 3 feet (60 or 90 centimeters) from thebase of the gin pole, and put a cleat above andbelow this to keep it from slipping. This is wherethe snatch block is secured.

5. Now, reeve your tackle so that the haulingpart passes from the head block, through thesnatch block, to the source of power.

6. To keep the pole from skidding while beingerected and to keep it in place while a load is beinghoisted, set up a picket holdfast about 3 feet (90centimeters) from the pole base, and tie a linefrom the holdfast to the pole base.

7. Before erecting the gin pole, make SUREthe lashings are made properly and that hooks aremoused.

Erecting

Gin poles not over 50 feet (12 meters) in lengthmay be raised easily by hand, but longer polesmust be raised by supplementary rigging or powerequipment. About 10 or more crew members maybe needed to erect a gin pole properly, the numberdepending largely on the weight of the pole. Usethe following procedure as a guide in erecting thepole:

1. Dig a hole for the base between 6 inches(15 centimeters) and 1 foot (30 centimeters) deep,depending on the type of soil and the weight tobe lifted.

2. Lay out each guy as far as its anchorage.If tackle is NOT used on the after guys, one crewmember controls the slack of each with turnsaround the anchorage as the pole is raised.

6-5

3. You can do one of two things to bring themovable block down within reach. You can tiea line to the hook of the movable block, or youcan overhaul the tackle until it is longer than thelength of the pole, and secure it to an anchorageopposite the base.

4. To raise the pole easily, start raising it byhand to about 3 or 4 feet (0.9 or 1.2 meters) fromthe ground. Then, round in the blocks of the afterguys. While raising the pole, keep tension on theforward guys; otherwise, the pole may swing andthrow all the weight to one side.

5. When the pole is upright; make all guysfast.

6. You can move the top of the pole fromvertical to 15° forward without moving the base.This is called DRIFTING and should be done onlywhile the pole is NOT loaded, unless you canregulate the tension of all guys by tackle that issecured at the end of each. You will drift the poleforward when lifting the load.

SHEAR LEGS

The SHEAR LEGS is formed by crossing twotimbers, poles, planks, pipes, or steel bars andlashing or bolting them together near the top. Asling is suspended from the lashed intersection andis used as a means of supporting the load tacklesystem. (See fig. 6-9.) In addition to the nameshear legs, this rig is often referred to simply asa shears. (It has also been called an A-frame.)

The shear legs is used to lift heavy machineryand other bulky objects. It may also be used asend supports of a cableway and highline. A majorreason for using the shears in fieldwork is thatit can be quickly assembled and erected.

A shears requires only two guy lines and canbe used for working at a forward angle. Theforward guy does not have much strain imposedon it during hoisting. This guy is used primarilyas an aid in adjusting the drift of the shears andin keeping the top of the rig steady when a loadis being hoisted or placed. The after guy is animportant part of the shears’ rigging, as it is underconsiderable strain when hoisting. It should bedesigned for a strength equal to one half of theload to be lifted. The same principles forthrust on the spars apply; is, the thrustthat

hearincreases drastically as the sperpendicular.

legs go off the

Figure 6-9.—Shear legs.

Rigging

6-6

In rigging the shears, place your two spars orpoles on the ground parallel to each other withtheir butt ends even. Next, put a large block ofwood under the tops of the legs just below thepoint of lashing, and place a small block of woodbetween the tops at the same point to facilitatehandling of the lashing. Now, separate the polesa distance equal to about one third of the diameterof one pole.

For lashing material, use 18- or 21-threadsmall stuff. In applying the lashing, first makea clove hitch around one of the legs. Then, takeeight or nine turns around both legs above thehitch, working towards the top of the legs.Remember to wrap the turns tightly so that thefinished lashing will be smooth and free of kinks.To apply the frapping (tight lashings), make twoor three turns around the lashing between the legs;then, with a clove hitch, secure the end of the lineto the other leg just below the lashing (fig. 6-9).

Now, cross the legs of the shears at the tip andseparate the butt ends of the two legs so that thespread between them is equal to one half of theheight of the shears. Dig shallow holes about 1foot (30 centimeters) deep at the butt end of eachleg. The butts of the legs should be placed in these

holes in erecting the shears. Placing the legs inthe holes will keep them from kicking out inoperations where the shears is at an angle otherthan vertical.

The next step is to form the sling for thehoisting falls. To do this, take a short length ofline, pass it a sufficient number of times over thecross at the top of the shear, and tie the endstogether.

Now, reeve a set of blocks and place the hookof the upper block through the sling; then securethe hook by mousing. Fasten a snatch block tothe lower part of one of the legs, as shown infigure 6-9.

If you need to move the load horizontally bymoving the head of the shears, rig a tackle in theafter guy near its anchorage.

The guys—one forward guy and one afterguy—are secured next to the top of the shears.Secure the forward guy to the rear leg and theafter guy to the front leg, using a clove hitch inboth instances. (See fig. 6-9.)

Erecting

Several crew members are needed for safe,efficient erection of the shears, the number beingdetermined largely by the size of the rig. To helpensure good results, the erection crew should liftthe top of the frame and walk it up by hand untilthe after guy tackle system takes over the load.When this point is reached, complete the raisingof the shears into final position by hauling in onthe tackle.

Remember to secure the forward guy to itsanchorage before raising the legs, and maintaina slight tension on the line to control themovement. Also, after the shears has been raised,lash the butt ends with chain, line, or boards tokeep them from spreading when a load is applied.

TRIPOD

A tripod consists of three legs of equal lengthlashed together at the top. (See fig. 6-10.) The factthat the tripod can be used only where hoistingis vertical places it at a distinct disadvantage incomparison with other hoisting devices. Its usewill be limited primarily to jobs that involvehoisting over wells, mine shafts, or otherexcavations. A major advantage of the tripod isits great stability. In addition, it requires noguys or anchorages, and its load capacity isapproximately 1 1/2 times greater than for shearsmade of the same size timbers.

6-7

Figure 6-10.—Tripod.

The legs of a tripod generally are made oftimber poles or pipes. Materials used for lashinginclude fiber line, wire rope, and chain. Metalrings joined with short chain sections are alsoavailable for insertion over the top of the tripodlegs.

Rigging

The strength of a tripod depends largely onthe strength of the material used for lashing aswell as the amount of lashing used. The followingprocedure for lashing applies to line 3 inches (75millimeters) in circumference or smaller. For extraheavy loads, use more turns than specified in theprocedure given here; for light loads, use fewerturns than specified here.

As the first step of the procedure, take threespars of equal length and place a mark near thetop of each to indicate the center of the lashing.Now, lay two of the spars parallel, with theirTOPS resting on a skid (or block). Place the thirdspar between the two with the BUTT end restingon a skid. Position the spars so that the lashingmarks on all three are in line. Leave an intervalbetween the spars equal to about one half of the

diameter of the spars. This will keep the lashing means other than hand power is available forfrom being drawn too tight when the tripod is erection.erected.

With the 3-inch (75-millimeter) line, make aclove hitch around one of the outside spars; putit about 4 inches (10 centimeters) above the lashingmark. Then make eight or nine turns with the linearound all three spars. (See view A, fig. 6-11.) Inmaking the turns, remember to maintain theproper amount of space between the spars.

Now, make one or two close frapping turnsaround the lashing between each pair of spars.Do not draw the turns too tight. Finally, securethe end of the line with a clove hitch on the centerspar just above the lashing, as shown in view A,figure 6-11.

There is another method of lashing a tripodthat you may find preferable to the method justgiven. It may be used in lashing slender poles upto 20 feet (6 meters) in length, or when some

Figure 6-11.—Lashing for a tripod.

First, place the three spars parallel to eachother, leaving an interval between them slightlygreater than twice the diameter of the line to beused. Rest the tip of each pole on a skid so thatthe end projects about 2 feet (60 centimeters) overthe skid. Then, line up the butts of the three spars,as shown in view B, figure 6-11.

Next, make a clove hitch on one outside legat the bottom of the position the lashing willoccupy, which is about 2 feet (60 centimeters)from the end. Now, proceed to weave the line overthe middle leg, under and around the other outsideleg, under the middle leg, over and around thefirst leg, and so forth, until completing about eightor nine turns. Finish the lashing by forming aclove hitch on the other outside leg, as shown inview B, figure 6-11.

Erecting

In the final position of an erected tripod, itis important that the legs be spread an equaldistance apart. The spread between legs must benot more than two thirds, nor less than one half,the length of a leg. Small tripods, or those lashedaccording to the first procedure given in thepreceding section, may be raised by hand. Hereare the main steps that make up the hand-erectionprocedure.

Start by raising the top ends of the three legsabout 4 feet (1.2 meters), keeping the butt endsof the legs on the ground. Now, cross the topsof the two outer legs, and position the top of thethird or center leg so that it rests on top of thecross.

A sling for the hoisting tackle can be attachedreadily by first passing the sling over the centerleg, and then around the two outer legs at thecross. Place the hook of the upper block of thetackle on the sling, and secure the hook bymousing.

The raising operation can now be completed.To raise an ordinary tripod, a crew of about eightmembers may be required. As the tripod is beinglifted, spread the legs so that when it is in theupright position, the legs will be spread the properdistance apart. After getting the tripod in its finalposition, lash the legs near the bottom with lineor chain to keep them from shifting. (See fig.6-10.)

6-8

Where desirable, a leading block for thehauling part of the tackle may be lashed to oneof the tripod legs, as shown in figure 6-10.

In erecting a large tripod, you may need asmall gin pole to aid in raising the tripod intoposition. When you are called on to assist in theerection of a tripod lashed according to the firstlashing procedure described in the precedingsection, the first thing to do is to raise the topsof the legs far enough from the ground to permitspreading them apart. Use guys or tag lines to helphold the legs steady while they are being raised.Now, with the legs clear of the ground, cross thetwo outer legs and place the center leg so that itrests on top of the cross. Then, attach the slingfor the hoisting tackle. Here, as with a smalltripod, simply pass the sling over the center legand then around the two outer legs at the cross.

BOOM DERRICK

The BOOM DERRICK consists of a mast witha boom attached, as shown in figure 6-12. It maybe used to move weight in any direction. You willfind the boom derrick useful for loading andunloading trucks and flatcars when the base ofweight-lifting equipment cannot be set close to theobjects to be lifted. It is also used to advantageon docks and piers for unloading boats andbarges.

For medium loads, the boom may be riggedto swing independently of the mast, as shown infigure 6-12. For heavy loads, the boom may beset on a turnplate or turn wheel and it and themast rigged to swing as a unit. On morepermanent installations, it is good practice to rigthe mast separately and to strap another pole or

Figure 6-12.—Boom derrick.

6-9

mast to it. In such a case, one mast is fixed; theboom is rigged to the other mast, which is set ona turnplate. This provides rigid guying with aswing of more than 180° on the boom.

In case the proper size of line is not available,a set of tackle reeved with the same size line asthat used in the hoisting tackle may be used asa guy by extending the tackle from the top of thederrick to the anchorage. See that the blockattached to the derrick is lashed at that pointwhere the other guys are tied and in the samemanner.

Rigging

In fieldwork, you may be called on frequentlyto assist in rigging a boom derrick. For mediumloads, follow the rigging procedure given below.

The first step is to rig a mast and lash thetackle on, which is used as the topping lift. If thehauling part of the topping lift tackle comes fromthe movable block, lash a fairlead block to themast 2 or 3 feet (60 or 90 centimeters) below thetopping lift lashing.

POLE DERRICK

For your boom, select a pole, timber, steelpipe, beam, or laminated plank of the samediameter as the mast, but only about two thirdsof its length. Attach two cleats to the butt endof the boom and lash them with small stuff toform a fork, as shown in figure 6-12. This forkis to keep the boom from getting away from themast while a load is being moved from side to side.Use cleats long enough to extend from the buttend of the boom past the mast. About 4 feet (1.2meters) above the point where the boom meetsthe mast, attach two cleats into the mast, andplace a lashing of at least four turns of small stuffabove the cleats, keeping two ends free.

Using a sling attached to the topping lift, raisethe butt end of the boom as high as you want it.With the free ends from the lashing on the mast,make a sling to support the butt end of the boom.

Lash the movable block of the topping lift tothe top end of the boom, and lash the fixed blockof the boom tackle at the same point. The boomtackle is reeved so that the hauling part comesfrom the fixed block and passes through a fairleadblock lashed at the base of the mast.

Erecting

Raise the boom into position after the aboverigging is completed. When working with heavy

loads, see that the base of the boom rests on theground at the foot of the pole. When workingwith light loads, you may use a more horizontalposition, thus providing a greater radius. In nocase should the boom bear against any part of theupper two thirds of the mast.

To swing the boom, push directly on the loador pull the load with bridle lines or tag lines. Theangle of the boom to the mast is adjusted byhauling on the hauling part of the topping lift.The load is raised or lowered by the haulingpart of the boom tackle. A fairlead block(snatch block) is usually placed at the baseof the mast. The hauling part of the boom tackleis led through this fairlead block to a hand- orpower-operated winch for the actual hoisting ofthe load.

Various types of light-hoisting equipment aresometimes used on construction projects. Atypical example is the POLE DERRICK, alsoknown as a DUTCHMAN, shown in figure 6-13.This device is often powered by means of a hand-operated or engine-driven winch. It can be set upreadily in the field and moved about from job tojob.

Figure 6-13.—Pole derrick, or Dutchman.

6-10

The pole derrick is essentially a gin poleconstructed with a sill and with knee braces at thebottom. Also, guys usually are installed fore andaft. The pole derrick is suitable for lifting loadsof 1 or 2 tons (0.9 or 1.8 metric tons). Since itis light in weight and has few guys, the device canbe moved readily from place to place by a smallcrew.

OTHER HOISTING EQUIPMENT

The two sources of power you will use inhoisting are your work force and machine power.Of the two, machine power is more uniform. Ona single vertical line, a crew member of averageweight can pull with a force of 100 pounds (45kilograms), while on a single horizontal line, thesame crew member can pull with a force of only60 pounds (27 kilograms). When you get severalcrew members on a single line, there is no wayto measure the actual strength each crew memberputs into the combined pull. When you have touse a lot of crew members, you will not be ableto get enough personnel on a vertical line becauseof limited space. In this case, you should changethe line to a horizontal pull by using a snatchblock as a fairlead.

Machine power is much more predictable. Infact, all cranes have lift tables that show you theirlifting capacities on the basis of a single-line pull.The power from winches and other hoists is alsofigured on a single-line pull.

As you already know, you can change youradvantage by reeving different types of purchases.Always make the mechanical advantage fityour source of power. With some purchases,you have the extra feature of being able toincrease mechanical advantage without increasingfriction loss. A good example of this is the luffupon luff, which has twice the mechanicaladvantage of a threefold purchase, while thefriction loss of 60 percent is the same with both.Because the friction loss remains the same on aluff upon luff, the use of it saves wear and tearon equipment.

CHAIN HOISTS

Chain hoists provide a convenient means forhoisting heavy objects. When a chain is used, the

load can remain stationary without requiringattention. The slow lifting travel of a chain hoistis also advantageous in that it permits smallmovements, accurate adjustments of height, andcautious handling of loads.

Chain hoists differ widely in their mechanicaladvantage, depending upon their rated capacity.The mechanical advantage may vary from 5 to250; that is, the ratio 5:1 to 250:1. Two types ofchain hoists generally used for vertical hoistingoperations are the spur gear hoist and thedifferential chain hoist.

The SPUR GEAR HOIST (fig. 6-14) is bestfor ordinary operations that require frequent useof a hoist and that have a minimum number ofcrew members available to operate it. The spurgear hoist is about 85-percent efficient. In otherwords, about 85 percent of the energy exerted bythe operator is converted into useful work forlifting the load. The remaining 15 percent of theenergy is spent in overcoming friction in the gears,bearings, chains, and so on.

Figure 6-14.—Spur gear hoist.

6-11

The DIFFERENTIAL CHAIN HOIST (fig.6-15) is suitable for light loads and in situationsin which only occasional use of the hoist isinvolved. This hoist is only about 35-percentefficient.

A ratchet-handle pull hoist, commonly calleda COME-ALONG, can be obtained and willprove beneficial for making short, horizontal pullson heavy objects. A typical come-along, havinga rated capacity of 1 1/2 tons, is shown in figure6-16. You will find the come-along to be one ofthe most useful hoisting devices available. Thechain will not foul up because it is flexible andcannot kink. The chain is kept in place in thesheave by a hardened steel-load chain guide.

The load capacity of a chain hoist usually isstamped on the shell of the upper block. The ratedload capacity of hoists runs from 1/2 ton (0.45metric tons) upward to 40 tons (36 metric tons).

The lower hook is usually the weakest part inthe assembly of a chain hoist. This is intended asa safety measure so that the hook will start to

Figure 6-16.—Come-along.

spread open if overloaded. Spreading in a hookis a signal to the operator, warning that the chainhoist is nearing the overload point. Thus, closeobservance on the part of the operator is necessaryto detect any sign of overloading in time toprevent damage to the chain hoist. Under ordinarycircumstances, pull exerted on a chain hoist byone or two crew members in NOT enough tooverload the hoist.

Figure 6-15.—Differential chain hoist.

Frequent inspection of chain hoists isnecessary to ensure safe operation. A hook thatshows signs of spreading or excessive wear shouldbe replaced. If links in the chain are distorted,the chain hoist has probably been overloaded. Insuch a case, see that the chain hoist is condemnedand removed from service immediately.

WINCHES

Winches are frequently used as a source ofpower for operating hoisting rigs, particularly ginpoles, heavy-duty derricks, and light-hoistingequipment, such as pole derricks. A WINCH,generally speaking, is a device having one or moredrums on which fiber line or wire rope is wound.Winches are used for hoisting or hauling ofmaterials or objects. Both hand-operated andengine-driven winches of various types areavailable.

6-12

A single-drum, hand-operated winch similarto the one shown in figure 6-17 is suitable forlifting light loads. Single-drum hand winches areavailable in various capacities, including capacitiesof 2, 5, 6, and 15 tons (1.8, 4.5, 5.4, 12.5 metrictons).

Hand-operated winches are generally mountednear the foot of the rig, where they can beoperated efficiently. Notice the location of thewinch on the pole derrick shown in figure 6-13.

In hoisting and moving heavy objects in thefield, engine-driven winches may be used withtackle. Vehicular-mounted winches are alsowidely used (fig. 6-18). Sources of power forpower-driven winches include diesel, gasoline,compressed air, or steam engines as well as electricmotors. When vehicular-mounted winches areused, the vehicle should be placed so that theoperator can keep a close watch over the loadduring hoisting.

When setting up a power-driven winch tooperate hoisting equipment, make sure you givecareful consideration to these two factors: (1) theangle with the ground that the hoisting line makesat the drum of the hoist and (2) the fleet angleof the hoisting line winding on the drum.

In considering the ground angle, rememberthat if the hoisting line leaves the drum at an angleupward from the ground, the resulting pull on thewinch will tend to lift it clear of the ground. Inthis case, a leading block should be placed in thesystem at some distance from the drum to changethe direction of the hoisting line to a horizontalor downward pull. The hoisting line has to beoverwound or underwound on the drum, as maybe necessary, to prevent a reverse bend.

As for the fleet angle, bear in mind that thedistance from the drum to the first sheave of thesystem is the controlling factor. Place the drumof the winch so that a line from the last block

Figure 6-17.—Single-drum hand winch.

Figure 6-18.—Using a vehicular winch for hoisting.

passing through the center of the drum is atright angles to the axis of the drum. Theangle between this line and the hoisting line as itwinds on the drum is referred to as the FLEETANGLE.

As the hoisting line is wound in on the drum,it moves from one flange to the other, causingthe fleet angle to change during the hoistingprocess. See that the fleet angle does NOT exceed2°; and, where possible, keep it below this. A1 1/2° maximum angle is satisfactory and will beobtained if the distance from the drum to the firstsheave is 40 inches (100 centimeters) for each inch(2.5 centimeters) from the center of the drum tothe flange. The wider the drum of the hoist, thegreater the lead distance has to be when the winchis placed.

Most winches, even those made by the samemanufacturer, differ from each other in theiroperation. If you are not familiar with theoperation of a winch to be used on a job,study the operating procedure described inthe manufacturer’s manual beforehand. Thefundamentals of winch operation must be under-stood to ensure safe, efficient handling ofmaterials. The use of hand signals in givingdirections to operators of winches is especiallyimportant to the safety of both the crew memberand the material being hoisted.

CRANES

The crane is one of the most useful pieces ofconstruction equipment. It is also one of the mostversatile. For instance, by rigging the cranechassis with a boom and lifting hook, youhave an excellent device for lifting and movingheavy materials, machinery, and other objects.

6-13

(See fig. 6-19.) The capacity of the crane for liftingdepends on the boom length and angle. Thecapacity will be noted inside the cab of the crane,and this capacity should NOT be exceeded. Youwill not be required to operate the crane; that isthe job of the Equipment Operator. But there areother important jobs, such as that of hook-onman or signalman, and you have to be able tohandle either of these.

FIBER LINE

Fiber line is made from either natural orsynthetic fiber. Natural fibers, which come fromplants, include manila, sisal, and hemp. Thesynthetic fibers include nylon, polyester, andpolypropylene.

SYNTHETIC-FIBER ROPES

Synthetic-fiber ropes, such as nylon andpolyester, have rapidly gained wide use by theNavy. They are lighter in weight, more flexible,less bulky, and easier to handle and store thanmanila lines are. They are also highly resistant tomildew, rot, and fungus. Synthetic ropes arestronger than natural-fiber rope. For example,

Figure 6-19.—Crane rigged with boom and lifting hook.

nylon is about three times stronger than manila.When nylon line is wet or frozen, the loss ofstrength is relatively small. Nylon rope will holda load even though several strands may be frayed.Ordinarily, the line can be made reusable bycutting away the chafed or frayed section andsplicing the good line together.

SIZE DESIGNATION

Line that is 1 3/4 inches or less in circum-ference is called SMALL STUFF, and the size isusually designated by the number of THREADS(or yarns) that make up each strand. You mayuse from 6- to 24-thread strands, but the mostcommonly used are 9- to 21-thread strands(fig. 6-20). You may hear some small stuffdesignated by name without reference to size.One such type is MARLINE, a tarred, two-strand,left-laid hemp. Marline is the small stuff youwill use most for seizings. When you needsomething stronger than marline, you will use atarred, three-strand, left-laid hemp calledHOUSELINE.

Line larger than 1 3/4 inches in circumferenceis generally designated as to size by itscircumference in inches. A 6-inch manila line, forinstance, would be constructed of manila fibersand measure 6 inches in circumference. Line isavailable in sizes ranging up to 16 inches incircumference, but 12 inches is about the largestcarried in stock. Anything larger is used only onspecial jobs. (See fig. 6-20.)

6-14

Figure 6-20.—Some commonly used sizes of manila line.

If you should be tasked to order line, you mayfind that in the catalogs it is designated andordered by diameter. The catalog may also usethe term rope (rather than line).

ROPE YARNS for temporary seizings,whippings, and lashings are pulled from largestrands of old line that has outlived its usefulness.Pull your yarn from the middle, away from theends, or it will get fouled.

STRENGTH OF FIBER LINE

Overloading a line poses a serious threat tothe safety of personnel, not to mention the heavylosses likely to result through damage to material.To avoid overloading, you must know the strengthof the line with which you are working. Thisinvolves three factors: breaking strength, safeworking load, and safety factor.

BREAKING STRENGTH refers to thetension at which the line will part when a load isapplied. Breaking strength has been determinedthrough tests made by rope manufacturers, andtables have been set up to provide thisinformation. In the absence of manufacturers’tables, a rule of thumb for finding the breakingstrength of manila line is as follows:

C2 × 900 = BS

In the rule, C equals the circumference in inches,and BS equals the breaking strength in pounds.To find BS, square the circumference and thenmultiply the figure obtained by 900. With a 3-inchline, for example, you will get a BS of 8,100pounds, figuring as follows:

3 × 3 × 900 = 8,100 lb

The breaking strength of manila line is higherthan that of sisal line. This is caused by thedifference in strength of the two fibers. The fiberfrom which a particular line is constructed has adefinite bearing on its breaking strength.

The breaking strength of nylon line is almostthree times that of manila line of the same size.The best rule of thumb for the breaking strengthof nylon is as follows:

BS = C2 × 2400

for fiber line.The symbols in the rule are the same as those

For 2 1/2-inch nylon line,

BS = 2.5 × 2.5 × 2,400 = 15,000 lb

SAFE WORKING LOAD

Briefly defined, the “safe working load”(SWL) of a line is the load that can be appliedwithout causing any kind of damage to the line.Note that the safe working load is considerablyless than the breaking strength. A wide marginof difference between breaking strength and safeworking load is necessary to allow for such factorsas additional strain imposed on the line by jerkymovements in hoisting or bending over sheavesin a pulley block.

You may not always have a chart available totell you the safe working load for a particular sizeline-so what do you do then? Fortunately, thereis a rule of thumb that will adequately serve yourneeds on such an occasion.

SWL = C2 × 150

Where SWL equals the safe working load inpounds and C equals the circumference of the linein inches, you simply take the circumference ofthe line, square it, and then multiply by 150. Fora 3-inch line, here is how the rule works.

3 × 3 × 150 = 1,350 lb

Thus, the safe working load of a 3-inch line isequal to 1,350 pounds.

If the line is in good shape, add 30 percent tothe SWL determined by means of the rule; or ifit is in bad shape, subtract 30 percent from theSWL. In the example given above for the 3-inchline, adding 30 percent to the 1,350 lb would giveyou a safe working load of 1,755 lb. On the otherhand, subtracting 30 percent from the 1,350 lbwould leave you a safe working load of 945 lb.

Remember that the strength of a line decreaseswith age, use, and exposure to excessive heat,boiling water, or sharp bends. Especially with usedline, these and other factors affecting strengthshould be given careful consideration, and properadjustment should be made in the breakingstrength and safe working load capacity of theline. Manufacturers of line provide tables to showthe breaking strength and safe working loadcapacity of line. You will find such tables usefulin your work. You must remember, however,that the values given in manufacturers’ tables

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apply only to new line being used under favorableconditions. For that reason, you must pro-gressively reduce the values given inmanufacturers’ tables as the line ages ordeteriorates with use.

The SAFETY FACTOR of a line is the ratiobetween the breaking strength and the safeworking load. Usually, a safety factor of 4 isacceptable, but this is not always the case. In otherwords, the safety factor will vary, depending onsuch things as the condition of the line andcircumstances under which it is to be used. Whilethe safety factor should NEVER be less than 3,it often should be well above 4 (possibly as highas 8 or 10). For best, average, or unfavorableconditions, the safety factor indicated below mayoften be suitable.

BEST conditions (new line): 4

AVERAGE conditions (line used, but in goodcondition): 6

UNFAVORABLE conditions (frequently usedline, such as running rigging): 8

WIRE ROPE

During the course of a project, SEABEEsoften need to hoist or move heavy objects. Wirerope is used for heavy-duty work. Thecharacteristics, construction, and usage of manytypes of wire rope are discussed in the followingparagraphs. We will also discuss the safe workingload, use of attachments and fittings, andprocedures for the care and handling of wire rope.

CONSTRUCTION

Wire rope consists of three parts: wires,strands, and core (fig. 6-21). In the manufactureof rope, a number of WIRES are laid togetherto form the STRAND. Then a number ofSTRANDS are laid together around a CORE toform the ROPE.

The basic unit of wire rope construction is theindividual wire, which may be made of steel, iron,or other metal in various sizes. The number ofwires to a strand will vary, depending on thepurpose for which the rope is intended. Wire ropeis designated by the number of strands per ropeand the number of wires per strand. Thus, a1/2-inch, 6 by 19 wire rope will have 6 strandswith 19 wires per strand; but it will have the

Figure 6-21.—Parts of a wire rope.

same outside diameter as a 1/2-inch, 6 by 37 wirerope, which will have 6 strands with 37 wires ofmuch smaller size per strand.

Wire rope that is made up of a large numberof small wires is flexible. The small wires are,however, easily broken, so the wire rope does notresist external abrasion. Wire rope that is madeup of a smaller number of larger wires is moreresistant to external abrasion but is less flexible.

The CORE-the element around which thestrands are laid to form the rope-may be a hardfiber (such as manila, hemp, plastic, paper,asbestos, or sisal), a wire strand, or anindependent wire rope. Each type of core servesthe same basic purpose—to support the strandslaid around it.

A FIBER CORE offers the advantage ofincreased flexibility. Also, it serves as a cushionto reduce the effects of sudden strain and acts asa reservoir for the oil to lubricate the wires andstrands to reduce friction between them. Wirerope with a fiber core is used in places whereflexibility of the rope is important.

A WIRE STRAND CORE not only resistsheat better than a fiber core, but it also adds about15 percent to the strength of the rope. On theother hand, the wire strand makes the rope lessflexible than a fiber core would.

An INDEPENDENT WIRE ROPE CORE isa separate wire rope over which the main strandsof the rope are laid. It usually consists of six 7-wirestrands laid around either a fiber core or a wirestrand core. This core strengthens the rope more,provides support against crushing, and suppliesmaximum resistance to heat.

Wire rope may be made by either of twomethods. If the strands or wires are shaped toconform to the curvature of the finished ropebefore laying up, the rope is termed preformed.

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If they are not shaped before fabrication, the ropeis termed nonpreformed. When cut, preformedwire rope tends not to unlay, and it is moreflexible than nonpreformed wire rope. Withnonpreformed wire rope, twisting produces astress in the wires; and, when it is cut or broken,the stress causes the strands to unlay. Innonpreformed wire, unlaying is rapid and almostinstantaneous, which could cause serious injuryto someone not familiar with it.

The main types of wire rope used by the Navyhave 6, 7, 12, 19, 24, or 37 wires in each strand.Usually, the rope has six strands laid around afiber or steel center.

Two common types of wire rope, 6 by 19 and6 by 37 rope, are shown in figure 6-22. The 6 by19 type of rope, having 6 strands with 19 wiresin each strand, is commonly used for roughhoisting and skidding work where abrasion islikely to occur. The 6 by 37 wire rope, having 6strands with 37 wires in each strand, is the mostflexible of the standard six-strand ropes. For thatreason, it is particularly suitable when smallsheaves and drums are to be used, such as oncranes and similar machinery.

GRADES OF WIRE ROPE

Wire rope is made in a number of differentgrades, three of which are mild plow steel, plowsteel, and improved plow steel.

MILD PLOW STEEL rope is tough andpliable. It can stand up under repeated strain andstress, and it has a tensile strength of 200,000 to220,000 pounds per square inch (psi).

PLOW STEEL wire rope is unusually toughand strong. This steel has a tensile strength(resistance to lengthwise stress) of 220,000 to240,000 psi. This rope is suitable for hauling,hoisting, and logging.

IMPROVED PLOW STEEL rope is one ofthe best grades of rope available, and most, if not

all, of the wire rope in your work will probablybe made of this material. It is stronger, tougher,and more resistant to wear than either plow steelor mild plow steel. Each square inch of improvedplow steel can stand a strain of 240,000 to 260,000psi.

MEASURING WIRE ROPE

The size of wire rope is designated by itsdiameter. The true diameter of a wire rope isconsidered as being the diameter of the circle thatwill just enclose all of its strands. Both the correctand incorrect methods of measuring wire rope areshown in figure 6-23. Note, in particular, that theCORRECT WAY is to measure from the top ofone strand to the top of the strand directlyopposite it. The wrong way is to measure acrosstwo strands side by side. Use calipers to take themeasurement; if calipers are not available, anadjustable wrench will do.

To ensure an accurate measurement of thediameter of a wire rope, always measure the ropeat three places, at least 5 feet apart. Use theaverage of the three measurements as the diameterof the rope.

SAFE WORKING LOAD

The term safe working load (SWL), as usedin reference to wire rope, means the load that canbe applied and still obtain the most efficientservice and also prolong the life of the rope. Mostmanufacturers provide tables that show the safeworking load for their rope under variousconditions. In the absence of these tables, youhave to apply a thumb-rule formula to obtain theSWL. There are rules of thumb that may be used

Figure 6-23.—Correct and incorrect methods of measuringwire rope.Figure 6-22.—Two common types of wire rope.

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to compute the strength of wire rope. The onerecommended by the Naval Facilities EngineeringCommand (NAVFAC) is as follows:

SWL (in tons) = D2 × 4

This particular formula provides an amplesafety margin to account for such variables as thenumber, size, and location of sheaves and drumson which the rope runs, and such dynamic stressesas the speed of operation and the acceleration anddeceleration of the load, all of which can affectthe endurance and breaking strength of the rope.

In the above formula, D represents thediameter of the rope in inches. Suppose you wantto find the SWL of a 2-inch rope. Using theformula above, your figures would be as follows:

SWL = (2)2 × 4

SWL = 4 × 4 = 16

The answer is 16, meaning that the rope hasan SWL of 16 tons.

It is important to remember that any formulafor determining SWL is only a rule of thumb.In computing the SWL of old rope, worn rope,or rope that is otherwise in poor condition, youshould reduce the SWL as much as 50 percent,depending on the condition of the rope.

The manufacturer’s data concerning thebreaking strength (BS) of wire rope should be usedif available. But if you do not have thatinformation, one rule of thumb recommended isas follows:

BS = C2 × 8,000 lb

As you know, wire rope is measured by thediameter (D). To obtain the circumference (C)required in the formula, multiply D by pi (π),which is approximately 3.1416. Thus, the formulato find the circumference is C = Dπ.

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CHAPTER 7

ALARM SYSTEMS

Many buildings and complexes beingconstructed today are equipped with some typeof intrusion detection and fire alarm systems.You, as a Construction Electrician, will bechallenged to install, troubleshoot, and maintainthese systems. Numerous detection and fire alarmsystems are in existence today. In this chapter, wewill discuss the function and operation of atypical detection system and of various firealarm systems. When you are in charge of theinstallation or maintenance of either a detectionor a fire alarm system, you should acquirereference material, such as manufacturer’sliterature. If such material is unattainable, lookat NAVFAC MO-117, Maintenance of FireProtection Systems, which provides an excellentdescription of several fire alarm systems. DesignManual 13.02, Commercial Intrusion DetectionSystems (IDS), provides descriptions of variousintrusion detection systems.

The purpose of any alarm system is to eitherprotect life or property or to detect an intrusion.Alarm systems are set up to (1) give early warningso occupants may evacuate the building and (2)notify the fire department and/or security soonenough that they have time to react.

TYPES OF FIRE ALARM SYSTEMS

Building alarm systems may be local or localwith base alarm system connections. They maybe coded or noncoded and may operate either online-voltage or low-voltage electric power. Theircharacteristics are described in the followingparagraphs.

NONCODED ALARM SYSTEMS

A noncoded alarm system has one or morealarm-indicating appliances to alert the buildingoccupants of a fire but does not tell thelocation or the type of device that has been

activated (manual alarm or automatic protectionequipment). The audible and/or visual alarmappliances operate continuously until they areturned off, until a predetermined time has passed,or until the system is restored to normal.The location or type of device originating thealarm condition can be determined by using anannunciator system. An annunciator is a visual-indicating device that will be discussed later in thischapter.

CODED ALARM SYSTEMS

A coded alarm system has audible and/orvisual alarm signals with distinctive pulsing orcoding to alert occupants to a fire condition andto the location or type of device that originatedthe alarm. Coding the audible appliances may helppersonnel to distinguish the fire alarm signal fromother audible signals. Clear and early recognitionof the signal should encourage a more orderly anddisciplined evacuation of the building. A commoncharacteristic of coded alarm systems, especiallyof selective coded and multiplex coded systems,is that the coded alarm identification providedby the audible alarm signals is not repeatedcontinuously. Normally, after four completerepetitions of the coded signal, the codingprocess ends.

THEORY OF OPERATION

In the event of a fire, a certain sequence ofevents has to occur for any alarm system to beeffective. First, the fire has to be detected. Thiscan be done by any of the following means:visually and by operation of a manual pull box,heat detectors, water pressure/flow switches,flame-actuated detectors, or smoke detectors. Anyof these devices will initiate a signal to the firealarm control unit, which is powered by a reliable

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power supply. (See fig. 7-1.) Second, the controlunit accepts the signals from the initiating circuitsand, through relays or other circuitry, providesthe power to operate the indicated devices. Thesealarm devices may include, but are not limitedto, horns, bells, chimes, flashing lights, orannunciators. Finally, operation of the alarm willalert personnel to evacuate and assist fire-fightingpersonnel in locating the fire, thus protecting lifeand property.

In the following paragraphs, we will discussthe principle of operation of the associatedequipment that makes up an alarm system.

EQUIPMENT DESCRIPTION

Figure 7-1 shows how the basic parts of alocal fire alarm system are interconnected.The devices in the diagram are grouped forconvenience in labeling. Physical location andzoning of devices vary for different applications,and many systems do not have all the devicesshown.

POWER SUPPLIES

Fire alarm systems are in two general cate-gories, as determined by the voltage at which thesystems operate: line voltage or low voltage.Regardless of the operating voltage, a system maybe noncoded or coded.

Many older local alarm systems are poweredby alternating current (ac) power only withno provision for standby battery power. Inthese cases, two separate ac circuits (usually120/240 Vac) are used: one to power thefire alarm system operating circuits andanother to power the trouble-signaling cir-cuits of the system. Low-voltage alarm systems,especially those provided with battery standbypower, are most often found where someform of automatic fire detection or automaticfire extinguishing is connected to the alarmsystem. However, recent conversion by mostalarm system manufacturers to solid-stateelectronic design, which is essentially a low-voltagedirect-current (dc) technology, means thatmost recent installations are of the low-voltagetype.

Figure 7-1.—Local fire alarm system diagram.

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System Power Supply

Power supply refers to the circuitry andcomponents used to convert the ac line voltageto low-voltage ac or dc for operating the alarmsystem and for charging standby batteries.If the system is an older one with a dry cell,nonrechargeable standby battery (no longerpermitted by NFPA standards), the power supplyprobably contains a switching arrangement forconnecting the battery to the system when acpower fails. Figure 7-2 is a simplified diagramof a typical dc power supply for powering alow-voltage dc alarm system and for charging arechargeable standby battery.

Transformer T drops the line voltage from 120volts ac to a voltage in the range of 12 to 48 voltsac. The low ac voltage is rectified by diode bridgeD, and the resulting dc voltage powers the alarmsystem through relay contacts S1 and chargesbattery B through the current limiting resistor R.When normal ac power is available, energizingrelay coil S, contacts S1 are closed. If ac powerfails, S1 opens and S2 closes, connecting the

battery to the alarm system. Fuse F1 protectsagainst a defect in the power supply or the alarmsystem during normal ac operation. Fuse F2protects against alarm circuit defects that wouldcause a battery overload during dc-poweredoperation. Removal of resistor R eliminates thebattery-charging feature and allows the use of adry cell battery, which sits idle until ac power fails.At that time, S1 opens and S2 closes, connectingthe battery to the alarm system.

There are many variations of this basic powersupply design. These variations add such featuresas voltage regulation, current limiting, andautomatic high-rate/low-rate charging, controlledby the state of battery charge. All designsnormally provide current and voltage meters, pilotlamps, and switches for manual control ofcharging rate.

Smoke Detector Power Supply

When smoke detectors are used in an alarmsystem, their internal electronic circuits are usuallypowered from the main fire alarm power supply.

Figure 7-2.—Typical dc power supply and battery charger.

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Some types of smoke detectors have a more strictpower supply requirement than other parts of thefire alarm system, especially with regard to purityof the dc voltage level. The power supply ofthose smoke detectors must have output voltageregulation and filtering not otherwise required bythe fire alarm system. In those cases, the basicpower supply may be upgraded to power thesmoke detectors as well as the control unit, or aseparate smoke detector power supply may beused in addition to the basic supply. In either case,if the system has battery standby, it is usuallycommon to both power supplies.

CONTROL UNIT

The fire alarm control unit provides termina-tion points for all initiating circuits, indicatingcircuits, remote annunciators, and other auxiliarydevices. The control unit accepts low currentsignals from the alarm-initiating circuits and,through relays or other circuitry, provides thelarger current required to operate the alarm-indicating devices and/or auxiliary devices. Thecontrol unit also continuously monitors thecondition of the alarm initiating and indicatingcircuit wiring and provides a trouble indicationin the event of an abnormal condition in thesystem, such as an ac power failure or a wiringfailure.

The control unit is usually housed in a sheetmetal cabinet (fig. 7-3). The control unit usuallyprovides annunciation of signals (telling where asignal originates).

Because all circuits end at the control unit, itis a convenient test location. Test switches (ifprovided) are usually inside the locked door ofthe control unit. If the switches are key operated,they may be on the control unit cover rather thaninside the cabinet.

Local Alarm Signaling

Because of the critical nature of fire alarmsystems, a feature known as “electrical super-vision” has been designed into these systems.Alarm systems must be in service at all times;electrical supervision causes a warning (trouble)signal if some potential or actual electricalproblem exists in the alarm system. This troublesignal is clearly distinguishable from a fire

Figure 7-3.—Control unit with annunciation.

alarm signal. Figure 7-4 shows a typical localalarm signaling circuit using electrical super-vision.

A continuous small electrical current, suppliedby the fire alarm control panel, flows through theseries loop formed by one side of the initiatingcircuit, the end-of-line resistor, and the other sideof the initiating circuit as indicated by the arrow.The fire alarm control panel reacts to this constantlow current as a no-alarm or normal condition.

Under normal conditions, the alarm andtrouble relay coils have the same low value ofsupervisory current flow. This value is inadequateto close the normally open contacts of the alarmrelay. The trouble relay, being more sensitive, isenergized by the supervisory current, and thenormally closed contacts (TR1) are held open. Ifthe supervisory current drops to zero because ofa broken wire anywhere in the initiating circuit,the trouble relay is de-energized, and the TR1contacts close, causing an audible and visualtrouble signal. Also, the portion of the circuitbeyond the broken wire will not operate in theevent of an alarm.

If no wires are broken, closing the contactsof an initiating device provides a low-resistance

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current path, short-circuiting the end-of-lineresistor and increasing the alarm relay coil current.The alarm relay is energized, causing its contacts(AR1) to close and the alarm bells to ring.Continued fire alarm operation with a broken wiredepends upon the location of the break and whichinitiating device is actuated.

Remote Alarm Signaling

Because of excitement, a lack of knowledge,or a lack or responsible personnel on the premises,

people frequently do not react properly to a localfire alarm signal. Therefore, it is usually desirableto connect building alarm systems to a remotereceiving station manned at all times by competentpersonnel who can take the proper action-toextinguish the fire and evacuate the building ifnecessary or to see that necessary maintenance iscompleted. Most fire alarm and supervisory alarmcontrol panels have provision for connection toa remote receiving station. These connectionsare usually in the form of auxiliary relaycontacts that can be connected to operate an alarmtransmitter.

Figure 7-4.—Typical local alarm signaling circuit.

7-5

Figure 7-5 shows a typical remote alarmsignaling circuit, a commonly used arrangementfor fire department connection to individualbuilding alarm systems. The alarm transmitter caneither be a part of the fire alarm control cabinetor be operated by it.

If, instead of a fire condition occurring, oneof the two telephone wires is broken, thesupervising current supplied by the transmitter willdrop to zero, closing the receiver module relaycontacts, lighting the lamp, and sounding thebuzzer. The meter indication will be zero, markedon the meter face as “T” (trouble).

If a telephone wire is broken before an alarmcondition occurs, the voltage will be reversed bythe alarm transmitter, but the “no current”condition at the alarm receiver will not bechanged, and no alarm will be caused. The troublecondition will continue until the broken wire isrepaired.

In the circuit shown in figure 7-5, if an alarmcondition occurs, the transmitter contactstransfer, reversing voltage and current polarity ofthe telephone line pair. The meter in the receivermodule changes indication from N (normal) toA (alarm). Current flow through the receivermodule relay is blocked by diode D1, and thereceiver module relay contacts close, lighting thelamp and sounding the buzzer. The current for

meter alarm indication flows through the meterand diode D2.

Auxiliary Devices

A building alarm system control unit may haveauxiliary contacts that operate auxiliary functionswhen an alarm occurs. For auxiliary devices, thepower source can be either the main fire alarmpower supply or line power, if battery standbypower is not required for the auxiliary functions.A failure of auxiliary functions should notadversely affect the primary function of the alarmsystem, which is to warn the occupants of a threatof fire.

One auxiliary function included in themajority of fire alarm systems today is theheating, ventilation, and air conditioning (HVAC)fan shutdown. Auxiliary contacts are connectedinto the motor starter circuit for each fan that isto be shut down upon alarm.

It may be more convenient to use an alarmvoltage output from the control unit to cause fanshutdown. A relay with multiple contacts (amultipole relay) for controlling multiple fans islocated near the motor control center or thetemperature control panel. The relay coil isenergized by alarm voltage from the alarm controlunit, causing contacts to open in the individual

Figure 7-5.—Typical remote alarm signaling circuit.

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fan control circuits, thereby stopping all the or a manual fire alarm. A manual fire alarmfans. system may include many initiating devices.

Other auxiliary devices controlled by the alarmsystem can perform the following functions: firedoor closure, ventilation louver closure, and/orrelease of extinguishing agent. Consult themanufacturer’s literature and/or base blueprintsto determine the options included in your firealarm system.

ALARM-INITIATING DEVICES

An alarm device initiates a fire alarm signaleither as a result of manual operation, such as amanual fire alarm station, or automatically, asin the case of heat, smoke, flame, or water-flowdetectors. Initiating devices, with rare exceptions,have normally open contacts that close on analarm condition.

Normally closed devices are intended only forsuch applications as operating the shutdowncontrol for fans or other auxiliary devices.

Manual Fire Station

Figure 7-6 shows a manual fire station, whichis also called a manual pull box, a manual firebox,

Figure 7-6.—Manual pull box.

The manual fire alarm devices are to providea means of manually activating the fire alarmsystem. They are used in all types of fire alarmsystems. They may be the only type of initiatingdevices provided or they may be used withautomatic initiating devices, such as heat or smokedetectors.

Manual fire stations are generally located nearmain exits from a building or from a floor of amultistory building and in certain work areascontaining unusual fire hazards, valuableequipment, or records subject to fire damage.Paint shops, aircraft repair areas, computerrooms, and telephone equipment rooms areexamples of such work areas.

Single-action and double-action devices areboth used. The single-action device requires oneaction to cause an alarm, and a replaceable glassrod is broken with each operation. The double-action device requires two actions to cause analarm: first, the glass window is broken; second,the alarm lever is pulled. The glass elements inthese two examples are necessary parts to retainall the design features. Both devices can be testedwithout breaking the glass parts by opening thedevice. To open a manual fire alarm box, you mayhave to loosen a setscrew or operate a latchwith a hexagonal (allen) wrench, screwdriver, orkey.

Manual initiating devices should be visuallyinspected monthly for physical damage, such asthat caused by vandalism or painting. At this time,count the devices to be sure that none have beenconcealed or removed. Correct deficienciespromptly. Test repaired units by mechanicaloperation and transmission of local and remotesignals without glass breakage. Be sure to informbuilding and fire department personnel that thetest is to be performed.

Test all manual devices on a rotation scheduleso that all devices are tested semiannually. Somedevices should be tested each month, at least onefrom each initiating circuit (zone) or remotesignaling circuit, in the case of coded fire alarmboxes. Keep accurate records of devices tested,their locations, and the rotation scheme. Store acopy of building system diagrams and test recordsin the control unit.

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Figure 7-7.—Low-profile heat protector.

Heat Detectors

Heat detectors are probably the most widelyused initiating device for general-purposeautomatic fire alarm systems. Some commontypes of heat detectors are discussed below.

SPOT TYPE OF FIXED-TEMPERATUREDETECTORS.—Fixed-temperature heatdetectors that are categorized as spot type havea detecting element or elements that respond totemperature conditions at a single point or in asmall area.

These detectors are shown in figures 7-7 and7-8. Other fixed-temperature detectors aremanufactured in the style shown in figure 7-9. The

Figure 7-8.—Replaceable-element fixed-temperature heatdetector.

Figure 7-9.—Combination fixed-temperature/rate-of-riseheat detector.

spot type of fixed-temperature detectors is usedmainly in unattended spaces to detect smolderingfires that increase the temperature of a detectorabove its design value, usually 135°F to 145°F or185° to 200°F. The higher temperature devices areused in spaces that may reach higher temperaturesunder ordinary conditions, such as boiler rooms,attics, or cooking areas.

The device usually is actuated by the meltingor fusing of an element made of a fusible metalalloy. Actuated devices usually can be detectedby visual examination.

In the devices shown in figures 7-7 and 7-8,the smaller diameter part in the center drops away.In figure 7-9, the dimple becomes a hole when thedetector operates.

Fixed-temperature devices are often designedfor one-time operation, and the whole device(figs. 7-7 and 7-9) or the element (fig. 7-8) needsto be replaced.

RATE-COMPENSATED DETECTORS.—This type of detector is shown in figure 7-10. Forlow rates of temperature change (up to 5°F perminute), rate-compensated detectors operate likefixed-temperature detectors. For higher rates oftemperature change, the detector anticipates therise in temperature to its set point and operatesfaster than the usual fixed-temperature detector.It automatically resets and is reusable when the

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Figure 7-10.—Rate-compensated heat detector.

temperature drops below its design value. Thereis no difference in external appearance betweenan actuated device and an unactuated device;therefore, its status must be checked electrically.

RATE-OF-RISE DETECTORS.—Thesedetectors are found in the styles shown in figures7-7 and 7-9. Rate-of-rise detectors cause an alarmwhenever the rate of temperature rise exceedsabout 15°F per minute. Heating causes an increasein air pressure inside the detector. A slow increasein pressure bleeds off through a breather valve,while a fast increase operates a bellows type ofdiaphragm, which operates the alarm contact,causing a signal. The detectors automatically resetafter actuation and are reusable. Actuation is notvisually indicated.

COMBINATION DETECTORS.—Thesedetectors are found in the styles of figures 7-7 and7-9. The combination detectors contain bothfixed-temperature and rate-of-rise elements. Ifeither element actuates, an alarm results. Thefixed-temperature element is visible and actuatesonly once. If the fixed-temperature elementactuates, the whole device must be replaced. Therate-of-rise element automatically resets and isreusable.

TESTING HEAT DETECTORS.—Test heatdetectors semiannually on a rotation schedule toensure that all devices will be tested over a 5-yearperiod. During the semiannual tests, select at leastone detector from each initiating circuit (zone) for

testing. Nonreusable detectors with replaceableelements can be tested by removing and rein-stalling the element. Test and replace all non-reusable detectors in a 5-year period. The testingprovides training opportunities and improves thealarm system reliability.

Keep accurate records of devices tested, theirlocations, and the rotation scheme so no devicesare overlooked and so that other personnel cando the testing.

The spot type of heat-actuated detectors canbe tested using various sources of heat. If thedetector is located in a hazardous area that maycontain explosive fumes or other highlyflammable materials, use an explosionproof lamp.For nonhazardous areas, the heat source may bean infrared lamp, a hair dryer, or a hot-air gun.Be careful to avoid heat or smoke damage toreusable detectors and to the surroundings.

To test combination detectors that have anonreuseable fixed-temperature element, test boththe rate-of-rise and fixed-temperature features.First, use a higher heat level for a shortperiod and direct it away from the fusiblefixed-temperature element, if possible, to actuateonly the rate-of-rise element. When an alarmoccurs, allow cooling; reset; and then apply moregradual heat to actuate the fixed-temperatureelement.

Smoke Detectors

Smoke detectors are faster acting than heatdetectors. They are frequently used in fast-actingautomatic fire detection systems that incorporatean extinguishing agent release function to protecthigh value or highly combustible storage and workareas. Computer rooms, aircraft storage andrepair areas, explosive processing areas, andtelephone equipment rooms are frequentlyprotected in this way.

Smoke-actuated detectors may be of thephotoelectric type used in spot, beam, or ductdesigns or the ionization type, which is appliedin the spot or duct design. The principle ofoperation is the same, regardless of design.

PHOTOELECTRIC SMOKE DETECTORS.—Most modern photoelectric detectors of the spottype use the light-reflection principle to detect

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smoke. The diagram in figure 7-11 shows a typicalarrangement of functional parts. A pulsed lightbeam from a light-emitting diode (LED) with itsassociated optics is projected across the interiorof a blackened chamber that may contain smoketo be detected. A photocell, with its optics,looks toward the projected beam along a lineperpendicular to the beam. When smoke entersthe chamber, the smoke particles reflect a smallportion of the light beam toward the photocell,which provides a voltage to be amplified andcauses an alarm. The light source may bemonitored ahead of the smoke chamber andregulated to prevent variation of the lightintensity from causing erratic detector behavior.

In detectors of the beam type, the light sourceand photocell are mounted near the ceiling onopposite sides of the protected room. Whensmoke obscures the light below a predeterminedvalue at the photocell, an alarm results.

Detectors of the duct type are intended fordetecting smoke in an air-handling system. Adetector of this type is mounted directly on the

outside of an air duct or nearby with a samplingtube extending about three quarters of theway across the inside of the duct. The airflows into the smoke detection chamber mountedon the outside of the duct, and back intothe duct through a return tube, having a holeor holes directed downstream. As long asthere is airflow in the duct, a portion of thatair continuously flows through the detectionchamber.

IONIZATION SMOKE DETECTORS.—Asmall amount of radioactive material ionizes theair inside a chamber that is open to the ambientair. A measured, small electrical current is allowedto flow through the ionized air. The small, solidparticle products of combustion that enter thechamber as a result of fire interfere with thenormal movement of ions (current), and when thecurrent drops low enough, an alarm results. Atwo-position switch to control sensitivity may beprovided. A detector of this type is shown infigure 7-12.

Figure 7-11.—Typical arrangement of photoelectric smoke detector components.

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Figure 7-12.—Ionization Smoke detector.

Modern ionization detectors have additionalmeans to improve stability and immunity toatmospheric effects. A reference chamber isvented to the outside through a small orifice,which does not readily admit smoke particles.Temperature, humidity, and pressure changes aresensed by both the reference chamber and thesmoke chamber, and their effects on alarmsensitivity are eliminated by electronic balancing.

The major difference between detectors of thespot and duct types is the method of moving thesmoke into the detection chamber. The spot typedetects or relies on convection of air in a room.The duct type is intended. for detecting smoke inan air-handling system and is mounted directlyon the outside of an air duct or nearby withsampling and return tubes extending completelyacross the duct.

TESTING SMOKE DETECTORS.—Beforetesting detectors that are connected to auxiliaryfunctions, such as release of a fire extinguishingagent, release of fire doors, or fan shutdown,disconnect or bypass the auxiliary functions(unless the test is specifically intended to testthese features). Before the test, notify the firedepartment and persons where the audible signalscan be heard.

Most PHOTOELECTRIC detectors have abuilt-in test feature. In some models, a test lightsource actuated by a key-operated test switch orby a magnet held near a built-in reed switch causeslight to reach the normally dark, smoke-sensingphotocell in a quantity approximately the light ofan average smoke test. In other detector models,the smoke simulation is performed by insertinga reflective surface into the smoke chamber so thatthe actual source light is reflected to the smoke-sensing photocell. Test at least one detector ineach initiating circuit (zone) monthly. Follow arotation schedule so that all detectors are testedsemiannually.

Test failures or false alarms may result froman excessive accumulation of dust or dirt causedby an adverse environment. Blow out the smokechambers with low-pressure air. (Partial dis-assembly of the detectors and disconnection ofdetectors’ power, following the manufacturer’sinstructions, are required.) Since the photocell isnormally dark, disassemble and clean it in adarkened area to minimize the photocell recoverytime after cleaning before repowering thedetectors. Allow approximately 30 minutes forrecovery after reassembly of the detectors beforereconnecting power.

Disconnecting power by unplugging one detec-tor may also disconnect power from the other

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detectors further from the power source.Inform the fire department before or during anyextended testing period.

Special equipment that may be required forcleaning consists of a low-pressure air source forblowing out dust and a suction cup for chambercover removal.

If the cleaning does not correct the false alarmsor failure to alarm, return the detectors to themanufacturer for repair.

Test at least one IONIZATION detector ineach initiating circuit (zone) monthly. Follow arotation schedule so that all ionization detectorsare tested semiannually, following the manu-facturer’s instructions. Any detectors that producefalse alarms between semiannual tests or do nottest satisfactorily should be checked for sensitivity,following the manufacturer’s instructions andusing test equipment available from the manufac-turer or other sources. An aerosol synthetic smokeis available from some manufacturers for testingtheir detectors.

Unsatisfactory tests or erratic operation mayindicate a need to remove accumulated dust ordirt. The frequency of cleaning should be basedon results of regular tests and local conditions.Clean, check, and test operation and sensitivity,following the manufacturer’s instructions. Forloose dust deposits, blow the area with low-pressure air after removing a protective cover. Formore stubborn deposits, disassemble and clean,using a liquid recommended by the manufacturer.Recheck sensitivity and adjust if necessary aftercleaning and drying thoroughly.

WARNING

Some smoke detectors of this type producean electrical shock that may not be severeenough to cause injury directly but couldcause a fall from a ladder. Some manufac-turers, because of such possible injury topersonnel or damage to the detectors, donot recommend servicing by anyone otherthan factory-trained personnel. Personnelin the customer service departments ofmost manufacturers can give advice on thetelephone for specific problems. Beprepared to give the equipment modelnumber and other pertinent information.

Flame-Actuated Detectors

Flame-actuated detectors are optical devicesthat “look at” the protected area. They

Figure 7-13.—Infrared flame detectors.

generally react faster to a fire than nonopticaldevices do.

INFRARED FLAME DETECTORS.—Figure 7-13 shows two typical infrared (IR) flamedetectors. IR flame detectors respond directly tothe IR, modulated (flickering at 5 to 30 cycles persecond) radiation from flames. The sensor designusually incorporates a delayed response, selectablein the range of 3 to 30 seconds, to minimizeresponses to nonfire sources of radiation. Thus,alarms are caused only by sustained, flickeringsource of IR radiation.

The IR flame detector is ineffective forsmoldering or beginning fires. It is used wherepossible fires would develop quickly (fuels, suchas combustible gases and liquids, or loose cottonfiber), and it is capable of protecting a large areaif it is mounted high on a ceiling or wall (30 to50 feet).

The sensitivity of IR detectors to a fire isaffected by the distance of the device from the

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fire. For example, if the distance is doubled, thefire has to be four times as large to be detected.To maintain immunity to possible nonfire sourcesof alarms, you should usually select longerresponse delays (10 to 30 seconds) for low (8-foot)ceiling mounting. Shorter delays, in the range of3 to 10 seconds, are used when detectors aremounted on higher ceilings. For high-hazardareas, the detector can be mounted on a lowceiling and a low delay setting used to obtainsensitivity and fast response. Shields to eliminatepossible false alarm sources from the field of viewof the detector are sometimes used, especially ina high-sensitivity application of the device.

Some detector models designed for fastresponse do not have the “flicker” discriminationfeature, but instead have two sensors withdifferent spectral responses. These sensors are

used to distinguish between an actual fire andother sources of IR radiation.

Glowing ember detectors are nondiscriminatingand fast acting. Ambient light levels must bemaintained below 20 footcandles. Location andshielding are important for this type to avoidfalse alarms caused by incandescent lamps andsunlight.

ULTRAVIOLET FLAME DETECTORS.—The ultraviolet (UV) flame detector is extremelyfast and is used in high-hazard applications,such as aircraft maintenance areas, munitionsproduction, and other areas where flammable orexplosive liquids or solids are handled or stored.The detector responds to UV radiation notvisible to humans. Figure 7-14 shows a typical UVdetector. The detector and circuitry may be in asingle housing or in separate housings. They act

Figure 7-14.—Ultraviolet flame detector.

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together as a normally open switch that becomesmomentarily closed, causing an alarm, when UVradiation enters the detector viewing window.Response time is typically less than 25 millisecondsfor an intense UV source. Some models have abuilt-in short time delay (3 seconds, nominal)to reduce responses to lightning and othermomentary events.

Frequently, separate relay contacts areprovided for immediate and delayed alarmoutputs, adjustable up to 30 seconds. A visualindicator, visible through the viewing window,usually indicates detector actuation.

The UV detector is capable of use in explosiveatmospheres, and some models have swivelmounts for directing them at specific hazards.Various models have angular fields of viewranging from 90 to 180 degrees. Sensitivity isusually factory set for the application.

TESTING FLAME-ACTUATED DETEC-TORS.—Flame-actuated detectors should beinspected monthly for physical damage, accumu-lation of lens deposits, and paint. A spot of painton a lens can prevent the detector from “seeing”a critical area in the protected space. Remove orprotect the detectors when painting is being done.

Be sure that auxiliary functions of the flamedetection system are deactivated before testing isdone unless these features are intentionally beingtested. Before the test, inform the fire departmentand persons who would hear the alarm.

False alarms or failure to detect during a testmay be caused by environmental factors or theaiming of the detector. During the monthlyinspection, check that detectors are not blockedand that lenses are shielded from direct rays ofthe sun and other sources of IR, such as weldingequipment, in the case of UV detectors.

If a detector has a clean lens but fails anoperating test, make adjustments and/or performother field maintenance, following the manufac-turer’s instructions. Obtain field service by afactory-trained technician or return the equipmentto the manufacturer for repair.

Infrared Detectors.—On IR detectors (fig.7-13), the dark spot or dome at the bottom centerof each IR device is the lens. Detector lenses mustbe kept clean to ensure the earliest possibledetection of a fire. Test at least one detector ineach initiating circuit (zone) monthly. Follow arotation schedule so that all detectors are testedsemiannually.

A small soldering iron held 6 inches in frontof a glowing ember detector can serve as a heatsource for testing. A 250-watt IR heat lampseveral feet from the detector can serve as a flamesubstitute in testing an IR flame detector.

Ultraviolet Detectors.—Keep UV detectorlenses totally clean. A gradual buildup ofcontaminants frequently found in high-hazardspaces (oil, gasoline, petrochemicals, salt, anddust) block UV radiation. A layer thin enough tobe undetectable to the human eye can cause a UVdetector to be completely blind. Clean lensesaccording to the manufacturer’s instructions.

A test feature designed into some detectorsallows for checking the optical integrity of thedevice. A small UV source inside the detectorhousing is shielded from directly illuminating thesensor. Local or remote operation of a test switchdeactivates alarm circuits and illuminates the testlamp. The test lamp rays then pass through thefront window to the sensor. Detector response tothe test indicates that the window is clean and thatthe sensor and electronic circuits are operational.

Water-Flow-Actuated Detectors

Sprinkler water-flow alarm-initiating devicesare switches, just as fire alarm initiating devicesare. Normally open switches that close upon alarmare frequently used in end-of-line resistor circuits,though some normally closed switches are usedin normally closed loop circuits. However, thealarm-initiating devices for sprinkler water-flowmount differently and sense different conditionsfrom fire-alarm-initiating devices.

Sprinkler water-flow detectors are generallypressure actuated or vane actuated. Pressureswitches are used on both wet- and dry-pipesprinkler systems. Vane switches are widely usedon wet-pipe sprinkler systems.

PRESSURE TYPE OF WATER-FLOWDETECTORS.—Numerous styles of water-flowpressure switches of the pressure-increase type arefound in wet- and dry-pipe systems. (Figure 7-15shows one style.) The usual arrangement forswitch actuation includes a sealed accordionlikebellows that is assembled to a spring and linkage.The spring compression or tension controls thepressure setting of the switch and may beadjustable and/or factory set to the desiredpressure. As water or air pressure in the bellowsincreases, it expands, providing motion againsta spring. The linkage converts the motion of the

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Figure 7-15.—Pressure-increase type of water-flow detector.

bellows into the desired motion to actuate theelectrical switch. If the pressure switch is used ona wet-pipe system, it is usually mounted at the topof a retarding chamber, which reduces the speedof pressure buildup at the switch.

There are also water-flow pressure-increasedetectors that incorporate a pneumatic retardingmechanism within the detector housing. Theretard time is adjustable to a maximum of90 seconds with usual settings in the 20- to70-second range. The retarded switch would beconnected to the alarm port of a wet sprinklersystem alarm check valve. The usual pressuresettings for these switches are in the range of 8to 15 psi.

Pressure-drop detectors can be used in wet-pipe sprinkler systems equipped with a check valvethat holds excessive pressure on the system sideof the check valve. These detectors are mostfrequently used where a water surge or hammercauses false alarms with other types of water-flowdetectors.

The construction of pressure-drop detectorsis similar to that for pressure-increase detectors.The switch for a pressure-drop detector isarranged to actuate on a drop in pressure, andthere is no retarding mechanism or chamber. Atypical switch of this type would be adjusted forsome normal operating pressure in the 50- to130-psi range. The alarm pressure would beadjustable to 10 to 20 psi below the normalpressure.

VANE TYPE OF WATER-FLOW DETEC-TOR.—A vane type of water-flow detector,

Figure 7-16.—Vane type of water-flow detector.

used only in wet-pipe sprinkler systems, is shownin figure 7-16. The vane (a flexible, almost flat,disk) is made of corrosion-resistant material. Thedetector is assembled to the pipe by drilling a holein the wall of the sprinkler pipe. The vane isrolled up to form a tube and inserted into the pipethrough the hole. Once inside the pipe, the vanesprings open, almost covering the inside crosssection of the pipe. The whole detector assemblyis clamped to the pipe with one or two U-bolts.Gaskets and other sealing devices prevent leakageof water out of the riser pipe and into thedetector housing. Operation of a sprinkler causeswater to flow in the system, moving the vane. Amechanical linkage connects the vane to anadjustable retarding device in the detector.

The retarding device, which is usually apneumatic dashpot, actuates the alarm switch orswitches and/or signal transmitter if the vane isstill deflected at the end of the adjustable delayperiod. The retarding device prevents spuriousalarms by delaying the mechanical actuation ofthe alarm switch(es) and/or transmitter to allowthe vane and retarding mechanism to return totheir normal positions after momentary watersurges. The retarding-device setting is usually inthe range of 30 to 45 seconds, though themaximum setting may be as high as 90 seconds.

7-15

TESTING WATER-FLOW-ACTUATEDDETECTORS.—Water-flow-actuated detectorsshould be inspected monthly for physical damageand for paint on information plates and labels.Replace or repair damaged devices immediately.Clean or replace painted plates and labels.Correct other deficiencies promptly.

Test wet-pipe-sprinkler-system-water-flowdevices by causing a flow of water equal to thatfrom one sprinkler by opening the inspector’s testvalve fully. This valve is usually near the end ofthe sprinkler system on the opposite side of thebuilding from the system riser. For sectionalwater-flow detectors, the inspector’s test valve isusually on the opposite side of the section of thebuilding from the riser. The inspector’s test valveis left open to allow full flow until an alarm isindicated at the local control unit or, if thecontrol unit is connected to the base alarm system,until a clear alarm is received at the alarm head-quarters. One person with radio or telephonecommunications at the test valve and one personat each alarm-receiving location are usuallyneeded for testing.

The delay between the start of full flow andreceipt of the alarm signal should be between 15to 90 seconds for retarded signals. Detectors thatsense a pressure drop should respond in less than15 seconds. If the alarm has not been receivedafter water has been flowing for 3 minutes, stopthe test and determine the cause of the problem.

Dry-pipe sprinkler systems have an alarm testvalve at the sprinkler riser in the trim piping thatallows water from the supply side of the dry-pipevalve to exert supply pressure on a water-flowdetector of the pressure-increase type. The alarmtest valve is frequently a small lever valve butmay be a globe valve. It should be permanentlytagged Alarm Test Valve to expedite futuretesting.

The regular trip test of a dry-pipe sprinklersystem to check the operating condition of thesprinkler system can also be used to test the water-flow detector and alarm system if the tests arecoordinated. However, it is not practical totrip-test the dry-pipe valve for every alarm systemtest. Do not open the inspector’s valve at the endof a dry-pipe sprinkler system for an alarm systemtest unless a trip test is desired.

The purpose of these initiating devices is todetect a fire condition and provide that informa-tion to the control unit. The control unit energizesthe indicating circuit to warn building personnelfor evacuation and to inform fire personnel of afire.

ALARM-INDICATING DEVICES

Alarm-indicating devices are the lights orsounding devices that indicate a fire alarm orabnormal condition. These lights and sounds mayalso provide information about where the signaloriginates.

Indicating devices are divided into two majorcategories: visual (annunciators) and audible(bells, horns, chimes, and so forth).

Annunciators

Annunciators give a visual indication of the“zone” or general area where an alarm originated.In some cases, such as a sprinkler water-flowalarm, the annunciator can be arranged toidentify the individual initiating device. In othercases, such as heat detectors, many initiatingdevices can activate the same indicator on theannunciator.

The annunciator indicator can be operateddirectly by auxiliary contacts in the initiatingdevice or from a connection to the fire alarmcontrol unit. A trouble or maintenance conditionin the system wiring is also frequently annunciatedby zone. Usually, a yellow or amber light indicatestrouble and a red light indicates an alarm signal.

An annunciator may be incorporated into thefire alarm control unit, in which case it isgenerally actuated by connection to the controlunit. It may also be located at a remote point, inwhich case it may be actuated either by thecontrol unit or by auxiliary contacts in theinitiating devices. Some installations may have afire alarm control unit with an integral zoneannunciator and a remote annunciator providedelsewhere. Frequently, the control unit standbybattery is used to provide power for annunciatoroperation during power failure.

Annunciator visual indicators may be of thedrop type or the lamp type. Those of the droptype (which are essentially obsolete) use electro-magnetic devices to move a flag into or away froma window to indicate a change in zone condition.Annunciators of the lamp type use pilot lightassemblies to indicate an alarm or troublecondition (usually red for alarm, amber fortrouble). The more common type of annunciatorin use today is the lamp type. Figure 7-17 showsa frequently used incandescent lamp annunciator.

More recent annunciator designs use matricesor arrays of light-emitting diodes (LEDs). Theadvantages of LEDs are low current, long life,and small size, allowing annunciation of manyzones in a small space.

7-16

Figure 7-17.—Remote annunciator (weatherproof)

Audible Signal Devices

Any device that sounds an audible signal isclassified as an audible signal appliance. Theaudible signal appliances most frequently usedin building alarm systems are bells and horns.In addition, there are chimes, cowbells, buzzers,sirens, speakers, air horns, and steam whistles.Audible signals can be used to indicate eithera fire alarm or a system-malfunction (trouble)condition. The audible signal appliances areconnected to audible signal circuits for alarmor trouble indication (depending on theirfunction) at the control unit. Figure 7-18 showssome of the commonly used audible signalappliances.

Audible signal appliances have varying levelsof sound output. Louder devices are forareas with high ambient sound levels or

where the devices cannot be located near thearea to be warned. Hospitals might use softerdevices, such as chimes, to avoid frighteningpatients.

Coded building alarm systems normally usesingle-stroke versions of bells or chimes so thecoded signal can be clearly produced. Vibratorybells, chimes, or horns are used for noncodedsystems but can also be used in coded systems ifthe mechanism used can respond rapidly enoughto provide an accurate rendition of the codebeing transmitted.

In a building that uses audible signalsroutinely, such as bells for announcing classperiods in school, the fire alarm audibleappliances must have a distinct, easily identifiedsound. If the fire alarm signal is coded, thecoding provides the distinctive sound, andit is feasible (though not normal) to usethe same bells for both functions. For a non-coded fire alarm system, necessary distinctionof sound can be obtained by using a com-pletely different type of audible signal appliance,such as a horn or siren, for sounding fire alarmsignals.

Testing Alarm-Indicating Devices

Test alarm-indicating devices monthly withthe monthly inspection. When convenient, thetest may be combined with a fire drill.Test by operating the drill switch or thetest switch at the control unit or by actuatingan initiating device. If the test switch or aninitiating device is used, notify the remote alarmheadquarters because remote signal transmitters

Figure 7-18.—Audible signal appliances.

7-17

and other auxiliary features will be actuated by TROUBLESHOOTINGsuch a test. CIRCUIT FAULTS

While there is an alarm condition, check allthe indicating devices and note any that fail tooperate properly. Audible devices should produceloud, clear, consistent tones, and coded systemcodes should be clearly recognizable. Visualdevices should be bright and steady or pulsating,as intended.

Because of the variations in equipmentfrom manufacturer to manufacturer and thenumerous types of circuits and devices in use,it is important to have the following referencematerials available to personnel responsible forservicing:

Test annunciator lamps by operating a “lamptest” switch if it is provided; otherwise, cause analarm and a trouble condition on each zone. Itis usually convenient to cause these conditions atthe control unit initiating circuit terminals.

Wiring and Equipment SchematicDiagrams.

Complete, accurate wiring diagrams of eachtype of device in use, of each circuit as installed,and equipment schematic diagrams.

When a single indicating’ device fails tooperate, it is usually defective. If a group ofdevices fails to operate, the fault is usually adefective circuit.

Manufacturers’ Data Sheets.

The descriptive information in manufacturers’data sheets on all equipment in use and

Figure 7-19.—Typical fire alarm system schematic diagram.

7-18

manufacturers’ instructions for any special testingand maintenance.

System Revision Information.

Information on all extensions or modificationsto existing fire alarm systems.

Tags.

Identification of wires removed from ter-minals during repair or testing is essentialto ensure accurate reconnection. Improperlyconnected wires may make a fire alarm deviceor circuit ineffective or may actually damageequipment.

In general, detectors are returned to themanufacturer as a complete package for repair.However, control units and annunciators are largeand interconnected with a number of other systemcomponents, and there should be some attemptat local repair before you ship the total unit tothe manufacturer.

Circuit faults may occur in the connectionto the power source, in the alarm-initiatingcircuits, and in the alarm-indicating circuits.Procedures for locating the fault dependon which one of these is involved. Figure7-19 represents a typical building fire alarmsystem.

POWER SUPPLY CIRCUIT FAULTS

The common components in low-voltagecontrol units that may require occasionalreplacement or maintenance are relays, resistors,capacitors, diodes, transformers, fuses, switches,lamps or LEDs, meters, and wiring. In addition,a modular control unit has replaceable modules.The modules plug into the main control unitassembly. The modules vary in construction butusually contain solid-state devices mounted on oneor more printed circuit boards (PCBs). Sometimesthe modules are sealed, but more often they canbe disassembled for repair. Each module mayrepresent one zone or a group of zones, or it mayperform a nonzoned function, such as one of thefollowing:

Providing a time delay (such as shuttingoff bells after 15 minutes)

Providing output contacts for a remoteauxiliary function (such as fan shutdown)

Transferring power (from commercialpower to standby power and back)

Sounding a local trouble buzzer

Controlling audible signal devices

Providing a reverse polarity alarm output(for remote station connection)

Use the manufacturer’s diagrams and servicinginformation to narrow down any problemsto a small area. If a problem can be isolatedto one of these modules or if a problemappears to be related to a zone module,the most immediate repair is to replace themodule. If the module is not sealed, inspectit for a condition such as an overheatedresistor or transistor, a poorly soldered con-nection, a bent connector pin, or a malfunctioningrelay. Repair or replace the parts, resolderthe connection, or straighten the connectorpin. For other conditions more difficult toanalyze, replace the module. (Keep spares onhand.)

CAUTION

Any soldering that is performed, especiallyin replacement of solid-state devices onprinted circuit boards, must be performedwith care, following good commercialsoldering practice.

Grounded and Short Circuits

A ground fault in the power source wiringwill typically cause the building circuit breakerfor the fire alarm system to trip. The equip-ment will continue to operate on standbybattery, if one is provided. If the batteryis discharged or if no battery is provided,the equipment affected will be out of service,and fire alarm protection will be nonexistent.Because battery capacity is limited and com-plete discharge should be avoided to preventpermanent damage to the battery, repair the faultimmediately.

7-19

START

Ac power failure. Circuit breakertrips.

Disconnect both ends of powersource wiring and tape equipmentends of wire separately.

CAUTION: Ensurepower is off beforetouching wires.

Check for continuity to conduitfrom source end of power wiresusing ohmmeter R × 1 scale.

Measurable low resistance confirmsground fault in wiring.

Separate circuit wiring in halves at a con-venient junction box, taping new exposedends. Check both halves of each wire forcontinuity to conduit.

Wire section that shows continuity toconduit is the grounded section. Redivideit in halves and check both halves asbefore.

When grounded section is found, examinewire and splices for bare wire thatcould explain the continuity to theconduit.

Infinite resistance rules out power sourceground as the cause of the power failure.

Check for continuity between each powercircuit wire and each of the other powercircuit wires.

Measurable low resistance Infinite resistancefor any reading indicates readings rule outshort circuit between power power source wiringcircuit wires for which low as the cause of thereading was obtained. power failure.

See figure 7-21 forshort-circuit trouble-shooting.

Check equipmentfor internal shortcircuit or ground.

ENDInsulate bare wire with insulating tape orinsulate splice with wire connector or in-sulating tape. Recheck continuity toground to confirm repair.

Reconnect disconnected wires and restorepower.

END

Figure 7-20.—Troubleshooting chart for a power circuit ground fault.

7-20

START

CAUTION: Ensurepower is off beforetouching wires.

Continuity between power circuitwires indicates short circuit.

Separate circuit wiring in halves ata convenient junction box, tapingnew exposed ends. Check bothhalves for wire-to-wire continuity.

Section of wiring that shows con-tinuity between wires is the short cir-cuited section. Redivide it in halvesand check both halves as before.

Continue dividing in halves untilshort circuited section is found. Ex-amine wires and splices for bare ad-jacent wires, which could explain theshort circuit.

Insulate bare wire with insulatingtape or insulate splice with wire con-nector or insulating tape. Recheckcontinuity between separate powerwires to confirm repair of shortcircuit.

Reconnect disconnected wires andrestore power.

END

Figure 7-21.—Troubleshooting chart for a short circuit fault in a power circuit.

Figure 7-20 is a power circuit ground faulttroubleshooting diagram. Figure 7-21 is a similardiagram for a short-circuit fault in the same wiring.

Open Circuits

An open-circuit fault in one of the linessupplying the fire alarm system will cause

signs of power failure, but circuit breakersor fuses may show normal conditions. If thefire alarm control unit has a power failureor trouble signal feature, it will be activated,indicating that a problem exists. Refer tofigure 7-22, which is a troubleshooting chart forthis condition.

7-21

START

AC power failure. Circuit breaker not tripped.Indicates “open” power circuit fault.

Disconnect both ends of power source wiring. Twistwires together and connect to electrical ground or to con-duit with auxiliary wire, if necessary.

Check for continuity at equipment end of wiring withohmmeter. Measure resistance from each wire to elec-trical ground or to conduit. Wire for which measure-ment is infinite is open wire.

One wire shows infinite resistance toground. Open junction boxes betweenpower panel and equipment and inspectfor loose splices in wire of color show-ing infinite resistance.

Loose splice(s)found. Correctloose splices.Recheck con-tinuity.

Infinite resistance remains. At approximatehalfway point, connect power circuit wires

as before at equipment end.together and to ground and recheck continuity

All wires show low resistance to ground.Open circuit fault is in position betweenpresent ground and previous ground.

Open junction boxes in suspicious sec-tion of conduit and inspect for loosesplices in wire of color showing infiniteresistance.

or elsewhere.

All wires show low resistance toground or conduit. This indicatesoriginal problem was loose connec-tion at one of disconnected terminals

Pull on wires individually at equip-ment end until one to two inches ofadded wire is obtained at equipmentend. Recheck continuity as beforeafter confirming ground connectionat power panel end is still good.

All wires show low resistance to ground.Reconnect wires with power off.Tighten terminals. Restore power andconfirm normal operation.

END

All wires show low resistance toground. Reconnect wires with poweroff. Tighten terminals. Restore powerand confirm normal operation.

Loose splice(s) found. Correct loosesplice(s). Recheck continuity as testedwhen last infinite resistance reading wasobtained.

END

Infinite resistance remains. At ap-proximate midway point of suspi-cious section of conduit, at aconvenient junction box, connectpower circuit wires together and toground. Separate wires toward equip-ment end and remove previousground connection at that point.Check for continuity from each wireto ground.

Continue process until open sectionis isolated and can be replaced orrepaired.

END

Figure 7-22.—Troubleshooting chart for an open fault in power circuit.

7-22

INITIATING CIRCUIT FAULTS

Initiating circuits, like power supply circuits,may experience shorts, opens, or ground faults.Operating tests of initiating circuits to locate andrepair faults are best performed after normalworking hours to avoid disruption of normalactivities.

Short Circuit

A short circuit between two points on the sameside of the circuit does not harm systemoperation and is normally not detected unless theshort circuit also involves one or more groundfaults. A short circuit between wires on oppositesides of the circuit causes an alarm. A clue to thiscondition is the fact that an alarm conditionexists for an initiating circuit, but inspection showsthat none of the initiating devices connected tothat circuit have operated. The following trouble-shooting steps will guide you in finding andrepairing the fault:

1. Tag and disconnect the initiating circuitloop at the control unit or annunciator terminals.

2. Measure the initiating circuit resistancewith an ohmmeter. A value of 100 ohms or lessconfirms a short circuit. The lower the value, thecloser to the source the fault is located. Ameasurement equal to the end-of-line resistorvalue or slightly higher is normal and suggestslooking in the control unit or annunciator for thefault. (Determine the proper value of the resistor,usually 1,000 to 2,000 ohms, from referencematerials on the equipment.)

3. If resistance measured is low, confirminga short circuit, move to a point that is electricallyabout halfway between the source and the end-of-line resistor for the next resistance measure-ment. A low resistance, near zero, indicates theshort circuit is quite near the test point. Aresistance of 50 to 100 ohms indicates that thecircuit is a long one of smaller gauge wire and thatthe short-circuit fault is near the end of thecircuit. At each new test location, break bothsides of the circuit by disconnecting wires at aconvenient initiating device or junction box.Measure circuit resistance in the direction towardthe end of the circuit.

4. Low resistance measured from the secondlocation, less than 100 ohms, indicates theshort circuit is still farther toward the endof the circuit. High resistance, approximating

the end-of-line resistor value, indicates that theshort circuit is closer to the control unit.

5. Continue moving toward the short circuit,dividing the circuit approximately in halves eachtime, and repeat the measurement of resistancetoward the end of the circuit using the guidelinesin Step 4 as the rule for interpreting eachsucceeding measurement.

6. When the fault is located, repair it,reconnect the disconnected wires, and restore thecircuit to normal service.

Open Circuit

An open-circuit fault in an initiating circuitstops the supervising current. The troublerelay at the control unit or annunciator de-energizes, and trouble indicators are activatedfor the circuit. Initiating devices closer tothe control unit or annunciator than the openfault may continue to function. Devices beyondthe fault cannot operate. If an open-circuitfault occurs, turn off any audible troublesignals by operating the trouble silence switch.Continue troubleshooting by using the followingsteps:

1. Tag and disconnect the initiating circuitloop at the control unit or annunciator terminals.

2. Measure the initiating circuit resistancewith an ohmmeter. An infinite reading (no changein meter reading from the reading with the meterdisconnected from the circuit) confirms an open-circuit fault. A measurement equal to the end-of-line resistor value, or slightly higher, is normaland suggests looking in the control unit orannunciator for the fault.

3. If the open-circuit fault is confirmed, leavethe two circuit wires off their terminals, tapedseparately. Move to a point that is electricallyabout halfway between the source and the end-of-line resistor for the next resistance measure-ment. Choose a convenient initiating device orjunction box and measure resistance across thetwo sides of the initiating circuit. If the measure-ment is still infinite, the open-circuit fault is stillfarther along the circuit toward the end-of-lineresistor. If the measurement is now about equalto the end-of-line resistor value, the open-circuitfault is between the present measurement pointand the source.

4. Move toward the fault to a pointelectrically about halfway between the presentmeasurement point and the end-of-line resistor or

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the source, and measure resistance across thecircuit.

5. Infinite readings indicate the open-circuitfault is toward the end-of-line resistor from thenew test point. Readings approximating the end-of-line resistor value indicate the open-circuit faultis toward the source.

6. Continue taking new readings, advancingtoward the fault. Look especially for looseconnections at splices and at initiating-devicescrew terminals.

7. When the fault is located, repair it,reconnect wires at the control unit or annunciator,and restore alarm service.

Grounded Circuit

A single ground fault on an initiating circuitshould not cause any malfunction, but a circuittrouble indication may be caused at the controlunit or annunciator if ground-fault detection isa feature of the equipment. Even a single faultshould be corrected so that a possible additionalfault will not cause a serious deficiency in thealarm system. Two ground faults on oppositesides of the initiating circuit cause a short circuitbetween the two faults. Follow troubleshootingdirections described earlier for a short-circuitfault.

Troubleshoot for a single ground fault usingthe following steps:

1. Tag and disconnect the initiating circuit atthe control unit or annunciator terminals.

2. With an ohmmeter, check for continuitybetween each end of the circuit and an unpaintedspot on the electrical conduit or another groundconnection, such as a cold-water pipe.

3. Continuity confirms that at least onecircuit ground fault exists. An infinite readingsuggests looking in the control unit or annunciatorfor the ground fault.

4. At a point that is electrically about halfwaybetween the source and the end-of-line resistor,break both sides of the circuit by disconnectingwires at a convenient initiating device or junctionbox. Check for continuity between each wire andground separately.

5. Each time continuity to ground is found,move toward the ground fault at a new test pointabout halfway between the present test point andthe last previous test point or the end of thecircuit in that direction (source or end-of-lineresistor). Look especially for wet, pinched, anddamaged wire.

6. When the fault is located, repair it,reconnect wires at the control unit or annunciator,and restore alarm service.

INDICATING CIRCUIT FAULTS

An open- or short-circuit fault in an indicatingcircuit causes a trouble indication at the controlunit. A ground fault may also cause a troubleindication if ground-fault detection is a featureof the control unit.

Short Circuit

A short-circuit fault in an indicating circuit isdifficult to detect by the usual test methodsbecause the normal circuit resistance is quite low.A short circuit is just a low resistance in parallelwith the low-resistance indicating devices.

The symptoms would be a blown fuse at thecontrol unit or power supply during a routinesystem test or fire drill and audible devices thatdo not operate as loudly as usual.

If you suspect a short-circuit fault, thefollowing troubleshooting steps may help locatethe fault:

1. There may be several indicating circuitspowered from one power supply or fuse in thecontrol unit. Separate the several circuitsfrom each other by tagging the wires anddisconnecting them from the control. unitterminals. It may be necessary to make continuitymeasurements to confirm that the wires from eachcircuit are tagged separately. Compare theresistance readings for the indicating circuitsusing the × 1 resistance range of the ohmmeter.If there is a short-circuit fault, that circuit shouldhave a lower resistance reading than the others.Insulate with tape the individual bare wires of thecircuit being checked.

2. Determine how the circuit wires are routed,using the best available information you may haveto trace the wire or conduit route. Move to a pointelectrically about halfway between the control unitand the most distant indicating device for thenext check. At a convenient initiating device orjunction box, separate the wires leading back tothe control unit from those leading to the moredistant indicating devices by disconnecting themat device terminals or at splices. Measure circuitresistance in both directions. The short-circuitfault should be in the direction of the lowerresistance.

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3. Move toward the fault to a new test pointabout halfway between the present test point andthe last test point or the end of the circuit in thatdirection (power source or last indicating device).Separate the wires toward the control unit fromthose leading away from the control unit andagain measure the circuit resistance on the × 1scale of the ohmmeter in both directions. Thefault will be in the low-resistance direction.

4. Continue to move toward the fault, lookingfor pinched and damaged wires and forimproper connections at indicating devices. Makecareful measurements at each new test point sincethe difference between normal and abnormalresistance may be only slight.

5. When the fault is located, repair it,reconnect all wires, test the indicating devices, andrestore the alarm system to service.

Open Circuit

In a two-wire parallel circuit, one open-circuitfault near the control unit would deactivate allthe indicating devices. The only sign of an open-circuit fault is the failure of one or more indicatingdevices during an alarm system test or fire drill.The following troubleshooting steps will helplocate the fault:

1. Operate the system test or drill switch atthe control unit and check the operation of eachindicating device on the suspected faulty circuit.

2. Check the circuit connections at any devicewith intermittent or weak signals. If a groupdoes not work, check circuit connections at theworking and nonworking devices at each end ofthe group. Make sure that terminal screws areclean and snug and that there are no broken wiresat the devices checked.

3. If the fault was not located in Step 2, checkthe wiring between working and nonworkingdevices, looking especially for poor spliceconnections at junction boxes.

4. If all the indicating devices on a circuitfail to work, check for a blown fuse or poorconnections at the control unit or at the firstindicating device on the circuit.

5. When the open-circuit fault is found, repairthe fault and retest the indicating circuit toconfirm that all indicating devices work properly.

Grounded Circuit

A single ground fault in an indicating circuitmay not cause any symptoms unless the indicating

circuit is ac-line powered. If the ground fault ison the “hot” side of the ac circuit and theindicating circuit is tested, a fuse or circuitbreaker at the control unit or at the power panelsupplying the alarm system will blow. A groundfault on the neutral side of the indicating circuitcauses no symptoms. Two ground faults onopposite sides of the indicating circuit are also ashort circuit. Troubleshooting for the shortcircuit may be accomplished as described earlier.

Troubleshoot for a ground fault using thefollowing steps:

1. Tag and disconnect the indicating circuitwires at the control unit.

2. With an ohmmeter, check for continuitybetween each circuit wire and an unpainted spoton the electrical conduit or another groundconnection, such as a cold-water pipe.

3. Continuity confirms that there is at leastone circuit ground fault. An infinite readingsuggests looking in the control unit for the groundfault.

4. If a ground fault in the indicating circuitis confirmed, insulate the bare ends of the circuitwires with tape. Move to a point electrically abouthalfway between the control unit and the mostdistant indicating device on the circuit. At aconvenient indicating device or junction box,separate the wires leading back to the control unitfrom those leading to the more distance devicesby disconnecting them at device terminals or atsplices. Check again for continuity between eachwire and ground separately.

5. Each time continuity to ground is found,move toward the ground fault at a new test pointabout halfway between the present test point andthe last test point or end of the circuit in thatdirection. Look especially for wet, pinched, anddamaged wires.

6. When the fault is located, repair it,reconnect all wires, and test the indicating circuitby operating the drill or test switch. If all devicesoperate properly, restore the alarm system toservice.

INTRUSION ALARMS

So many types of intrusion alarm systems orcombination systems are available today that adetailed discussion here would not be practical.Each alarm system is of a special nature, and notwo systems will ever be identical. For moreinformation on intrusion detection systems, referto Design Manual 13.02.

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In this section, we will cover one intrusionsystem developed to be used by all branches ofthe service. This system is called joint serviceinterior intrusion detection system (JSIIDS). Thesystem has been designed to protect small arms,ammunition, and sensitive materials in storage.

Purpose

JSIIDS was designed to DETECT, notprevent, an attempted intrusion. The mainpurpose of JSIIDS or any other alarm is to givethe earliest possible notice of an attemptedintrusion. The more notice the reaction force(security police) has before the intruder gets pastthe outer boundaries, the better the chance thatthe intruder will be caught.

Components

The various components of JSIIDS are of twogeneral classes: (1) the control unit and its sensorcomponents and (2) the monitor and displayequipment.

CONTROL UNIT.—The control unit is thecentral control element of the JSIIDS. It is locatedwithin the protected area. It receives and processesthe intrusion tamper and duress alarm signalsgenerated at the sensors.

The control unit contains an emergencystandby power supply (battery) with an automaticswitchover when primary ac power is lost. Itoperates in much the same manner as emergencylights do.

The JSIIDS mode of operation is controlledby a key switch mounted on the control unit door.Three modes of operation are provided as follows:

1. Secure—when the protected area is notopen to authorized personnel. In this mode, allalarms are processed.

2. Access—when the area is open to authorizedpersonnel. In this mode, only tamper and duressalarms are processed.

3. Test/Reset—when electricians performtests and maintenance. All alarms are processed,and a sounding device operates for 10 seconds atthe control unit to aid in testing.

SENSOR.—There are four classes of sensorcomponents associated with the control unit. Theyare classified as follows:

1. Penetration sensors-those designed todetect penetration into the protected area through

doors, windows, walls, floors, ceilings, and otheropenings in the room.

2. Motion sensors-those designed to detectmovement of a person within the protected area.

3. Point sensor-those designed to detect theattempted removal of an item from its normalposition in the protected area, such as removalof a rifle from a weapons rack.

4. Duress sensor-those designed to beactivated by guard personnel to call for help undera duress situation.

MONITOR CABINET.—The monitoring anddisplay equipment is the primary notificationequipment of the JSIIDS. The monitor cabinethas a self-contained signal module and primaryand emergency power supply. The signal moduledisplays the status of the monitor cabinet powersupply; that is, operation on the primary oremergency power source.

DISPLAY EQUIPMENT.—The displayequipment is located in an area where monitoringpersonnel are on duty 24 hours a day. Themonitoring equipment consists of a status moduleor an alarm module, one for each control unit.

Status Monitor Module.—The status monitormodule displays the status and mode ofoperation of one control unit. By looking atthe lights on the status monitor module, themonitoring personnel can tell what is taking placein the protected structure.

Alarm Monitor Module.-The alarm monitormodule is used in the monitor cabinets whenonly an alarm indication is required.

THEORY OF OPERATION

JSIIDS operates on the basic theory of a20-volt dc circuit that has less than 2,000 ohmsof resistance being supplied to the detector ordetector processors. This voltage is provided fromthe control unit. A rise in ohmic value of thecircuit to 100,000 ohms will trigger an alarm ortamper condition in the control unit.

If you think about that for just a minute, isn’tthat the way our supervised fire alarm circuitoperates? Sure it is! One main point to rememberin any alarm system is that a small change incurrent flow (less than one-tenth of an ampere)can be used to activate an alarm. Our basic Ohm’slaw provides that a rise in resistance causes a dropin amperage in the same circuit.

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When the control cabinet receives an alarm ortamper signal, it then transmits the signal overtelephone lines to the monitor cabinet.

INSTALLATION

The installation of components of the JSIIDSmust comply with the current edition of theNational Electrical Code® (NFPA No. 70) andwith the following requirements for componentmounting, conduit, and conductors.

Component Mounting

Wall-mounted components are designed to beheld by fasteners that are accessible only throughthe open door or cover of the component. Beforecomponents are mounted, conduit holes shouldbe cut in the enclosure if they are not alreadyprovided. All holes should be made with a half-inch chassis punch.

CAUTION

NEVER use a hole saw, since it producesmetal shavings that can harm the perform-ance of the equipment.

Conduit

All conductors except phone lines outside theprotected area are to be installed in rigidgalvanized steel conduit or intermediate metalconduit in accordance with article 345 of theNEC®. Conduit outlet boxes, pull boxes, junctionboxes, conduit fittings, and similar enclosures areto be cast metal or malleable metal with threadedhubs or bodies. Conduit for JSIIDS circuits areNOT to contain any building wiring.

Conduit is required to be at least one-half inchin size. All requirements for tapered threads,supports, bends, locknuts, and bushings are thesame as discussed under hazardous wiring.

Covers on pull and junction boxes used in theinstallation of the system have to have a tamperswitch installed, or be tack-welded, brazed,filled with epoxy, or provided with twist-offscrews.

Interior Conductors

Power conductors for 120-volt ac power tocontrol units and monitor cabinets are to be solidcopper, no smaller than No. 14 AWG, type RWor RH-RW or THW insulation.

Low-voltage conductors are to be no smallerthan No. 22 AWG. They are to be installedusing crimp-on spade terminal lugs at all wireconnections to threaded screws on componentterminal boards.

All neutral conductors and noncurrent-carrying metal parts of equipment have to begrounded.

A wiring diagram of the installed system willbe drawn up for each protected area. The diagramshould indicate which sensors are installed andshow color-coded interconnections between eachsensor and the control unit. The diagram will aidin maintenance and troubleshooting. The diagramshould be classified confidential and placed in anappropriate security container.

Connections

All requirements for installation and compo-nent connections for the JSIIDS will be found inthe manufacturers’ literature. Foldouts areprovided, showing block diagrams that includeeach component used by the JSIIDS. One pointyou should remember is that JSIIDS componentsare manufactured by several manufacturersusing government specifications. Always checkthe terminal boards before connecting yourconductors. Although one system may haveterminals numbered from left to right, theterminals on the next system you install may benumbered from right to left. Always check beforeyou connect.

MAINTENANCE

The JSIIDS should be inspected on a monthlybasis as part of your shop’s recurring maintenanceprogram. Always inform the reaction force or lawenforcement desk before you begin. The systemis vulnerable to compromise during maintenance,and for this reason, personnel of the alarm crewshould request a security person to accompanythem for their own protection. You should alterthe schedule of your inspections with a differentroutine each month.

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General maintenance of the JSIIDS includesa visual inspection of all equipment, conduits, andboxes. Look for signs of tampering and loosestraps or screws, and observe the generalcondition of flexible cords or conduits.

Perform an operation test on all installedsensors, check the power supply for propervoltages, and check the condition of the battery.Return all functions of the system to normaloperation, and call the law enforcement deskbefore leaving.

Maintenance procedures for the control unitand each sensor component are listed in themanufacturers’ literature.

REPAIR

TROUBLESHOOTING

The JSIIDS was designed for fast, easytroubleshooting. Inside the control unit is acomponent called the status processor.

Mounted inside the processor are printedcircuit boards (PCBs). There is one PCB for theduress switches and one for each group ofadditional sensors. This means that the group ofmotion sensors terminate to one PCB, the doorcontacts to another PCB, and so on. LEDs areinstalled in the last PCB. An LED looks like asmall red lamp that illuminates when the processorreceives the initial alarm input. The LED willremain illuminated until the system is reset.

When you open the control unit door, you cansee immediately what sensor group triggered analarm by checking for an illuminated LED.

Each PCB has test points for a voltmeter. Thestatus of each sensor group can be checked atthese test points for a tamper or alarm condition.

An alarm condition will give a 20-volt dc reading.When the problem is cleared and the system isreset, the voltage should drop off to zero.

Most system malfunctions and troubles willcome from a faulty power supply. The JSIIDSrequires a constant 20 volts + or - 1 volt tooperate. When the power supply starts breakingdown, the voltage will start creeping up or down.A voltage reading of less than 19 volts dc or morethan 21 volts dc requires the replacement of thepower supply.

The major JSIIDS components are designedin modules. Repairs to the system are normallymade by replacing the defective module. Anexample is the power supply. It can be replacedafter disconnecting and tagging all conductors andremoving four screws. The status processor canalso be replaced by removing four screws, or asingle PCB in the processor can be replaced bya snap-and-pull action. The new PCB is theninserted into the processor.

Minor repairs on some components can becompleted with the aid of a soldering gun. Thesecomponents are toggle switches, fuse holders, themode switch, and so on.

Your main concern is to repair the system assoon as possible and bring it back on line. Thedefective components can then be shipped backto the manufacturer for replacement.

The main point to remember when replacingJSIIDS components is to TAG YOUR CONDUC-TORS. One conductor out of place can cause youhours of downtime troubleshooting.

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APPENDIX I

GLOSSARY

AMPLIFIER—The device that provides COEFFICIENT OF UTILIZATION—amplification (the increase in current, voltage, or Concerning the light from a luminaire, the ratiopower of a signal) without appreciably altering of lumens received on the work plane to thethe original signal. lumens emitted by the luminaire lamp.

ANNUNCIATOR—An electrical signalingdevice that displays a visual indication, usuallya flashing light.

COLLECTOR—The element in a transistorthat collects the current carriers.

APPROACH LIGHTS—A configuration ofground lights located in the extension of a runwaybefore the threshold to provide visual approachand landing guidance to pilots.

COMMON BASE—A transistor circuit inwhich the base electrode is the element commonto both the input and the output circuits.

AUTOMATIC FIRE ALARM SYSTEM—A system using fire detectors, such as heat,smoke, and flame detectors, to initiate alarmsautomatically.

COMMON COLLECTOR—A circuit con-figuration in which the emitter is the elementcommon to both the input and the output circuits.

DIELECTRIC—A nonconductor of elec-tricity; an insulator or insulating material.

BALLAST—A device used with an electric-discharge lamp to obtain the necessary circuitconditions (voltage, current, and waveform) forstarting and operating.

DIFFUSER—A device to redirect or scatterthe light from a source.

BASE—The element in a transistor thatcontrols the flow of current carriers.

DIODE—A two-element solid-state devicemade of either germanium or silicon. It isprimarily used as a switching device.

CANDELA (FORMERLY CANDLE)—Theunit of luminous intensity used to measure theintensity of light radiated from a light source.It is the average luminous intensity of theinternational candle. This intensity is usuallyexpressed as CANDLEPOWER instead of ascandles of luminous intensity.

DONOR—An impurity that can make asemiconductor material an N-type by donatingextra “free” electrons to the conduction band.

DOPING—The process of adding impuritiesto semiconductor crystals to increase the numberof free charges that can be moved by an external,applied voltage. Doping produces N-type orP-type materials.

CATHODE—The negative terminal of aforward-biased semiconductor diode, which is thesource of the electrons.

DUSTPROOF LUMINAIRE—A luminaireso constructed or protected that dust will notinterfere with its successful operation.

CATHODE-RAY TUBE (CRT)—An electrontube which has an electron gun, a deflectionsystem, and a screen. This tube is used to displayvisual electronic signals.

DUST-TIGHT LUMINAIRE—A luminaireso constructed that dust will not enter theenclosing case.

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ELECTRIC-DISCHARGE LAMP—A lampin which light is produced by the passage of anelectric current through a vapor or a gas.

EMERGENCY LIGHT—Lighting designedto supply illumination essential to safety of lifeand property in the event of failure of the normallight.

EMITTER—The element in a transistor thatemits current carriers (electrons or holes).

EXPLOSION-PROOF LUMINAIRE—Acompletely enclosed luminaire capable of with-standing an explosion within it and preventing theignition of a gas or vapor surrounding theenclosure by sparks, flashes, or explosion. Theexternal temperature at which it is operated mustbe such that a surrounding flammable atmospherewill not be ignited.

FIELD-EFFECT TRANSISTOR (FET)—Atransistor consisting of a source, a gate, and adrain. Current flow is controlled by the transverseelectric field under the gate.

FLOODLIGHT—A system designed forlighting a scene or an object to a luminance greaterthan that of its surroundings.

FLUORESCENT LAMP—A low-pressuremercury electric-discharge lamp in which afluorescing coating on its inner surface transformssome of the ultraviolet energy generated by thedischarge into light.

FLUORESCENT-MERCURY LAMP—Anelectric-discharge lamp having a high-pressuremercury arc in an arc tube and an outer envelopecoated with a fluorescing substance that trans-forms some of the ultraviolet energy generated bythe arc into light.

FOOTCANDLE —The illumination intensityor luminous density on a surface 1 foot distantand perpendicular to the rays emitted by a lightsource of 1 candlepower.

FORWARD BIAS—An external voltage thatis applied to a PN-junction in the conductingdirection so that the junction offers only mini-mum resistance to the flow of current. Con-duction is by the majority current carriers (holesin P-type material; electrons in N-type material).

HIGH-INTENSITY DISCHARGE LAMPS—A general group of lamps consisting of mercury,metal halide, and high-pressure sodium lamps.

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HOLE FLOW—In the valence band, aprocess of conduction in which electrons moveinto holes, thereby creating other holes thatappear to move toward a negative potential. (Themovement of holes is opposite the movement ofelectrons.)

FULL-WAVE RECTIFIER—A circuit thatuses both positive and negative alternations in analternating current to produce direct current.

GENERAL-PURPOSE FLOODLIGHT—Aweatherproof fixture so constructed that thehousing forms the reflecting surface. Theassembly is enclosed by a glass cover.

GIN POLE—An upright guy pole withhoisting tackle and a foot-mounted snatch blockused for vertical lifts.

GLARE—Light from a source or a reflectingsurface that interferes with proper vision or causeseye discomfort. The amount of glare depends onthe brightness of the light source, the contrastbetween the source and the background, and thelocation of the light source in respect to the fieldof vision.

GROUND—A conducting connection,whether intentional or accidental, between anelectrical circuit or equipment and the earth.

GROUNDING CONDUCTOR—A con-ductor used to connect equipment or the groundedcircuit of a wiring system to a grounding electrode.

GROUNDING ELECTRODE—A conductorembedded in the earth for maintaining groundpotential on conductors connected to it.

HALF-WAVE RECTIFIER—A rectifierusing only one-half of each cycle to changealternating current to pulsating direct current.

HAZARDOUS LOCATION—An area whereignitable vapors or dust may cause a fire orexplosion created by energy emitted from lightingor other electrical equipment.

INDICATING DEVICE—A device thatindicates an alarm, supervisory, or troublecondition. Frequently, audible and visual devices,such as lamps and flashing lights, are used asindicating devices.

INITIATING DEVICE—A device used toinitiate the sequence of electrical events that resultsin a detection or fire alarm or supervisory signal.

INTEGRATED CIRCUIT—A circuit inwhich many elements are fabricated and inter-connected by a single process (into a single chip),as opposed to a “nonintegrated” circuit in whichthe transistors, diodes, resistors, and othercomponents are fabricated separately and thenassembled.

IONIZE—To convert totally or partially intoions (charged particles). This principle is used insome smoke detectors.

LIGHT-EMITTING DIODE (LED)—APN-junction diode that emits visible light whenit is forward biased. Depending on the materialused to make the diode, the light may be red,green, or amber.

LINE—Strands of natural or synthetic fibertwisted together, sometimes referred to as rope.

LUMEN—The unit of light output or lightflux. A 1-candlepower light source in the centerof a hollow sphere 2 feet in diameter delivers 1footcandle of light at every point on the innersurface of the sphere. Since the inside surface ofthe sphere is 12.57 square feet, the light sourceproduces 12.57 lumens. However, to allow forlosses, common practice puts the ratio of lumensto candle power at 10 to 1.

LUMINAIRE —A complete lighting unitconsisting of a lamp or lamps together with theparts designed to distribute the light, to positionand protect the lamps, and to connect the lampsto the power supply.

MAINTENANCE—Day-to-day, periodic, orscheduled work required to preserve or restore afacility or equipment so that it can be effectivelyused for its designed purpose. It includes workto prevent damage to or the deterioration of afacility that would otherwise be more costly torestore.

MAINTENANCE FACTOR—A factor usedto denote the ratio of the illumination on a givenarea after a period of time to the initialillumination on the same area.

METAL HALIDE LAMP—A discharge lampin which light is produced by the radiation froma mixture of a metallic vapor (such as mercury)and the products of the disassociation of halides(such as halides of thallium, indium, or sodium).

MOUNTING HEIGHT (ROADWAY)—Thevertical distance between the roadway surface andthe center of the light source.

MOUSING—Turns of cordage around theopening of a block hook.

NPN—A type of transistor that is formed byintroducing a thin region of P-type materialbetween two regions of N-type material.

OVERHANG—The horizontal distancebetween a vertical line passing through theluminaire and the curb or edge of the roadway.

PHOTOCELL—A light-controlled variableresistor that has a light-to-dark resistance ratioof 1:1,000. Used in various types of control andtiming circuits.

PHOTOMETER—An instrument thatmeasures luminous intensity or brightness,luminous flux, or light distribution.

PNP—A type of transistor that is formed byintroducing a thin region of N-type materialbetween two regions of P-type material.

PRINTED CIRCUIT BOARD—A flatinsulating surface upon which printed wiring andminiaturized components are connected in apredetermined design and attached to a commonbase.

RECTIFIER—A device that by its conductioncharacteristics converts alternating current to apulsating direct current.

REEVING—Threading or placement of aworking line.

REFLECTOR—A device used to change thedirection of the light rays and redirect them in thedesired direction.

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REFRACTOR—A transparent medium thatpasses light rays but bends or deflects them inthe desired direction to obtain proper lightdistribution.

REVERSE BIAS—A condition in which anexternal voltage is applied to a PN-junction so thatthe junction offers a high resistance to currentflow.

RUNWAY THRESHOLD—The beginning ofthe runway usable for landing.

SHEAVE—(Pronounced “shiv”) A groovedwheel or pulley used to support a cable or rope.

SILICON-CONTROLLED RECTIFIER(SCR)—A semiconductor device that functions asan electrically controlled switch.

SOLID-STATE DEVICE—An electronicdevice that operates by the movement of electronswithin a solid piece of semiconductor material.

STREETLIGHTING LUMINAIRE—Acomplete lighting device consisting of the lightsource, globe, reflector, refractor, housing, andsupport. The pole, post, or bracket is notconsidered part of the luminaire.

TRANSISTOR—A semiconductor devicewith three or more elements.

TRIAC—A three-terminal device that issimilar to two SCRs back to back with a commongate and common terminals. Although similar in

construction and operation to the SCR, the triaccontrols and conducts current flow during bothalternations of an alternating current cycle.

UNIJUNCTION TRANSISTOR (UJT)—Athree-terminal, solid-state device that resemblesa transistor but is stable over a wide range oftemperatures and allows a reduction ofcomponents when used in place of a transistor.It is used in switching circuits, oscillators, andwave-shaping circuits.

VISUAL APPROACH SLOPE INDICA-TOR SYSTEM (VASIS)—A system of angle-of-approach lights consisting of two bars of lightson each side of the runway near the threshold.These lights show red and white or a combinationof both (pink) to the approaching pilot, dependingupon the position of the aircraft with respect tothe glide path.

WIRE ROPE—A rope formed of wireswrapped around a central core-a steel cable.

ZENER DIODE—A PN-junction diodedesigned to operate in the reverse-bias breakdownregion.

ZONE—An area or division of a buildingprotected by one fire alarm initiating circuit.Sometimes the area and the circuit are referredto interchangeable as the zone. The fire alarminitiating circuit may be connected to representa certain group of initiating devices instead of aparticular area or division of the building.

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APPENDIX II

FORMULAS AND CONVERSlON TABLES

AII-1

FORMULAS

CONVERSION FACTORS AND CONSTANTS

π = 3.14 2π = 6.28

π2 = 9.87 (2π)2 = 39.5

ε = 2.718 √2 = 1.414

√ 3= 1.732 LOG = 0.497

Temperature

(F to C) C = 5/9 (F - 32)

(C to F) F = 9/5 C + 32

(C to K) K = C + 273

Power

1 kilowatt = 1.341 horsepower

1 horsepower = 746 watts

cos A = b Adjacent Sidec = Hypotenuse

a Opposite Sidetan A = b=

Adjacent Side

cot A = b Adjacent Sidea

=Opposite Side

B

c a

A Cb

OHM’S LAW - DIRECT CURRENT

OHM’S LAW - ALTERNATING CURRENT

SINUSOIDAL VOLTAGES AND CURRENTS

Effective Value = 0.707 × Peak Value

Average Value = 0.637 × Peak Value

Peak Value = 1.414 × Effective Value

Effective Value = 1.11 × Average Value

Peak Value = 1.57 × Average Value

Average Value = 0.9 × Effective Value

TRIGONOMETRIC FORMULAS

a Opposite Sidesin A =c

=Hypotenuse

SPEED VS. POLES FORMULAS

F = NP N = F 120 P = F 120120 P N

F = frequency

N = speed of rotation

P = number of poles

120 = time constant

POWER FACTOR

PF actual power = watts= = kW Rapparent power volts × amperes kVA = Z

AII-2

SINGLE-PHASE CIRCUITS

kVA = E I kW kW = kVA × PF1,000 PF

I P P P= E × PF E = P F = E × II × PF

P = E × I × PF

TWO-PHASE CIRCUITS

PI = 2 × E × PF E = P2 × I × PF P F = P

E × I

kVA = 2 × E × I kW kW = kVA × PF1,000=

PF

P = 2 × E × I × PF

THREE-PHASE CIRCUITS,BALANCED WYE

THREE-PHASE CIRCUITS,BALANCED DELTA

E phase = E line

I L = √ 3 IP = 1.73 IP

IP = IL

3= 0.577 IL√

POWER: THREE-PHASE BALANCEDWYE OR DELTA CIRCUITS

P = 1.732 × E × I × PF VA = 1.732 × E × I

PE = PF × 1.73 × I= 0.577 × P

PF × I

PI =PF × 1.73 × E

= 0.577 × PPF × E

PF P 0.577 × P= 1.73 × I × E= I × E

VA = apparent power (volt-amperes)I phase = I line

P = actual power (watts)

E = line voltage (volts)ELEP =√ 3

= 0.577 EL I = line current (amperes)

AII-3

CONVERSION TABLES

LENGTH CONVERSION

When You Know: You Can Find: If You Multiply By:

inchesinchesfeetfeetyardsyardsmilesmilesmillimeterscentimeterscentimetersmeterscentimetersmetersmeterskilometersmetersnautical miles

millimeterscentimeterscentimetersmeterscentimetersmeterskilometersmetersinchesinchesfeetfeetyardsyardsmilesmilesnautical milesmeters

25.42.54

300.3

900.91.6

1 6000.040 40.032 83 30.010 91.10:000 6210.60.000 54

1 852

VOLUME CONVERSION

When You Know: You Can Find: If You Multiply By:

teaspoons milliliterstablespoons millilitersfluid ounces milliliterscups literspints litersquarts litersgallons litersmilliliters teaspoonsmilliliters tablespoonsmilliliters fluid ouncesliters cupsliters pintsliters quartsliters gallonscubic feet cubic meterscubic yards cubic meterscubic meters cubic feetcubic meters cubic yards

515300.240.470.953.80.20.0670.0344.22.11.060.260.0280.765

35.31.31

AII-4

CONVERSION TABLES—CONTINUED

WEIGHT CONVERSION

When You Know: You Can Find:

ouncespoundsshort tons (2,000 lbs)gramskilogramsmegagrams (metric tons)

gramskilogramsmegagrams (metric tons)ouncespoundsshort tons (2,000 lbs)

If You Multiply By:

28.30.450 90.035 32.21.1

TEMPERATURE CONVERSION

When You Know: You Can Find: If You

degrees Fahrenheit degrees Celsius subtract 32 then multiply by 5/9

degrees Celsius degrees Fahrenheit multiply by 9/5 then add 32

degrees Celsius kelvins add 273.15°

When You Know: You Can Find: If You Multiply By:

square inches square centimeterssquare inches square meterssquare feet square centimeterssquare feet square meterssquare yards square centimeterssquare yards square meterssquare miles square kilometerssquare centimeters square inchessquare meters square inchessquare centimeters square feetsquare meters square feetsquare centimeters square yardssquare meters square yardssquare kilometers square miles

AREA CONVERSION

6.450.000 6

9290.092 9

8 3600.8362 60.155

1 5500.001

10.80.0001.20.4

AII-5

APPENDIX Ill

REFERENCES

Chapter 1

Design and Application of Roadway Lighting, Street and Highway SafetyLighting Bureau, Cleveland, Ohio.

Facilities Engineering—Electrical Exterior Facilities, NAVFAC MO-200,Naval Facilities Engineering Command, Alexandria, Va., April 1979.

General Electric Lighting System, Product Application Guide, GET-6704General Electric Company, Hendersonville, N. C.

National Electrical Code®, 1990 edition, NFPA-70-1990, National FireProtection Association, Quincy, Mass., 1989.

Chapter 2

AM-2 Airfield Landing Mat and Accessories, NAVAIR 51-60A-1, NavalAir Systems Command, Washington, D.C., September 1981.

Expeditionary Airfields, NAVAIR 51-35-7, Naval Air Systems Command,Washington, D.C., March 1974.

Lighting and Marking Systems for Expeditionary Airfields, NAVAIR51-40ABA-7, Naval Air Systems Command, Washington, D.C., April1981.

Visual Landing Aids Design Standards, Landbased Installations, NAVAIR51-50AAA-2, Naval Air Systems Command, Washington, D.C., April1966.

Chapter 3

National Electrical Code®, 1990 edition, NFPA-70-1990, National FireProtection Association, Quincy, Mass., 1989.

Chapter 4

Instruction Manual for Voltage Regulator Models: SR4A and SR8A,Publication Number 9 0177 00 990, Basler Electric Company, Highland,Ill., February 1983.

LC75, “Z Meter” Capacitor-Inductor Analyzer, Operation, Application,and Maintenance Manual, Sencore, Inc., Sioux Falls, S. Dak.

AIII-1

NEETS, Introduction to Solid-State Devices and Power Supplies, Module7, NAVEDTRA 172-07-00-82, Naval Education and Training ProgramDevelopment Center, Pensacola Fla., 1982.

NEETS, Introduction to Test Equipment, Module 16, NAVEDTRA172-16-00-84, Naval Education and Training Program DevelopmentCenter, Pensacola, Fla., 1984.

SC61 Waveform Analyzer, Operation, Application, and MaintenanceManual, Sencore, Inc., Sioux Falls, S. Dak.

Sencore News release pertaining to Transistor/FET Tester TF46, Sencore,Inc., Sioux Falls, S. Dak.

Tactical Generator Set, Diesel Engine Driven, NAVFAC P-8-629-34, NavalFacilities Engineering Command, Alexandria, Va., January 1974.

Chapter 5

Kurtz, Edwin B. and Thomas M. Shoemaker, The Lineman’s andCableman’s Handbook, 7th edition, McGraw-Hill Book Co., NewYork, 1986.

National Electrical Code®, 1990 edition, NFPA-70-1990, National FireProtection Association, Quincy, Mass., 1989.

Chapter 6

Builder 3 & 2, Volume 1, NAVEDTRA 10646, Naval Education andTraining Program Management Support Activity, 1987.

Steelworker 1, NAVEDTRA 10654-E1, Naval Education and TrainingProgram Management Support Activity, 1989.

Chapter 7

Commercial Intrusion Detection Systems (IDS) DM.13.02, SN0525-LP-300-9100, Naval Facilities Engineering Command, Alexandria,Va., September 1986.

Electrician, Volume 3 (AFSC 54250), Department of the Air Force,Extension Course Institute and Air University, Gunter AFB, Alabama,1982.

Maintenance of Fire Protection Systems, NAVFAC MO-117, NavalFacilities Engineering Command, Alexandria, Va., October 1981.

AIII-2

INDEX

A

Advanced base planning, 5-28 to 5-34Airfield lighting, 2-1 to 2-24

airfield lighting systems, 2-1 to 2-21airfield layout, 2-1 to 2-2airfield lighting vault, 2-2 to 2-6

constant-current regulator, 2-5 to2-6

power supply, 2-4 to 2-5remote control, 2-6safety, 2-2 to 2-4

condenser discharge lighting system,2-16 to 2-21

master sequence timer cabinet,2-18 to 2-21

strobe light system, 2-16 to 2-18tower control unit, 2-21

lighting circuits, 2-6 to 2-15approach lights, 2-8 to 2-12beacon lights, 2-12 to 2-15obstruction lights, 2-1 2runway edge lights, 2-7taxiway lights, 2-8

types of fixtures and lamps, 2-15 to2-16

maintenance of airfield lighting systems,2-21 to 2-24

routine maintenance, 2-21 to 2-22condenser discharge light system,

2-22operational check, 2-21 to 2-22underground distribution sys-

tems, 2-22visual inspection, 2-21

troubleshooting circuits, 2-23 to 2-24types of trouble, 2-23underground lighting problems,

2-24Alarm systems, 7-1 to 7-28

equipment description, 7-2 to 7-18alarm-indicating devices, 7-16 to 7-18

annunciators, 7-16audible signal devices, 7-1 7

Alarm systems-Continuedequipment description-Continued

alarm-indicating devices-Continuedtesting alarm-indicating devices,

7-17 to 7-18alarm-initiating devices, 7-7 to

7-16flame-actuated detectors, 7-12 to

7-14heat detectors, 7-8 to 7-9manual fire station, 7-7smoke detectors, 7-9 to 7-12water-flow-actuated detectors,

7-14 to 7-16control unit, 7-4 to 7-7

auxiliary devices, 7-6 to 7-7local alarm signaling, 7-4 to

7-5remote alarm signaling, 7-5 to

7-6power supplies, 7-2 to 7-4

smoke detector power supply,7-3 to 7-4

system power supply, 7-3theory of operation, 7-1 to 7-2troubleshooting circuit faults, 7-18 to

7-28indicating circuit faults, 7-24 to

7-25grounded circuit, 7-25open circuit, 7-25short circuit, 7-24 to 7-25

initiating circuit faults, 7-23 to 7-24grounded circuit, 7-24open circuit, 7-23 to 7-24short circuit, 7-23

installation, 7-27component mounting, 7-27conduit, 7-27connections, 7-27interior conductors, 7-27

intrusion alarms, 7-25 to 7-26components, 7-26purpose, 7-26

INDEX-1

Alarm systems—Continuedtroubleshooting circuits faults-Continued

maintenance, 7-27 to 7-28power supply circuit faults, 7-19 to

7-22grounded and short circuits, 7-19

to 7-21open circuits, 7-21 to 7-22

repair, 7-28theory of operation, 7-26 to 7-27troubleshooting, 7-28

types of fire alarm systems, 7-1coded alarm systems, 7-1noncoded alarm systems, 7-1

Area lighting systems, 1-1 to 1-29floodlights, 1-19 to 1-28

flooding aiming, 1-23 to 1-25isofootcandle diagrams, 1-25 to 1-26light intensity calculations, 1-26 to 1-28maintenance factor, 1-26manufacturer’s literature, 1-25mounting height and spacing, 1-22 to

1-23selection of luminaire, 1-21utilization graph, 1-26

outdoor lighting, 1-1 to 1-11components and controls, 1-6 to 1-11

constant-current transformer, 1-7to 1-9

control circuits, 1-9 to 1-11light circuits, 1-5 to 1-6

multiple circuits, 1-6series circuits, 1-5 to 1-6

luminaire types and fixtures, 1-1 to 1-5electric-discharge lighting, 1-2fixtures, 1-4 to 1-5fluorescent lighting, 1-3high-intensity discharge (HID)

lighting, 1-2 to 1-3luminaire ballasts, 1-3 to 1-4

security lighting, 1-28 to 1-29alternate power sources, 1-28 to 1-29lighting control, 1-28security area classification, 1-28

streetlighting, 1-11 to 1-19lighting intensity, 1-11 to 1-12lighting intensity calculations, 1-16 to

1-19manufacturer’s literature, 1-14 to 1-16

isofootcandle curves, 1-16maintenance factor, 1-16utilization curve, 1-14 to 1-16

mounting height and spacing, 1-13 to 1-14selection of luminaire, 1-12 to 1-13street and area classification, 1-11

B

Boom derrick, 6-9 to 6-10erecting, 6-10

rigging, 6-10Branch circuits, determination of number and

size of, 3-6 to 3-7

C

Capacitor banks, 5-27 to 5-28Capacitors, testing, 4-25 to 4-31

capacitor dielectric absorption, 4-30capacitor leakage, 4-27 to 4-30capacitor value, 4-25 to 4-27reforming of electrolytic capacitors, 4-30

to 4-31Chain hoists, 6-11 to 6-12Circuits, light, 1-5 to 1-6

multiple circuits, 1-6series circuits, 1-5 to 1-6

Circuits, lighting, 2-6 to 2-15approach lights, 2-8 to 2-12beacon lights, 2-12 to 2-15obstruction lights, 2-12runway edge lights, 2-8taxiway lights, 2-8

Coded alarm systems, 7-1Components and controls, 1-6 to 1-11

constant-current transformer, 1-7 to 1-9control circuits, 1-9 to 1-11

Condenser discharge lighting system, 2-16 to2-21

master sequence timer cabinet, 2-18 to2-21

strobe light system, 2-16 to 2-18tower control unit, 2-21

Conductor, sizing of neutral, 3-8 to 3-10Conductors, sizing of service-entrance, 3-7 to

3-8, 3-13Control unit, 7-4 to 7-7

auxiliary devices, 7-6 to 7-7local alarm signaling, 7-4 to 7-5remote alarm signaling, 7-5 to 7-6

Conversion tables and formulas, AII-1 toAII-5

Cranes, 6-13 to 6-14

D

Devices, protective, 5-25 to 5-27ground wire, 5-27lighting arresters, 5-27switches and fused cutouts, 5-25 to 5-27

INDEX-2

Direct current power supplies, 4-5 to 4-6Distribution centers, 5-18 to 5-19Distribution transformer, 5-20 to 5-22

transformer installation 5-20 to 5-21transformer installation rules, 5-21 to

5-22Dual-trace oscilloscope, 4-21 to 4-25

front panel controls, 4-22 to 4-24process of locating the trace, 4-24test probe frequency compensation,

4-24test probe ground connections, 4-25

E

Electrical load requirements, 3-1 to 3-15electrical installations in hazardous loca-

tions, 3-14 to 3-15classification of hazardous locations,

3-14wiring methods in hazardous loca-

tions, 3-14 to 3-15equipment and fittings, 3-14grounding, 3-14 to 3-15sealing and bonding, 3-14

ground fault interrupters, 3-13industrial buildings and shops, 3-10 to

3-13sizing of service-entrance conductors,

3-13types of industrial load, 3-10 to 3-12

general lighting loads, 3-10 to3-12

general-purpose receptacle loads,3-12

motor loads, 3-12special appliance loads, 3-12

voltage drop calculation, 3-12 to 3-13single-family dwelling, 3-1 to 3-10

demand factors, 3-3 to 3-6electric clothes dryer load, 3-4electric range load, 3-4 to 3-6fixed appliance loads, 3-4general lighting and receptacle

loads, 3-3 to 3-4heating and air-conditioning

loads, 3-6motor loads, 3-6water heater load, 3-6

determination of number and size ofbranch circuits, 3-6 to 3-7

sizing of neutral conductor, 3-8 to3-10

Electrical load requirements—Continuedsingle-family dwelling—Continued

sizing of service-entrance conductors,3-7 to 3-8

type of dwelling unit load, 3-1 to 3-3general lighting load, 3-1small appliance and laundry

load, 3-1 to 3-2special appliance load, 3-3

Equipment description, 7-2 to 7-18alarm-indicating devices, 7-1 6 to 7-18alarm-initiating devices, 7-7 to 7-1 6control unit, 7-4 to 7-7power supplies, 7-2 to 7-4

Equipment, other hoisting, 6-11 to 6-14chain hoists, 6-11 to 6-12cranes, 6-13 to 6-14winches, 6-12 to 6-13

F

Feeders, primary, 5-16 to 5-18Field rigging and hoisting systems, 6-1 to 6-18

fiber line, 6-14 to 6-16safe working load, 6-15 to 6-16size designation, 6-14 to 6-1 5strength of fiber line, 6-15synthetic-fiber ropes, 6-14

field-erected hoisting devices, 6-1 to 6-11boom derrick, 6-9 to 6-10

erecting, 6-10rigging, 6-10

gin pole, 6-4 to 6-6erecting, 6-5 to 6-6rigging, 6-4 to 6-5

holdfasts, 6-1 to 6-3combination-log-picket holdfast,

6-2combination-picket holdfast, 6-2deadman holdfast, 6-3natural types, 6-1rock holdfast, 6-2 to 6-3single-picket holdfast, 6-1 to 6-2steel-picket holdfast, 6-3

pole derrick, 6-10 to 6-11shear legs, 6-6 to 6-7

erecting, 6-7rigging, 6-6 to 6-7

tripod, 6-7 to 6-9erecting, 6-8 to 6-9rigging, 6-7 to 6-8

other hoisting equipment, 6-11 to6-14

chain hoists, 6-11 to 6-12

INDEX-3

Field rigging and hoisting systems—Continuedfield-erected hoisting devices—Continued

cranes, 6-13 to 6-14winches, 6-12 to 6-13

wire rope, 6-16 to 6-18

Fixtures and lamps, types of, 2-15 to 2-16Fixtures and luminaire types, 1-1 to 1-5

construction, 6-16 to 6-17grades of wire rope, 6-17measuring wire rope, 6-17safe working load, 6-17 to 6-18

Flame-actuated detectors, 7-12 to 7-14Floodlights, 1-19 to 1-28

flooding aiming, 1-23 to 1-25isofootcandle diagrams, 1-25 to 1-26light intensity calculations, 1-26 to

1-28maintenance factor, 1-26manufacturer’s literature, 1-25mounting height and space, 1-22 to 1-23selection of luminaire, 1-21utilization graph, 1-26

Formulas and conversion tables, AII-1 toAII-5

G

Generation and distribution, power, 5-1 to5-34

Gin pole, 6-4 to 6-6erecting, 6-5 to 6-6rigging, 6-4 to 6-5

Glossary, AI-1 to AI-4Ground fault interruptions, 3-13Guying of poles, 5-22 to 5-25

H

Hazardous locations, classification of, 3-14Hazardous locations, electrical installations

in, 3-14 to 3-15Heat detectors, 7-8 to 7-9Heating and air-conditioning loads, 3-6Holdfasts, 6-1 to 6-3

combination-log-picket holdfast, 6-2combination-picket holdfast, 6-2deadman holdfast, 6-3natural types, 6-1rock holdfast, 6-2 to 6-3single-picket holdfast, 6-1 to 6-2steel-picket holdfast, 6-3

Indicating circuit faults, 7-24 to 7-25grounded circuit, 7-25open circuit, 7-25short circuit, 7-24 to 7-25

Inductors, testing, 4-31 to 4-32inductor opens, 4-31 to 4-32inductor ringing, 4-32inductor value, 4-31

Industrial buildings and shops electrical loadrequirements, 3-10 to 3-13

types of industrial load, 3-10 to 3-12Initiating circuit faults, 7-23 to 7-24

grounded circuit, 7-24open circuit, 7-23 to 7-24short circuit, 7-23

Installation, 7-27Installation, generator, 5-4 to 5-10

feeder cable connections, 5-7 to 5-10generator connections, 5-6 to 5-7generator set inspection, 5-5 to 5-6sheltering of generators, 5-4 to 5-5site selection, 5-4

Intrusion alarms, 7-25 to 7-26components, 7-26purpose, 7-26

Isofootcandle diagrams, 1-25 to 1-26

INDEX-4

K

Key leakage test, 4-19 to 4-20rectifier diode testing, 4-19silicon controlled rectifier testing, 4-20

L

Lighting systems, area, 1-1 to 1-29floodlights, 1-19 to 1-28outdoor lighting, 1-1 to 1-11security lighting, 1-28 to 1-29streetlighting, 1-11 to 1-19

M

Maintenance of airfield lighting systems, 2-21to 2-24

routine maintenance, 2-21 to 2-22condenser discharge light system,

2-22operational check, 2-21 to 2-22underground distribution systems, 2-22visual inspection, 2-2 1

troubleshooting circuits, 2-23 to 2-24

I

Manual fire station, 7-7Manufacturer’s literature, 1-14 to 1-16

isofootcandle curves, 1-16maintenance factor, 1-16utilization curve, 1-14 to 1-16

Multiple circuits, 1-6

N

Noncoded alarm systems, 7-1

O

Oscilloscope, using, 4-25Outdoor lighting, 1-1 to 1-11

components and controls, 1-6 to 1-11light circuits, 1-5 to 1-6luminaire types and fixtures, 1-1 to 1-5

Overload protective relay, 4-15Overvoltage protective relay, 4-12 to 4-13

P

Plant operations, generating, 5-10 to 5-15basic operating precautions, 5-14 to 5-15emergency shutdown, 5-14equipment, plant 5-10 to 5-11parallel plant operation, 5-12 to 5-14single plant operation, 5-11 to 5-12

Pole derrick, 6-10 to 6-11Power generation and distribution, 5-1 to 5-34

advanced base planning, 5-28 to 5-34power distribution, 5-16 to 5-28

capacitor banks, 5-27 to 5-28distribution centers, 5-18 to 5-19distribution system maintenance, 5-28distribution transformers, 5-20 to

5-22transformer installation, 5-20 to

5-21transformer installation rules,

5-21 to 5-22guying of poles, 5-22 to 5-25 Rprimary feeders, 5-16 to 5-18

loop, or ring, distributionsystem, 5-17

network distribution system,5-17 to 5-18

primary selective system, 5-18radial distribution system, 5-17

Power generation and distribution—Continuedpower distribution—Continued

primary mains, 5-19 to 5-20protective devices, 5-25 to 5-27

ground wire, 5-27lighting arresters, 5-27switches and fused cutouts, 5-25

to 5-27substations, 5-16

power generation, 5-1generating plant operations, 5-10 to

5-15basic operating precautions, 5-14

to 5-15emergency shutdown, 5-14parallel plant operation, 5-12 to

5-14plant equipment, 5-10 to 5-11single plant operation, 5-11 to

5-12generator installation, 5-4 to 5-10

feeder cable connections, 5-7 to5-10

generator connections, 5-6 to 5-7generator set inspection, 5-5 to

5-6sheltering of generators, 5-4 to

5-5site selection, 5-4

generator selection, 5-1 to 5-4computation of the load, 5-2 to

5-4power and voltage requirements,

5-2power plant maintenance, 5-15 to

5-16operator maintenance, 5-15 to

5-16preventive maintenance, 5-16

Power supplies, 7-2 to 7-4smoke detector power supply, 7-3 to

7-4system power supply, 7-3

Protective relays, solid-state, 4-12 to 4-15

Receptacle loads and general lighting, 3-3 to3-4

Rectifier diode, 4-1 to 4-2, 4-16References, AIII-1 to AIII-2Reverse-power protective relay, 4-14 to 4-15Ropes, 6-14, 6-16 to 6-18

INDEX-5

S

Security lighting, 1-28 to 1-29alternate power sources, 1-28 to 1-29lighting control, 1-28security area classification, 1-28

Series circuits, 1-5 to 1-6Shear legs, 6-6 to 6-7

erecting, 6-7rigging, 6-6 to 6-7

Single-family dwelling electrical loadrequirements, 3-1 to 3-10

Small appliance and laundry load, 3-1 to 3-2Smoke detectors, 7-9 to 7-12Solid-state devices and circuits, 4-1 to 4-32

applications of solid-state devices, 4-5 to 4-15direct current power supplies, 4-5 to

4-6solid-state protective relays, 4-12 to

4-15overload protective relay, 4-15overvoltage protective relay, 4-12

to 4-13reverse-power protective relay,

4-14 to 4-15underfrequency protective relay,

4-14undervoltage protective relay,

4-13 to 4-14voltage regulators, 4-6 to 4-12

silicon controlled rectifierregulator, 4-6 to 4-10

transistor voltage regulator, 4-10to 4-12

semiconductor devices and symbols, 4-1to 4-5

integrated circuit, 4-4 to 4-5rectifier diode, 4-1 to 4-2silicon controlled rectifier, 4-2 to 4-3transistor, 4-3 to 4-4unijunction transistor, 4-4zener diode, 4-2

testing capacitors and inductors, 4-25 to4-32

testing capacitors, 4-25 to 4-31capacitor dielectric absorption,

4-30capacitor leakage, 4-27 to 4-30capacitor value, 4-25 to 4-27reforming of electrolytic

capacitors, 4-30 to 4-31testing inductors, 4-31 to 4-32

inductor opens, 4-31 to 4-32inductor ringing, 4-32inductor value, 4-31

INDEX-6

Testing solid-state devices, 4-15 to 4-21key leakage test, 4-19 to 4-20rectifier diode testing, 4-16silicon controlled rectifier testing, 4-17testing integrated circuits, 4-20 to 4-21transistor testing, 4-18 to 4-19unijunction transistor testing, 4-17 to 4-18zener diode testing, 4-16

Transistor, 4-3 to 4-4, 4-18 to 4-19

Solid-state devices and circuits-Continuedtesting solid-state devices, 4-15 to 4-21

key leakage test, 4-19 to 4-20rectificer diode testing, 4-19silicon controlled rectifier

testing, 4-20rectifier diode testing, 4-16silicon controlled rectifier testing,

4-17testing integrated circuits, 4-20 to

4-21transistor testing, 4-18 to 4-19

transistor gain, 4-18transistor leakage, 4-18 to 4-19

unijunction transistor testing, 4-1 7 to4-18

zener diode testing, 4-16waveform analysis of solid-state devices,

4-21 to 4-25dual-trace oscilloscope, 4-21 to 4-25

front panel controls, 4-22 to4-24

process of locating the trace,4-24

test probe frequency compensa-tion, 4-24

test probe ground connections,4-25

using the oscilloscope, 4-25Streetlighting, 1-11 to 1-19

lighting intensity, 1-11 to 1-12lighting intensity calculations, 1-16 to

1-19manufacturer’s literature, 1-14 to 1-16

mounting height and spacing, 1-13 to1-14

selection of luminaire, 1-12 to 1-13street and area classification, 1-11

Strobe light system, 2-16 to 2-18Substations, 5-16Synthetic-fiber ropes, 6-14

T

Tripod, 6-7 to 6-9erecting, 6-8 to 6-9rigging, 6-7 to 6-8

Troubleshooting circuit faults, 7-18 to 7-28Troubleshooting circuits, 2-23 to 2-24

types of trouble, 2-23underground lighting problems, 2-24

U

Underfrequency protective relay, 4-14Undervoltage protective relay, 4-13 to 4-14Unijunction transistor, 4-4, 4-17 to 4-18Utilization graph, floodlights, 1-26

V

Vault, airfield lighting, 2-2 to 2-6constant-current regulator, 2-5 to 2-6power supply, 2-4 to 2-5remote contol, 2-6safety, 2-2 to 2-4

Voltage drop calculation, 3-12 to 3-13

Voltage regulators, 4-6 to 4-12silicon controlled rectifier regulator, 4-6

to 4-10transistor voltage regulator, 4-10 to 4-12

W

Water heater load, 3-6Water-flow-actuated detectors, 7-14 to 7-16Waveform analysis of solid-state devices,

4-21 to 4-25dual-trace oscilloscope, 4-21 to 4-25using the oscilloscope, 4-25

Winches, hoisting equipment, 6-12 to 6-13Wire rope, 6-16 to 6-18

construction, 6-16 to 6-17grades of wire rope, 6-17measuring wire rope, 6-17safe working load, 6-17 to 6-18

Wiring methods in hazardous locations, 3-14to 3-15

Z

Zener diode, 4-2 to 4-16

INDEX-7

Assignment Questions

Information: The text pages that you are to study areprovided at the beginning of the assignment questions.

Assignment 1

Textbook Ass ignment : "Area L igh t ing Sys tems . " Pages l - l t h rough 1 -29 .

l-l.

1-2.

L e a r n i n g O b j e c t i v e : I d e n t i f ythe various types of components ,c i r c u i t s , a n d c o n t r o l s f o r a r e al igh t ing sys t ems .

Which of the fol lowing is one ofthe primary problems associatedwi th incandescen t l i gh t bu lbs?

1. Aging2. Manufacturing3. Durability4. Installation

Which of the following devicesprevents increased current flowas electric-discharge lamps heatup?

1. Constant-current regulator2.3.

Isolation transformerBallast

4. Capacitors

1-3. What is the main drawback ofthe older type of sodium lights?

1. Poor color quality2. High ini t ial cost3. Increased maintenance cost4. Reduced light output

1-4. The base o f h igh- in tens i ty -d i scha rge l i gh t ing shou ld bemaintained below what maximumtemperature?

1. 190°F2. 210°F3. 400°F4. 500°F

1-5. Which of the followingprocedures wi l l r educe thestroboscopic effect producedby AID lights?

1. Ins t a l l i ncandescen t l ampsin eve ry o the r f ix tu re

2. Connect HID l ights in as e r i e s w i r i n g c i r c u i t

3. Main ta in a cons tan t cu r ren ton CCR transformer

4. Connect adjacent lamps todifferent power phases

1-6. High-intensi ty mercury-vapor andmetal-halide lamps should NOT beopera ted i f t he ou te r g lobe i sbroken, punctured, or missing.

1. True2. False

1-7. What special precautions mustbe taken if HID equipment isi n s t a l l e d i n a s e r i e s w i r i n gc i r c u i t ?

1. Provide protect ion from highvo l t ages tha t occur du r ingh o t r e s t a r t s

2. E n s u r e t h a t t h e b a l l a s t i smounted within 24 inches ofthe l amp f ix tu re

3. I n s t a l l t i m e r s t o p r e v e n tthe l amps f rom s t a r t ing a tthe same time

4. Use HID equipment only ino v e r h e a d s e r i e s c i r c u i t s

1-8. Fluorescent lamps use what typeo f i n t e r i o r c o a t i n g t o g i v e o f fl i g h t ?

1. Mercury2 .3.

SodiumMetal hal ide

4. Phosphor

1

1-9.

1-10.

1-11.

1-12.

1-13.

1-14.

Ballasts provide which of thefol lowing functions?

1. Limit current f low throughthe lamp

2. Prov ide cor rec t vo l t age tothe lamp

3. Provide power factorcor rec t ion

4. All of the above

A the rmal ly p ro tec ted ba l l a s tapproved by Underwriter 'sL a b o r a t o r i e s i s c l a s s i f i e d a s a

1. Class A ba l l a s t2. C lass D ba l l a s t3. C lass P ba l l a s t4. C lass T ba l l a s t

Which of the fol lowing devicesa re used wi th l amp f ix tu res tochange the qua l i ty o f l i gh tproduced?

1. Ref lec to r s2. Lenses3. Both 1 and 2 above4. Hard glass covers

When HID l ighting f ixtures aremoun ted on po les , t he ba l l a s t sshould be mounted

1. a t the base o f each po le2. within 24 inches of the

l i g h t f i x t u r e3. in a group, c lose to the

d i s t r i b u t i o n t r a n s f o r m e r4. a s c lose to the cons tan t -

cur ren t r egu la to r a sposs ib l e

A cons tan t -cur ren t r egu la to r i ssized to provide 6.6 amperes ofc u r r e n t t o a l i g h t i n g c i r c u i t .I f h igher amperage i s r equ i red ,which of the fol lowing devicesa re used to inc rease the cu r ren tcapacity?

1. Current t ransformers2. Autotransformers3. Dis t r ibu t ion t r ans fo rmers4. Po ten t i a l t r ans fo rmers

Which of the fol lowing devicesprevents a lamp fai lure fromi n t e r r u p t i n g t h e e n t i r e s e r i e sc i r c u i t ?

1. I so la t ion t r ans fo rmer2. B a l l a s t3. Cons tan t -cur ren t r egu la to r4. Fi lm-disk cutout

1-15. When you are running conductorsover a g rea t d i s t ance to supp lys t r e e t l i g h t s i n a p a r a l l e lc i r c u i t , w h i c h , i f a n y , o f t h efollowing is a DISADVANTAGE?

1. Excessive voltage drop2. Excessive current drop3. D i f f i c u l t y i n

troubleshooting4. None of the above

1-16. I f bo th conduc to r s o f a se r i e sl i g h t i n g c i r c u i t a r e i n s t a l l e don the same pole, the system isknown as what type of circui t?

1-17.

1-18.

1-19.

1. Radial- loop2. Open-loop3. Combination-loop4. Closed-loop

I n s u l a t o r s t h a t a r e i n s t a l l e d o ns e r i e s s t r e e t l i g h t i n g c i r c u i t sshould be of what color to dis-tinguish them from those ono t h e r d i s t r i b u t i o n c i r c u i t s ?

1. Gray2. Blue3. Brown4. White

O n s e r i e s s t r e e t l i g h t i n gc i r c u i t s , what size of hard-drawn copper conductor isnormally used?

1 . No. 10 AWG2 . No. 8 AWG3. No. 6 AWG4 . No. 4 AWG

Which of the fol lowing factorsdetermines the output vol tagera t ing o f a t r ans fo rmersupp ly ing s t r ee t l i gh t ing in ap a r a l l e l c i r c u i t ?

1. Vol tage ra t ing o f theindividual lamps

2. Cur ren t r a t ing o f theindividual lamps

3. Voltage drop of thel i g h t i n g c i r c u i t

4. Size of the secondaryconductor

2

1-20. What i s the bas ic p r inc ip leinvo lved in the ope ra t ion o fa c o n s t a n t - c u r r e n t r e g u l a t o r ?

1. A ba lanced l ever r eac t s tocu r ren t f lowing th rough i t ssprings

2. The moving coil reactsd i r e c t l y t o t h e c h a n g e i no i l t e m p e r a t u r e i n t h ecooling fins

3. The moving coil clamps holdthe moving coil away fromt h e s t a t i o n a r y c o i laccording to load demand

4. The moving coil moves withinthe magne t i c f i e ld o f thes t a t i o n a r y t o p r o v i d e t h edes i red secondary cur ren t

IN ANSWERING QUESTIONS 1-24 THROUGH1-26, SELECT FROM COLUMN B THE TYPE OFSTREET CLASSIFICATION THAT MATCHES THEDEFINITION GIVEN IN COLUMN A. NOT ALLRESPONSES IN COLUMN B ARE USED.

A. DEFINITIONS

1-24. Roadways usedp r i m a r i l y f o rd i r e c t a c c e s st o r e s i d e n t i a l ,commercial , ori n d u s t r i a l a r e a s

1-21. Cons tan t -cur ren t r egu la to r s maybe overloaded to what percentwithout damage to the regulator?

1-25. Roadways thatse rve as thep r i n c i p a l n e t -work for throught r a f f i c

1. 5 1-26. Roadways serving2. 10 t ra f f i c be tween3. 15 major and local4. 20 roadways

1-22. Which of the following devicesmay be ins t a l l ed to r e l i eveconstant-current t ransformersthat are sl ightly overloaded?

1. Autotransformers2. Potential transformers3. Booster transformers4. Isolation transformers

IN ANSWERING QUESTION 1-23, REFER TOTABLE l-l IN YOUR TEXTBOOK.

1-27. What type of luminaire shouldyou se lec t to l igh t a roadway i fthe luminaire is to be mountedon the side of the roadway witha width of not over 2.7 t imesthe mounting height?

1. Type I2. T y p e I I3. Type III4. Type IV

1-23. To supply 140 1,000-lumen,6.6-ampere, s t r a i g h t - s e r i e slamps, you would need aregu la to r o f wha t s i ze?

1. 7.5 kW2. 10 kW3. 15 kW4. 20 kW

Learning Objective: I d e n t i f ythe spacing and heightr e q u i r e m e n t s f o r s t r e e t -l i g h t i n g l u m i n a i r e s .

B. TYPES OFSTREETCLASSIFI-CATION

1. I n t e r -mediate

2. Col l ec to r

3. Local

4. Major

3

IN ANSWERING QUESTIONS 1-28 THROUGH1-30, SELECT FROM COLUMN B THE STREET-LIGHT MOUNTING TERMINOLOGY THAT MATCHESTHE DEFINITION GIVEN IN COLUMN A. NOTALL RESPONSES IN COLUMN B ARE USED.

1-28.

1-29.

1-30.

A. DEFINITION

Distancemeasured upand down theleng th o f aroad

Distancemeasuredacross thewidth of theroad

Dimension betweenthe curb and ap o i n t d i r e c t l ybe low the l igh tf i x t u r e

B. STREET-LIGHTINGMOUNTINGTERMINOLOGY

1. Transversed i r e c t i o n

2. Longi-tud ina ld i r e c t i o n

3. Overhang

4. Mountinghe igh t

1-31. When the width of a roadwayapproaches two mounting heightswide, what mounting arrangementshould be used?

1. Opposite2. Staggered3. One-side4. Overlap

1-32. Which of the followings ta t emen t s bes t desc r ibes theinformation that can be obtainedf rom a u t i l i za t ion curve?

1. The total amount of l ightgenerated by the luminaire

2. The amount of usable l ightt h a t a c t u a l l y s t r i k e s t h ea rea to be l igh ted

3. The amount of overlapprovided by the luminaire

4. The total amount of l ightgenerated by the luminairea f t e r 2 yea r s o f opera t ion

1-33. Which part of the manufacturer 'sl i terature shows the magnitudeand d i r ec t ion o f i l l umina t ion a tany point on the roadwaysur face?

1. Isofootcandle curve2. Ut i l i za t ion curve3. Maintenance factor4. C o e f f i c i e n t o f u t i l i z a t i o n

1-34. The fac to r used in l igh t ingcalculat ions to compensate forg radua l lo s ses o f i l l umina t ionis known as what kind of factor?

1. Lamp2. Uniformity3. I l lumina t ion4. Maintenance

1-35. Which of the fol lowing factorsin f luence ( s ) the se l ec t ion o fthe luminaire?

1-36.

1-37.

1. Budget constraints2. A v a i l a b i l i t y3. S tock l eve l s i n the supp ly

system4. All of the above

What must be calculated beforet h e c o e f f i c i e n t o f u t i l i z a t i o ncan be determined?

1. Amount of wasted light ont h e s t r e e t s i d e

2. Amount of wasted light onthe house s ide

3. Both 1 and 2 above4. Amount of light produced by

the luminaire

The uniformity of i l luminationi s expressed in t e rms o f a r a t ioof

1. average fcminimum fc

2. average fcmaximum fc

3. maximum fcminimum fc

4. i n i t i a l f caverage fc

4

1-38. How can the minimum value ofl igh t s t r ik ing a roadway su r facebe determined?

1. By ca lcu la t ing thec o e f f i c i e n t o f u t i l i z a t i o n

2. By plotting the roadway onan isofootcandle curve

3. By multiplying the lampfactor by the maintenancef a c t o r

4. By plotting the roadway ona topographical map

Learning Objective: Iden t i fythe spac ing and he igh t r equ i re -men t s fo r f lood l igh t lumina i re s .

1-39. When you are instal l ing af lood l igh t sys t em, i t i s moree f f i c i en t to use a l a rge r numbero f sma l l f l ood l igh t s t han to usea smaller number of largef l o o d l i g h t s .

1. True2. False

IN ANSWERING QUESTION 1-40, REFER TOFIGURE 1-19 IN YOUR TEXTBOOK.

1-40. The Nat iona l E lec t r i ca lManufacturer 's Associat ion(NEMA) has classified flood-l ight ing luminaires into howmany types according to beamspread degrees?

1 . 1 02 . 93 . 74 . 4

1-41. The suggested area that can becovered by a s ingle pole is howmany times the mounting height?

1. Five2. Two3. Three4. Four

1-42. If the corner poles are NOT usedin pe r ime te r loca t ions , thed i s t ance f rom the l a s t po le tothe edge of the area should NOTexceed how many times themounting height?

1. Five2. Two3. Three4. Four

1-43. The 2X-4X rule can be used toc a l c u l a t e t h e

1. number of f loodlights perpole

2. he igh t o f the po les3. l i g h t i n g i n t e n s i t y o f t h e

area4. minimum number of poles

1-44. The h ighes t l i gh t l eve l af lood l igh t can p roduce a t adistance from the pole occurswhen the maximum intensity isaimed to form approximately a3 , 4 , 5 t r i a n g l e .

1. True2. False

1-45. The 3 , 4 , 5 t r i ang le a imingmethod can be useful fordetermining

1. spacing between the poles2. he igh t o f the po le3. number of f loodlights per

pole4. maximum number of poles

1-46. When se l ec t ing l igh t ing f ix tu rest o l i g h t a n a r e a , a l w a y s s e l e c ta f ix tu re tha t has a beam spreadt h a t i s

1. l e s s than the a rea2. s u f f i c i e n t t o c o v e r t h e a r e a3. g r e a t e r t h a n t h e a r e a4. twice as l a rge as the a rea

1-47. The performance specif icat ionsof each model, type, and size ofluminaire can be obtained from

1. the manufac tu re r ' sl i t e r a t u r e

2. the IES Lighting Handbook3. the Na t iona l E lec t r i ca l

Code®

4. NAVFAC MO-200

1-48. What piece of manufacturer 'sl i t e ra tu re shows wha t the l igh tl eve l wi l l be a t any g ivenpoint?

1. U t i l i z a t i o n d a t a2. NEMA classification number3. Isofootcandle diagram4. Maintenance factor

5

1-49. T h e i n i t i a l f o o t c a n d l e t a b l eg ives the foo tcand le va lue fo reach isofootcandle curve basedon the

1. mounting height of the pole2. number of f ixtures per pole3. u t i l i z a t i o n d a t a4. NEMA classification number

1-50. You can determine the averagelumens per square foot of agiven area by using the

1. maintenance factor2. u t i l i z a t i o n g r a p h3. isofootcandle diagram4. pho tomet r i c t e s t da ta

1-51. Which of the followingmaintenance factors may be usedfor an open floodlamp when them a n u f a c t u r e r ' s l i t e r a t u r e i s n o tava i l ab le?

1. 0.50 1-55. The power source for securi ty2. 0.56 l ight ing systems should be3. 0.65 independen t o f a l l o the r4. 0.76 l igh t ing sys t ems .

Learning Objective: Iden t i fythe components and controls fors e c u r i t y l i g h t i n g .

1-52. S e c u r i t y l i g h t i n g a t a c t i v i t i e sshould provide enough l ight todo which of the fol lowing tasks?

1. Iden t i fy pe r sonne l2. P r e v e n t i l l e g a l e n t r y3. De tec t in t ruders4. All of the above

1-53. Which of the followingstatements concerning thecon t inuous type o f secur i tyl igh t ing sys t ems i s co r rec t?

1. The system is on 24 hoursa day

2. The system is on duringthe hours of darkness only

3. The system is act ivatedby motion detectors

4. The system is powered byemergency generators only

1-54. Which of the followingpub l i ca t ions p rov ides thes p e c i f i c a t i o n s f o r s e c u r i t yl igh t ing?

1. IES Lighting Handbook2. Navy Physical Securi ty

Manual3. NAVFAC MO-2004. NAVFAC MO-117

1. True2. False

1-56. The switches and controls forsecu r i ty l i gh t ing shou ld belocated in which of thefollowing areas?

1. Near the main gate2. Inside the emergency

generator room3. Ins ide a cen t ra l ly loca ted

guard s t a t ion4. Both 2 and 3 above

6

A s s i g n m e n t 2

Textbook Assignment: "Ai r f i e ld L igh t ing . " Pages 2-1 through 2-24. " E l e c t r i c a lLoad Requirements." Pages 3-1 through 3-10.

Learning Objective: Recognizethe various components in ana i r f i e l d l i g h t i n g s y s t e m .

2-1. A i r f i e l d l i g h t i n g c o n f i g u r a t i o n son naval bases in the UnitedStates and overseas conform tothose s t anda rds e s t ab l i shed by

1. the Federal Aviat ionAdministrat ion

2. Ai r Force regu la t ions3. the Department of

Transpor ta t ion4. in te rna t iona l ag reement

2-2. Which of the fol lowing types ofa i r f i e lds i s des igned to be usedby a detachment of KC-130 tankera i r c r a f t ?

1. Ver t i ca l t akeof f and l and ing(VTOL)

2. S t ra t eg ic exped i t iona rylanding field (SELF)

3. Both 1 and 2 above4. Ver t i ca l shor t t akeof f and

landing (VSTOL)

2-3. Which, i f any , o f the fo l lowingcomponents is located in thea i r f i e l d l i g h t i n g v a u l t ?

1. L igh t ing con t ro l pane l2. Emergency generator3. Master sequence t imer4. None of the above

2-4. The l ight ing vaul t should belocated approximately how manyfeet from the runway to preventin te r fe rence wi th opera t ions?

1. 1,5002. 2,0003. 2,5004. 3,000

2-5. I f t h e c o n t r o l c a b l e l e a d ste rmina te in to ac tua t ing co i l so f t h e p i l o t r e l a y s , a t w h a tmaximum number of feet from thel igh t ing vau l t can the con t ro ltower be located?

1. 5,8752. 7,3503. 8,2504. 10,000

2-6. When you are grounding thel igh t ing vau l t , approx ima te lyhow many feet apart should youplace the ground rods?

1 . 52 . 63 . 74 . 8

2-7. What is the primary purpose ofthe i so la t ion t r ans fo rmer?

1. To maintain constant currenti n a s e r i e s c i r c u i t

2. To maintain constant currenti n a p a r a l l e l c i r c u i t

3. To maintain a closed loop inthe p r imary o f a se r i e sc i rcu i t when a l amp fa i lu reoccurs

4. To maintain a closed loopin the p r imary o f a pa ra l l e lc i rcu i t when a l amp fa i lu reoccurs

2-8. What voltages are found ont h e b u s b a r s i n t h e a i r f i e l dl i g h t i n g v a u l t ?

1. 2,400 volts and 240/120v o l t s

2. 4,160 volts and 240/120v o l t s

3. 2,400 volts and 480/240v o l t s

4. 2,400/4,160 vol ts and480/240 vol ts

7

2-9.

2-10.

2-11.

2-12.

2-13.

An automatic changeover switchi s u s e d t o

1. pick up emergency power2. t r a n s f e r v a u l t c o n t r o l t o

the tower3. tu rn on the beacon l igh t a t

dusk4. s h i f t c o n t r o l t o t h e p i l o t

relays

Why are constant-currentr e g u l a t o r s u s e d i n a n a i r f i e l dl ight ing system?

1. To isolate the primarycircuit from the runwaylight

2. To provide constant powerto the con t ro l tower

3. To p reven t shor t - c i r cu i tf au l t s i n the runway l igh t s

4. To maintain correct outputlevel, depending on the load

Which of the following devicesa re used to ob ta in a cons tan t -cu r ren t ou tpu t i n the l i gh t ingcircuit?

1. Sa tu rab le reac to r s2. Resonant circui ts3. Moving transformer cores4. Silicon-controlled

rectifiers

Which of the following devicescompensate for voltage drop inan a i r f i e ld l i gh t ing con t ro lcircuit?

1. Cons tan t -cu r ren t r egu la to r s2. Transformers3. Low-burden pilot relays4. Coaxial cables

The runway lights may becontrolled from two differentlocat ions. What devicedetermines which locat ion isused?

1. Transfer-relay cabinet2. P i lo t - r e l ay cab ine t3. Changeover switch4. Master sequence timer

Learning Objective: I d e n t i f ythe ins t a l l a t ion and ma in tenanceprocedures and sa fe ty p re -c a u t i o n s r e l a t e d t o a i r f i e l dl igh t ing sys t ems .

2-14

2-15.

2-16.

2-17.

2-18.

2-19.

What color are runway edgelights?

1. White (c lea r )2. Green3. Red4. Blue

Runway edge l ights are equallyspaced along both s ides of therunway at distances not toexceed how many feet?

1. 1002. 2003. 3004. 400

The minimum loading for airfieldl igh t ing cons tan t - cu r ren tregu la to r s i s wha t pe rcen t o fthe r a t ed k i lowa t t ou tpu t?

1. 252. 503. 754. 85

What color identif ies taxiwaylights?

1. White (clear)2. Green3. Red4. Blue

What is the preferred length ofan approach lighting system?

1. 500 f t2. 1,000 f t3. 1,500 f t4. 3,000 f t

The visual approach slopeindicator (VASI) l ighting systema s s i s t s t h e p i l o t t o

1. de te rmine the s t a r t o f therunway

2. make a ground-controlledapproach landing

3. make a visual-gl ide-slopeapproach landing

4. determine the length of therunway

8

2-20.

2-21.

2-22.

2-23.

2-24.

The power for the runway-d i s t ance -marke r l i gh t s shou ldbe supplied by

1. the approach l igh t ingc i r c u i t

2. t h e t a x i w a y l i g h t i n g c i r c u i t3. t he th re sho ld l i gh t ing

c i r c u i t4. a s e p a r a t e s e r i e s c i r c u i t

The purpose o f th resho ld l igh t si s t o mark

1. obs t ruc t ions a t t he end o fthe runway

2. the en t rance to the t ax iway3. the over run a rea o f the

runway4. the beginning and ending of

the runway

What co lo r iden t i f i e so b s t r u c t i o n l i g h t s ?

1. White (clear)2. Green3. Red4. Blue

How many feet apart shouldobstruct ion l ights be mountedon a 750- foo t t r ansmi t t ingtower?

1. 1002. 1503. 2004. 250

Which of the fol lowingd e s c r i p t i o n s c o r r e c t l y p o r t r a y sa n a i r p o r t b e a c o n l i g h t f o r am i l i t a r y a i r s t a t i o n ?

1. Red and green2. Red and white3. Green and double-peaked

white4. Blue and double-peaked

white

2-25. A hazard beacon light mountedon a smokestack flashes how manytimes per minute?

1. 182. 263. 454. 60

2-26.

2-27.

2-28.

A beacon l igh t loca ted l e s s than800 fee t f rom the vau l t i susual ly supplied with which ofthe fol lowing power supplies?

1. 80/110 vol ts2. 120/24O volts3. 249/480 volts4. 2 ,400 vo l t s

The 1 ,000- foo t l igh t ba r o f as t r o b e l i g h t s y s t e m i s a l s oknown as the

1. downwind bar2. upwind bar3. abort bar4. decision bar

The strobe l ight system may beturned on and off independentlyo r con t ro l l ed by wha t l i gh tswitch?

1. Approach2. Threshold3. Runway4. Taxiway

2-29. A strobe l ight in a runwaylighting system peaks at whatcandlepower?

2-30

2-31

1. 3,0002. 30,0003. 3,000,0004. 30,000,000

What component controls thef i r ing sequence o f the s t robelights?

1. Fu l l -wave b r idge rec t i f i e r2. 120-volt ac t iming signal3. Autotransformer4. 22-ki lohm resis tor

The purpose of the green l ightmounted on the s trobe l ightloca l r emote con t ro l pane l i st o i n d i c a t e t h a t

1. the un i t i s swi t ched toloca l con t ro l

2. the un i t i s swi t ched toremote control

3. t h e r e i s a f a u l t i n t h esystem

4. one or more strobe l ightshave burned out

9

2-32. The main power transformer inthe mon i to r and con t ro l chass i so f a s t robe sys t em i s ene rg izedby what power supply?

1. 95-volt dc2. 120-volt ac3. 120-volt dc4. 240-volt ac

2-33. The adjusted resistance of 7,333ohms in the monitoring circui to f a s t robe sys tem i s equa l to

1. a 22-kilohm resistance atthe l i gh t un i t

2. two 22-ki lohm resis tors inpa ra l l e l

3. th ree 22-k i lohm res i s to r sin pa ra l l e l

4. three 22-kilohm resistorsi n s e r i e s - p a r a l l e l

2-34. To turn off the "lamps out"a la rm in the s t robe l igh tcircuit,

1. move the selector switchto the next posi t ion

2. r e a d j u s t t h e s e n s i t i v i t yrheostat

3. change the va r i ab le r e s i s to r4. change the voltage set t ing

taps on the transformer

2-35. When the master sequence timeri s c o n t r o l l i n g t h e s t r o b e l i g h tsystem, each contact closes howmany times per second?

1. One2. Two3. Three4. Four

2-36. During visual inspect ions ofa i r f i e ld l i gh t ing sys t ems ,cables should be checked for

1. cuts and bruises2. proper size3. proper length4. correct locat ion

2-37. During maintenance, molded plugconnectors are connected,seated, and then

1. instal led2. checked for moisture3. taped4. tested with a hi-pot

2-38. For how many continuous hoursshou ld each a i r f i e ld l i gh t ingcircuit be operated at maximumbr igh tness du r ing an ope ra t iona lcheck?

1. 12. 23. 64. 8

2-39. The normal amount of timerequ i red fo r a f l a sh capac i to rto bleed down is

1. 5 seconds2. 10 seconds3. 1 minute4. 5 minutes

2-40. The normal radius for anunderground cable bend is howmany t imes the cable diameter?

1. 3 t o 52. 5 t o 123. 7 t o 94. 9 t o 12

2-41. What danger exists if too manylamps burn out in the secondaryof an a i r f i e ld l igh t ing sys tem?

1. The isolat ion transformerwil l overload

2. The remaining lamps willdim

3. The primary current may risehigh enough to damage theregulator

4. The excessive voltage coulddamage the distr ibut iontransformer

2-42. I f a s t r i n g o f l i g h t s i n acircuit does NOT light, morethan l ikely, t h e t r o u b l e i s

1. an open circui t2. a short to ground3. a c ross c i r cu i t4. improper power

2-43. The maximum run of ducted cablebetween manholes is how manyfeet?

1. 5002. 6003. 7504. 1,000

10

2-44.

2-45.

2-46.

2-47.

Learning Objective: Point outthe r equ i remen t s in theins t a l l a t ion o f a dwe l l ingfeeder system.

The to ta l load o f a dwel l ingunit can be divided into howmany categories?

1 . One2 . Two3. Three4 . Four

The NEC® s t a t e s t h a t r e c e p t a c l e srated 20 amperes or less may becalculated with what loadcategory?

1 . Laundry load2 . Small appliance load3 . Spec ia l app l i ance load4 . Genera l l i gh t ing load

The genera l l i gh t ing load fo ra 35- foo t by 60- foo t s ing ledwelling is how many volt-amperes (VA)?

1 . 2,1002 . 4,2003 . 5,5004 . 6,300

How many 20-ampere branchc i r c u i t s m u s t b e i n s t a l l e d i nt h e k i t c h e n , p a n t r y , b r e a k f a s troom, and dining room only?

1 . One2 . Two3 . Three4 . Four

2-48. The l aundry b ranch c i rcu i t in adwe l l ing shou ld usua l ly se rve a tl e a s t o n e a d d i t i o n a l r e c e p t a c l ebes ides the l aundry recep tac le .

1 . True2 . Fa l se

2-49. Which, i f any , o f the fo l lowingappliances may be supplied byt h e g e n e r a l l i g h t i n g c i r c u i t s ?

2-50.

2-51.

2-52.

2-53.

2-54.

2-55.

Determine the general l ightingand recep tac le load fo r adwell ing that has a 6,300-VAlighting load, two 1,500-VAappl iance c i r cu i t s , and one1,500-VA laundry circuit .

1. 3,000 VA2. 4,250 VA3. 5,730 VA4. 7,800 VA

Which of the following demandfac to r s may be app l i ed i f the reare four or more f ixedapp l i ances on a b ranch c i rcu i t ?

1. 66 pe rcen t2. 75 pe rcen t3. 80 percent4. 100 percent

What is the demand load, ink i l o w a t t s , fo r one c lo thes d rye rr a t e d a t 5 k i l o w a t t s ?

1. 4 .52. 5 .03. 6 .04. 7 .5

What is the demand load, ink i l o w a t t s , fo r a 12-k i lowat thouseho ld e lec t r i c r ange?

1. 82. 8 3/43. 9 1 /24. 12

Which of the following demandfactors should you use when youde te rmine the b ranch c i rcu i tconduc to r s i ze fo r hea t ingequipment?

1. 75 percent2. 100 percent3. 125 percent4. 150 percent

Al l motor loads a re c l a s s i f i edas

1. i n t e r m i t t e n t d u t y2. heavy duty3. noncontinuous duty4. cont inuous duty

1 . Garbage disposal2 . Dishwasher3 . Ai r cond i t ioner4 . None of the above

11

IN ANSWERING QUESTIONS 2-56 THROUGH2-62, REFER TO THE APPROPRIATE DEMANDTABLES IN CHAPTER 3 OF THE TEXT AND USETHE FOLLOWING INFORMATION:

A ce r t a in 2 ,100-sq- f t dwe l l ing has twosmal l app l i ance c i r cu i t s and onelaundry c i r cu i t w i th the fo l lowings p e c i a l a p p l i a n c e c i r c u i t s :

2-56.

2-57.

2-58.

2-59.

One 9 -kVA rangeOne 1.5-kVA dishwasherOne 5.5-kVA water heaterOne 15 -kVA central heater

What is the minimum size branchc i r c u i t r e q u i r e d t o s u p p l y t h ee l e c t r i c r a n g e ?

1. 35 amperes2. 40 amperes3. 50 amperes4. 60 amperes

What is the minimum size branchc i r c u i t r e q u i r e d t o s u p p l y t h ewate r hea te r?

1. 25 amperes2. 30 amperes3. 35 amperes4. 40 amperes

What is the minimum size branchc i rcu i t r equ i red to supp ly thec e n t r a l h e a t e r ?

1. 60 amperes2. 70 amperes3. 80 amperes4. 90 amperes

The most important point toremember when determining thes ize o f the se rv ice -en t ranceconduc to r s i s t o

1. s ize the conductors one sizela rge r than necessa ry toal low for expansion

2. s ize the conductors twos izes l a rge r than necessa ryto al low for expansion

3. ensure that the conductorsare large enough to carrythe load

4. ensure that the conductorsare large enough to carry80 pe rcen t o f the to t a ldemand

2-60.

2-61.

2-62.

A service-entrance conductor fora s ing le - fami ly dwel l ing wi ths ix o r more two-wi re c i rcu i t s i srequ i red to have a th ree -wi reservice and a minimum of howmany amperes?

1. 602. 1003. 1254. 200

If phase A on a 240-volt ,s ing le -phase - sys tem ca r r i e s a60-ampere, 120-volt load, andphase B carries an 80-ampere120-volt load, what maximumcur ren t ( in amperes ) i s theneu t ra l conduc to r r equ i red tocarry?

1. 202. 603. 804. 140

When computing the size of theneutral conductor , you can omita l l s ing le -phase and th ree -phase240-volt loads except feederssupplying which of the fol lowingappliances?

1. Electric ranges2. Water heaters3.4.

Central heatersAir condit ioners

12

A s s i g n m e n t 3

Textbook Assignment: "Electrical Load Requirements." Pages 3-10 through 3-15."So l id -S ta te Dev ices and Ci rcu i t s . " Pages 4-1 through 4-32.

Learning Objective: Iden t i fythe r equ i remen t s in thei n s t a l l a t i o n o f a n i n d u s t r i a lfeeder systems.

3-1 . A load is considered continuousdu ty i f t he app l i ance o r moto roperates a minimum of how manycontinuous hours?

1. 62. 23. 34. 8

3-2. Receptacle loads may be includedin the l i gh t ing loadc a l c u l a t i o n s f o r i n d u s t r i a la r e a s .

1. True2. Fa l se

3-3 . Any l igh t ing loads iden t i f i ed a scontinuous duty must be computeda t wha t pe rcen tage o f the to ta lconnected load?

1. 75 percent2. 100 percent3. 125 percent4. 150 percent

3-4 . What i s the load fo r 20 fee t o fmul t i -ou t l e t a s sembl i e s se rv ingl i g h t , noncontinuous loads?

1. 720 VA2. 900 VA3. 1,800 VA4. 3,600 VA

3-5 . What i s the to t a l connec ted loadfor 16 recep tac les se rv ic ingloads used 8 hours each day?

1. 2,355 VA2. 2,880 VA3. 3,600 VA4. 4,200 VA

3-6.

3-7.

3-8.

If the conductors are supplyinga g roup o f motors , the co r rec tp rocedure fo r ca lcu la t ingconductor s ize is to compute

1. t h e f u l l - l o a d c u r r e n t r a t i n gof the l a rges t moto r p lus125 percent of the sum oft h e f u l l - l o a d c u r r e n t r a t i n gof the remaining motors

2. the sum of the fu l l - loadcur ren t r a t ing o f the twolargest motors plus the sumo f t h e f u l l - l o a d c u r r e n tra t ing o f the r emain ingmotors

3. the sum of the fu l l - loadc u r r e n t r a t i n g o f a l l o f t h emotors only

4. 125 pe rcen t o f the fu l l - loadc u r r e n t r a t i n g o f t h elargest motor plus the sumo f t h e f u l l - l o a d c u r r e n tra t ing o f the r emain ingmotors

The to ta l vo l t age d rop o f acombination feeder/branchcircuit should not exceed whatmaximum percentage?

1. 5 percent2. 2 percent3. 3 percent4. 6 percent

I f t h e v o l t a g e d r o p i n a c i r c u i texceeds the p resc r ibed l imi t s ,wha t co r rec t ive ac t ion can betaken?

1. The supply voltage can beincreased

2. A larger size conductor canb e i n s t a l l e d

3. The c i rcu i t l eng th can beshortened

4. Either 2 or 3 above,whichever seems moref e a s i b l e

13

3-9.

3-10.

3-11.

3-12.

Learning Objective: Recognizethe func t ion , ope ra t ion , andi n s t a l l a t i o n o f g r o u n d f a u l ti n t e r r u p t e r ( G F I ) c i r c u i tbreakers.

3-13. For genera l wi r ing in a C lass I ,division 1 location, the NEC®permits the use of which of thefo l lowing types o f condu i t ?

1. Rigid metal l ic conduit2. Rigid nonmetal l ic conduit3. E l e c t r i c a l m e t a l l i c t u b i n g4. All of the above

A ground fau l t in te r rup te r (GFI )opera te s on the p r inc ip le o f animbalance of current between thel ine conductor and

1. ano the r l ine conduc to r2. the grounding conductor3. the grounding electrode

conductor4. the neu t ra l conduc to r

3-14. When ins t a l l i ng f l ex ib leconnect ions to motors locatedin C lass I I , D iv i s ion 1locations, you may use which ofthe fo l lowing types o fmaterials?

Which, i f any , o f the fo l lowingrecep tac les i s r equ i red to bepro tec ted by a GFI c i rcu i tbreaker or GFI receptacle?

1. Flexible metal conduit2.3.

Hard usage cordType AC armored cable

4. L iqu id - t igh t f l ex ib le me ta lconduit

3-15.

1. Receptacle supplying a gasdryer

2. Recep tac le ins ta l l ed ina bathroom

3. Receptacle supplying agarage door opener

4. None of the above

I f a condu i t i s run th rough anenclosure containing spark-producing devices, a conduitsea l has to be in s t a l l ed nofa r the r f rom the enc losure thana maximum of how many inches?

1. 122. 183. 244. 30

Learning Objective: Iden t i fyres t r i c t ions p laced one l e c t r i c a l s y s t e m s i n s t a l l e din hazardous locat ions.

3-16. What grounding techniques areused in hazardous locat ions?

Locations where flammable gasesor vapors are normally presentin the a i r a re des igna ted as

1. Double locknuts only2. Locknut and bushing only3. Bonding jumpers4. Double locknuts and bushing

1. Class I , Division 12. Class I , Division 23. Class II , Division 14. Class I I I , Division 2

Learning Objective: I d e n t i f ysemiconductors used ine l e c t r o n i c c i r c u i t s .

4 f lammable storage locker is 3-17.considered a

Se lec t the purpose ( s ) o f ther e c t i f i e r d i o d e .

1. Class I, D iv i s ion 1 loca t ion2. Class I, D iv i s ion 2 loca t ion3. Class II , Division 1

location4. Class II , Division 2

location

1. T o a m p l i f y o n l y2. To rectify only3. To rectify and amplify4. To switch

14

3-18. Which of the fol lowing isthe schematic symbol of ther e c t i f i e r d i o d e ?

3-19.

3-20.

3-21.

What is the total number ofconnections in a zener diode?

1. One2. Two3. Three4. Four

What is the purpose of the zenerd iode in an e l ec t ron ic vo l t ageregulator?

1. To p rov ide vo l t age re fe rence2. To regu la te ou tpu t vo l t age3. To provide frequency

reference4. To compensate for low supply

voltage

An SCR operates much like ano r d i n a r y r e c t i f i e r d i o d e e x c e p tthat it

1. conduc t s cu r ren t i n on ly onedirection

2. r e q u i r e s r e v e r s e b i a s t ooperate

3. has a lower breakdownvoltage

4. must be f i red to conduct

3-22. An SCR is turned on by apos i t ive pu l se o f cu r ren tapp l i ed to the ga te l ead . Whatact ion turns off the SCR?

3-23.

3-24.

1. Removing the posi t ive pulsefrom the gate lead

2. I n s e r t i n g a p o s i t i v e p u l s eon the ga te l ead

3. Revers ing the cu r ren t o f themain power supply

4. Inc reas ing the cu r ren t o fthe main power supply unti lthe SCR saturates

Trans i s to r s a re used to ampl i fya l l o f t h e f o l l o w i n g f a c t o r sEXCEPT

1. r e s i s t a n c e2. c u r r e n t3. voltage4. power

What are the three elementso f a t r a n s i s t o r ?

1. Emi t te r , co l l ec to r , and base2. Anode, base, and co l l ec to r3. Ca thode , base , and co l l ec to r4. C o l l e c t o r , e m i t t e r , a n d

cathode

3-25. How, i f a t a l l , d o e s t h eun i j unc t ion t r ans i s to r ( U J T)d i f fe r f rom a conven t iona ltransistor?

1. The UJT has two collectors2. The UJT has a second base

i n s t e a d o f a c o l l e c t o r3. The UJT has a second emitter

i n s t e a d o f a c o l l e c t o r4. There i s no d i f fe rence

3-26. The UJT has which of thefol lowing advantages overt h e t r a n s i s t o r ?

1. Fewer terminals2. Larger bandpass3. Less bias requirement4. Increased temperature

stability

15

3-27. A device that combines bothact ive and passive components ofa comple te c i r cu i t i n a s ing lec h i p i s c a l l e d

1. mic roe lec t ron ics2. a n i n t e g r a t e d c i r c u i t3. a p r in ted c i r cu i t boa rd4. an in t eg ra ted c i r cu i t boa rd

Learning Objective: Point outt h e a p p l i c a t i o n s o f s o l i d - s t a t ecomponents used in NCFequipment.

3-28. The primary function of ther e c t i f i e r s e c t i o n o f a p o w e rsupp ly i s t o

1. increase average voltageoutput

2. decrease average voltageoutput

3. convert dc to ac4. convert ac to dc

3-29. A b r i d g e r e c t i f i e r c i r c u i t c a nb e e a s i l y i d e n t i f i e d b e c a u s e i tcon ta ins

1. a transformer and fourdiodes

2. two diodes with a crossr e s i s t o r

3. three diodes4. a cen te r - t apped t r ans fo rmer

3-30. Which of the followingcond i t ions wou ld ex i s t i f oned i o d e i n a b r i d g e r e c t i f i e rc i r c u i t f a i l e d ?

1. No output voltage2. No change in output voltage3. Hal f -wave rec t i f i e r ou tpu t

vo l t age4. Fu l l -wave rec t i f i e r ou tpu t

voltage

3-31. The e r ro r s igna l app l i ed to thee r r o r a m p l i f i e r c i r c u i t o f a nSCR voltage regulator consistso f the d i f fe rence be tween therec t i f i ed genera to r ou tpu t anda voltage developed across the

3-32. In an SCR voltage regulator,wha t i s the func t ion o f thee r ro r ampl i f i e r?

1. To provide the regulatorwith proper voltage

2. To provide phase anglecontrol for f i r ing the SCRs

3. To sense output vol tage4. To sense deviat ion in

genera to r vo l t age

3-33. The value of current supplied tothe exciter f ield depends uponthe

1. resistance-capacitance (RC)network

2. s e r i e s - b o o s t c i r c u i t3. conduction time of the SCRs4. capac i t ance o f the exc i t e r

f i e l d

3-34. Which circuit of the SCR voltageregu la to r p reven t s over -cor rec t ion fo r a change ingenerator voltage?

1. Power inpu t c i r cu i t2. Sens ing c i r cu i t3. S t a b i l i t y c i r c u i t4. E r r o r d e t e c t o r c i r c u i t

3-35. What is the purpose of the K1relay in an SCR voltageregu la to r?

1. To con t ro l exc i t e r f i e ldcur ren t

2. To prevent buildup ofe x c i t e r f i e l d v o l t a g e

3. To provide a current pathto the SCRs

4. To provide automatic voltagebuildup

3-36. The paral lel compensationcircuit of an SCR voltageregu la to r a l lows the pa ra l l e l edgenera to r to

1. e s t ab l i sh the g r id f r equency2. es t ab l i sh the g r id vo l t age3. sha re the r eac t ive load4. sha re the r e s i s t ive load

1. g e n e r a t o r f i e l d2. s t a b i l i z i n g c i r c u i t3. vo l t age -ad jus t rheos ta t4. zener diode

16

3-38.

3-37. T h e r e a c t i v e d i f f e r e n t i a lcompensat ion circui t can be usedonly when al l the generatorsconnec ted in pa ra l l e l havei d e n t i c a l p a r a l l e l i n g c i r c u i t sinc luded in the loop .

1. True2. False

F i e l d c u r r e n t r e g u l a t i o n i n at r a n s i s t o r v o l t a g e r e g u l a t o r i saccomplished by using

1. an SCR2. a sa tu rab le core t r ans fo rmer3. high-voltage diodes4. a s e r i e s c u r r e n t r e s i s t o r

3-39. Power fo r the sa tu rab le coret rans fo rmer i s ob ta ined f rom the

1. sensing transformer2. power ou tpu t t r ans i s to r s3. cur ren t t r ans fo rmers4. l i n e a r r e a c t o r

3-40. The purpose of the amplif ierc i r c u i t i n a t r a n s i s t o r v o l t a g er e g u l a t o r i s t o

1. p rov ide cu r ren t to thee x c i t e r f i e l d

2. ampl i fy the re fe rencevo l t age

3. d e t e c t d e v i a t i o n i ngenera to r vo l t age

4 . c o n t r o l e x c i t e r f i e l dc u r r e n t

3-41. The ac tua l genera to r ou tpu tvo l t age i s de te rmined by the

1. zener-diode bridge2. o p e r a t o r ' s v o l t a g e - a d j u s t

r h e o s t a t3. vector-summing circuit4. vo l t age - feedback rheos ta t

3-42. T h e i n i t i a l f i e l d c u r r e n t f o re x c i t i n g t h e g e n e r a t o r i sp rov ided by a f i e ld - f l a sh ingc i r c u i t f r o m t h e

1. s t a t i c e x c i t e r2. o u t p u t r e c t i f i e r s3. sa tu rab le core t r ans fo rmer4. bat tery bank

IN ANSWERING QUESTIONS 3-43 THROUGH3-47, SELECT FROM COLUMN B THE FUNCTIONOF THE PROTECTIVE RELAY LISTED INCOLUMN A. RESPONSES IN COLUMN B MAY BEUSED MORE THAN ONCE.

A. PROTECTIVE B. FUNCTIONSRELAYS

3-43. Overvoltage 1. Pro tec tthe load

3-44. Undervoltage2. Pro tec t

3-45. Underfrequency thegenera to r

3-46. Reverse-power

3-47. Overload

3-48. An undervoltage relay wil loperate when the generatorvo l t age dec reases to approx i -mately what percentage ofra t ed ou tpu t vo l t age?

1 . 6 52 . 7 53 . 8 54 . 9 5

3-49. When the load of a generatorexceeds 130 percent of the ratedc u r r e n t , which of the fol lowingeven t s occur ( s )?

1. Engine secures2. Annuniciator alarms3. Generator breaker opens4. Both 2 and 3 above

Learning Objective: Recognizeproper t echn iques fo r t roub le -shoo t ing e l ec t ron ic dev ices andc i r c u i t s .

3-50. Compared to the vacuum tube, theso l id - s t a t e dev ice has which o fthe fo l lowing l imi ta t ions?

1. More sensi t ive totemperature

2. Use l imi ted to radarequipment

3. D i f f i c u l t t o a d a p t t ocommercial products

4. Each of the above

17

3-51. To check t r ans i s to r s , you shou ldavoid using an ohmmeter that iscapab le o f p rov id ing a cu r ren tof more than

1. 0.1 mill iampere2. 1.0 mill iampere3. 10.0 mill iamperes4. 1.0 ampere

3-52. Which o f the fo l lowing t e s t s i sa convenient method of checkinga r e c t i f i e r d i o d e ?

1. The subst i tut ion of a newdiode fo r the ques t ionab leone

2. A dynamic electr ical checkw i t h a d i o d e t e s t s e t

3. A forward and reverseres i s t ance check wi th anohmmeter

4. A forward and reverseres i s t ance check , us ingtwo different ohmmeters

3-53. When test ing a zener diode, youshould use a variable dc powersupply to

1. l imi t cu r ren t t h rough thezener diode

2. supply enough current tocause the zener diode toconduct

3. supply enough voltage tocause the zener diode toconduct

4. i so la t e the zene r d iodefrom chassis ground

3-54. Which, i f any , of the fol lowingactions would cause an SCR toconduc t when i t i s t e s t ed wi than ohmmeter?

1. Short ing the anode to thecathode

2. Short ing the anode to thega te

3. Shor t ing the ca thode to thega te

4. None of the above

3-55. A h igh res i s t ance read ing ac rossbase 1 and base 2 of aun i j unc t ion t r ans i s to r i nd ica t e st h a t t h e t r a n s i s t o r i s

3-56. O f a l l t h e t e s t s u s e d i nt roub leshoo t ing t r ans i s to r s ,which two are the mostimportant?

1. Gain and leakage2. Gain and breakdown3. Breakdown and switching4. Leakage and breakdown

3-57. Which of the followingconditions would cause at r a n s i s t o r t o t e s t b a d i n t h ecircuit but good when removedf rom the c i rcu i t ?

1. A low-impedance shunt patha round the t r ans i s to r

2. A f a u l t i n t h e c i r c u i t3. Excess leakage in the

t r a n s i s t o r4. All of the above

3-58. Al though no t spec i f i ca l lyd e s i g n e d f o r i t , t h e t r a n s i s t o rt es te r wi l l t e s t SCRs fo r whichof the fol lowing condit ions?

1. Breakdown and leakage2. Switching and leakage3. Switching and breakdown4. All of the above

3-59. When the t r ans i s to r t e s t e r i sbeing used, if an SCR isshor ted , bo th pos i t i ons o f t het e s t w i l l i n d i c a t e

1. low leakage2. high leakage3. low resistance4. h igh re s i s t ance

3-60. A device that can be of greatva lue in t roub le shoo t ingi n t e g r a t e d c i r c u i t s ( I C s ) i sthe

1. ohmmeter2. t r a n s i s t o r t e s t e r3. logic probe4. osc i l lo scope

1. open2. shorted3. grounded4. good

18

3-61.

3-62.

3-63.

What i s the p r inc ipa l use o f theca thode- ray tube osc i l loscope?

1. Ana lys i s o f vo l t agewaveforms

2. Analysis of Currentwaveforms

3. Measurement of frequencyof rotat ing machines

4. Measurement of microwaveenergy

In a dua l - t r ace osc i l loscope theh o r i z o n t a l a x i s r e p r e s e n t sampl i tude in vo l t s , and thev e r t i c a l a x i s r e p r e s e n t s t i m e i nseconds.

1. True2. Fa l se

The osc i l loscope t e s t p robeshou ld be ca l ib ra t ed be fo reeach use to

1. reduce high capacitancein RC c i rcu i t s

2. block frequency signalsabove 500 MHz

3. reduce high inductancein RL c i rcu i t s

4. prevent waveform distort ion

3-64. I t i s a lways necessa ry to g roundeach t e s t p robe to p reven tinterference or other waveformdis to r t ion on h igh- f r equencys i g n a l s .

1. True2. False

3-65. To ana lyze an e lec t ron ic c i rcu i te f fec t ive ly wi th anosc i l lo scope , you mus t f i r s tde te rmine the cor rec t

1. vo l t age requ i rements fo reach component

2. cur ren t r equ i rements fo reach component

3. waveform by consulting them a n u f a c t u r e r ' s l i t e r a t u r e

4. waveform by comparison withsimilar equipment

3-66. Capacitor fai lures are commonlycaused by which of the fol lowingcond i t ions?

1. Excess ive d ie lec t r i c l eakage2. A n i n c r e a s e i n d i e l e c t r i c

abso rp t ion3. Change in capacity value4. Each of the above

3-67.

3-68.

3-69.

A punc tu re in the d ie lec t r i cm a t e r i a l o f a c a p a c i t o r i susual ly caused by

1. high-voltage spikes2. l o n g s h e l f l i f e3. low-voltage operat ion4. p a r a l l e l o p e r a t i o n

D i e l e c t r i c a b s o r p t i o n i s t h ei n a b i l i t y o f a c a p a c i t o r t odo what action?

1. Fu l ly cha rge to r a t edvoltage

2. Completely discharge to zero3. Operate at high frequencies4. Main ta in the co r rec t vo l t age

requirements

E l e c t r o l y t i c c a p a c i t o r s t h a tindicate low value or highleakage because of long shelflife may be salvaged by

1. opera t ing the capac i to r a tone-ha l f the r a t ed vo l t age

2. opera t ing the capac i to r a ttwice the r a t ed vo l t age

3. hea t ing the capac i to r in anoven for 1 hour

4. reforming the capacitor witha c a p a c i t o r t e s t e r

3-70. Which of the following is NOT acause o f induc to r co i l f a i lu re?

1. Shor t ed co i l t u rns2. Open coil turns3. Low power factor4. Changes in inductor value

3-71. I f you pe r fo rm the r ing ing t e s ton an inductor coi l and theresu l t s a re some , bu t l e s s than1 0 , r i n g i n g c y c l e s , t h e c o i l i s

1. open2. grounded3. shorted4. the wrong value

19

A s s i g n m e n t 4

Textbook Assignment: "Power Generation and Distr ibution." Pages 5-1 through 5-34.

Learning Objective: Iden t i fythe p rocedures fo r ca lcu la t inggenerator load and the funda-men ta l s o f s e l ec t ing un i t s bys ize and type .

4 -1 . A power distr ibution systemc o n s i s t s o f t h e

1. generators and powerhouse2. equipment between the

genera to r s and thecus tomer ' s se rv ice en t rance

3. equipment between theprimary mains and the powerload

4. h igh-vo l t age t r ansmiss ionl i n e s

4-2. The annual load factor of anadvanced base is found byd iv id ing the

1. load demand by the diversi tyf a c t o r

2. demand factor by the peakpower

3. true power by the apparentpower

4. average power by the peakpower

4-3 . Which of the followingpercen tage pa i r s r ep resen t sacceptable values of the annualload factor and power factor ofan advanced base?

1. 40 percent , 95 percent2. 45 percent , 95 percent3. 50 percent , 80 percent4 . 60 percent , 75 percent

4-4. Which of the followinggenera t ing requ i rements fo rcommunications and lighting canbe met with a S-kilowattgaso l ine -d r iven genera to r?

1. 120 vol ts , s ing le -phase ,60 hertz

2. 120 /208 vo l t s , s ing le -phase ,60 hertz

3. 120 /208 vo l t s , t h ree -phase ,60 hertz

4. All of the above

4-5. The demand factor for a groupof loads is determined byd iv id ing the

1. actual maximum demand bythe to t a l connec ted load

2. average power demand by thepeak power demand

3. average power demand by thetrue power demand

4. actual load demand by theannua l load fac to r

4-6. The to ta l connec ted load fo ryour repair shop is 60k i lowat t s , and the maximumdemand is 40 ki lowatts . Whatis the demand factor?

1. 26 percent2. 50 percent3. 66 percent4. 75 percent

Learning Objective: Apply thep r i n c i p l e s o f d i r e c t i n gpe r sonne l in the se l ec t ion andi n s t a l l a t i o n o f g e n e r a t o r s .

4 -7 . A generator supplying power foran advanced base should beloca ted nea r the

1. b a r r a c k s s i t e2. edge of the base3. points of small demand4. points of large demand

20

4-8. One way to get r id of excessengine heat in and around ag e n e r a t o r s e t t h a t i s i n s t a l l e dins ide a bu i ld ing i s by

1. p r o v i d i n g s u i t a b l e e x i t s f o rexhaust gases

2. opening al l the doors andha tches on the genera to r se t

3. providing large louveredopen ings in the s ide o f t heg e n e r a t o r s e t

4. providing large louveredopenings in the bui ldingwal l s a t the f ron t and backof the genera to r se t

4-9. What is the best way to get r idof carbon monoxide gas that ismanufactured by a diesel-enginegenera to r?

1. Extend the engine 's exhaustp ipe to the ou t s ide o f thebu i ld ing

2. Cool the gas in a cold-waterba th be fo re i t goes to theexhaust

3. P rov ide f r e sh a i r duc t s inthe roof o f the genera to rbu i ld ing

4. Open al l doors and hatcheson the genera to r se t

4-10. Afer the genera to r se t i si n s t a l l e d , the next s tep youor your crew should do is to

1. t e s t - o p e r a t e t h e u n i t t ocheck voltage and frequency

2. place the uni t under 110percen t load fo r 2 hours

3. conduc t a v i sua l ove ra l li n spec t ion

4. p lace the genera to r inopera t ion

4-11. You can shorten the warming-upper iod fo r a l a rge genera to r by

1. opening and latching the fancover

2 . c los ing the bypass shu t t e r sand doors

3. covering the engine exhausts t acks

4. c los ing the roof ha tches ands ide louver s

4-12. T h e i n s t a l l a t i o n r e s i s t a n c e o fthe s t a to r and ro to r wind ings o fa 120/208-volt generator shouldbe checked with a megohm meterb e f o r e o p e r a t i o n , b u t t h e t e s tvol tage should not exceed

1. 250 v o l t s dc2. 250 v o l t s ac3. 500 v o l t s dc4. 500 v o l t s ac

4-13. When the manufacturer'si n s t r u c t i o n s a r e n o t a v a i l a b l e ,brushes for integral horsepowerand integral ki lowatt machinesa re to be se t wi th a b rushpressure o f

1. 1.0 t o 2.0 p s i2. 2.0 t o 2.5 p s i3. 3.0 t o 3.5 p s i4. 4.0 t o 4.5 p s i

4-14. The changeover board on anadvanced-base generator is usedas a means of

1. d i sconnec t ing the genera to rl eads f rom the po ten t i a ltransformers

2. d i sconnec t ing the genera to rleads from the currentt r ans fo rmers

3. rea r rang ing the genera to rleads to change phaser o t a t i o n

4. rea r rang ing the in te rna la l t e r n a t o r l e a d s t o g i v ea spec i f i ed ou tpu t vo l t age

4-15. The grounding electrode for agenerator set should have ares i s t ance - to -g round read ing o fno more than how many ohms?

1 . 1 02 . 2 53 . 5 04 . 7 5

4-16. Genera to r load cab les tha t a replaced underground (directburial) must be of a type knownas

1. RHW (heat and moisturer e s i s t a n t )

2. TW (thermoplast ic-insulated)3. WP (waterproof)4 . R ( rubber - insu la ted ,

rubber - j acke ted)

21

4-17.

4-18.

4-19.

4-20.

Learning Objective: Recognizethe p rocedures to fo l low inoperat ing and maintaining anadvanced-base generator plant .

The purpose of keeping ag e n e r a t o r s t a t i o n l o g i s t o

1. help determine when ap a r t i c u l a r p i e c e o fequipment needs preventivemaintenance

2. record the fuel consumptiono f a l l g e n e r a t o r s

3. p rov ide a h i s to ry o f cu r ren tdemands by all customers

4. record the au tomat ico p e r a t i o n s o f t h e f u e ltransfer pump

The p rocedure tha t a s su res tha ta l l sys t ems and con t ro l s a rep roper ly a l igned fo r ope ra t ioni s found in the

1. p r e s t a r t c h e c k l i s t2. operator maintenance manual3. intermediate maintenance

manual4. shutdown checklis t

Before two generators can beopera ted in pa ra l l e l , t hey mus tbe brought into synchronism.When they are in synchronism,which of the fol lowingcond i t ions mus t ex i s t ?

1. The terminal voltages mustbe equal

2. The frequencies must beequal

3. The voltage sequences mustbe in phase

4. All of the above

One of the primary con-s i d e r a t i o n s i n p a r a l l e l i n ggenera to r se t s i s ach iev ingthe p roper d iv i s ion o f load .What charac te r i s t i c o f thegenera to r se t accompl i shest h i s d i v i s i o n o f l o a d ?

1. Vol tage regu la to rs e n s i t i v i t y

2. Vol tage regu la to r r ange3. Governor speed droop4. Governor load l imit

4-21.

4-22.

4-23.

4-24.

4-25.

Of th ree genera to r s opera t ing inp a r a l l e l , how many are set atzero on the speed droop dial?

1 . One2.3.

TwoThree

4. Four

The frequency of the slavemachine should be s l ight lyh igher than tha t o f the mas te rmachine when the circuit breakeri s c losed to ensu re tha t t he

1. slave machine assumes asmall amount of load

2. slave machine assumes alarge amount of load

3. master machine assumes asmall amount of load

4. master machine assumes alarge amount of load

I f t he synchron iz ing l igh t sbl ink on simultaneously and offsimultaneously, which of thefo l lowing cond i t ions ex i s t ( s ) ?

1. The frequencies are equal2. The voltages are equal3. The voltage sequences are

in phase4. Al l o f the above

I f you no t i ce tha t the synchro -n iz ing l i gh t s a r e b l ink ing onand o f f a l t e rna te ly , wha t ac t ionshould you take?

1. Ad just the speed of theincoming generator

2. Adjust the speed of theon- l ine genera to r

3. Adjus t the vo l t age o f theincoming generator

4. Interchange any two loadcables of the incominggenera to r

When you are paralleling byus ing the synchron iz ing l i gh t s ,when should you close thec i r c u i t b r e a k e r t o p l a c e t h eincoming generator on the l ine?

1. A t t h e i n s t a n t b o t h l i g h t sgo out

2. A t t h e i n s t a n t b o t h l i g h t sgo on

3. Whi le bo th l igh t s a re ou t4. While both l ights are on

22

4-26. The power factor of ane l e c t r i c a l l o a d i s d e t e r m i n e dby dividing the

1. true power by the peak power2. true power by the apparent

power3. apparent power by the peak

power4. peak power by the average

power

4-27. Capacitors may be used toimprove the power factor of asystem when the reduced powerfactor has been caused by thee f fec t s o f which o f thefollowing components?

4-28.

4-29.

1. Lagging reactive2. Leading reactive3. P u r e l y r e s i s t i v e4. Each of the above

You can divide the react ive loadbetween two generators byad jus t ing the

1. speed o f the genera to r s2. vo l t age o f the genera to r s3. speed droop of the governors4. capac i t ance- reac tance o f the

vo l t age r egu la to r s

What is the purpose ofins t a l l i ng bo th a mechan ica lc lock and an e lec t r i c c lock a ta power plant?

1. To ensure cor rec t genera to routput frequency

2. To compensate for powerf a i l u r e s

3. To ensure cor rec t genera to rou tpu t vo l t age

4. To indicate improper divisiono f r e a c t i v e l o a d

4-30. All of the fol lowing maintenancechecks are performed by theoperator EXCEPT

1. check ing the l eve l o f thecoo lan t

2. g r e a s i n g t h e f u e l t r a n s f e rpump

3. d ra in ing wa te r f rom the fue ltank

4. add ing o i l t o the c rankcase

4-31.

4-32.

4-33.

4-34.

Learning Objective: I d e n t i f ycomponents and types ofd i s t r ibu t ion sys t ems and po in tout advantages and disadvantagesof each.

For which of the fol lowingreasons is an overheadd i s t r ibu t ion sys tem pre fe r redover an underground system?

1. I t i s n o t a f f e c t e d b yclimate

2. It can accommodate largerconductors

3. I t uses lower primaryvo l t ages

4. I t o f f e r s g r e a t e rf l ex ib i l i t y t o chang ingcondit ions

In the loop d i s t r ibu t ion sys t em,how many breakers are instal ledn e a r t h e d i s t r i b u t i o ntransformers to open eachprimary cable?

1. One2. Two3. Three4 . Four

A network system and a radialsys tem d i f fe r wi th r e spec t tothe

1. type of t ransformers used2. type of fuses used3. way the secondaries are

connected4. way the primaries are

connected

If a new primary feeder systemmust be f lexible because ofprobable future growth, whattype of system should yourecommend?

1. Network2. Radial3. Loop4. Each of the above

23

4-35. The vo l t age a t t he d i s t r ibu t ioncenter can be maintainedprac t i ca l ly cons tan t byins ta l l ing a f eede r vo l t ager e g u l a t o r a t t h e

1. d i s t r i b u t i o n c e n t e r2. subs t a t ion3. gene ra t ing s t a t ion4. d i s t r ibu t ion t r ans fo rmer

4-36. The fused cutouts locatedbetween the primary mains andthe t r ans fo rmer p ro tec t thetransformer against which ofthe fol lowing occurrences?

1. High-voltage surges2. S h o r t c i r c u i t s3. Overloads4. Both 2 and 3 above

Learning Objective: Recognizefactors used in implementing at r a n s f o r m e r i n s t a l l a t i o n .

4-37. L igh tn ing a r res t e r s fo r ad i s t r ibu t ion t r ans fo rmer shou ldbe located between the

1. primary mains and fusedcu tou t s

2. primary and secondary sidesof the t r ans fo rmer

3. fused cutouts and thesecondary bushings of thetransformer

4. secondary side of thet rans fo rmer and the se rv icedrop

4-38. Which of the fol lowing types ofd i s t r ibu t ion t r ans fo rmersr e q u i r e ( s ) t h e i n s t a l l a t i o n o fex te rna l p ro tec t ive dev ices?

1. Conventional2. Se l f -p ro tec ted3. Both 1 and 2 above4. Comple te ly se l f -p ro tec ted

Figure 4A

IN ANSWERING QUESTIONS 4-39 THROUGH4-41, REFER TO THE TRANSFORMERINSTALLATION REPRESENTATION IN FIGURE4A.

4-39. What is the maximum demand basedon a 0.9 demand factor?

1. 5.6 kVA2. 6.9 kVA3. 10.4 kVA4. 11.5 kVA

24

4-40.

4-41.

4-42.

What is the minimum size oftransformer needed to supplythe average demand?

1. 10 kVA2. 15 kVA3. 25 kVA4. 37.5 kVA

The mos t su i t ab le loca t ion fo rthe t r ans fo rmer i s a t po le

1. J2. K3. L4. M

Transformers larger than 100 kVAare usually mounted on a

1. pad or platform2. pole below the secondary

mains3. pole above the secondary

mains4. cluster mount above the

primary mains

Learning Objective: Recognizet h e s t e p s r e q u i r e d t o s e l e c tthe size and type of guy wireand anchor cor rec t ly .

4-43. A cor rec t ly ins t a l l ed guypro tec t s the po le l ine f romdamage caused by

1. improperly sagged l ineconductors

2. large transformer banks3. t h e s t r a i n o f t h e l i n e

conductors

4-44. What e f fec t , i f any , wi l l anychange in d i r ec t ion o f thet r ansmiss ion l ine have on l ineconductor tension?

1. Inc rease the t ens ion2. Decrease the tension3. Double the tension4. None

4-45. Which of the followingl e a d - t o - h e i g h t g u y r a t i o s i sp r e f e r r e d t o r e d u c e s t r e s s e son the pole?

1. .75 to 1.02. 1.0 to 1.03. 1.0 to 1.54. 1.5 to 1.0

4-46. The holding power of an anchordepends upon which of thefol lowing condit ions?

1. The area of the anchorplate

2. The depth set t ing3. The type of soi l4. All of the above

Learning Objective: Iden t i fythe components and requirementsneeded to provide protect ion ona power distr ibution system.

4-47. L igh tn ing a r res t e r s p ro tec tthe primary l ines from

1. overcur ren t su rges2. undervoltage condit ions3. overvoltage caused by

lightning4. low power factor condit ions

4-48. When ins t a l l ing a s ing le -phase ,100-kVA transformer with anoperat ing voltage of 2,400volts, wha t s i ze o f fuse l inkdo you need?

1. 502. 653. 1004. 150

4-49. When ins ta l l ing a th ree -phase ,150-kVA transformer bank withan operat ing voltage of 12,000v o l t s , wha t s i ze o f fuse l inkdo you need?

1. 102. 153. 204. 40

4-50. I n a t h r e e - p h a s e i n s t a l l a t i o n ,where is the wire from the topo f e a c h l i g h t n i n g a r r e s t e ra t t ached?

1. To the secondary l ine2. To the transformer housing3. To the primary l ine4. To the main ground wire

25

4-51. Where is the ground wire onan ove rhead d i s t r ibu t ion l inenormally mounted?

1. Below the primary l ines2. Below the secondary l ines3. Alongside the neutral wire4. Above the primary l ines

4-52. Which of the fol lowing act ionswill improve the power factorof a power distr ibution systemwi th l agg ing cu r ren t s?

1. Ins t a l l ing a capac i to r bank2. Inc reas ing the s i ze o f the

primary conductors3. P lac ing a r e s i s t ive load

i n p a r a l l e l w i t h a r e a c t i v eload

4. All of the above

4-53. You can protect primary feedercapacitor banks from l ightningdamage by instal l ing

1. l i gh tn ing rods2. ground rods3. h igh-vo l t age fused cu tou t s4. l i g h t n i n g a r r e s t e r s o f t h e

l ine type

4-54. At what point in a powerdis tr ibut ion system should youi n s t a l l a c a p a c i t o r b a n k f o radded load capacity?

4-55. Before shor t - c i r cu i t ing thet e r m i n a l s o f a c a p a c i t o r a f t e ri t has been de-energized, youshould wait a minimum of howmany minutes?

1 . 52 . 1 03 . 1 54 . 3 0

4-56. Fac i l i t i e s a re found in wha tarea of the NAVFAC P-437?

1. Par t 1 of Volume I2. Par t 2 of Volume I3. P a r t 1 of Volume I I4. Par t 2 o f Volume I I

4-57. Components are defined as agrouping of

1. equipment and materials thathas no spec i f i c func t ion o rmission

2 . personnel and equipment thathas a spec i f i c func t ion o rmission

3. pe r sonne l and ma te r i a l s tha thas a spec i f i c func t ion o rmission

4. pe r sonne l and ma te r i a l s tha thas no spec i f i c func t ion o rmission

1. Transformer bank2. Load center3. Substat ion4. Genera t ing s t a t ion

26

A s s i g n m e n t 5

Textbook Assignment: "Field Riggings and Hoist ing Systems."Pages 6-1 through 6-18.

5 - 1 .

5 - 2 .

5 - 3 .

5 - 4 .

Learning Objective: Recognizepr inc ip le s o f des ign ing ande rec t ing s imple ho i s t ingdev ices .

F ie ld -e rec ted ho i s t ing dev icesbas ica l ly cons i s t o f a b lock-and-tackle system arranged onsome form of skeleton structureconsist ing of wooden poles orsteel beams.

1. True2. False

When natural holdfasts ofsuf f i c ien t s t reng th a re NOTa v a i l a b l e , which of thefollowing devices can be used?

1. Log deadman only2. Combination-log-picket

ho ld fas t on ly3. Combinat ion-picket holdfast

only4. Any man-made holdfast

When using trees as holdfasts ,you should always at tach theguys near

1. a s turdy branch to avoids l i pp ing

2. the cen te r o f the t runko f a t r e e

3. ground level

Af te r a guy l ine to a p icke tho ld fas t i s t i gh tened , wha tmeans should be used to securethe guy l ine?

1. A clove hi tch2. Two clove hitches3. A ha l f h i t ch4. Two half hi tches

5-9.

5-8.

5-7.

5-6.

5-5. The simplest type of holdfasttha t i s su i t ab le fo r an anchorguy and that can bear loads upto 4,000 pounds is a 3-2-lcombination picket .

1. True2. False

Suppose a picket holdfast wil lbe used for several days. Whatshould the guys be made of?

1. Smal l s tu f f2. Galvanized wire3. Both 1 and 2 above

Which of the fol lowing is thebes t desc r ip t ion o f thecombination-log picket?

1. The guy is connected to thecen te r o f a log bur i ed inthe ground

2. The guy is connected to thecen te r o f a log l a shed tothe t runks o f two t r ees

3. The guy is anchored to alog or t imber supportedaga ins t fou r o r s ixcombinat ion-picket holdfasts

How should the holes for a rockh o l d f a s t b e d r i l l e d ?

1. 1 to 2 feet deep andstraight up and down

2. 1 1/2 to 3 feet deep and ata s l ight angle away from thed i r e c t i o n o f p u l l

3. 1 1/2 to 3 feet deep and ata s l igh t ang le towards thed i r e c t i o n o f p u l l

When a s t ee l -p icke t ho ld fas t i sbeing used, t h e r e i s a nadvantage to using two or moreunits in combinat ion.

1. True2. False

27

5-10.

5 - 1 1

5 - 1 2

Determine the maximum height ofat t imber gin pole that has an8-inch diameter.

1. 10 f e e t2. 28 f e e t3. 48 f e e t4. 50 f e e t

Determine the minimum distancefrom the base of the gin pole tothe anchorage of the guy l inesfo r a 15- foo t g in po le .

1. 15 f e e t2. 30 f e e t3. 45 f e e t4 . 60 f e e t

What part of a gin pole assemblyi s mos t l i ke ly to be the weakes tpo in t?

1. Load line2. F a l l l i n e3. Holdfast4. Af te r guy l ine

5 - 1 3 . To have the LEAST amount ofstress on the guys, you shouldhave the gin pole in whatpos i t i on?

1. Almost horizontal2. V e r t i c a l3. At a 45° angle

5-14

5-15

When rigging a gin pole, youshould use a square knot to

1. hang the guys on the pole2. t i e t he guys to the

ho ld fas t s3. t i e the fo rward guys to

the back guys4. secure the ends of the

lashings

When laying out the guy line onthe ground before the erect ionof a 12-foot pole, you shouldmake them how many feet long?

1 . 1 22 . 2 43 . 4 84 . 7 2

Figure 5A

IN ANSWERING QUESTIONS 5-16 AND 5-17, REFER TO FIGURE 5A.

2 8

5-16. When preparing to use a deadmanas an anchor for a guy, youshould begin by making anexcava t ion s imi la r to the oneshown at

1 . A2 . B3 . C

5-17. A deadman should be buried andthe guy wrapped around it asshown at

1. A only2. B only3. C only4. Either A, B, or C, whichever

i s p r e f e r r e d

5-18. To keep a gin pole from skiddingwhile being erected, what shouldyou do?

1. Reeve t ack le to the rea r o ft h e p o l e a n d a t t a c h i t t o as t a t i o n a r y o b j e c t

2. Have pa r t o f the e rec t ionc r e w t i e i t o f f a t t h e b a s eof the pole and pull forwardwhi le the res t o f the c rewra i ses the po le f rom ther e a r

3. Se t up a p icke t ho ld fas tabou t 3 fee t fo rward o f thep o l e b a s e a n d t i e i t o f f a tthe base o f the po le

5-19. Gin po les o f 50 fee t o r l e s s canbe easi ly handled by hand.

1. True2. False

5-20. To e rec t a g in po le p roper ly ,you should have a crewconsisting of how many members?

1. 10 o r more2. 6 t o 93. 3 t o 5

5-21. The ho le fo r the base o f the g inpole should be how deep?

5-22. When raising the gin pole, whatcan you do to get the block inreach?

1. T ie a l ine to the hook o fthe movable block

2. O v e r h a u l t h e t a c k l e u n t i l i ti s l onge r than the po le , andsecure i t to an anchorage

3. Roth 1 and 2 above

5-23. What is meant by "drif t ing"?

1. Moving an object lef t orr i g h t

2. Moving the top of the pole15° without moving the base

3. Hoi s t ing o r p l ac ing a load

5-24. Besides l i f t ing heavy machineryor bu lky ob jec t s , shea r l egs canbe used for

1. un load ing t rucks and f l a t -ca rs

2. hoist ing over wells , mines h a f t s , and otherexcavations

3. support ing ends of acableway and highline

5-25. As pa r t o f the shea r s ' r igg ing ,the af ter guy should be s trongenough to lift how much of theload?

1. One fourth2. One half3. Three fourths

5-26. After wrapping the tops of thepo les fo r shea r l egs wi th sma l ls t u f f , you should t ighten andsecure the l a sh ing by

1. mousing2. shearing3. guying4. frapping

5-27. When preparing to erect a40- foo t shea r , how fa r apar tshould you dig the holes thatwi l l suppor t t he l egs?

1. 6 t o 12 inches2. 16 t o 18 inches3 . 20 t o 24 inches

1. 10 f e e t2. 16 f e e t3. 20 f e e t4 . 24 f e e t

29

5-28. How deep in the ground shouldholes be dug to keep shear legsfrom kicking out while inoperat ion?

1. 1 foot2 . 2 f e e t3. 1.5 f e e t4 . 6 inches

5-29. When a load i s app l i ed , i t i s agood p rac t i ce to l a sh the bu t tends o f the shea r s wi th cha in ,l i n e , or boards to keep themfrom spreading.

1. True2. False

5-30. Which of the fol lowing is anadvantage of using the t r ipodin a ho i s t ing ope ra t ion?

1. I t i s s t a b l e2. I t r equ i re s no guys o r

anchorage3. I t h a s a c a p a c i t y g r e a t e r

than that of shears madeof material of the sames i z e

4. Each of the above

Figure 5B

IN ANSWERING QUESTION 5-31, REFER TOFIGURE 5B.

5-31. When erect ing a 35-foot t r ipodwithout the aid of mechanizedequ ipmen t o r aux i l i a ry ho i s t s ,which arrangement shown infigure 5B should you use forl a sh ing the po les be fo ree rec t ion?

1 . A2 . B3 . C4 . D

5-32. The proper spread for the legsof a t r ipod is between one halfand two thirds of the length ofa l eg .

1. True2. False

Figure 5C

IN ANSWERING QUESTION 5-33, REFER TOFIGURE 5C.

5-33. As viewed from the top, ap roper ly e rec ted t r ipod lookslike which part of f igure SC?

1 . A2 . B3 . C4 . D

5-34. If a 20-foot- long boom is neededto provide the desired workingrad ius fo r a boom der r i ck , themast is approximately how manyfee t long?

1 . 2 02 . 3 03 . 4 04 . 6 0

30

5-35. When rigging a boom derrick,you should keep the bottom endof the boom from slippingdownward on the mast by securingi t w i t h

1. c l e a t s2. t h e t o p p i n g l i f t3. a s l i n g4. guys

5-36. What blocks should be at tachedat the same point on a boomder r ick?

1. Fair lead block and f ixedtack le b lock

2. Fixed tackle block and f ixedt o p p i n g l i f t b l o c k

3. Running topping l i f t blockand fa i r l ead b lock

4. Fixed tackle block andrunning topping l i f t b l o c k

Figure 5D

IN ANSWERING QUESTION 5-37, REFER TOFIGURE 5D.

5-37. The recommended heavy-loadposition of the boom on a boomder r i ck i s shown in f igure 5D a t

1 . A 1. Spur gear assembly2 . R 2. Chain lock assembly3 . C 3. Upper hook4 . D 4. Lower hook

5-38. The average person can pull witha force of nearly 100 pounds ona s i n g l e v e r t i c a l l i n e . Thesame person can pull on a s inglehor izon ta l l ine wi th a fo rce o fhow many pounds?

1 . 302 . 603 . 904 . 120

5-39. Which of the fol lowing is anadvantage in using a chain hoistover other devices?

1. Loads can remain stat ionarywi thou t r equ i r ing a t t en t ion

2. Loads can be handledcau t ious ly

3. Heights can be adjustedaccura te ly

4. Each of the above

IN ANSWERING QUESTIONS 5-40 THROUGH5-42, SELECT FROM COLUMN B THE HOISTBEST SUITED FOR THE OPERATION IN COLUMNA. RESPONSES IN COLUMN B MAY BE USEDONCE, MORE THAN ONCE, OR NOT AT ALL.

A. OPERATIONS B. HOISTS

5-40. L i f t ing o rd ina ry 1. D i f f e r -loads f r equen t ly e n t i a l

chain5-41. L i f t i n g l i g h t h o i s t

loads occas iona l ly2. Ratchet-

5-42. Pull ing heavy handleo b j e c t s h o r i - pu l lzon ta l ly ove r h o i s tshor t d i s t ances (come-

along)

3. Spurgearh o i s t

5-43. What part of a chain hoista s sembly i s i n t en t iona l lymanufactured to be the weakestpa r t?

31

5-44.

5-45.

5-46.

5-47.

5-48.

5-49.

The hooks or l inks of a chainho i s t t ha t show s igns o fspreading or excessive wearshould be replaced before theho i s t i s u sed aga in .

1. True2. False

Af te r e rec t ing a po le de r r i ckfo r a l i f t i ng job , where shou ldyou ins t a l l a hand-opera tedwinch?

1. At l eas t one po le l eng thbeh ind the de r r i ck

2. To the r igh t o f the po leusing a snatch blockand fa i r l ead

3. On ei ther s ide of the kneebraces

4. Near the foo t o f the de r r i ck

Suppose a power-driven winch iss e t u p s o t h a t t h e h o i s t i n g l i n eleaves the drum at an angleupward from the ground. Whichof the fo l lowing ac t ions shou ldyou t ake to avo id l i f t i ng thewinch clear of the ground?

1. Inc rease the s i ze o f thewinch

2. Move the load slowly3. Place a leading block in

the system to change thed i r e c t i o n o f p u l l

4. All of the above

As a ho i s t ing l i ne i s be ingwound on a drum, you must makesure tha t the f l ee t ang le doesNOT exceed a maximum of how manydegrees?

1 . 62 . 23 . 84 . 4

The l i f t ing capac i ty o f a c raneis dependent upon the

1. diameter of the winch2. s i z e o f t h e f l e e t a n g l e3. s i ze o f the l i f t i ng hook4. boom length and angle

Which of the fol lowing factorsi s u sed to des igna te the s i zeo f s m a l l s t u f f ?

1. Diameter2. Circumference3. Number of strands4. Number of threads per strand

5-50.

5-51.

5-52.

5-53

5-54

The l a rges t s i ze man i l a l ineo r d i n a r i l y c a r r i e d i n s t o c k i show many inches?

1 . 82 . 23 . 1 24 . 1 6

Which of the following formulascan be used to f ind theapproximate breaking strength(BS) of manila l ine?

1 . BS = c 2 x 900

2 . BS = C2 x 2400

3 . BS = D2 x 900

4 . BS = D2 x 2400

A wide margin between the safeworking load (SWL) and thebreak ing s t r eng th o f f ibe r l inei s des i rab le fo r wha t r eason?

1. To a l low fo r the s t r a inimposed only by jerkymovements

2 . To a l low fo r the s t r a inimposed only when the lineis bent over sheaves

3. To a l low fo r the s t r a inimposed by jerky movementsand when the l ine is bentover sheaves

4. To a l low for the d i f fe rencein the va r ious types o ff ibe r s used

What is the formula for f indingthe SWL of f iber l ine ( inpounds)?

1. SWL = D x 150

2. SWL = C x 150

3. SWL = D2 x 150

4. SWL = c2 x 150

What is the SWL of a f iber l inewhose circumference is 6 inches?

1. 1,800 pounds2. 2,400 pounds3. 3,800 pounds4. 5,400 pounds

32

5-55. The normal SWL for a new fiberl ine can be increased by whatpercentage?

1. 10%2. 20%3. 30%4. 40%

5-56. A used f iber l ine in goodcond i t ion has wha t sa fe tyf a c t o r f i g u r e d i n ?

1. Eight2. Six3. Three4. Four

IN ANSWERING QUESTIONS 5-57 THROUGH5-59, SELECT THE TYPE OF STEEL INCOLUMN B THAT IS BEST DESCRIBED BYTHE STATEMENT IN COLUMN A. NOT EVERYRESPONSE IN COLUMN B IS USED.

A. DESCRIPTIONS B. STEELSFigure SE

5-57. I t h a s a t e n s i l e 1.s trength of 200,000to 220,000 poundsper square inch( p s i ) . 2.

Improvedplows t e e l

5-58. I t i s s u i t a b l e f o rhau l ing , h o i s t i n g , 3 .and logging.

Plows t e e l

Mildplows t e e l

R a i l -roads t e e l

5-59. Most of the wirer o p e y o u w i l l u s e 4 .will be made oft h i s m a t e r i a l .

IN ANSWERING QUESTION 5-60, REFER TOFIGURE SE.

5-60. What i s the s i ze o f the wi rerope shown?

1. 1 inch, 6 x 192. 1 inch, 6 x 243. 3 1/8 inch, 6 x 374. 7/8 inch, 6 x 24

5-61. To measure the diameter of awire rope, you should use whatmethod?

1. Measure in one place nearthe middle

2. Measure in two places nearthe middle, 10 fee t pa r t .Average the results

3. Measure in three places,10 fee t apar t . Average ther e s u l t s

4 . Measure in three places, 5f e e t a p a r t . Average ther e s u l t s

33

5-62. What is the NAVFAC formula for 5-64.finding the SWL of wire rope

The SWL of old wire rope should

in tons?be reduced by what percentage?

1. 15%1. SWL = C x 4 2. 25%

3. 50%2. SWL = D x 4 4. 70%3. SWL = C2 x 4

4. SWL = D2 x 4

5-63. What is the SWL, in tons,of a 1 1/2-inch wire rope?

1 . 1 22 . 93 . 74 . 6

34

A s s i g n m e n t 6

Textbook Assignment: "Alarm Systems." Pages 7-1 through 7-28.

Learning Objective: Recognizethe p r inc ip les o f ope ra t ion o fa f i r e a la rm sys tem.

6-1. The primary purpose of abuilding alarm system is to

1. t e s t t he sp r ink le r sys t em2. c lose f i r e doors and shu t

down fans3. p r o t e c t l i f e , p r o p e r t y , a n d

con t inu i ty o f ope ra t ions4. provide a convenient method

f o r h a v i n g f i r e d r i l l s

6 -2 . The capabil i t ies of a noncodeda la rm sys tem a re such tha t i t

1. can iden t i fy the loca t ion o fthe device causing the alarm

2. may identify the source ofthe alarm by using anannunciator system

3. may cause be l l s to r ing ina d i s t i n c t i v e p a t t e r n

4. may cause audible s ignalsto sound in a march-timecadence

6-3 . A mult iplex alarm system isconsidered to be

1. coded2. noncoded3. old-fashioned4. an undesirable and

nonapproved in s t a l l a t ion

6-4 . The trend in operat ing voltagef o r s o l i d - s t a t e - c o n t r o lc i r c u i t r y i s t o w a r d

1. low-voltage dc2. high-voltage dc3. low-voltage ac4. high-voltage ac

IN ANSWERING QUESTIONS 6-5 AND 6-6,REFER TO TEXTBOOK FIGURE 7-2.

6 -5 . A building f ire alarm powersupply typically does NOTcontain which of the fol lowingdevices?

1. Relays2. I n i t i a t i n g d e v i c e s3. Terminals4. Transformers

6-6. Fuse F2 p ro tec t s aga ins t c i r cu i tdefects that would cause

1. ac power fai lure2. t r ans fo rmer shor t c i r cu i t3. ba t t e ry ove r load4. d iode b r idge f a i lu re

6-7 . A fire alarm system power supplydoes NOT perform which of thefol lowing functions?

1. Convert ac l ine voltageto low-voltage ac

2. Rec t i fy low-vo l t age ac toproduce low-voltage dc

3. Charge the system standbyb a t t e r y

4. Direct ly power the buildingfans

6-8. some smoke detectors requirepower supplies that can bedescribed in which of thefollowing ways?

1. More sophist icated than thepower supplies required byo t h e r p a r t s o f t h e f i r ealarm system

2. Less soph i s t i ca ted than thepower supplies required byo t h e r p a r t s o f t h e f i r ealarm system

3. Half-wave power supplies4. Saw-tooth wave power

supp l i e s

35

6 - 9 .

6-10.

6-11.

6-12.

The control uni t continuouslymoni to r s the c i r cu i t w i r ing toind ica te a / an

1. ac power fa i lu re2. dir ty smoke detector3. d e f e c t i v e f i r e a l a r m b e l l4. d e f e c t i v e s p r i n k l e r c o n t r o l

valve

The fea tu re in f i re a la rmsys tems tha t warns o f po ten t i a lo r ac tua l e l ec t r i ca l p rob lemsis known as

1. s ignal monitoring2. sp r ink le r supe rv i s ion3. e l e c t r i c a l s u p e r v i s i o n4. trouble monitoring

I f an open fau l t occurs in asuperv i sed c i r cu i t , how i s thesuperv i so ry cu r ren t typ ica l lya f fec ted?

1. I t d rops to ze ro2. I t i n c r e a s e s , b u t t h e f a u l t

causes a fa l se a la rm3. I t i n c r e a s e s , b u t t h e f a u l t

causes a t roub le s igna l4. I t r emains cons tan t , bu t

the f au l t causes a t roub les igna l

Learning Objective: Iden t i fythe function and operat ion ofauxil iary equipment used int h e i n s t a l l a t i o n o f f i r e a l a r mequipment.

For which of the fol lowingreasons a re bu i ld ing a la rmsystems connected to a remotes i g n a l r e c e i v i n g s t a t i o n ?

1. The occupants of thebuilding may not know howto respond to f i r e a l a rmsc o r r e c t l y

2. The occupants of thebuilding may be exci ted

3. The building may not beoccup ied a t t he t ime o fthe alarm

4. All of the above

IN ANSWERING QUESTION 6-13, REFER TOTEXTBOOK FIGURE 7-5.

6-13. Which of the followingdesc r ip t ive s t a t emen t s i scorrect concerning a remotes t a t i o n t y p e o f f i r e a l a r msystem?

6-14.

6-15.

6-16.

1. I t is normally a codedsystem

2. I t r e q u i r e s a p a i r o f w i r e sfor each alarm signal

3. I t p rov ides s igna l ing f romt r a n s m i t t e r s o f t h emunicipal type

4. I t does not use annunciat ion

Which of the fol lowing devicesi s u s e d t o c o n t r o l v e n t i l a t i o nfan opera t ion by us ing f i r ealarm system power supply?

1. Double-throw-over switch2. Remote transmitter3. Relay with mult iple contacts4. Knife switch

Which, i f any , o f the fo l lowingdesc r ip t ions app l i e s to thecontacts of most approvedi n i t i a t i n g d e v i c e s ?

1. Normally open contacts thatclose on alarm

2. Normally closed contactsthat open on alarm

3. Double se t s o f con tac t s ,one pa i r fo r t roub le andone pa i r fo r a l a rm

4. None of the above

Which, i f any , of the fol lowingac t ions shou ld you t ake to t e s tt h e e l e c t r i c a l f u n c t i o n o f amanual pull box?

1. Break the g lass r e ta ine r2. Remove the pull box and

s h o r t - c i r c u i t t h e t e r m i n a l son the back

3. Open the pull box with anappropr i a t e too l

4. None of the above

36

6-17. You should test al l manualdev ices on a ro ta t ion schedu les o t h a t a l l d e v i c e s a r e t e s t e dat what frequency?

1. Monthly2. Quar te r ly3. Semiannually4. Annually

6-18. Yost general-purpose automaticfire alarm systems are probablyi n i t i a t e d b y h e a t d e t e c t o r s .

6-19.

6-20.

6-21.

1. True2. False

A fixed-temperature detector maybe checked for actuation by

1. superv i so ry cu r ren t2. v i sua l i n spec t ion3. signal monitoring4. a u x i l i a r y c o n t a c t s

How should a rate-compensateddetector be checked forac tua t ion?

1. By aux i l i a ry con tac t s2. By visual inspect ion3. E l e c t r i c a l l y4. Manually

R a t e - o f - r i s e d e t e c t o r s u s u a l l yopera te on the p r inc ip le o f

1. d i f f e ren t i a l expans ion o fmetals with temperature

2. inc reas ing a i r p ressu re wi thinc reas ing t empera tu re

3. g e n e r a t i o n o f e l e c t r i c i t y a ta bond o f d i s s imi la r me ta l s

4. me l t ing o f a me ta l a l loy a thigh temperature

6-22. When should fixed-temperaturede tec to r s wi th fus ib le e l ementsbe hea t t e s t ed?

1. Only when an inspectionshows a possible defect

2. Quar te r ly3. Every year4. Every 5 years

6-23. H e a t d e t e c t o r s i n s t a l l e d i n ahazardous storage area may behea t t e s t ed by us ing a / an

1. explosionproof lamp2. infrared lamp3. ha i r d rye r4. ho t -a i r gun

6-24. Photoelectr ic smoke detectorsmay operate on which of thefo l lowing p r inc ip les?

1. The l ight is obscured bysmoke

2. T h e l i g h t i s r e f l e c t e dby smoke

3. The l igh t i s b locked o rpart ial ly blocked by smoke

4. All of the above

6-25. Ionizat ion smoke detectors candetect smoke by which of thefollowing methods?

1. The solid smoke part iclesin te r fe re wi th cur ren t f lowin a i r i on ized by a r ad io -a c t i v e s o u r c e

2. A rad ioac t ive source ion izesthe smoke, causing aninc rease in cur ren t

3. The ions in the smoke causean increased current betweentwo high-voltage plates

6-26. The major difference betweensmoke detectors of the spot andduc t t ypes i s t he

1. a r rangement o f e l ec t ron icp a r t s

2. method of powering thed e t e c t o r

3. method of moving smoke intot h e d e t e c t o r

6-27. A photoelectr ic smoke detectormay need

1. pe r iod ic c l ean ing o f thesmoke chamber with detergent

2. replacement of an LED at thej o b s i t e

3. r ecovery in b r igh t l i gh ta f t e r c l e a n i n g

4 . occasional removal of dustwi th low-pressure a i r

37

6-28. Each ionizat ion smoke detectorshould be smoke tested at whatfrequency?

1. Monthly2. Quar te r ly3. Semiannually4. Annually

6-29. Which of the followingstatements concerning theequipment manufacturer 'scustomer service departmenti s c o r r e c t ?

1. You should contact i t onlywhen a l l r epa i r a t t emptsf a i l

2. You shou ld ca l l i timmediately when theequipment fai ls

3. I t s pe r sonne l can t e l l youthe equipment serial numberi f you desc r ibe theequipment

4 . I ts personnel may be ablet o g i v e h e l p f u l r e p a i rsuggest ions and/orm a n u f a c t u r e r ' s l i t e r a t u r e

6-30. In f ra red f l ame de tec to rs candist inguish f lame from nonflamelight sources by using which,i f any , o f the fo l lowingdevices?

1. An IR source inside thed e t e c t o r

2. A f l i cke r -de lay- responsec i r c u i t

3. IR fi l ters on the windowo f t h e d e t e c t o r

4. None of the above

6-31. The u l t r av io le t f l ame de tec to ri s ex t remely f a s t and i s usedin which of the fol lowing areas?

1. Berthing2. Office spaces3. Aircraft maintenance4. Galleys

6-32. How is the flow of waterd e t e c t e d i n a f i r e a l a r msprinkler system?

1. By an increase in waterp ressure

2. By a drop in water pressure3. By the movement of a vane

ins ide the p ipe4. All of the above

6-33. Alarm-indicating devices aredivided into what two majorca tegor ies?

1. Visual and audible2. Smoke and heat3. Pho toe lec t r i c and ion iza t ion4. Pressure and vane

6-34. Annunciators may provide av i sua l ind ica t ion fo r whichof the fo l lowing a reas o fp ro tec t ion?

1. General areas or zones2. I n d i v i d u a l i n i t i a t i n g

devices3. Mul t ip l e in i t i a t ing dev ices4. All of the above

6-35. A t roub le cond i t ion i s u sua l lyannunciated by using a

1. f l a s h i n g l i g h t2. yel low or amber l ight3. r ed o r p ink l i gh t4. b lue o r g reen l igh t

6-36. An audible s ignal device in af ire alarm system should havea d i s t inc t ive sound so tha t

1. the bel l can be hearda t a g r e a t e r d i s t a n c e

2. t h i s b e l l c a n b e d i s -t inguished from otherb e l l s

3. a tone tha t causes l e s sdiscomfort to the eardrumscan be produced

Learning Objective: Discusst roub leshoo t ing , r epa i r s , andsa fe ty p recau t ions a s soc ia t edwith f ire alarm systems.

6-37. When numerous wires are removedfrom terminals at one location,i t i s good p rac t i ce to

1. try to remember which wirecame from each terminal

2. make up a poem to rememberthe o rder o f the wi re co lo r s

3. tag each wire with theterminal number it camefrom

4. remove a l l the wi res f i r s t ,then tag each wire with aterminal number

38

6-38. which of the fol lowing act ionsmay the replaceable modules ina modular control unit do?

1. Con t ro l aud ib le s igna ldev ices

2. Transfer power from acommercial source tostandby

3. Provide a reversing outputvo l t age fo r r emote s igna l ing

4 . All of the above

6-39. An open fault in a power circuitusua l ly causes which , i f any , o fthe fo l lowing re su l t s?

1. A blown fuse or t r ippedc i r c u i t b r e a k e r

2. An indicat ion of powerf a i l u r e

3. A low-voltage dc alarms i g n a l

4 . None of the above

6-40. Which of the fol lowing is arecommended procedure forl o c a t i n g a s h o r t - c i r c u i t f a u l ti n a n i n i t i a t i n g c i r c u i t ?

1. Assume al l connections areloose , and t ighten thembefore taking ohmmeterreadings

2. Disconnec t a l l t e rmina l sat each junct ion box andtake ohmmeter readings

3. D i v i d e t h e c i r c u i t i nha lves , taking ohmmeterread ings un t i l you loca tet h e f a u l t

4. Disconnec t the end-of - l ineresistor and work your wayback to the power sourceu n t i l y o u l o c a t e t h e f a u l t

6-41. A ground fault on the neutrals i d e o f a n i n d i c a t i n g c i r c u i twil l usual ly produce which ofthe fo l lowing re su l t s?

1. A blown fuse or t r ippedc i r c u i t b r e a k e r

2. In te rmi t t en t f a l se a la rms3. Automatic shutdown of

hea t ing and ven t i l a t ionfans

4. No symptoms

6-42. Wha t i s t he pu rpose o f the jo in ts e r v i c e i n t e r i o r i n t r u s i o ndetection system (JSIIDS)?

1. To de tec t an in t rus ion2. To prevent an at tempted

in t rus ion3. T o p r e v e n t t h e t h e f t o f

government property

6-43. What are the two general classesof JSIIDS components?

1. The con t ro l un i t and i t sdisplay equipment and themoni to r and i t s s enso rcomponents

2. The con t ro l un i t and themonitor

3. The con t ro l un i t and i t ssensor components and themonitor and displayequipment

4. The con t ro l un i t and i t ssensor and the d i sp layequipment

6-44. Where should the control unito f a JSI IDS be ins ta l l ed?

1. In a p ro tec ted a rea2. In an access area3. In the monitor cabinet4. In the same area as the

sensors

6-45. Wha t con t ro l un i t s enso r i sdesigned to detect movementwi th in the p ro tec ted a rea?

1. Pene t ra t ion2. Motion3. Point4. Duress

6-46. What is the normal No Alarmvol tage o f a JSI IDS c i rcu i tto the de tec to r s?

1. 20 v o l t s ac2. 20 v o l t s dc3. 24 v o l t s ac4. 24 v o l t s dc

6-47. The signal module in themonitoring cabinet displayst h e s t a t u s o f

1. the motion sensors2. the con t ro l un i t3. a l l s e n s o r s4 . the monitor cabinet

power supply

39

6-48.

6-49.

6-50.

6-51.

What monitor module is usedin the mon i to r ing cab ine t t odisplay mode changes in thepro tec ted a rea?

1. S ta tus2. Alarm3. Motion4. Pene t ra t ion

I t i s p e r m i s s i b l e t o i n s t a l lalarm conductors in the samecondu i t a s the bu i ld ing wi r ing .

1. True2. Fa l se

The wire of al l low-voltageconductors in the JSIIDS shouldbe of what size?

1 . No. 16 AWG2 . NO. 18 AWG3 . No. 20 AWG4 . No. 22 AWG

At what intervals should theJSIIDS be inspected?

1. Monthly2. Quar te r ly3. Semiannually4. Annually

6-52. For an alarm condit ion, youshould have what voltage readingon the PCB test points?

1. Zero voltage2. 18 vol ts dc3. 20 vol ts dc4. 20 vol ts ac

6-53. What is the main point toremember when replacing JSIIDScomponents?

1. Get the system back on l ineas soon as possible

2. Ensure tha t a l l connec t ionsa re p roper ly so lde red

3. Tag your conductors4. Replace the power supply

fuse a f t e r comple t ion o fr e p a i r s

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