ABCE AIR - americanradiohistory.com · ABCE AIR cosVITION/4,6 An accurate simplified, tech-nical review of the fundamen-tals of this latest branch of engineering, including servi-cing

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ABCE

AIRcosVITION/4,6

An accurate simplified, tech-nical review of the fundamen-tals of this latest branch ofengineering, including servi-cing data on present-day units

by Paul D. Harrigan

A GOLDEN OPPORTUNITYFOR ALERT MEN IN

THE NEXT GREAT INDUSTRY

AIR CONDITIONINGSERVICE MANUAL

THE idea of electricians, radio service men and othermechanically inclined men, servicing Air Condition-

ing and Refrigeration Units is self-evident and thethought has occurred to some untold thousands eversince air conditioning equipment has been installed inpublic auditoriums, theatres, studios, department stores,office buildings and manufacturing plants. The tre-mendously broad possibilities in this new industry arebound to give employment and success to men far-sightedenough to see its advancement and development. Wequote an excerpt from Mr. Hugo Gernsback's editorialwinch recently appeared in Everyday Science and Mech-anics magazine.

"I advise young and progressive men to gointo the air-conditioning business during thenext few years; because, this, without a doubt,is tile coming industry in this country. Thous-ands of small firms will spring up, undertakingto air-condition private houses, small businessoffices, factories, etc. We are not going totear down every building in the United Statesimmediately. It will be a gradual growth; yetsmall installation firms will air-condition smallhouses, and even single offices in buildings."

This is only partial proof of the certain success ofthis new field. Further assurance is, that engineeringschools have already added many important courses enair conditioning to their regular curriculum. Architectsand building contractors are giving considerable thoughtto installation of this equipment in structures whichare now being planned and built. The beginning ofthis business will probably be similar to the autoand radio industries, but in a few short years it willsurpass these two great fields.

Official Air Conditioning Service Manual352 Pages

Over 600

Illustrations

9x12 Inches

Flexible, Looseleaf

Leatherette Cover

$5.00 List

The OFFICIAL Alit CONDITIONING SERVICE MANUAL is edited byL. K. Wright, who is an expert and a leading authority on air conditioning andrefrigeration. He is a member of the American Society of Refrigerating En-gineers, American Society of Mechanical Engineers, National Association efPractical Refrigerating Engineers; also author of the OFFICIAL REFRIGERATIONEERVICE MANUAL and other volumes.

In this Air- Conditioning Service Manual nearly every page is illustrated;every modern installation and individual part carefully explained; diagrams fur-nished of all known equipment; special rare given to the servicing and installationend. The tools needed are illustrated and explained; there are plenty ofcharts and page after page of service data.

Remember there is a big opportunity in this new field and plenty of money_to be made in the servicing end. There are thousands of firms selling installationsand parts every day and this equipment must be cared for frequently. Eventuallyair conditioning systems will be as common as radios and refrigerators in homes,offices and industrial plants. Why not start now-increase your earnings with afull- or spare4ime service business.- Here are some of the chapter heids of the OFFICIAL AIR CONDITIONL.NGSERVICE MANUAL:

CONTENTS IN BRIEFHistory of Air Conditioning; Fundamental -Laws; Methodsof Refrigeration;

Ejector System of Refrigeration; Compression SyStem of Refrigeration; Refrig-erants; Lubricating Oils; Liquid Throttle Devices; Servicing Expansidn and FloatValves; Servicing Refrigerating Systems; Control Devices; Thermodynamics of AirConditioning; Weather in the United States; The Field of Air Conditioning;Insulating Materials; Heat Transmission Through Walls; Complete Air Condition-ing Systems; Estimating Requirements for the Home, Small Store, Restaurant;Layout of Duct Systems; Starting Up a System; Operating and Sery sing AirConditioning Systems; Air Filtration, Ventilating and Noise Eliminating Devices;Portable Electric Humidifiers and Room Coolers; Automatic Humidifiers; AirConditioning Units for Radiator System and \Varm Air Systems; Central Con-ditioning Units, etc.

[Send remittance of $5.00 in form of check or money order foryour copy of tho OFFICIAL AIR CONDITIONING SERVICEMANUAL. Register letter if it contains cash or currency.THE MANUAL IS SENT TO YOUR POSTAGE PREPAID.

GERNSBACK PUBLICATIONS, Inc. 99T HUDSON STREETNEW YORK, N. Y.

ABCof

AIRCONDITIONING

An! accurate simplified, technical review of the fundamentalsof this latest branch of engineering, including

servicing data on present-day units.

by Paul D. Harrigan

GERNSBACK PUBLICATIONS, Inc.Publishers

99 HUDSON STREET NEW YORK, N. Y.

ContentsPage

Chapter 1. The Future of Air Conditioning _____ 4

Chapter 2. Uses and Benefits of Air Condition-ing 6

Chapter 3. Elementary Refrigerating Systems 11Chapter 4. Types of Winter and Summer Air

Conditioning Installations and theirOperation 24

Chapter 5. Service and Control Applied to AirConditioning Systems 37

Chapter 6. Ventilation Data for Air Condition-ing 52

Chapter 7. Definitions Used in Air Conditioning 58Chapter. 8. Glossary of Air Conditioning Books 62

Printed in U.S.A.Copyright 1936 by G.P. Inc.

Preface

This book has been prepared especially for the useof those who are interested in the art of air condition-ing, and thus it contains the fundamental principleswhich underlie all the more practical and commonlyused systems. It has been written with the intent toshow the application of these principles for the produc-tion of comfort, and efficiency, where applied to com-mercial and industrial installations.

Further study of this subject is of course practicallyunlimited as there are many branches of air condition-ing, and many unknown factors to be worked upon. Atthe present time, however, there is a dearth of informa-tion sufficiently elementary to permit the reader toprepare himself for more intensive study. It is thepurpose of this little book to fill that need.

It is the writer's suggestion that you consult the ap-pendix of definitions frequently, as an effort has beenmade to include therein not merely technical definitionsof words, but sufficient explanatory matter to thorough-ly familiarize the reader with the term.

PAUL D. HARRIGAN.

CHAPTER 1

The Future of Air ConditioningALTHOUGH air conditioning is in

its first stage, its progress will berapid as both science and inventionare working on this new device forthe comfort and well being of human-ity.

Cooling by refrigeration is the ob-vious method, but we are alreadyusing methods of cooling by steam.Although the question of cost is aparamount obstacle, even that is be-ing solved by new inventions, as weshall learn later in this chapter. Manyof our early inventions were expen-sive, but have, due to the ingenuityof the inventors, come within thereach of the common man. With newinventions, and with large production,costs are always reduced, and thetime will certainly come when wewould no more think of renting ahome or office that is not air condi-tioned than we would at present con-sider a domicile without heating orplumbing facilities.

Air conditioning has already be-come practical for installation in thehome, and will keep an entire houseat an even temperature of 70 degrees,or the desired temperature, regardlessof whether the outside temperature iszero or one hundred in the shade. Theobvious convenience and comfort ofsuch an arrangement is perhaps oneof the things which caused the de-velopment of air conditioning to beregarded as the greatest inventionmarking progress in human comfortat the recent Chicago Century ofProgress Exposition.

Air conditioning is now awaitingsome business genius who will bringit within the reach of the commonman, selling and installing the ap-paratus at a price which will be with-in the reach of everyone.

As regards air conditioning in fac-tories, the biggest question is, "Willit pay for itself in my own business?"We shall learn from a later chapterof the various process work which is

4

greatly aided by air conditioning, andalso of the increased efficiency of theworkers under such conditions, butthe real problem remains with eachindividual prospective user. He mustfigure its installation cost, its possi-ble profits to him, and then determinethe advisability of its installation inhis plant. It is obviously essentialthat the installation plans be madecarefully, and the cost accountingdone with great care and delibera-tion.

However, when we speak of thecost of air conditioning, we do notmean only the installation expense.There is also the matter of runningexpenses. For large factories, wherethe drain upon electric power is great,and also for homes where this un-usual constant use of electricity willbe required, this cost presents a def-inite set -back.

At the present time there is beingprepared for the market a unit whichwill take the place of the electricgenerator to supply the home withsufficient electricity for all purposes,including lighting, cooking, refrigerat-ing, all household uses, and air con-ditioning. This unit will make airconditioning not only possible for theaverage homeowner, but actually apractical and economical system ofheating and cooling. This unit is al-so being made in sizes which will per-mit its use for office buildings, hotels,apartment houses, clubs, laundriesand all other places which requiresuch additional power.

It is not only an electric power unitthough, inasmuch as it will have themerits of supplying light, power andheat to all buildings where it is in-stalled.

The experimental unit now in oper-ation consists of a 26 HorsepowerDiesel -type engine, connected to agenerator. There is a constant volt-age delivery by the generator to allloads, without the use of a voltage

ABC OF AIR CONDITIONING 5

regulator, due to the construction ofthe unit. The engine is run withfurnace oil, of the type used in theregulation oil burner. It will burnany oil that a Diesel engine will burn,and many that a Diesel engine cannotsuccessfully burn.

This engine will be placed in thecellar, and is fully encased to insurequiet operation. It is specificallymounted to prevent vibration reachingthe house itself. Its operation is tobe controlled by a house thermostat,similar to those used today for auto-matically turning oil burners on andoff to meet the required need forheat.

It has been proven by laboratorytests that this unit will heat any or-dinary house, and burn half theamount of oil used by an oil burner.At the same time it will supply thehouse with electricity for cooking,household uses, refrigerating, and airconditioning apparatus.

Therefore, the operating cost of airconditioning homes which has been solarge a factor in retarding the pro-gress of this type of installation, willbe very greatly diminished. This costhas been largely due to the fact thata large amount of electric power wasrequired, and supplying this need raninto enormous figures.

Another field for the future of airconditioning on which experiments arealready being made is for use inbuses and private automobiles. Onemanufacturer has announced refrig-erating apparatus for buses, trucksand Diesel driven railway trains. Fuelfor this apparatus is supplied in tanksin liquid form under pressure. Itfirst creates refrigeration by expan-sion, which principle is thoroughly ex-plained in the chapter on ElementaryRefrigeration, and then passes to themotor. If this proves successful, itwill permit truck service for perish-able foods.

No one would contend that thereis not a difference between condi-tioned air and the exhilerating air of

a fine day in the country. This dif-ference is due to ions, which are inreality infinitesimally small electricalcharges.

As a crowd in a room increases,the ions decrease in direct proportionto the number of persons enteringthat room. Conversely, as personsleave the room, the ion count risesrapidly. The reason for this phe-nomenon has not yet been discovered.Influence of ions on the body is alsostill to be fully discovered.

However, it is not necessary forowners to consider these matters, andno one planning an air conditioninginstallation need delay it for fear ofobsolescence because of ionization.When these ions are more fully un-derstood, equipment for their controlwill be added as a supplement tomodern air conditioning installations.

We shall certainly see changes inthe future apparatus installed, eventhough the present apparatus is ratherwell standardized. Even though thesechanges may be of a radical nature,it will undoubtedly be some time be-fore they will be under way.

Therefore, we conclude that own-ers may safely install their air con-ditioning systems provided two para-mount facts are kept in mind: first,the design of the system should be solaid out as to require a minimum ofexpenditure with the maximum thatcan be consistently expected in thematter of good service; and second,an ample depreciation allowanceshould be permitted.

The facts remain that if we are tobe comfortable, healthy and modern,we must have air conditioning. Whenit is installed, ample allowance shouldbe made for future developments.

Air conditioning is not a fad. Itis a factor in modern living which ishere permanently. It will take itsplace with heating, and mechanicalrefrigeration as a sound investmentin comfort and health which will paylarge dividends over a long period ofyears.

CHAPTER 2

Uses and Benefits of Air Conditioning

THERE are several distinct func-tions of a complete air condition-

ing system, but these are usually di-vided into two classes, namely thoserequired for summer air conditioning,and those required for winter.

In the winter we must have distri-bution of air, cleaning of air, heatingand humidifying. Distribution of airincludes distributing air from the airconditioning apparatus to the variousrooms to be so conditioned, the speedof the air in the pipes or ducts whichcarry it to the various rooms, themovement of the air within eachsingle room and the equalization ofair motion in various rooms co pre-vent stagnant air in one room, anddrafts in another.

It is necessary to comfort andhealth that the air be clean. Thisrequires the removal of dust, soot,odors, pollen and bacteria, which isobtained by passing the air througha filter.

The function of heating the air isunderstood by everyone, as we havelong been familiar with systems ofheating during cold weather.

Humidifying simply means to addmoisture to the warm air in the build-ing. This is done for two purposes.First, to bring greater comfort andimproved health; and second to per-mit of comfort at lower tempera-tures than can be enjoyed when in-sufficient moisture is in the air. Air,like a sponge, can hold only so muchmoisture. When the air contains lessthan it can hold, the amount held isstated at its percentage, and what-ever this percentage happens to be iscalled the "Relative Humidity." Theability of the air to absorb moisture,depends upon its temperature. Warmair can absorb more moisture thancold air. Therefore, air which iswarmed before adding moisture has alowered relative humidity. For ex-ample, a given amount of outdoor

6

air at a temperature of zero, with atypical relative humidity of 40 percent will, when heated to 70 degrees,have a relative humidity of only 5 to6 per cent. This explains why in-door air is too dry in winter, andwhy it is necessary to add moistureto it.

In the Summer, for air condition-ing we must have the same elementsof air distribution and cleansing, towhich are added the functions ofcooling and dehumidifying.

Cooling is accomplished by puttingartificially chilled air into circulation.This has been chilled by passing itover coils cooled with cold water, ormechanical refrigeration, or by pass-ing the air over ice, or through acold water spray.

In the summer, since the uncom-fortable condition we wish to com-bat is the opposite to that which weare attacking in winter-namely heatinstead of cold-we must remove themoisture from the indoor air, by pass-ing the air through a cold waterspray, which takes moisture out ofthe air because it is cold. Or else itcan be passed over cold coils, uponwhich the moisture collects. It canalso be done chemically by passingthe air through a chemical solution,or bed of crystals, which absorbs themoisture.

In the Temperate Zone, men liveon a high plane of energy. Theyare vigorous which is largely due tothe wide changes in climate. In theTropics and the Orient no suchchanges occur, and excess energy isnot created. Human beings are notcapable of standing an unlimitedamount of this stimulation of coldand heat, and under too great stressshow signs of breaking. Suicides,mental breakdowns and nervous dis-orders are more frequent in rigorousclimates. Thus, the Southerner hasthe advantage of greater stability of

ABC OF AIR

mind and body, but a lower energy,which leaves him more subject to in-fections. Certain diseases show atendency to be recurrent in their re-lation to barometric changes. For in-stance, acute appendicitis and suicidesoccur mainly before storms, whilecolds and pneumonia come with afalling thermometer. Great changesin climate from day to day producemany cases of sinus trouble, arthritisand the like.

These facts as to climate are gen-erally recognized, athough not alwaysthought out. It is generally acknowl-edged that Florida and Californiaare, due to their climatic conditions,restful climates.

The human body tries to maintaina constant temperature, being aidedin winter by clothes and artificialheat. In the summer, we wear lessclothes in an effort to counteractthat natural heat.

As heat can only flow from awarmer to a cooler substance, bodyheat transfer is reduced in summer.It ceases entirely when air tempera-ture reaches body heat. Perspiration,however, produces cooling by evapora-tion, and by this means our bodiescontinue to try to maintain an eventemperature.

The average body gives off slightlymore than 2 lbs. of water per day at70 degrees. If the temperature risesto 84, this amount is nearly doubled.Meanwhile the body gives off about400 B.T.U. (which term will be foundexplained in the section on defini-tions) when clothes are on, and thebody it at rest. If active work isdone, this increases to nearly sixtimes this amount.

To persons sensitive to dust, vapor,pollens, or odors which may occasionhay fever, rose fever or sinus trou-ble, air conditioning comes as a bless-ing. While air conditioning cannotcure the trouble, as the sensitivitycontinues when exposed to outsideair, it nevertheless permits restfulperiods of sleep and relaxation, un-tormented by the affliction.

This problem of dust does not ap-ply only to the home, as there aremany industrial processes where dustis prevalent, and particularly danger-ous to employees. Various types of

CONDITIONING 7

filters now available, of water film,centrifugal collector, dry mat, elec-trical precipitator, or washer con-struction, which help solve this con-dition.

Doctors have complained for yearsof the heating system used in ourbuildings, claiming they were largelyresponsible for the colds we contract.A fluid exists in the mucous mem-brane of the nose and throat whichnormally adds moisture to the air, be-fore it reaches the lungs. When theair becomes overly dry, this mucousmembrane gradually dries out, due tooveruse. This causes irritation to themembranes, resulting in inflammationand swelling. In this area we have aharbor for germs, and the resultingcolds, coughs, grip, laryngitis and in-fluenza.

By means of air conditioning thiscan be eliminated. Although we knowthat the relative humidity of DeathValley is 23 per cent and that noplant life can exist there, we seldomstop to consider that the averageheated home or building has a rela-tive humidity of 15 to 20 per cent,which is dryer than any outdoor airrecorded anywhere in the world.

Since this superdry air drawsmoisture, it absorbs it from the hu-man bodies, leaving them with a low-ered resistance, and more subject todisease. Pans of water are placednear radiators in some instances inan attempt to combat this difficulty,but the moisture so obtained is veryinadequate.

In the summer, an air conditioningsystem permits us to keep windowsclosed, yet enjoy fresh air Thiscloses out dust. In the congesteddistrict of many large American cities,as much as 229 tons of dust rise persquare mile, per month. This is mixedwith impurities of all kinds. Thegerm -laden dust drifts into the win-dows of our homes, offices and fac-tories; each man is estimated to con-sume 11A lbs. of dust per year. Nat-urally the elimination of this factorin our lives, would bring about amore healthy condition.

These closed windows in addition toshutting out dust also shut out noise,which distracts our attention,, breaksinto the concentrated effort of men

8 ABC OF AIR CONDITIONING

CONSTANT TEMPERATURE75 F DRY BULB

AIR MOVEMENT 15 TO 25 F.P.M.FULLY CLOTHED

75ii

O

0

j 70H

65 101. 50Z, 100%

RELATIVE HUMIDITY

WHAT HAPPENS WHEN THEHUMIDITY RISES

of affairs, and acts as a nerve strainto practically everyone.

One of the interesting phases ofair conditioning is its relation to ef-ficiency. In an office there is alwaysan argument as to the lowering orraising of windows. This separatesthe staff into two warring factions,who, at least for the moment, refuseto cooperate in getting their workaccomplished, as well as leaving thesetwo groups preoccupied with their ar-gument.

Executives find it difficult to con-centrate in excessively hot rooms.Sometimes meetings are even ad-journed until a later date due to theweather, and these delays have uponoccasion run into money.

Any appointed job takes twice aslong when the weather is hot, and isusually done in a half-hearted man-ner.

The average person is comfortableat 71 degrees temperature in summerand 66 in winter. Those who areused to a very warm climate willperhaps find that they wish to raisethese figures as much as 5 degrees.But it is not the heat, but the hu-midity, which really makes us un-comfortable. For example, when the

thermometer is at 75, note how theeffective temperature rises as the hu-midity increases. Chart No. 1 showsthis clearly.

Travelers crossing a western desertwhere the humidity is slight, say theyfeel no more heat than in easterncities with a lower temperature.

Ther- Humid- Effectivemometer ity Temp.

Western Desert 90 20 77Eastern City 80 80 78

We used to think that the air in acrowded room became unpleasant dueto the inhalation of oxygen and theexhalation of carbon dioxide. Thishas been proven a falacy. Discom-fort is caused by humidity, odors andheat. These cause headache, nausea,and a drowsy sensation. These sensa-tions arise long before the oxygensupply becomes low, or the carbondioxide high.

This problem of keeping humanscomfortable was first recognized bythe theatres. Moving picture housesinstalled air conditioning systems, andfound that they no longer suffered afalling off of business in summer. Itis today actually more comfortable tosit in an air conditioned theatre thanon a sunny porch on a summer after-noon. Acceptance of a cooling sys-tem is now quite general in movingpicture houses. Some owners oftheatres have claimed that it has beena problem to solve what appeared tobe a real stumbling block in the ad-vance of the industry-namely thepublic's indifference to any pictureduring the summer months. Of 3,000class A movie theatres in the coun-try, about 300 were air conditionedin 1932. These were mostly locatedin downtown sections, as neighbor-hood houses could seldom afford therequired investment. Since these the-atres vary in the number of personsin attendance at each show, it is es-sential that their systems be so regu-lated as to vary to meet changingconditions. There is also the prob-lem of opening and closing doorswhich necessitate a control to keepthe temperatures at an even point.

Hotels have an unusual change re-corded as a result of the installationof air conditioning systems. Thepresent lowest priced rooms, which

A B C OF AIR CONDITIONING 9

are located facing back air shafts, orat noisy points of the building, canbe as comfortable and quiet as anyothers in the hostelry. This permitsa hotel so conditioned to raise theprice of the rooms which have pre-viously brought in small revenue. Theobvious advantage of a hotel offeringa cooled room in which to sleep on ahot night, over one where the roomsare sweltering, need not be com-mented upon.

Restaurants have also been amongthe pioneers in the installation of airconditioning systems, and have foundthat it has greatly increased theirsummer patronage. The cooler at-mosphere in summer has not onlydrawn persons in, but has stimulatedjaded appetites.

Department stores find their tradeincreased where they have installed acooling system. In the departmentselling women's apparel there hasbeen a great decrease in spoilageusually due to excessive perspirationwhile trying on garments. Depart-ment stores are particularly fortu-nate in making installations in thatthey usually have a power plant oftheir own, or are in a position tocarry their expense at the reducedrate to which large users of electriccurrent are entitled. Stores also profitby a winter air conditioning system,as it is a well known fact that per-sons who are comfortabe are easierto sell, more readily pleased, andmuch less trying upon the sales force.

Office buildings have found thatthey can rent their offices more read-ily, and for a higher sum, when airconditioned. A building in the Loopin Chicago was having difficulty inrenting space, due to noise. It is nowoccupied in its entirety, since it hasbeen air conditioned. In one of theeastern cities, a poorly located build-ing is always rented, even whenothers, more advantageously situated,are vacant. This is due again to thebadly located building having air con-ditioning as an inducement to itstenants.

Extreme dryness of air caused bywinter heating is injurious to books,records and paintings, as they becomebrittle. In summer, the excessivehumidity cases molding. Sulpher di-

oxide from smoke is bad fox paper.It is, therefore, obvious that cleaningand control of humidity are the pointsof greatest interest to the libraryand museum.

Certainly hospitals should be airconditioned, both for health and agreater comfort to the patients. Un-fortunately the cost is almost pro-hibitive. But it is within possibilityto air condition small sections of ahospital, such as delivery rooms, oper-ating rooms, etc., at not tao greatexpense.

Due to the fact that schools arehabitually closed during the summermonths, cooling systems are not re-quired. But the value and need forwinter air conditioning, with its clean,healthy air is generally recognized.

Confectionery makers have alwaysfound their products difficult to pro-duce and display in hot weather, dueto melting. This condition can beovercome by a cooling system.

Fruits and vegetables are often pre -cooled before loading into cars cir-culating washed and cooled air throughthe stacked crates. Artificial ripen-ing by using gas is beginning to beused. This apparatus also includesair conditioning.

Where fruits are canned, air con-ditioning is a great aid in preventingfruit spoilage, and also in preventingsweating of the cans.

The various processes used in themanufacture and preparation of foodof all kinds are greatly benefited bythe use of air conditioning in someform or another. A meat packingplant controls the humidity along withits usual refrigeration. Weight shrink-age is stopped, the meat holds itsmoisture, and the product's appear-ance is improved as there is noshrivelling.

If the humidity is too high in aflour mill, it causes clogging. Onthe other hand, if the humidity is toolow, the flour loses moisture andweight. The miller loses if the stand-ard moisture content does not re-main in his flour. Also high tem-peratures change the meshes inscreens and thus change their sift-ing capacity. About one ton of airis blown through each barrel of flourthat is ground. In order to prevent

10 A B C OF AIR CONDITIONING

spoiling, this air must be free fromdirt, and from wild spores whichmight later cause trouble in baking.

Definite temperature must be main-tained in order for dough mixing tobe right. In order to prevent dryingand the formation of a skin, or crust,or holes, the fermenting room mustbe kept at exactly the right tempera-ture. These conditions can be metwith air conditioning.

Breweries and distilleries avoid thecontamination of wild yeast with theaid of air conditioning. Formerlythe vapors were carried off by ad-mitting large quantities of outsideair, but this outside air may be in-fected. Now the air admitted intothe fermenting rooms is also cleanedto avoid contamination. This permitsoperation during the summer months.

Drug manufacturers condition airfor cleanliness and to avoid spoilageof hygroscopic substances.

Fur is extremely sensitive to changesin humidity. The hair cannot absorbdyes if the humidity is high, and ifthe humidity is low, the hair ac-quires a permament curl. Aside fromthe dying process, there is the stor-age of precious pelts to prevent fad-ing and spoilage by moths. In 1929over $200,000,000.00 worth of furswere stored in air conditioned rooms.

Vegetables and animal fibres suchas cotton, hemp, linen, wool, paperand hair take up moisture from theair, and alter their shape in so do-ing. Proper humidity in textile millsis, therefore, most important. Thispeculiar condition is caused by theability of the fibres to condensewater in the pores. When the humid-ity is too low, it causes dust and cre-ates bad static conditions, which seri-ously lower the output of the fac-tory. When too dry, the fibres breakin carding. Dry air causes frayingand uneven work in drawing andcombing. In spanning, the heat fromthe machines tends to dry the air,and gives poor quality yarn of un-even weight. In weaving, varyingtemperatures and humidity give vary-ing quality. Yet a certain amountof humidity is necessary to "set thetwist" in yarn, to prevent kinking.

Similarly, when paper is too drythe static causes it to stick together,and when it is too wet, it swells andloses shape. Air must be conditionedto a perfectly uniform degree at alltimes to insure perfect production.

Printers, too, eliminate color regi-stry and static troubles when the hu-midity is controlled.

In the tobacco industry, air con-ditioning is used to settle the intol-erable dust and keep the tobacco inproper condition. Cigar manufac-turers in Philadelphia recognize hu-midifying equipment as an essentialin the production of high qualitycigars. In normal summers, due totemperature and humidity conditionsin the plant, production fell off from4,000 cigars per machine per day to3,600 cigars per machine per day.This was a 10 per cent decrease inproduction. With complete air con-ditioning the machines continued toproduce at full capacity all summer.Also according to the American CigarCompany, the installation resulted ina general improvement in the healthof their employees.

Furniture makers reduce the dam-age of dust settling on high finisheswhile drying by means of air condi-tioning.

Electrical manufacturers need dryair in making certain apparatus, suchas condensers, and also for testingpurposes.

Air conditioning is equally essen-tial in automobile body plants wheredust may play havoc in spraying andfinishing chambers.

Railroads today constantly adver-tise air conditioning on their trains,and its use is generally known. Asrapidly as the new equipment can beinstalled, this particular applicationof air conditioning is spreading. Atthe end of 1934 nearly 3,000 carswere so equipped, and the work isstill going forward.

Passenger ships which make tropi-cal runs have in a few instancesbeen air conditioned for the comfortof their patrons.

Buses and private automobiles arebeing experimented with, but havenot as yet made much progress.

CHAPTER 3

Elementary Refrigerating Systems

THE ART of cooling bodies belowthe temperature of the atmosphere

is one that has been practiced for cen-turies. One of the early methodsconsisted of evaporation of the liquidto be cooled by putting it into porousvessels which were hung in an airstream. This procedure was followedin localities where the atmospherewas warm and dry.

Another early method consisted ofthe construction of caves and cellarsin the ground in which goods wereplaced to prevent their decaying, asit is possible to obtain a 50 or 60 de-gree temperature in these under-ground storage places. Low tempera-tures were also obtained by the useof freezing mixtures, such as waterand saltpetre, snow or ice and salt-petre, etc. In a like manner ice washarvested in the winter, stored in un-derground caves, and used to pre-serve food stuffs during the sum-mer months.

It can be seen that until quite re-cently only the above types of cool-ing were possible, and it was not un-til 1775 that the first means of pro-ducing refrigeration with machinerywere experimented with.

During the next 75 years, manyexperimental machines were con-structed. There were vacuum ma-chines, water machines, sulphuric acidmachines, and many others now ob-solete.

The real foundation for the de-velopment of the compression re-frigerating machine was made in1823, when it was discovered thatcertain fluids could be liquified afterbeing compressed to a high pressure.To Michael Faraday of England, weare indebted for this discovery. Thefirst real compression machine wasdeveloped in 1834, using ether. Al-though crude, it was the first ma-chine to produce ice, being developedby Jacob Perkin, an American in-ventor of Massachusetts. In the year

11

1850 refrigeration by means of acold air machine was invented byJohn Dorrie. Five years later, thefirst absorption machine was invented,by Ferdinand Carrie, of France.

In 1865 the first transparent icewas made from distilled water inNew York State. This same yearsteam coils were used to evaporateammonia. In the year 1873 to 1875the first successful ammonia compres-sion machine was introduced by C.E. G. Lindt of Germany, and DavidBoyle of the United States. Duringthe next 15 years, this system maderapid advances.

Up to this time, little or no usecould be found for the manufacturedice. But in 1890 the greatest short-age of natural ice ever experiencedoccurred in this country. It may besaid that from this year on, machine -made ice had an outstanding placein commerce. During the past 45years, many developments have beenworked out and improved upon so thattoday we have very efficient coolingand ice making machines.

Among the commercial, practicalrefrigerating systems, the followingare the most important and widelyused.

1. Natural or manufactured ice.2. Vapor compression systems,

using fluids that can be evaporatedand liquified such as Freon, sulphurdioxide, ammonia, etc.

3. Absorption, using liquid am-monia.

4. Steam ejector systems.Other less common methods of pro-

ducing refrigeration are:1. Cooling by evaporation of li-

quids.a. Water.b. Ether or the like.

2. Cooling by melting of solids.3. Cooling by freezing mixtures.

a. Ice and salt.b. Ice and calcium chloride.c. Snow and salt.

12 ABC

_-=1.41C.tl =11

OF AIR CONDITIONING

SMALL DROPSOF WATER

COOLING BY EVAPORATION

This methodFig. 1

relies on evaporationcooling.

d. Water and saltpetre.4. Cooling by sublimation.

a. Carbon dioxide ice.5. Indirect cooling by evaporation

of liquids.a. Vapor compression.b. Absorption.c. Adsorption.d. Vacuum.

Cooling by EvaporationAs this was one of the earliest

methods, it would be well to pointout that even today it is being usedby tourists crossing Death Valley, andis accomplished by immersing a porousjar in water and then filling this jarwith water, or whatever material it isdesired to cool, and placing the filledjar in the air current such as thefront of an automobile. Thus theevaporation of water contained in theporous walls of the jar is sufficient tolower the temperature of the materialinside the jar as much as thirty de-grees.

The water held in the pores of thejar was in a liquid form, but whenexposed to the air stream, it evapo-rated. This evaporation requiredheat, and the heat came from thematerial stored in the jar. This isillustrated in Fig. 1.

The actual amount of cooling de-pends solely upon the amount ofmoisture already in the air, as weknow that when the surrounding airis already saturated, there will be noevaporation of water from the earthenjar, and no cooling effect can be pro-duced thereby. However, when theair contains only a portion of themoisture which it is capable of car -

for

rying (depending upon the tempera-ture) it is evident that moisture canbe added to it from an outside body,such as the porous jar.

A liquid such as alcohol or ether ifplaced on the body in a liquid form,evaporates, and in doing so producesa cool sensation. This is caused byevaporation of the liquid and absorb-tion of heat from the body to do so.

Cooling by Melting of SolidsIn order to change the form of a

material from a solid to a liquid, adefinite amount of heat must be addedto the solid. This is dependent uponthe kind of substance used and itstemperature and pressure. The heatadded to make this change from solidto liquid is called "latent heat," asno change of temperature takes placein the solid.

For instance, a pound of ice at 32degrees requires 144 B.T.U. (BritishThermal Units) to change it to waterat the same temperature. Thus, thispound of ice in changing to a liquidform will absorb the 144 B.T.U. fromthe air, or its surrounding object,thereby producing a cooling effect(see Fig. 2). Obviously cooling be-low 32 degrees is not possible by thismethod.

Cooling by Freezing MixturesLower temperatures may be ob-

tained by the use of freezing mix-tures, such as ice and salt. The ac-tion of the material is such that thetemperature of the mixture will be afew degrees below 32 degrees f. The

( ICE 32°n-asu.

;-1 INSULATION\

II ti AIRJI I IA -4- 40*TO 45°

ill 11#

ct OUTSIDE;Atii AIR AT'r 70*TO 80*

COOLING BY MELTING ICE

Fig. 2The common method of cooling by melt-

ing ice.


actual amount of cooling depends up-on the proportion of salt and ice inthe mixture. When the two solidsare mixed together, a certain amountof heat is absorbed because both ma-terials change from a solid to liquiddue to their being mixed. A brinesolution is thereby formed. The heatrequired to dissolve the salt and iceis taken from the mixture itself,rather than surrounding temperature,so it is possible to cool below thetemperature of pure, solid ice. Ifthe mixture contained 15 per centsalt, the resulting temperature wouldbe 11 degrees f.

If two parts of snow are mixed withthree parts of calcium chloride crys-tals, the resulting temperature will beapproximately 50 degrees below zero.Or if acetone and solid carbon dioxideare mixed, it is possible to obtain atemperature as low as 70 degrees be-low zero. This principle is illustratedin Fig. 3.

Cooling by SublimationNormally, any solid changing to a

vapor or gas must go through a li-quid state. However, carbon dioxidechanges from a solid to a vapor or gaswithout going through a liquid state.It has a normal temperature of 110degrees below zero and the advant-age of not wetting containers or ma-terials that are placed in contact withit. Carbon dioxide is commonly knownas dry ice, and when changing froma solid to a gas or vapor absorbslatent heat and produces a coolingeffect.

ICE CREAM WOODENCAN ) /CONTAINER

ICE & SALTMIXTURE

TEMPERATUREOF MIXTURE 11°

FREEZING TEMP.OF CREAM 26°

COOLING BY FREEZING MIXTURE

Fig 3A mixture of snow and calcium chloride

produces freezing.

LIQUID AMMONIA BOILING

ELEMENTARY EVAPORATING

Fig. 4The vapor absorbs heat producing "cold."

Indirect Cooling by Evaporationof Liquids

All mechanical systems utilize someliquid refrigerant, evaporating at alow temperature. During evaporation,the liquid is changed into a vapor, ab-sorbing heat. An elementary systemusing a volatile (easily evaporated)liquid is shown in Fig. 4.

The refrigerant may be any of thecommonly used ones, such as am-monia. If the ammonia in the con-tainer is open to the atmosphere, thetemperature of the liquid will beminus 28 degrees, or 28 degrees be-low zero. At this condition, the con-tainer as shown could be cooled tozero degrees, depending upon the con-struction of the walls of the con-tainer and the outside temperature.Although a constant temperature ofminus 28 will exist during the pro-cess of evaporation in the liquid, thetemperature of the container musttake other conditions into considera-tion.

In the case of ammonia liquid atminus 28 degrees, a definite amountof heat is required to change it froma liquid to a gas. Thus, the ammoniaabsorbs its latent heat at a low tem-perature and produces a cooling ef-fect. The heat coming through thecompartment walls, or materials storedin the compartment, changes the re-frigerant into a gas, which escapesthrough the atmosphere as shown inFig. 4.

Under certain conditions, it is de-sirable to use brine, illustrated in Fig.5.


AMMONIAVAPOR

/ ATMOSPHERE 80°

30°F

0°F

.INSULATION

BRINE LIQUID AMMONIABOILING AT -28° F

ELEMENTARY BRINE SYSTEM

Fig. 5Refrigerating with a brine solution.To maintain the insulated com-

partment at 30 degrees, a vessel con-taining liquid ammonia, open to theatmosphere, is inserted into a quan-tity of brine, which would be cooledto approximately zero degrees. Theheat from the 80 degree atmosphereis transmitted through the walls intothe 30 degree section. This in turnis transmitted by the air to the brine,which in turn imparts it to the am-monia, which is at minus 28 degrees,causing the ammonia to evaporate.

For use in making ice, a system asshown in Fig. 6 is employed.

In this instance a vessel containingliquid ammonia at minus 28 degreesis inserted in a brine solution, whichwill be cooled to approximately 12 de-grees. At this low temperature thewater in cans surrounded by brine willfreeze to a solid. As illustrated, theammonia vapor is permitted to escapeafter it has absorbed its latent heatfrom the brine, which in turn ab-sorbs heat from the water.

Vapor compression is a system thatuses a motor -driven compressor, towithdraw the low temperature vapor,as for example from the ammoniacontainer in Fig. 6 which is the evap-orator. This gas is then compressedto a high pressure and temperature,so that it may be cooled and con-densed back to a liquid by water orair. Thus the complete cycle is di-vided into four principle parts:

1. Evaporation of liquid at lowtemperature.

2. Compression of gases or va-pors.

3. Condensing of vapor at rela-tively high temperatures.

4. Controlling liquid supply.The gases may be compressed by a

reciprocating, centrifugal or rotarycompressor. Figure 7 illustrates thereciprocating compressor which is theone most commonly used.

To facilitate the return of the lu-bricating oil, the evaporator should notbe installed more than fifteen feet be-low the compressor, but may be usedat any height above the compressor.

In the illustrated system, ammoniais used as the refrigerating medium.With a pressure of 19 lbs. per sq. in.in the evaporator, the temperature ofthe ammonia will be 5 degrees. So itcan be seen that the heat flows fromthe refrigerator, which is at 30 de-grees, into the ammonia, causing itto evaporate. This ammonia vapor isthen drawn from the evaporator intothe compressor, and a complete cycleis as follows:

The compressor raises the tempera-ture and pressure of the ammoniavapor to a pressure and temperatureat which it can be condensed. Thuswith a water supply of 70 degrees,and the water passing through thecondenser, the water temperature in-creases to 80 degrees.

It is then possible to condense theammonia vapor which will have a re-sulting temperature of 86 degrees,and a corresponding pressure of 155lbs. Therefore, the compressor with-draws the ammonia vapor from theevaporator as quickly as it is formed

AMMONIAVAPOR

INSULATION

WATER

ICE

LIQUIDAMMONIA

ELEMENTARY ICE FREEZINGSYSTEM

Fig. 6An elementary method for making ice.


OUTSIDE AIR 8e

EVAPORATOR5°-19 LBS. li

11

REF RIG. AT30°F

IIIIIII

11

sr I[ 1

I' 1ff---r-:-- ....---,:-._

REFRIGERATOR

.5'119 LBS.

WATER SUPPLY AT 700

00/0.0 210-155 LBS.

WATERPAN

'11111

EXPANSIONVALVE

?86°

0 0

CONDENSER

0 COMPRESSORrjr

"11,' ,111

10 WATER OVERFLOWAT 80°

155 LBS.

COMPRESSION REFRIGERATING SYSTEM

t RECEIVER860-155 LBS

Fig. 7. The fundamentals of refrigerating by compression.

at a pressure of 19 lbs., and com-presses this vapor to a pressure of155 lbs.

It is evident that the pressure andtemperature in the evaporator will de-pend upon the temperature desired inthe refrigerated space. The tempera-ture and pressure in the condenserwill depend upon the temperature ofthe water supply. When the evapo-rating pressure is 19 lbs. per sq. in.,the ammonia comes to the compressorin a dry state. The temperatureafter compression will approximate210 degrees. Therefore, the con-denser cools the hot ammonia gasfrom 210 degrees to the condensingtemperature of 86 degrees, and theheat is absorbed from the ammonia,which is at a high temperature, bythe water which is at a lower tem-perature, until all the refrigerant iscondensed to a liquid state.

Then the liquid ammonia at 86 de-grees is piped from the condenser toa liquid receiver or storage tank. Thistank is connected to the expansionvalve, and the condition of the am-monia at the valve will be a liquid at86 degrees, and 155 lbs. pressure. Sothe refrigerant expanding from this

high pressure to a low pressure of19 lbs. will have a correspondinglylow temperature, and can absorb heatto re -evaporate it so that it may beused over and over again.

This cycle is characteristic of allcompression systems of refrigeration.They differ only insofar as the actualrefrigerant that may be used, whichof course would change the pressuresand temperatures correponding to theparticular refrigerant, but in no wayeffect the principle of operation.

Absorption refrigerating machinesare used extensively where extremelow temperatures are necessary, andwhere an ample supply of steam isavailable. As illustrated in Fig. 8,the essential parts of the system arethe condenser, the expansion valve,evaporator and receiver.

These are exactly the same as usedin a compression system. The realdifference between the two systemslies in the method of abstracting thegas from the evaporator. The vaporcoming from the evaporator is dis-solved in a weak solution of ammoniaand water. This part of the systemis called the absorber, as you willnote in the illustration. It consists


of a shell for retaining the solution ofammonia and water, a device for in-troducing the vapor from the evapo-rator into the ammonia solution, awater coil for removing heat fromthe absorber, and a strong and weaksolution.

The ammonia vapor from the evap-orator is first condensed and then dis-solved in a weak aqua -ammonia solu-tion in the absorber. This change ofstate gives up heat which is absorbedby water flowing through the coolingcoil, and maintains the absorber at aconstant temperature, which will al-ways be a few degrees above the aver-age temperature of the water in thecoil. The percentage of ammoniawhich this solution will absorb de-pends upon the evaporating tempera-ture and temperature that is main-tained in the absorber. When the so-lution has absorbed all the ammoniait can hold at the pressure and tem-perature, it is then led through apump which discharges the strongsolution into the generator. The pres-sure of the absorber correspondsclosely to the pressure of the evapo-rator. The pressure of the generatorcorresponds closely to the pressure ofthe condenser. The pump is usedsimply to remove the strong solutionfrom the absorber, and discharge itto the generator. So by applying

steam to the heating coils of the gen-erator, it is possible to bring the solu-tion to a boiling point and distil theammonia.

The temperature of the boilingsolution in the generator will be con-trolled by the condenser pressure, andthe percentage of the ammonia in theweak solution, as it leaves the gen-erator, passes through the condenser,and back to the absorber.

The temperature of the steam inthe steam coil will always be a fewdegrees higher than the boiling solu-tion in the generator. Thus heat willflow from the steam into the solutioncausing it to boil off the ammoniavapor. The ammonia vapor thenpasses to the condenser where it iscondensed to a liquid, and returns tothe expansion valve.

Adsorption systems are character-ized by the use of Silica Gel, whichoperates on an intermittent cycle sim-ilar to the absorption system. Silicagel is a hard glassy material of ex-tremely porous character, and it is be-lieved that one cubic inch of this ma-terial has the equivalent of a totalsurface area of 50,000 sq. ft. Thepresence of these minute pores obvi-ously give silica gel a high moistureabsorption characteristic. After ab-sorbing moisture, the silica gel can beheated, and the moisture driven out,

EVAPORATOR--- COILS

111991

IL

II

( REFRIGERATOR

REGULATING VALVEON WEAK AQUA

CONNECTION

EXPANSIONVALVE

WATER_2,1\

CONDENSER -N 1111111hm

(GENERATOR

IL- --

STRONG AQUA

STEAMCOIL

AQUAPUMP

t

(37-L, , _LI

WATER COIL

ABSORBER

RECEIVER

ABSORPTION REFRIGERATING SYSTEM

Fig. 9. The principles of refrigeration by absorption.

A B C OF AIR CONDITIONING

making it possible to use it over andover indefinitely. No power is re-quired in this system as the heat isapplied directly to the silica gel, andthe common commercial silica gel willabsorb approximately 50 per cent ofits weight of water from saturatedair. Temperatures of 250 degrees orhigher are required to drive off thismoisture. This is technically knownas reactivating. The operation of thissystem is illustrated in Fig. 9.

The vacuum, or steam ejector sys-tem is based on the principle thatwater will boil or vaporize, depend-ing upon the extent of vacuum cre-ated above it. Thus water at ordin-ary atmospheric pressure boils at 212degrees, f. At high altitudes wherethe atmospheric pressure is reduced,it will boil at 160 degrees, showingthat by reducing the pressure, it ispossible to boil or evaporate water atlower temperatures.

To obtain a vaporization, or boil-ing, in the vicinity of 50 degrees, f.,it is necessary to provide a constantvacuum of about .36 -in. of mercury.This is equivalent to 19 lbs. absolutepressure. The above is a reversecycle of storing heat in liquids, as inthe case of steam generation of 100pounds absolute pressure, the tem-perature will be 327.8 degrees. The

17

DRY GASOUT ,-COOLER

ADSORPTION

S.G.

4 ACTIVATION

-4-

WET GAS IN HEATER

2 BEDS SINGLE STAGEADSORPTION

Fig. 9S. G. in this sketch refers to silica gel.

water and steam being at the sametemperature. If a steam valve wereopened to the atmosphere, the heatstored in the water would continue toflash into steam until the entire con-tents were reduced to 212 degrees,and the water would stop boiling.However, if a vacuum is created onthe boiler, evaporation will continuedepending upon the extent of thevacuum produced.

This process of cooling is illustratedin Fig. 10, in which A is a nozzle

SHEET METAL HOUSING DUCT SYSTEM

COOLING -50..._ AIR

55°F

3

HEATABSORBER

70° FDRY FILTER

CONDENSER

71(c

f=t0

LIVE t i' f tSTEAM

CHILLEDWATERTANK

5OF

6

FLASHCHAMBER h

TI

II -

0,3

000

0°0 0

ROOF COOLING TOWER/

rIJITI( 111100

sill, 0!\0

,

(0)J

CENTRIFUGAL PUMPS

STEAM CONDENSATION

Fig. 10. The steam ejector system in which a vacuum is created to increase vaporization


containing a series of jets, from whichlive steam is discharged at a highvelocity with pressures ranging from75 to 300 lbs. per square inch.

As the steam rushes through thecontracted tube B, a vacuum is cre-ated at the opening C, which opensdirectly into the chamber F. Thewater supply line D, from the coolingcoil, enters the flash chamber and asthe water is sprayed into the lowpressure area, some of it naturallyevaporates, thus absorbing heat fromthe particles or drops that do notevaporate. The heated vapor rises in-to opening C and flows through theventuri tube B to the condenser noz-zle E. The object in removing the heatof evaporation is achieved by the lowvacuum, and the remainder of thewater drops through the flash cham-ber and then to the storage tank. Thesteam and water vapor expand as

they enter nozzle E, and the steam ex-pands further as it encircles the tubeand condenser G. The reason for itexpanding is due to the pressure beinglower. Water is circulated throughthese tubes, and the steam flowsaround them, which is condensed backto water, and is pumped to the highpressure boiler by pipes H and H-1,to be regenerated into steam. An-other pump, J, is connected to thecondenser tubes which circulate thecondenser water to the cooling toweron the roof, where this water issprayed and caused to evaporate inpart. Thus we have a similar partialevaporation to that occurring in theflash chamber, but, of course, thewater temperature will not be as lowbecause it is exposed to the at-mosphere.

From the above description, it isevident that cooling is simply the re -

CHART 2

FREON (CCL2F2)Gauge Density Lbs./Cu. Ft. Total Heat From -40°

Temp. Press.Liquid Vapor BTU./Lbs. BTU./Lbs."F. Lbs./Sq. In.

32 30.1 87.02 1.10 15.21 66.6236 33.4 86.55 1.18 16.10 66.1740 37.0 86.10 1.26 17.00 65.71

44 40.7 85.66 1.35 17.91 65.2448 44.7 85.19 1.44 18.82 64.7452 48.8 84.71 1.53 19.72 64.27

86 93.2 80.63 2.57 27.72 59.65100 116.9 78.80 3.14 31.16 57.46120 157.1 76.02 4.17 36.16 53.99

CHART 3

METHYL CHLORIDE (CH3CL)Gauge Density Lbs./Cu. Ft. Total Heat From -40°

Temp. Press.Liquid Vapor BTU./Lbs. BTU./Lbs.°F. Lbs./Sq. In.

32 21.9 59.91 .372 23.4 174.4

36 24.8 59.65 .401 24.9 173.4

40 27.9 59.49 .433 26.5 172.4

44 31.4 59.13 .467 27.9 171.448 34.9 58.88 .503 29.5 170.4

52 38.8 58.62 .538 31.0 169.4

86 80.8 56.30 .962 43.9 160.2

100 104.1 55.33 1.17 49.4 156.3120 144.9 53.94 1.43 57.5 150.6


moval of heat from one place andstorage or dissipation in another. Themost commonly known refrigerantsevaporate or boil at the various tem-peratures and pressures shown in thefollowing tables. These tables alsocontain the B.T.U. absorbed by theevaporation of 1 lb. of each sub-stance, at various pressures.

Transferring of RefrigerationUp to this point, we have discussed

the methods of securing refrigeration.We now turn to ways of using the re-frigeration so acquired, and Fig. 11shows a common bunker room, evapo-rator coils for cooling the air, aircirculating fans and connections, be-tween the evaporator surface and re-frigerator.

The evaporator coil may be con-nected to any pipe refrigerating ma-chine that produces a refrigerant at atemperature below the temperatureat which the air circulates. Thus theair is cooled in the bunker room andthen forced to the space to be cooled,where it absorbs heat, and the tem-perature of the refrigerator or coolercan be automatically controlled byregulating the amount of air which iscirculated through it. As can be seen,no drain connection is provided forin the bunker room because we arenot attempting to abstract any mois-ture from the air. Where indirectcooling by brine is desired, either be-cause of local fire regulations or thepossibility of ammonia leak effectingfood stuffs. Figure 12 shows a typi-

CHART 4

Temperature Table

SATURATED AMMONIA

PressureGauge Lbs.Per Square

Inch

Tempera-toreOF

Volume ofVapor

Cubic Feetper Lb.

Latent HeatB. T. U.per Lb.

0.0 -28° 18.00 589.31.3 -25° 16.66 587.23.6 -20° 14.68 583.66.2 -15° 12.97 580.09.0 -100 11.50 576.4

12.2 -5° 10.23 572.615.7 0° 9.116 568.919.6 5° 8.150 565.023.8 10° 7.304 561.128.4 15° 6.562 557.133.5 20" 5.910 553.139.0 25' 5.334 548.945.0 30° 4.825 544.851.6 35° 4.373 540.558.6 40° 3.971 536.266.3 45° 3.614 531.874.5 50" 3.294 527.383.4 55° 3.008 522.892.9 60° 2.751 518.1

103.1 65° 2.520 513.4114.1 70° 2.312 508.6125.8 75° 2.125 503.7138.3 80° 1.955 498.7151.7 85' 1.801 493.6165.9 90° 1.661 488.5181.1 95° 1.534 483.2197.2 100° 1.419 477.8214.2 105° 1.313 472.3232.3 110° 1.217 466.7251.5 115° 1.128 460.9

t . tittitItttttltCIRCULATEDIII AIR 11111

1ttit111iiIiin'1111 i1 1i

Nttt 111t 11 iit 1, 1

fri

REFRIGERATOR

AIR FAN )

F

REFRIGERANTOUTLET

CIRCULATEDAIR

C' EVAPORATOR

FORCED AIR REFRIGERATING SYSTEM

REFRIGERANTINLET

Fig. 11. The "forced air" method of cooling a room or space.

20 A B C OF All? CONDITIONING

i I I

(41V 111

REFRIGERATOR

BRINECOILS

BRINEPUMP

4- 1

REFRIGERANTOUTLET

-11---T

by -

BRINE COOLERS

BRINE REFRIGERATOR

REFRIGER ANTINLET

SYSTEM

Fig. 12. The "brine cooler

cal installation, which consists of abrine cooler for cooling the brine, thebrine coils in the space to be cooled,together with suitable brine connec-tions.

Brine cooler coils may be connectedto any refrigerating machine thatproduces a low evaporator tempera-ture in the coils. Thus it can beseen that heat is transferred firstfrom the air to the brine in the re-frigerator or cooler, then from thebrine to the evaporating refrigerantin the brine cooler. It is necessaryto maintain two different tempera-tures; first, between the evaporatingrefrigerant and the brine; and sec-ond, between the brine and the room.So it will be necessary to have thebrine below the room temperatureand the refrigerant below the brinetemperature. Although at first thissystem appears to be large, it offersthe advantage of flexible control ofoperation and safety.

The brine spray system is one inwhich the brine is sprayed directly inthe air being cooled, and is shown inFig. 13. The system consists of abrine spray header, provided withseveral spray nozzles, a brine proofbunker, a brine pump, and brinecooler. Discharging from the spraynozzle, the brine is in the form offine drops, and before they fall to thebunker floor, they are heated a fewdegrees, the heat coming from theair in the room, or materials storedtherein. The air, being cooled, tendsto fall to the bottom of the cooler,

system of refrigeration.

and the warm air rises to the top andcomes into immediate contact withthe brine spray, so that a natural aircirculation is set up in the room. Inthis system, the evaporating refriger-ant is a few degrees below the tem-perature of the brine, and the brineis a few degrees below the tempera-ture of the cooler. The brine pumpmust have sufficient capacity to cir-culate the required amount of brineand to discharge it at the nozzles at apressure of not less than 10 lbs. persq. in., in order to break up the li-quid brine and expose more of it todirect contact with the air. The finerthe spray of brine, the more area ofbrine is exposed to the air. This sys-tem has its greatest application inmeat coolers and packing houses.

Part of a Refrigerating SystemCentrifugal compressors find their

most important fields of applicationin systems which operate at low orsub -atmospheric pressure and handlelarge volumes of gas. They are welladapted to such systems because theycan run at high speeds and have novalve to cause trouble. A small unitis capable of large refrigerating ca-pacity. The cost of the unit is lowconsidering the size of the system,and the control is simple. These sys-tems operate best under constant loadconditions and therefore are welladapted to large installations like the-atres, office buildings, etc., but arenot adapted for use in small systemsor under fluctuating loads.


Rotary compressors are used quiteextensively because of their simplicityof design. They are used in caseswhere the volume of gas handled is:lot too large. If the volume of gasto be handled is large, the compressoralso must be large, or run at exces-sively high speed, which brings us tothe trouble usually encountered withthe use of rotary compressors; this isthat the present-day valve design willnot stand the high speed required.

Gear pumps are not used to anyextent because of the high power con-sumption and low efficiency underwhich they operate.

The reciprocating compressor ismore widely used today than any ofthe others especially in the field ofair conditioning, and icebox refrigera-tion. As compared with the othercompressors, the reciprocating unithas many advantages, such as the factthat it is easy to service. It operatesat low speeds and has a range ofsizes to fit any type of installation.Also it is quiet in operation, the prin-ciple of operating is easily under-stood, and it is dependable in per-formance, having only a few movingparts. The over-all running efficien-cy is high.

The purpose of the condenser is todischarge to the outdoors the heatwhich is absorbed by the refrigerantin the evaporator, and such heat as isgenerated in the compressor. The de-sign of the condenser has a consider-

f/SUCTION LINEBRINE EXPANSION

COOLER) If VALVEBRINE

cPUMP

able effect on the performance of thesystem since raising or lowering thecondenser temperature has a decidedeffect upon the efficiency of the sys-tem. The two general types are airand water cooled condensers. Sinceair is not nearly as effective for ab-sorbing heat as water, air condensersare larger than the water cooled type.The air condenser is usually of thefin -tube type, the refrigerant circu-lating inside the tubes and the airfor cooling being blown over the out-side surface, which condenses the re-frigerant.

Water-cooled condensers are moreefficient than air cooled and are gen-erally constructed of one of the threefollowing types. One is the counterflow, double tubed, the refrigerantbeing circulated through a tube whichhas a smaller tube in it that carriesthe water to cool the refrigerant. Thewater and the refrigerant flow in op-posite directions and one tube is in-side the other. The shell and tubetype consists of a metal shell thathas water coils built into it. Thewater flowing through the coils con-denses the refrigerant, which is in-side the shell and around the coils.The third type of water cooled con-denser is the reverse of the shell andtube type. The refrigerant is insidethe tube, surrounded by the waterwhich is inside the shell.

Evaporators are either one of twotypes,- flooded or dry. The flooded

-- -- - -, --'---_-1----f--;--7f,-_,_T--T-_-_..-=. N,

-\-- -----A-------------------------------- , 1

i i i

0 COLD AIR --4j1t\\ J/1/\'N`,coOLER, /' /\ \\ ,....:---1./ /

Fig. 13. The "brine spray" refrigerating system using a warm air flow.


Fig. 14The header of a flooded type evaporator.

evaporator is generally of the headerand tube type and partially filled withliquid, instead of a saturated gas asin the case of dry expansion. Theheat transferred through the pipe isgreater than that of the dry evapora-tor. The success of a flooded typeevaporator depends on the construc-tion of the header, as there is alwaysa certain amount of dead or flash gasrepresenting about 15 per cent in thecase of ammonia. This is broughtabout by admitting the ammonia tothe evaporator or low pressure areaand part of it flashing. Since the

A dry typeBy Courtesy of the Buffalo Forge Co.

Fig. 15series tube evaporator.

flash gas can do no work in a re-frigerating load, there is no need forpumping it through the entire evapo-rator, and it is essential that this gasbe removed as quickly as it is formed.If it were to remain in the evapora-tor, it would crowd the liquid refrig-erant from the walls of the pipe, andthereby reduce the effectiveness ofthe flooded sytem.

The flash gas is removed by the useof headers, to which the evaporatingtubes are connected. As the refrig-erant vaporizes in the tube, the vaporwill quickly find its way to the suc-tion header and be pumped back tothe compressor. This header alsoprovides for a surge caused by therapid evaporation of the refrigerant,and the header should have a capac-ity of from 25 to 50 per cent ofthat of the evaporator coils. Figure14 is an illustration of this system.

As in all compressors and methodsof refrigeration, the lubricating oil ismixed directly with the refrigerant.So with the flooded type of evapora-tor it is necessary to provide for anoil return.

Dry evaporators are always of theseries tube non -recirculating type asshown in Fig. 15.

The length of coil used ineach system will govern theefficiency and capacity. Ifthe coil is too short, the re-frigerant vapor will leave ina wet condition, and resultin a loss due to liquid re-frigerant returning to thecompressor. There is also apossibility of slugs of liquidgoing back to the com-pressor and causing untolddamage. If the coil is toolong, the vapor becomes su-perheated before enteringthe compressor. This "su-perheat" causes an increasein the total cubic feet ofrefrigerant per -pound per -minute to be handled by thecompressor, and thereforedecreases the efficiency andcapacity of the machine.

The purpose of the evap-orator is to allow for theexpansion of the refriger-ant, thereby lowering its


temperature and pressure so that heatmay be absorbed from the air or wa-ter, whichever surrounds it. As therefrigerant enters the coil, it is in aliquid form at a comparatively highpressure. Upon being released intoan area where the pressure is low,the refrigerant sprays and is still in aliquid form (minute drops). As thesefine drops pass through the tube, heatis absorbed through the surface. Therefrigerant is evaporated into a gas,at the same temperature. If we al-low this gas to continue further, itwill absorb additional heat and itstemperature will rise. This highertemperature is called superheat, be-cause it is not in direct contact withwet refrigerant, and the temperaturewill exceed that of a saturated gas atthe same pressure.

An expansion valve is necessary ina refrigerating system to providesome means of controlling the flow ofthe refrigerant. It is necessary toreduce the refrigerant from the con-densing pressure to evaporating pres-sure, and at the same time regulatethe quantity of refrigerant flowing.The simplest form of valve would, ofcourse, be a hand operated device,such as a pressure reducing valve.Starting at the receiver tank, wherethe refrigerant is stored at a highpressure, it passes through the ex-pansion valve, where the pressure isgreatly reduced. Most valves usedtoday are of the thermostatic, expan-sion type, which are more efficientin operation and offer a method ofcontrolling the amount of refrigerantentering the evaporator. It preventsthe return of liquid to the compressorand provides a way of obtaining acompletely wetted surface, inside ofthe evaporator, as well as allowingseparate temperature control on eachindividual circuit of evaporator sur-face.

The valve is operated by a smallamount of superheat in the suctiongas as it leaves the evaporator. Thevalve itself is located in the pipe lineat the evaporator inlet, and the bulbis placed on the suction line close to

23

Fig. 16expansion valve for controlling re-

frigerant flow.

the evaporator outlet and inside therefrigerated space.

The superheat leaving the evapora-tor causes an increase in the tem-perature and pressure of the liquidinside the bulb, which in turn exertsforce on an inlet orifice disc in theexpansion valve. This allows more re-frigerant to enter the evaporator.However, if there is no superheat, thetemperature and pressure at the suc-tion outlet will be low, and the actionof the thermostatic bulb would be toclose the expansion valve inlet orifice.As can be seen, this prevents morerefrigerant from entering the evapo-rator, which is the desired result, aswe already have as much refrigerantas can be utilized. An illustrationof an expansion valve will be notedin Fig. 16.

An

CHAPTER 4Types of Winter and Summer Air Conditioning

Installations and Their OperationOUR present-day air conditioning is

the outgrowth of the one timepopular hot air furnace, which whenproperly applied did a good job ofheating. However, this system gaveway to the one -pipe steam systemwhich, in turn was replaced by thevapor and hot water system. As thepublic in general became educated tothe fact that heating alone was notsufficient for ideal comfort, adaptionswere then made to the hot air fur-nace, in an attempt to supply clean,moist air during the heating season,as well as heated air.

When it is realized that during theheating season outside air leaks intothe heated rooms at a rate sufficientto change the air in the room fromone to three times per hour, it willbe evident that moisture must beadded to obtain a reasonable degreeof comfort. Assuming the outsideair to be at 30 degrees, and a rela-tive humidity of 70 per cent, eachpound of air at this condition con-tains 17 grains of moisture. Whenthis air is heated, of course, the sameamount of moisture is still in the air,but its relative humidity would dropto 15 per cent, because the heatedair can hold more moisture than a 30degree air.

A unit, as shown in Fig. 17, is be -

Fig. 17Flow of air current within the furnace

casing.

24

ing used to filter the air and someform of water pan, or drip screen isinstalled in the bonnet of the fur-nace.

As this type of system does notlend itself to automatic control, it israpidly giving way to a more com-plete blower and filter arrangement,as illustrated in Fig. 18.

This type of unit is equipped withwater spray nozzle to humidify andpartially cleanse the air. The con-trol of humidity is automatic and isaccomplished by opening or closingthe water valve located in the inletsupply pipe. Baffles, or eliminators,are installed with standard equipmentto prevent carrying over water par-ticles in suspension with the air. Ininsuring adequate humidification, it isusually necessary that the spray waterbe heated. This is because warmwater is more easily vaporized andpart of the heat required to evaporatethis water will come from the wateritself, rather than from out of theair, as is the case when the water isat (or below) the temperature of theair.

As shown in the illustration, theair to be conditioned enters the topand all dust and dry particles arewashed out by direct contact with thewater. As these particles settle onthe eliminator plates, they are washeddown to the bottom and find theirway to the drain.

This type of unit is equipped witha silent, belt driven, multivane fan,which forces the required amount ofair through the system, by means ofduct work, as illustrated in Fig. 20.

Any number of outlets may be pro-vided, each equipped with its ownautomatic temperature regulator, thusmaking it possible to hold differenttemperatures throughout the varioussections of a building. This plan iscommonly known as zone control, andis essential in such cases where theheat loss varies in different parts ofa building. Such a condition would


AIDCOMDLE-flYCONDITIOREC

WATER lop_tiATER 5ERAIN

WATER p9/15LRE CATPOEAMFOMATIC VALVE PJrHUMIDITY [CXil 9L

AtnarAP MEDIN I-IEATER

DEPENDADLE FPR5L0CIRCULATES REVITALIZED Alp

VARIABLE SPEED DRIVEWITH SAFETY GUARD

UNIVERSAL SELF ALIGNING PEARiNGWiTm CONVENIENT METI.19p OF LLI( CATION

AS AIR PASSES TFIRU SPRAY CliANUNEG Art:.VERTICAL FILTER IT 15 MUMMIFIED AND 1, -:Of OLY CLTANTED

SPRAY AUTOMATICALLY AND CONTINUALLY C_EANSET. FILTERORA117E.,

41126f.

0"..)1101710,r,.

courtesy of Furbla Co.

Fig. 18. A complete blower and filter system for automatic control.

exist if a cold North windwere blowing on one sideof the house, and the sunshining on the other. Inother words to accomplishthis, it is necessary thateach section be providedwith a thermostat whichopens its correspondingdamper, and starts theblower motor and heatgenerating unit.

The air is delivered tothe heating unit in a clean,moist condition, where itis heated to the propertemperature, ranging from100 to 150 degrees f., de-pending upon the designand location of the reg-ister outlets. The heateritself may be a speciallydesigned warm air furnace Fig. 19

A multi -vane blower for air circulation.

2G A B C OF AIR CONDITIONING

Courtesy Pox FurnaceFig. 20

The duct system for distributing conditioned air.

type, using any kind of fuel, or itmay be indirect in which steam coilsare installed and the air blown overthem.

The operation of this system illus-trated in Fig. 18 is as follows: Whenmoisture is required in the space be-ing conditioned, an electrical type hu-midistat automatically opens thewater valve, provided the blower isrunning. A thermostat located nearthe humidistat starts the blower mo-tor when the room temperature fallsbelow the setting of the thermostat.A second thermal switch is usuallyplaced in the heating element to in-sure the delivery of warm air, andprevents the blower from operatingunless there is heat or steam in thebeating element. It naturally followsthat if the thermostat calls for heatand the secondary switch is not closed,indicating that there is no heat, theblower motor will not start until heatis furnished to close the secondaryswitch.

An electric relay is also used toopen or close dampers, regulate a gasvalve, or turn on an oil burner atthe same instant the thermostat callsfor heat.

This type of unit has its 'greatestmarket in the domestic field, as it isespecially designed for this work, andpriced within reason.

Figure 21 illustrates a specially de-signed factory type humidifier, whichfinds its widest application in the tex-tile mills, and research laboratories.Because of its compactness and high

efficiency, any number ofunits may be used to sup-ply the required amount ofmoisture.

The humidifier consistsof a revolving rotor directlyconnected to a small elec-tric motor and fan. Waterfor evaporation is ledthrough a small copper tubeto a pin just back of therotor. In this way the wateris sprayed into the revolv-ing rotor, and is thrown bycentrifugal force, againstthe eliminator, which breaks

c. up the drops and spray in-to a very fine mist. Airis drawn through the rear

of the unit by the motor -driven fanand as it is forced forward, carriesthe fine mist and fog out throughthe mouth of the humidifier. Anyheavy particles of moisture are ar-rested by the specially designed un-even passage in the forward section,which prevents any solid drops ofwater being blown out with the moisthumidified air.

These small units have the abilityto condition spaces ranging from2,000 to 40,000 cubic feet of volume,depending, of course, upon the amountof moisture required in the air andthe prevailing outside conditions.

The control is automatic in that amagnetic valve shuts off the supplywater to the head, or turns it on, asthe humidity rises or falls. A prede-termined percentage of relative hu-midity may thus be maintained in theroom. A feature is that the motorand fan continue to run even after

Courtesy of American Moistening Co.Fig. 21

Cross section of Amtex Humidifier.


the water supply is shut off, so as tomaintain an air circulation in theroom at all times.

Figure 22 shows a typical installa-tion of humidifiers in a large textilemill.

Figure 23 illustrates an indirectwinter -air conditioner, equipped withblower, motor and water sprays,-alsoheating surface is installed in the up-per section of the unit as shownthrough which steam or hot watermay be circulated to heat the air asit passes through the fin surface.

Moisture may automatically be sup-plied by opening and closing a watervalve in the line of the spray nozzles.Dry -type filters are usually installedin the return duct connection justabove the blower motor. This unitmay also be equipped with zone con-trol as illustrated in Fig. 18.

In the above types of systems it ispossible to obtain (during the "heat-ing season") air circulation, controlof temperature, control of humidity,and filtering. Provision should bemade for the introduction of fresh airto the spaces being conditioned. Themost practical arrangement is a ductconnection from the outside directlyto a point near the filter. In doingthis an adequate supply of freshair can be obtained and forced intothe rooms being conditioned. Thisscheme will prevent the infiltration ofcold air around the window framesand tend to build up a pressure with-in the conditioned space. This willeliminate drafts around windows andalong the floor which are usually ex -

Courtesy of American Moistening Co.

Fig. 22A typical humidifying installation in a

textile mill twisting room.

27

tote.y of Lewis Air Conditicmers, Inc.

Fig. 23Construction of heat exchanger -humidifier.

perienced on cold days. The smallair pressure which is built up in thismatter causes air to be forced out ofthe cracks or openings in the con-struction of the air conditioned spacerather than permitting the naturalleakage of air through these crevicesinto the spaces which are now condi-tioned.

The following pages describe sim-ple methods of cooling and dehumidi-fying, particularly for comfort. Asexplained in a preceding section, itis necessary to add moisture duringthe heating season to maintain a con-dition of comfort. However, duringthe summer we must reverse this prin-ciple and take moisture out of theair to allow for normal moistureevaporation from the body. It is alsoessential to cool the air to enjoy acomfortable temperature.

In summer it is not unusual tohave an outside air temperature of95 degrees, and a 50 per cent relativehumidity, which represents a very un-comfortable condition. One poundof air as mentioned above contains124 grains of moisture, and in cool-ing this air to 80 degrees and 50 percent humidity, it is necessary to ab-stract from the air sensbile heat tolower its temperature to 80 degreestogether with 47 grains of moistureper pound, the moisture representingthe latent heat of the air.

Figure 24 illustrates a unit con-


Courtesy of Thermal Units Mfg. Co.

Fig. 24A cooling unit for direct expansion.

structed of copper or aluminum finsurface through which cold water ora refrigerant may be circulated, andby means of electrically operatedfans, air is forced over this surfaceand cooled to a temperature belowthe saturation or dew point temper-ature. In doing so, some of themoisture will be condensed out of theair.

This type of unit is obtainable inany number of sizes, and for alltypes of refrigerants. Control of oper-ation can be made automatic by theuse of an electrically operated valvein the cooling medium supply line,whether it be water, brine or refriger-ant. Application is limited only by

the size of the space to be cooled. Itis essential that units of this kind beinstalled high in the conditioned room,and the discharged air directed insuch a manner as to prevent draftsor blow directly upon any person orpersons who may be in the room.

Figure 25 illustrates the typicalconnections that are required to usea cooling unit such as shown in Fig.24, for direct expansion. The actualdistance between the condensing unitand the evaporator surface may beany length although it is advisable tokeep them within 50 ft. of eachother. The reason for this require-ment is to reduce the amount of fric-tion in the pipes caused by the veloci-ty of the refrigerant. The directionof the refrigerant in the suction andliquid lines is indicated by arrows.The control may be automatic byusing a plain "room thermostat" tostop or start the condensing unit, asoccasion may require. Although thefan in the cooling unit will operateduring such periods when no coolingis required.

This diagram illustrates the sim-plest form of cooling and dehumidi-fication of air. A vapor compressionmachine is used in conjunction withthis unit room cooler and for themost part our study will be on thistype of refrigeration.

Figure 26 clearly shows a watercooled, shell -tube, condensing unitand its component parts, all of which

SINGLE UNIT COOLER ON AUTOMATIC COMPRESSOR

AUTOMATICCOMPRESSOR

4_1

ROOM THERMOSTAT

SUCTION

,11111111110),

LINE

SHELL & TUBECONDENSER

LIQUIDLINE

DRY EXPANSION CC( F22

1 LINE

4SWITCH

-EXPANSION VALVE

STRAINER

Fig. 25. Connections for a single unit cooler to an automatic compressor.


have been explained indetail in various sectionsof the book.

In localities where thecost of water is prohibi-tive to the operation oflarge condensing units,a water cooling tower isgenerally used, the typeof which is shown in Fig.27. This particular unitis termed an atmosphericcooling tower and de-rives its name from thefact that no fans are re-quired to force the airthrough, or over thewater.

As shown in the illus-tration, the condenserwater is sprayed down-wards and natural air iscirculated through thesides, which are partiallyopen. The spraying of this water inthe air cools the water because a partof it evaporates into the air, and theheat for evaporation comes from thewater itself. The air that comes incontact with the water becomes satu-rated and is carried away by theslightest natural air motion.

The sides of these towers are usual-ly made of clear redwood, althoughin some cities local ordinances pro-hibit the use of wooden towers. Insuch cases, the same design may beobtained in metal.

A

Courtesy of York Ice Machinery Corp.Fig. 26

A water-cooled shell -tube condensing unit.

Courtesy of Binks

29

Mfg. Co.

Fig. 27water cooling tower for condensing.

Under ordinary operation lees than2 per cent of the water handled islost by driftage, the balance being re-turned to the condenser unit to again

heat and be resprayed inthe tower.

Figure 28 shows a typical circuit ofthe condensing unit and tower. Aby-pass is provided around the con -

WINTERBY-PASS

PUMP CONDENSERFig. 28

Circuit of a condensing unit and tower.


denser and is necessary because thewater pumped to the tower is usuallytwo times that which could be econo-mically pumped through the con-denser. A water circulating pumppumps water through the condenserto the tower. A storage tank isused, as shown on the illustration,only in such cases where cooling dur-ing freezing weather is desired. Onan installation where the machine willnot operate during the cold weather,a pan arrangement is installed directlyin the bottom of the tower, whichmay hold as much as 6 ins. of water.A service connection is made to thecity water supply line to a ball floatarrangement to maintain a constantlevel. The principle of this is simi-lar to that of a toilet ball and floatarrangement, and will automaticallymake up for such water as is carriedaway by drift.

The water in the cooling towers issprayed from nozzles as illustrated in

AIR OUTLET

FORCEDDRAFT_

TOWER7=-

Fig. 29. The construction of thesenozzles is such that they do not be-come clogged either from lime, sedi-ment or other foreign matter, usuallyencountered in air conditioning sys-tems.

In cases where it is impractical toinstall a cooling tower on the roof, adevice similar in characteristics maybe installed in the basement and con-nected to a blower that draws in out-side air, forces it through the towerand exhausts it outside. In this planthe water is cooled by evaporationas with an atmospheric roof tower,and requires only the addition of afan and motor to accomplish the sameresults. Figure 30 illustrates the con-nections between the condensing unitand the forced -draft tower, togetherwith the necessary valve arrangementto provide the use of city water tocool the condensing unit during suchtimes as repairs are being made toany part of the tower.

WARM WATER

11111

Courtesy of Binks Mfg. Co.

Fig. 29

The type of spraynozzle used for circu-lating water in awater cooling tower.

TO SEWER REFRIGERATINGUNIT

BYPASS14

FAN

I II

PUMP

!Z.

DRAIN CHECK VALVEFig. 30. Connections between the condensing unit and a forced -draft tower, with all valves.

_

CONDENSER

[CITY WATER41-


Figure 31 is a cross section of thistype of forced draft cooling tower.

As a general rule, it is advisableto allow the fan and pump to con-tinue operation during such periodsas the condensing unit is shut downdue to the conditioned space beingbrought to the desired temperature.This scheme will allow the waterwhich lies in the bottom of the towerand that which is in circulation to becooled slightly below the normal oper-ating temperature.

Figure 32 shows a typical arrange-ment of a central plant for summerconditioning, for which the refriger-ant is produced by a water cooledcondensing unit, connected to directexpansion cooling coils in the air con-ditioning compartment, that is gen-erally made up of heavy gauge metaland equipped with low speed multi -vane blowers, and blower motor, to-gether with a sufficient amount offilter surface to filter the mixed re-turn air and fresh air. As the air istaken into the conditioner throughthe fans, it is forced over the coolingcoil where dehumidification and cool-ing is obtained and the air when ex-hausted out of the top to a duct dis-tribution system, which conveys theconditioned air to any number of

SUCTIONLINE -\

31

Fig. 31A cross-section of the unit shown in Fig.

30.

rooms or spaces where it is required.A thermostat placed in the space be-ing conditioned will stop or start thecondensing unit but the fan will con-tinue to operate to insure an ade-quate supply of fresh air, which isusually brought in at the rate of 3/3

AIR SUPPLY

,

FYI

,, iTHERMOSTATIC III RETURN

C 1BULB i

1

\1

LIQUID LINE i

-I !DIRECT EXPANSIONI COOLING COILS -)

COMPRESSOR COND. Jr- 1 1

WATER-1 M, ,011

JI__. _1 ---e/VALVE 1

IFILTER

EXPAN-1 ISION i

Di VALVEI

FRESHAIR

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I IIIIIL 31

-, ;FiII

==

WATER0I INLET E&T

0 1

1111_1/:,1----14,_

i MOTOR

rj*=-J-,,- DRAIN

STARTER

MOTOR

/wiz,/CONDENSER STRAINER Courtesy of American Blower Corp.

& LIQUID RECEIVER PRESSURE SUCTION SWITCHFig. 32. A typical central plant for sununer air conditioning.


Courtesy of York Ice Machinery Corp.

Fig. 33An air cooled condensing unit.

of the total air distributed by the sys-tem. The indicating arrows show thedirection of flow of air to the condi-tioner, and also the direction ofwater in and out of the condensingunit as well as the flow of refriger-ant to and from the coil surface.

While the accompanying illustra-tion, Fig. 32, shows a water cooledconditioning unit, it must not be con-strued that only a water cooled unitwill work on such a system. It isalso practical to use an air cooled con-densing unit such as illustrated inFig. 33 or a counter flow double tubewater cooled condenser unit as shownin Fig. 34 can be used. Althoughthe air cooled units can be obtainedin the larger sizes, they are morereadily adapted to systems requiringin the neighborhood of 2 horsepower.The extended -fin type surface and Uturns is the condenser, through whichthe hot refrigerant is circulatedand the heat absorbed from it byroom air, which is circulated over thesurface by means of a fan directlyconnected to the driving motor shaft.

Courtesy of General Elec. Co.Fig. 34

A counter -flow water cooled condenser.

The principle types of filters usedin air conditioning systems are asfollows :

1. Dry type, pre-oxydized steel -wool enclosed in a steel frame. Thesefilters may be cleaned when necessaryby removing them from the condi-tioner and spraying hater throughthem or using a vacuum cleaner.

2. Spun glass wool which is furn-ished in a light weight cardboardframe and partially saturated with anadhesive solid. This type of filtermust be discarded when it becomesfilled with dirt and dust.

3. There is also the oil dippedsteel, or copper wool enclosed in ametal frame which may be cleaned byapplication of steam or a causticwater and re -used.

These, of course, are not all typesof filters which are on the market butthese three types represent the ma-jority of kinds which are popular inair conditioning installations. The ex-act effectiveness of each type of filteris covered entirely by the application

FRESHAIR

FORCEDINTAKE

FILTER

HUMIDITYCONTROL

.

COOLINGOR HEATING

EXHAUST

Fig. 35. The functions of an air conditioner shown in sections.


to which it is put, and it is recom-mended by all manufacturers that theair velocity through filters shall notexceed 300 F.P.M., or feet per minute.

Up to the present time we havediscussed in detail methods of winterair conditioning and simplified meth-ods of summer conditioning. In thissection, the study of a complete win-ter and summer system will be takenup.

It is evident that in most sectionsof the country it is just as importantto have the complete combination ofwinter and summer air conditioningas to have either part alone. How-ever, it is worth mentioning here thatthe term air conditioning to mostpeople represents simply a cooling sys-tem. With a little study it is def-initely proven that ALL functions arenecessary to have the maximum ofefficiency and comfort. To accomplishthis result, such a unit as illustratedin Fig. 36 can be installed.

This type of unit may be locateddirectly in the space being condi-tioned, or in an adjoining room orbasement. It takes fresh air fromoutdoors together with recirculatedair from the conditioned space andmixes them in a sheet metal duct con-nections at the filter end of the unit.

SURFACE NOT REG.WITH BYPASS

As the air enters the unit it passesthrough filters and is drawn througha set of automatic dampers which arecontrolled by a room thermostat dur-ing the cooling period. During theheating season they are controlled bya room thermostat together with apilot thermostat (see Fig. 36-13-S)located in the duct distribution sys-tem, to prevent the discharge of airat an uncomfortably low temperature.

Electrically the damper motor andthe steam supply valve (see Fig. 36-14-S) are arranged in parallel toopen or close simultaneously on callfor heat by either the pilot thermo-stat or the room thermostat, so thatwhile neither the thermostat or thepilot thermostat in the duct system iscalling for heat, the face dampers willbe closed and the air bypassed throughthe bypass damper section. The ex-act angle or the degree to which theface dampers are closed may be ad-justed to give an economic balanceand overcome the intermittent open-ing and closing of both the dampersand the steam supply valve.

(This scheme may be adopted byanyone for heating, but it cannot beused to bypass air around a coolingcoil unless permission is obtained

14S CONTROL USING BYPASS

ITHOUT BYPASS- CONTROL SURFACEBY 14S VALVE

13S CONTROL WITHOLBY PASS DAMPER

HEAT & SOUNDINSULATED CASING

DAMPER FACEMOTOR;

DAMPINLE

:

1 1 (FANSILENT ----

, % BEARINGSMOTOR

i 4 ) '-'--0 , , _

v) Z=J 20 I-0 <0 ,7.z _i_ O.<

z2lzr

t)=aj

,

=0

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= !

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ER

HEAVY CHANNELBYPASS DAMPER

Courtesy of American Blower Corp.Fig. 36. A small air conditioner which can be made to suit Varying conditions, as ex-

plained.

STEEL RUBBERDRIP PAN MOUNTING


from the owner of the patent rightsfor such a system.)

After the air passes through thedampers, it is directed across ex-tended heating -coil surface throughthe dehumidifier and cooling coils,which would be valved off during thewinter time. Then the air enters thesection indicated by heating coil orhumidifying device, where moisturewill be added to the air by any of theapproved methods explained elsewherein this book. The air now enters thefan and motor section, where it istaken in from both sides of a doubleinlet, double width blower and dis-charged to the outlet and duct dis-tribution system.

Figure 36 shows this in a small in-stallation, but the same principles ap-ply regardless of the size of the areato be conditioned. It will work justas efficiently in large or small in-stallations.

For summer, the fresh and recircu-lated air is again mixed just outsidethe unit, and taken through the filtersand damper arrangement, where someof the air may be directed into thebypass air channel and the balancetaken directly through the coolingsurface where it is cooled and dehu-midified. Both operations take placeon the same coil surface. As boththe bypassed air and the cooled airmust mix at the blower, it can beseen that in the event that the cooledair is at a temperature too low to bedelivered into the conditioned spacesits temperature can be raised by regu-lating the amount bypassed or mixed.The final mixed air is taken throughthe blower and discharged to the ductdistribution system.

Another of the advantages of thebypass damper is that when the roomthermostat is satisfied and the roomis cool enough, instead of having thecondensing unit or supply of refrig-erant closed off, this would remainopen or in operation and the facedamper would partly close while thebypass damper would be open. Fur-ther, a small amount of air will thuscontinue to pass through the coil sur-face and be cooled and dehumidified.As only a small portion is passingthrough the surface, it will be easilyreheated when mixed with the by-

passed air. But due to the low veloc-ity across the cooling surface as com-pared to the velocity when the totalair supply is directed over the sur-face, extreme dehumidification willresult and control of the relative hu-midity may be accomplished duringthe cooling season. As shown in thediagram, a drain connection is pro-vided to carry away the water whichis condensed out of the air duringthe cooling season, or to take awaywater that is not evaporated duringthe process of humidifying during theheating season. After careful study,it will be evident that the pilot ther-mostat will be an electric arrange-ment rather than the Fig. 36-13-Stype.

Where an air conditioning systemis installed and a unit similar to Fig.36 is used without the bypass damp-ers, the sequence will be as follows:Fresh air and recirculated air aremixed in a duct connection anddrawn through the filter surfacewhere, as in the other scheme, from90-95 per cent of the dust is re-moved. The total air supply will passthrough the first heating coil, ordin-arily termed a preheater, so that dur-ing the heating. season the mixed airwill be heated and controlled by avalve as explained in Fig. 36-13-S.The air then passes through thecooling coils which are closed off andthen goes through the main heaterwhich is controlled by a valve similarto Fig. 36-14-S. Immediately afterleaving this heating surface, the airis brought in contact with warmwater furnished either with spraynozzles or drip screens. Of coursein the case of the spray nozzles, elim-inator plates must be used in thespace between the motor and thespray nozzles, while drip screens donot require these eliminators, as littleor no water is carried over with theair. We now have warm, moist,clean air, ready for duct distributionat the fan outlet.

During the cooling season, the airpassage is the same as during theheating season up to the first heatercoil. This does not have steam in itas the steam supply is shut off. Asthe air passes through the dehumidi-fying and cooling coil, its temperature


is lowered below the dew point tem-perature for the air at that conditionand moisture is condensed out of theair and finds its way to the drain.Then the cooled air is drawn throughthe main heating coil which is alsoturned off and the humidification sec-tion which of course is not in opera-tion. At this point, the air entersthe motor and blower section and isdischarged to the duct system or di-rectly to the room being conditionedin case the unit is installed in theconditioned area.

In ordinary comfort cooling sys-tems where the ratio of latent heat tototal heat is one-third, sufficient de-humidification can be obtained by theuse of a refrigerant whose tempera-ture ranges between 30 and 40 de-grees. As the air leaving the coolingsurface may be 60 or 65 degrees, itcan be delivered to the room at thistemperature. However, without theuse of a bypass, and where the ratioof latent and total heat is greaterthan one third, it may be necessaryto cool the air to a temperature of50 degrees and then use the heatingcoil to heat the air from 50 degreesto a possible 65 degrees so that it maybe delivered to the conditioned spaceat a temperature which will not cre-ate discomfort and drafts.

Illustration Fig. 37 is an elevationRECIRCULATING

CONTROL TEMPERINGCOILS

AIR

FILTERSDIFFUSER

drawing of either a complete year-round air conditioning system or sim-ply a humidifying or dehumidifyingscheme, depending entirely on thetemperature of the spray water thatis delivered to the unit. While thissystem has been in use for manyyears, particularly in theatres, its ap-plication is usually confined to thelarger buildings when performing allthe functions of a year-round airconditioning system. From the illus-tration, it can be seen that fresh airand recirculated air are mixed, anddrawn through tempering coils anddry type filters then through thediffuser plates that are installed toevenly distribute the air through thespray chamber, where it is in directcontact with the water, which may bewell water, recirculated water, or pre -cooled water. It is evident then thatif the temperature of the spray wateris below the dew point temperatureof the entering air, the air will becooled and dehumidified in exactlythe same manner as when it passesover a cold evaporator surface. Thecool,through the eliminators that serve toarrest any solid particles of waterthat might be carried in the air bymechanical suspension.

From this point, the air travelsthrough the reheater surface and fan

AIR WASHER

ELIMINATORS

SPRAYCHAMBER

. "°.O.L;t1 .SUCTION STRAINER WATER LEVEL o' MOTOR

REHEATERFAN

Fig. 37. An elevation drawing of a device which may be used as a complete year-roundconditioner or as a humidity control.


to be discharged into the duct sys-tem, going back over the same coursefor winter operation, where humidi-fication is desired, the tempering coilsare used to raise the temperature ofthe incoming air to 45 degrees. Thisair, passing through the spray cham-ber, with water at a temperature of70 degrees or higher, becomes satu-rated at a temperature of 45 de-grees. In this plan, the heat forevaporation comes from the water it-self. The air is then directed throughthe eliminator plates, and the reheatersurface, where it is usually heated to70 degrees, and delivered to the con-ditioned rooms. When 45 degree sat-urated air is heated to 70 degreeswithout adding or subtracting addi-tional moisture, it will have a rela-tive humidity of 40 per cent.

In the case of recirculating water,that is by maintaining a definitelevel as shown by the water line, andmaking up for only such water as isvaporized into the air, a water pumpis used to force the spray waterthrough the nozzles, pick up thatwhich is not vaporized and recircu-late it. This method is commonlyknown as cooling by evaporation andmay be used quite successfully in sec-tions of the country where the wetbulb temperature and relative humidi-ty is low, so that the heat requiredfor evaporation is abstracted fromthe air, and its temperature lowered,but at a sacrifice of increasing the

wet bulb temperature and relative hu-midity in the conditioned spaces anddelivery air.

Under some conditions this type ofsystem is very satisfactory. Butwhere the outdoor relative humidityis high, this scheme has an adverseeffect by further raising the relativehumidity and causing a feeling ofoppressiveness, thereby defeating thepurpose for which it was installed.

Another possible combination adapt-able to this type of sytem is to placein the spray chamber and water tankblocks of ice over which water issprayed, thereby cooling and dehumid-ifying the air passing through thechamber.

From the above descriptions it canbe seen that this system offers atleast a dozen combinations to treatair for any conceivable condition.

It will be noted in the illustrationthat dry -type filters are used beforethe air enters the washer. This isbecause it has been definitely proventhat an air washer removes only 50per cent of the carbon particles presentin the air. However, the air washerwill remove soluble odors and gases,which of course easily pass throughthe filter, so that each has its indi-vidual purpose in the system, andwhere a choice must be made theselection will be governed by thekind or type of impurities in the air.

CHAPTER 5

Service and Control Applied to Air ConditioningSystems

TN AIR conditioning and refrigerat-1 ing systems, the service and controlare as important as the original de-sign. It is essential that the serviceman know all the functions and oper-ations of the various controls and, inthis way, it will be possible for himto quickly analyze trouble withouthaving had any previous experienceon the particular control involved. Onthe following pages are pictured il-lustrations of well known controlunits together with service "hints,"which will be helpful to the serviceman who wishes to familiarize him-self with the ever increasing popularvapor compression system. The ex-pansion valve is used on practicallyall types of air conditioning systemsand may cause trouble in the entiresystem if not properly installed oradjusted.

The valve itself does not need tobe installed directly in the condition-ing unit or refrigerated space butthe bulb must be inside and the valveinstalled as near as possible to elim-inate frosting of the line betweenvalve and evaporator, and to preventbuilding up of false pressures afterthe valve. The valve will be more sen-sitive if installed close to the evapora-tor. In the case of a system operatingfor some time with a lack of refriger-ant it has been found that the valveseat will cut and score because of thehigh velocity gas passing through thevalve seat instead of liquid. This, ofcourse, can be remedied only by add-ing more refrigerant and replacingthe valve seat.

Figure 38 illustrates the proper lo-cation of a thermostatic expansionvalve as used on a dry -type of evapo-rator. It is important that a goodcontact be made between the bulband pipe to insure the sensitivenessof this valve. If the bulb is installed

37

as shown by the dotted lines in theillustration it would remain cold dur-ing the shut -down period and whenthe compressor starts up it must firstpump the accumulated refrigerantout of the pocket before the bulbwill warm up and because of this thebulb operation would be sluggish anderratic. On the majority of valvesthere is only one adjustment whichvaries the compression of the balanc-ing spring and after the system hasbeen in operation f'or one hour itmay be adjusted to permit more re-frigerant to go through if the suc-tion refrigerant temperature is toohigh. In case the suction line frosts,it will be necessary to reduce theamount of refrigerant entering theevaporator. The importance of keep-ing dirt out of the valve cannot beover- emphasized and it is essentialthat a strainer be installed as close tothe valve as possible to prevent pipescale and foreign material from enter-ing the valve. When putting a newjob into operation it is advisable toblow out any foreign matter by by-passing the expansion valve or leav-ing an open connection. The ser-vice man must be sure that there isno water in the system as A wouldfreeze at the expansion valve so it is

Fig. 38Correct and incorrect positions for athermostatic expansion valve used on a

dry -type evaporator.


advisable to use a dryer installed inthe liquid line not as a permanentconnection but only during the test-ing and adjusting period.

If the valve fails to open and re-mains closed at all times, it has lostits charge and this may be caused bya broken diaphragm, a split in theconnecting tube or bulb or a badlywelded joint in the bulb. It will benecessary to replace the valve as-sembly.

If a valve fails to close and refrig-erant can be heard going through itduring the shut -down period it is evi-dent that the seat has been damagedand a replacement will be necessary.

Lack of refrigerant in the systemwill be indicated by warm liquid lines,warm evaporator, low suction pres-sures, low head pressures and a de-cided hissing of the expansion valve;the hissing noise will be the first evi-dence of low refrigeration.

AB C D EF GHJ K L

T S R QA ADJUSTING SCREWB MOISTURE -TIGHT PACKING

AROUND ADJUSTING SCREWC PACKING NUTD THERMOSTATIC POWERE FLEXIBLE CAPILLARY TUBEF MOISTURE -TIGHT JOINTG BAKELITE EXTENSIONH BELLOWS SEALJ MOISTURE -TIGHT JOINTK THERMOSTATIC BULBL STRAINER SCREENM COPPER GASKETN INLET CONNECTION FOR

COPPER TUBEO NEEDLE SWIVELP SOLDER -SEALED PLUGQ STEEL NEEDLE (STAINLESS)R STAINLESS STEEL SEATS OUTLET CONNECTIONT BAKELITE PUSH -ROD

4

Fig. 39The cross section detail of a typical ex-pansion valve for thermostatic control.

The action can be easily understood.

Figure 39 clearly illustrates a crosssection of a typical expansion valve.

An oversupply of refrigerant willbe indicated by a high head pressure,due to the liquid refrigerant collect-ing in the condenser decreasing thevolume and effectiveness of the con-denser tubes. The first symptom willbe short cycling of the condensingmotor which will cut out on high headpressure.

Figure 40 illustrates a back pres-sure control which is standard equip-ment and necessary on nearly alltypes of condensing units. The oper-ation is such that if the suction pres-sure at the condensing unit is too lowit will automatically interrupt theelectrical circuit to the compressormotor causing it to stop. Under con-ditions of a light load at the evapo-rator, it is necessary to stop the con-denser motor otherwise, a very lowsuction temperature would be ob-tained resulting in frost at the evapo-rator surface and restricting the airflow over the evaporator. Ordinarilya small copper tube connection ismade between this control and thecompressor crank case which is opento the suction line. In the same il-lustration there is shown a high pres-sure safety cutout which is connectedto the head of the compressor by cop-per tubing, and in event that thehead pressure becomes too high, pres-sure is exerted on the bellows whichin turn trip the main contacts andstop the compressor motor. Thesecontrols are always equipped with adifferential adjustment so that theunit may operate over a range ofpressure to provide a normal run-ning range.

In the case of a unit stopping andstarting too frequently, the range ad-justment should be set to give agreater differential between the "on"and "off" period. Most of these con-trols have a minimum differential of3 lbs. and a maximum differential of25 lbs. and, for the standard air con-ditioning system a 20 lb. difference isusually sufficient to compensate forthe varying loads. This applies onlyto the suction pressure. The highpressure cutout does not need ad-justment beyond the point that it willstop the unit at a predetermined high


CONTROL BELLOWS

pressure and allow it to restart at ap-proximately 30 lbs. below the highpressure.

If trouble is experienced in eitherthe contact spring or adjustment theremedy will be obvious and repairscan be made but, if either the lowpressure bellows or high pressure bel-lows are ruptured or leak it will benecessary to replace with new ones.

Figure 41 illustrates a standardservice connection valve. These valveswhen used on the suction line are at-tached directly to the crank case ofthe compressor and, from the dia-gram, it will be noted that by bring-ing the valve stem back or out weclose the opening port to the serviceplug connection which is usually 1/8

in. pipe thread made especially to re-ceive a pressure gauge. When thevalve is back seated in this manner,a direct opening will then be madebetween the refrigerant connectionand the compresser crank case. Withthe valve stem in this position, agauge can be installed without losingrefrigerant - now - by turning thevalve stem in a few turns a directconnection will be made between allthree points; that is, the refrigerantline, crank case and pressure gauge.Should it ever be desirable to closeoff the refrigerant connection, it maybe done by turning the valve stem inor front seating it as the name ap-plies. During normal operation, thestem should be back seated and thesealing nut made tight to prevent theescape of gas. Never leave the pres-

PERMANENTMAGNET

MOVABLEAUXILIARYCONTACTS

STATIONARYAUXILIARYCONTACTS

MAIN CONTACTS DIFFERENTIALADJUSTING SCREW

SAFETY CUT -011T

RANGEADJUSTING NUT

REFRIGERATOR HIGH PRESSURE SAFETYCU r -OUT BELLOWS

Courtesy of General Elec. Co.

Fig. 40

A back pressure control which automat-ically turns off the compressor if the suc-tion pressure at the condenser is too low.

Front seatRefrigerantconnection

Service plugBack seat

Valve seats

Compressor connection S'aLr'9Out

Fig. 41A service connection valve to permit ser-

vicing without losing refrigerant.

sure gauge on longer than is abso-lutely necessary.

This same type of valve as de-scribed above is used on the head ordischarge of the compressor as wellas on the low pressure suction side.Rarely if ever will any trouble be ex-perienced with this part of the equip-ment but, it is well to know the posi-tions in which the valve seat can beplaced.

Figure 42 shows the cross sectionof a magnetic liquid valve more oftencalled a solenoid valve. This valvefinds its greatest application wheremore than 1 such unit as illustratedin Fig. 24 is used and connectedto a single condensing unit and it isdesired to hold different temperaturesin the spaces being cooled by theFig. 24 unit. Thus, by the applicationof a thermostat in each room con-nected to a magnetic valve, we canregulate the flow of refrigerant toeach unit by opening and closing thevalve as called for by the thermostat.While there are many types of mag-netic valves it is essential that theyall be installed in a vertical positionin a horizontal pipe and the one il-lustrated is equipped with a pilotswitch that can be used to operatesome mechanical device, as a con-densing unit. The valve illustratedis of the lever type and the solenoidplunger operates the valve indirectlyso that when the coil is energized dueto action of the thermostat, theplunger is pulled up in the center ofthe solenoid and makes a firm contacton the pole face of the laminatedsolenoid frame. As the plunger trav-els upward it opens the valve andwhen it reaches the frame, the valveis wide open. As long as current ispassing through the coil, the plunger

40 ABC OF AIR

is held in this position in the centerof the solenoid and the valve remainsopen. When the space being condi-tioned reaches the cooled tempera-ture desired the thermostat acts tode -energize the solenoid and theplunger drops out and closes the valveby its own weight and the assistanceof the top spring automatically clos-ing off the supply of refrigerant tothe air conditioned unit. Trouble maybe experienced with these valves ifthey are not installed in a verticalposition; in case the solenoid coil isburned out; or the seat is damaged,thus permitting the valve to leak.

Ordinarily a line voltage with avariance not greater than 10 percent above or below the rated voltagewill not affect the continued opera-tion. However, a steady over -voltagemay eventually cause the coil to burnout. An under voltage for an ex-tended length of time reduces the pullof the magnet; the plunger will notlift up completely, and the coil mayburn out.

The valve itself should never be in-stalled where frost is likely to accu-mulate as this may penetrate the mag-net coil and short circuit causing aburned out coil. Moisture may alsofreeze on the lever arm causing it tobind and prevent the plunger frommoving far enough up into the solen-oid eventually causing the coil toburn out.

COVER

PILOT SWITCH

MAGNET

COIL (CAP

-GASKETS

MIEMEN.&

LEVERCONDUIT) ARMFITTING

SPRING

SHAFTCAM

VALVESEAT

Courtesy of Also Valve Co.Fig. 42

A magnetic liquid valve or solenoid valvefor individual control of temperature.

CONDITIONING

O

2

In the type of valve where a pack-ing is used, care must be exercisedin tightening the gland nut as thisadditional resistance may prevent theplunger from lifting.

It is not uncommon for these valvesto hum whenever the current is on.Generally this is due to the fact thatthe valve is tilted a little. This hummay be overcome by loosening thevalve and selecting a better position-vertically. It is possible to obtainthese valves for any type of serviceor voltage.

Water Regulating ValveFigure 43 clearly shows the cross

section of a water regulating valvesuch as is used on all water cooledcondensing units. Its function is toautomatically regulate the supply ofwater being delivered to the con-denser and is actuated by the headpressure of the compressor. For ex-ample, when the unit is not running,the heavy spring shown in the bottomsection of the valve holds the valveseat closed preventing the waste ofwater and with the unit running thepressure on the head of the com-pressor exerts force on the bellowsshown in the upper part of the illus-tration. This pressure compresses thebellows and forces the center pindown and the valve from its seat per-mitting water to pass through to thecondenser. This valve is adjustableover a wide range and should be setto open at pressures recommended bythe manufacturer of the condensingunit. Ordinarily these valves do notgive rise to any special trouble al-though it is recommended that astrainer be placed in the line beforethe valve.

Immersion ThermostatWhere it is desired, to control the

/ 4

er/a7/ NI10111

wen'

Ap

rAgrri

WATER REGULATING VALVEFig. 43A water regulating valve used on all

water cooled condenser units to regulatethe water supply.


temperature of brine or water an im-mersion type electric thermostat maybe used to complete the circuit bystopping and starting a condensingunit. Figure 44 covers the workingparts and its operation is as follows:parts 1, 2 and 3 are filled with an ex-panding liquid so when the bulb isheated the expanding liquid generatespressure in the system overcomingthe tension of the loading spring, 4,and the bellows, 3, expands actuatingthe switch, 5.

This control may be used withinthe limits of minus 50 degrees F. to600 degrees F. although field adjust-ment is limited to 50 degrees aboveor below the factory calibration. Ad-justments may be made by turningscrew 6 to the right for a highertemperature and left for a lowertemperature. The adjustment maybe locked by the nut 7. The wiringconnections are made through open-ing 8 to terminals 9.

Little or no trouble will be experi-enced with this control and in theevent of failure the cause would beevident upon removing the cover.Typical wiring diagrams are shown inFig. 45.

HumidistatWhere it is desired to control the

amount of moisture in the air of thespace being conditioned, it is neces-sary to have some control devicewhich will be effective by the presence

LINE SWITCH,LINE SWITCH`FUSES FUSES,

-1

LINE

THERMOSTAT)

LOAD 0 --

Fig. 44An immersion -type electric thermostatfor controlling the temperatur of water

or brine.

or absence of moisture in the air andin turn make or break an electricalcircuit. Such a device is illustratedin Figs. 46 and 47 and is calibratedto operate on a percentage of the

LINE

LOAD

RESISTANCE. /CONDENSER

LINE) THERMOSTAT)

LOAD

CONTACTOR

Fig. 45. Three circuits for the immersion thermostat.A-Shows its use for 110 or 220 volts A.C. single phase.B-shows its use for 110 volts D.C. load not exceeding 4 amps.C-shows a single or split phase circuit for heavy loads-A.C. or D.C.

42 ABC OF AIR

amount of moisture in the air. Theindicating dial is graduated from 10to 100 per cent which is a directreading of the relative humidity. Thehumidistat as shown in illustration 46consists of a set of actuating leversconnected to two multiple groups ofhuman hair which expand or contractas the amount of moisture present inthe air changes. The action of the

CONDITIONING

hair on the levers make or break anelectrical circuit which would openor close a solenoid water valve in thecase of a winter air conditioning sys-tem, or for a cooling system it maybe used to operate dampers, refriger-ant valves or stop and start a con-densing unit.

The maximum load that may becarried by this control is 110 volts

Courtesy of Frsez Instrument Co.Fig. 46 and 47. A Humidf.stat inside and out-a device for controlling the moisture inthe air.


Fig. 48. A conventional thermostat-inside

and 50 watts and with the exceptionof a small solenoid valve or damperregulator, a relay and transformerwill be necessary to operate heavyequipment such as motors, condensingunits, etc.

No attempt should be made tocheck the factory calibration of thisinstrument until it has operated in theconditioned room for several hours and

Courtesy of Friez Instrument co.

and out-for controlling air temperature.

becomes entirely acclimated to its newcondition nor should any check bemade unless the humidity has beenheld constant For several hours with ageneral air circulation over the con-trol. If, after several hours, of opera-tion it is found that the control needsadjustment it may be accomplishedby turning the large slotted screwjust inside the enlarged opening in


the bottom left hand corner of thecover. Moving this adjustment screwclockwise gives a higher control pointand for a lower control point itshould be turned counter -clockwise.A sling psychrometer together witha temperature humidity chart shouldbe used in checking the humidistat.

ThermostatFigure 48 shows a conventional

type thermostat with outside cover onand with the cover off exposing thethermostatic element which is affecteddirectly by any change in air tem-perature. With proper applicationthese thermostats will operate on aone degree differential total and suc-cessfully break loads up to 100 wattswithout recourse to relays and, ofcourse, where heavier loads have tobe handled the thermostat would thenbe used as a pilot switch to operatemagnetic starters, etc. The dial grad-uation is in degrees, f. From the il-lustration it will be observed that thecenter metal strip is a continuationof the curved bi-metal strip just overthe indicating dial and as this bi-metal strip is made up of two dissim-ilar expanding metals any change inthe air temperature surrounding itcauses it to change shape slightlythus moving the center strip eitherto the right hand lower contact or

H/4 HUMIDISTAT & T/4 THERMOSTATCOMPLETE CIRCUIT AT LOWH/5 HUMIDISTAT & T/5 THERMOSTATCOMPLETE CIRCUIT AT HIGH

SUPPLYLINE

110 V. MAX.

LOAD (LINE VOLTAGE MAX.WATTS, THERMOSTAT 100,HUMIDISTAT 50)SOLENOID VALVE OR THERMALDAMPER MOTOR ETC.

O FRIEZH/4 , T/4H/5 OR T/5

Fig. 49AConnections for a humidistat or thermo-

stat to 110 volt line.

left hand lower contact automaticallycompleting or breaking an electriccircuit, as the condition may require.

Where it is necessary to make ad-justments, it must be borne in mindthat these instruments are very sen-sitive so the utmost care must beused. The operation will be affectedif the contact points become dirty inwhich case they can be cleaned witha very thin piece of clean cardboardsuch as a calling card or, in eventthat they become pitted due to excessvoltage, and amperage, the contactsmay then be polished and used whilethe new set is being ordered.

The accompanying electrical dia-grams (Fig. 49, A to H) illustratethe various uses or methods of in-stalling and connecting either thehumidistat as described or this therm-ostat and, it will be noted that theymay be obtained to operate either onthe high voltage or the ordinary 16or 25 volt control system.

Automatic DefrostingIt may be necessary where an air

conditioning unit is used in connec-tion with a brine circulating systemor direct expanded refrigerant whosetemperature is below 25 degrees F.to provide some means of automaticdefrosting because with this low tem-perature refrigerant the moisture


0 FRIEZH/4 ,T/4

110V. OR H/5 0 R 115220 V

LOAD (LINE VOLTAGE MAXWATTS, THERMOSTAT 100,HUMIDISTAT 50)SOLENOID VALVE OR THERMALDAMPER MOTOR ETC

Fig. 4913Connections for humidistat or thermostat

to line at either 110 or 220 volts.


which is condensed out of the air asit passes over the surface freezes tosuch an extent that the air passagebetween the fins of the evaporatorsurface becomes clogged with ice.

In order to overcome this objec-tion, and where it is impossible toraise the refrigerant temperature, asmall electric air switch and magnetvalve may be installed as shown in


FRIEZ H/4 T/4 H/5 OR T/5

O

SUPPLY'LINE

LOAD (LINE

FRIEZ BOOSTER RELAYTYPE A/AA OR A/AB

Fig. 49CConnections for a humidistat or thermo-

stat with a relay for heavy loads.

FRIEZH/6 HUMIDISTAT

ORT/6 THERMOSTAT

113\ITRANS)

RUN THRUGROUND ASDESIRED

Fig. 49EConnections for a 1 -wire control by hum-idistat or thermostat by use of a ground

connection at 20 volts.

H/4 HUMIDISTAT & T/4 THERMOSTATCOMPLETE CIRCUIT AT LOWH5 HUMIDISTAT & T5 THERMOSTATCOMPLETE CIRCUIT AT HIGH

FRIEZH/4 H/5T/4 OR T/5

LOAD(LINE

VOLTAGE)

FRIEZ 2 -WIRE SYSTEM, RELAY -TRANSFORMER SET.TYPE A/BA OR A/BB

Fig. 49DConnections for humidistat or thermostat

with a relay and transformer.

FRIEZH/7 HUMIDISTAT

ORT/7 THERMOSTAT

C3

LOAD(LINE

VOLTAGE)

FRIEZ 3 -WIRE SYSTEM, HOLDINGCIRCUIT TYPE RELAY-TRANS.SETTYPE A/CA OR A/CB

Fig. 49FConnections for a 3 -wire system with

holding circuit relay and transformer.

4G A B C OF AIR CONDITIONING

111

FRIEZH/7 HUMIDISTAT

ORT/7 THERMOSTATHUMIDIFIER

(OR HEATER)LOAD. LINE VOLTAGE

DE -HUMIDIFIERFRIEZ DUAL) (OR COOLER)LOAD RELAY LOAD LINE VOLTAGETYPE A/DA, A/DB,OR A/DC

Fig. 49GConnections for a humidistat or thermo-

stat for heater and cooler control.

Fig. 49HConnections for a humidistat and thermo-stat with a "furnacestat" for complete

control.

Fig. 50 mounted inside the cabinetassembly with a vane in the path ofdelivered air from the unit. This aircurrent holds the switch closed en-ergizing the magnet valve, and keep-ing the refrigerant line open. Asfrost collects on the evaporator theamount of air passing through will bereduced because of the restrictions

AIR PASSINGTHRU COILSHOLDS AIRSWITCHCLOSED

AIR SWITCHCLOSED

NORMAL OPERATION

Fig. 50An air switch and magnet -valve for auto-matic defrosting.

and the vein of the air switch dropsautomatically opening the magnetvalve preventing further circulationof refrigerant. As the fan remainsin constant operation, the ice andfrost soon melt, air will pass throughthe surface, and the cycle beginsagain. Figure 51 shows this opera-tion during defrosting period. Whilethis device is illustrated on a floodedtype unit cooler, it may be adapted tocold storage rooms where the temper-ature does not go below 33 degreesand also may be used on an ordinarycentral plant air conditioning system.

The following electric diagrams Fig.52 show the application of an auto-matic defrosting air switch.

Where a year around air condi-tioning system is installed, similar tothe unit shown in Fig. 36 of the pre-ceding chapter, some method of con-trolling the temperature of the de-livery air during the heating seasonmust be provided. Where steam orhot water is available, a valve asshown in Fig. 53 is ordinarily usedto control the amount of steam orwater delivered to the heating sur-face. The valve mentioned is equip-ped with a long flexible tube D andthermostatic bulb A. The valve it-self is installed in the steam or hotwater line and the bulb A and B isinstalled in the air stream that isbeing delivered to the room or space


being conditioned. Section A of thebulb contains an expansible hydro-carbon oil which, on being heated,generates a pressure that is trans-mitted through copper tube D to tubeG which is the control element whereit moves a packless piston to operatethe valve K. The corrugated tube Bin the thermostatic bulb is controlledby the adjusting screw C and servessolely to vary the temperature atwhich the regulator valve functions.This is accomplished by changing theadjusting screw C and the relativelength of the corrugated tube B. Itwill be observed that if its length isincreased the oil in A has less spacefor expansion and the valve will beoperated at a lower temperature.

The control tube G contains cor-rugated tubing F which is exposed tothe expansive force of the liquid inA. This force is transmitted throughD and acts through piston H to movevalve stem I and open or close valveas desired. The spring J is opposedto the direction of expansion andtends to keep the valve K open sothat when the valve is exposed totemperatures above that for which itwas designed to operate, it will beclosed.

Ordinarily, this control valve should

AIR SWITCHOPEN

47

FROSTED COILSSTOP PASSAGE

OF AIR,OPENING AIR

SWITCH

DEFROSTING OPERATION

Fig. 51The action shown in Fig. 50 is illustratedduring the defrosting period of the cycle.be set to close the supply of heatwhen the delivery air temperature is65 degrees as at this temperaturethe air can be delivered to the con-ditioned space without causing thediscomforts of drafts in the area be-ing conditioned.

When it is found that this typevalve is not operating properly, andcannot be made to do so by turning

CONNECTION DIAGRAMS FOR AUTOMATIC DEFROSTING

RETURN LINE LINE; SUCTION LINE LINE SUCTION LINE LINE

-I,

,

I-131111111r

-Ili1 '-,_.,

VALVE

AIRSWITCH

-

--'4,-,;

,,x//,/'/,1

.._

VALVE 1/ i VALVES \\

AIRSWITCH

/ /

%

#er

,.

'

\AIR NI

SWITCH \IEINau

-,// ,//,'

Ri....k.

I1 11

SUPPLY LINE

CIRCULATEDREFRIGERANTS

CALCIUM CHLORIDE BRINEOR WATER

k I t4-1:7

LIQUID) EXPANSIONLINE VALVE

DRY EXPANSION.LIQUID INLET AT BOTTOMFOR CCIfz AND AT TOPFOR NH3 CH3CI3 SOz

LIQUID LINE

FLOODEDEXPANSION

AMMONIA (NH3)

Courtesy of Thermal Units Mfg. Co.Fig. 52. Connections for automatic defrosting. A-for circulated refrigerant; B-forflooded expansion; and C-for dry expansion systems.


Courtesy of Sareo Co.

Fig. 53A pilot thermostat used to prevent ex-tremely cold air from being delivered by

the air conditioner.

the adjustment screw C, the only rem-edy is complete replacement. In theabove statement, however, it is as-sumed that there is a definite sup-ply of steam or hot water availableat temperatures or pressures forwhich the control valve was specified.The control described and illustratedin Fig. 53 does not have any connec-tion with the temperature of the roomor space being conditioned and is usedmerely as a pilot thermostat to pre-vent the discharge of extremely coldair so it will be observed that a roomthermostat, additional heating surface

Courtesy of Wilbin Instrument Corp.

Fig. 54Control valve used with thermostat shownin Fig. 55 for supplying hot water or

steam to heater in Fig. 36.

and control valve will be necessary toautomatically maintain a comfortabletemperature in the conditioned spaceduring the cold weather. While thereare many such valves available onlyone will be illustrated and describedbelow. Figures 54 and 55 show thecontrol valve and thermostat that willautomatically supply steam or hotwater to the heating surface of Fig.36 in the preceding chapter. The ther-mostat is installed in the room beingconditioned and, as the temperaturedrops or raises, it opens or closes thevalve which is installed in the heat


supply line to the heating surface onthe fan side of the dehumidifying andcooling coil. The operation of thiscontrol device may easily be under-stood if reference be made to Fig.56 in which the thermostat is shownas No. 1 which has a chamber twocompletely filled with liquid. Arrangedin this chamber is the flexible bellows3 having its lowered end closed andthe upper end sealed to the top ofchamber. Attached to the inside ofthe bellows is the plunger 4 which ac-tuates the snap switch 5 which isnormally closed and opens with arising temperature. The valve 6 whichthe thermostat 1 controls is the re-verse acting type and isopened by the action of thethermostat and closed by thespring 7. Suspended belowvalve 6 is the heat motorand chamber 8 to which anelectric resistance heater 9is strapped. A flexible bel-lows 10 has the lower endclosed and the upper endsealed to the top of thepressure chamber 8. Thevalve operating plunger 11is fastened to the bottom ofthe bellows which is heldexpanded by the spring 12.When current is permittedto pass through, by theoperation of the thermostat,the heater 9 vaporizes aportion of the volatile fluidwith which chamber 8 ispartially filled. This buildsup a pressure in chamber 8which compresses bellows 10and moves the valve plunger11 upwards thus openingvalve 6. In the control boxmounted on the valve motoris a crank mechanism 13actuated by the travel ofthe plunger 11. This crankoperates two switches ar-ranged in the control box.Switch 14 is connected inseries with the thermostat1 and is normally closed sothat when the plunger 11is at the top of its strokethe crank 13 opens switch14 and interrupts the flowof current to the heater.

Chamber 8 immediately starts tocool assisted by the radiating finsand plunger 11 begins to travel down-wards. Switch 14 closes again so thatthe valve is held in the wide openposition as long as the thermostatswitch 5 remains closed. When thetemperature surrounding the thermo-stat 1 reaches a point at which it isset the plunger 4 opens switch 5 andinterrupts the current to resistor 9and the liquid in chamber 8 coolsrapidly and the plunger travels down-ward until valve 6 is closed. A slightfurther downward movement of theplunger causes crank 13 to closeswitch 15 and this switch is shunted

Courtesy of Wilbin Instrument Corp.

Fig. 55This thermostat is used with the valve in Fig. 54 tocontrol the flow of steam to the heating surface of the

unit shown in Fig. 36.


CLOSED

OPEN

..-- SPRING

/VALVE 0THERMOSTAT

"LAAmA_neihrinnnt

144444+1,144444444

ELECTRIC HEATER

Fig. 56

5.1114V4 WY

t,

110 V.A.C.

The connections for the parts of the con-trol described here.

across the thermostat connections andis normally opened. Closing switch15 puts current momentarily on theheat resistor causing a slight move-ment back and forth of the valveplunger without actually opening thevalves. This keeps pressure in cham-ber 8 so that it is instantly ready toopen the valve when the thermostatcalls for more heat. The above cycleis then repeated. This valve may beused on 110 volt A.C. or D.C. andtrouble will be experienced if thevoltage varies greatly beyond that forwhich it was designed and plainlymarked on the face of the controlbox. The presence of dirt or dust oncontact 5 may interfere with thesuccessful operation and may becleaned as described elsewhere in thisbook.

It is advisable to install a strainerin the supply line ahead of this valve.A strainer should also be installedin the line of valve (Fig. 53) to pre-vent scale or foreign material fromaccumulating on the valse seat.

FiltersOn a call for service on an air

conditioning system where filters areused almost invariably the first placeto look for trouble is the filters, re-gardless of the type used as mostpeople believe the place in which theylive or work is clean and that filtersare something that merely go to makeup an air conditioning system theydo not bother to check the filters orclean them. While it is true that asystem will operate without filters,one of the greatest benefits derivedfrom air conditioning would be sacri-ficed if they were removed or notkept in proper order.

Starters and SwitchesOn the larger type air conditioning

systems, where motors of 5 H.P. orover are used, thete is a general re-quirement by the local power com-panies that a reduced voltage start-ing control be used, so that when thecondensing unit starts only about 70per cent of the normal starting cur-rent will be drawn. There will alsobe a corresponding reduction in r.p.m.of the motor. This is accomplishedby the use of a telechron time limitswitch built into the automatic start-ing compensator and, after about 10seconds of reduced voltage operation,the action of the time switch closesthe main line contacts allowing thecondenser motor to quickly pick upspeed and full load operation. Thesecompensators are equipped with over-load heaters that will automaticallyinterrupt the main supply in event ofa continual overload and, after cool-ing off, the sequence can be re-started after pushing the reset buttonalthough an inspection should be madeto determine the cause of the over-load to prevent further interruptionswhich are most likely to occur at themost inopportune times.

The small magnetic switches asused to start fans etc., are alsoequipped with overload heater unitsbut do not have the timing mechanismor the reduced starting voltage fea-ture.

The proper size overload heatercoil is ordinarily indicated on a chartinside the cover of the control and,


it is advisable to check the manufac-turer's recommendation against thesize of the coil used for the particu-lar job.

Every effort has been made to havethe explanation of the various ser-vice problems complete, and the con-trol schemes adequately described.However, it must be obvious that a

small book cannot contain informa-tion covering all possible combinationsof heating and cooling equipment.We feel that with the informationcontained herein thoroughly assimi-lated, it will not be difficult for thereader to obtain and understandmore advanced or complete data, ashe may require it.

CHAPTER 6

Ventilation Data For Air Conditioning(Figuring the Infiltration and Heat Load to suit given conditions)

TIRACTICALLY all rooms and build -r ings in which men live have a cer-tain amount of natural ventilation,termed infiltration. Air seeps throughcracks in the floors, walls, aroundwindows and door frames and amountsto a surprising number of cubic feetper hour. Of course, the majorityof air entering a room or structurefinds its entrance via the cracksaround doors and windows, for somespace is necessary for windows anddoors to open easily.

Tables of infiltration intended foruse with air conditioning apparatusinvolve recognition of the fact thatconditioned rooms are maintained ata lower pressure than the outside con-ditions and that the air leakage isnaturally greater. The most practicalmethod of estimating infiltration is tobase it upon the cubical contents ofthe room. This is fundamentallywrong, but until accurate data areavailable it will constitute the onlymeans of arriving at a proper esti-mate.

The velocity of the air has a greatdeal to do with the amount of airwhich enters the rooms or structures,for during certain seasons of the yearthe velocity of the air will be highand more air will naturally passthrough the cracks than in other sea-sons.

For the average home, office andsmall shop where only a limited num-ber of persons gather, natural venti-lation is generally satisfactory.

The following table gives thechanges which may be expected fornormal construction. The structure

CHART 5Infiltration

Exposure ofroom

No. of changesper hour

One sideTwo sidesThree sidesFour sidesInside room

to 134 to 11/21 to 21 to 2

1/2 to %52

should be examined so that someidea of infiltration may be deter-mined.

Heating engineers have made avail-able considerable data given the mag-nitude of air leakage through wallsand windows, but it should be notedthat such infiltration tests were ap-plicable to rooms not having a me-chanical air supply, so that this datacannot be used without modification.

At the present time the most satis-factory method for estimating infil-tration appears to be based on thesize of the room or space to be con-ditioned. While this is fundamental-ly wrong, since the true leakage islargely determined by the size ofcracks about doors, windows and theporosity of the walls, besides thepressure differential, no entirely sat-isfactory data have been advanced.

Where infiltration data are attemptedby the estimation of infiltrationthrough cracks the results are usuallyvalueless and less accurate than theestimate based on the cubic feet ex-posure basis.

The following may be used as aguide for ordinarily tight structuresof average construction:

CHART 6Natural Air Changes for Rooms Under

Different Exposures-Per HourExposure

InsideNo windows or

outside doors1 side2 sides3 sides4 sides

No. of Changes Per Hr.1/2

3/4

11/21342

Another fault found with improp-erly installed apparatus or equipmentcarelessly operated, is that drafts aredetected. In drying and processingwork rapid air movement is impera-tive, but where human comfort isconcerned the conditioned air must be

ABC OF AIR

evenly and thoroughly distributedwithout sign of draft. In many casesthe operators shut down certain ofthe ducts, which increases the pres-sure at all of the open distributorsand results in noticeable drafts.

Estimating Infiltration LoadIf it is desirable to estimate the

sensible heat load of a room it maybe computed by use of the followingsimple formula:

H=V x (t. -t)n x 3360

whereH -Sensible heat in B.T.U. per

minute from infiltration.V -Volume of room in cubic feet.t. -Outdoor dry bulb temperature

assumption.t -Indoor dry bulb temperature.n -Number of hours required to

effect one complete change.Latent Heat Load of Infiltration

If the latent heat load is to beestimated it can be determined byuse of the following formula:

Hl -Ht -H.where

HI. -Latent heat load.Ht -Total heat load.H, -Total sensible heat load.

Refrigeration Demand for Cooling Airand Moisture Condition

Chart 7 which follows may be usedfor the calculation of the refrigera-tion demand requiring for the cool-ing of air and condensation of excessmoisture.

In the table given previously a

CONDITIONING 53

number of air changes were listed,depending upon the exposure. Forvery excellent construction the mini-mum infiltration figure may be em-ployed and for poor or old construc-tion the greater or maximum factorshould be used. For ordinary workthe table given herewith should beemployed. The estimator is cautionedto exercise judgment in employingany infiltration estimate, for a re-frigeration unit costs considerablymore than a heating unit and an un-der -estimated or over -estimated jobwill represent a costly error.

The previous table may be usedfor estimating the cooling and con-densation load by using the numberof changes of the room in accordancewith its exposure and multiplying thisby the volume of the room and thenmultiplying by the factor given inChart 7, which gives the refrigeratingeffect required per cubic foot. Or,taking the cubic feet required perhour and multiplying by the factorin the Chart provides a very con-venient method of determining thetotal load for any room.

Maintainance of HumidityMoist or properly humidified air

serves to prevent colds, bronchitis andpneumonia, so far as a health safe-guard is concerned. Further, paper,wood, plaster, rugs and cloth aremaintained with a proper moisturebalance, so that such materials arekept in proper condition. Dehydra-tion increases the fragility of all pro-ducts and in many cases causes achange in texture and color.

Under ordinary conditions, whenthe outdoor temperature makes it

CHART 7Refrigeration Load For Air Cooling

Temperature Reduction, °F.RelativeHumidity

% 5 6 7 8 9 10 11 12 13 14 15 16 17 1840 .045 .085 .120 .155 .195 .235 .280 .320 .365 .415 .460 .510 .560 .61545 .123 .165 .205 .245 .290 .335 .383 .428 .482 .530 .580 .640 .695 .75750 .200 .245 .290 .335 .385 .435 .485 :535 .590 .645 .700 .765 .930 .90055 .280 .352 .377 .425 .480 .528 .585 :642 .703 .765 .825 .895 .965 1.03860 .360 .410 .465 .515 .575 .630 .685 .750 .815 .885 .950 1.025 1.100 1.17565 .438 .488 .543 .598 .663 .720 .783 .850 .918 .990 1.170 1.155 1.235 1.31370 .515 .565 .620 .680 .745 .810 .875 .950 1.020 1.905 1.175 1.260 1.350 1.45075 .587 .648 .703 .763 .833 .895 .968 1.055 1.125 1.202 1.295 1.390 1.485 1.580The above load, expressed in B.T.0 per Cubic Foot of Air cooled, is the refrigerationdemand for air cooling and moisture condensation.


imperative to use the heating system,materials in the home and office, giveup their moisture to the air. This isshown by the condensation on win-dows during the frosty days of theheating season. During the heatingseason, rugs, plaster, and wood giveup a certain portion of their moisturecontent, for in building providedsolely with heating means, a slowacting dry kiln effect is created.

Where humidification apparatus isstarted toward the end of the heatingseason it will be observed that it isdifficult to maintain the proper hum-idity, for the wood, plaster, paper,rugs, concrete, etc., begin to drink inthe moisture lost during the dehydrat-ing period. Just as soon as the hum-idity is raised a few per cent, the ma-terials take up some more. Eventual-ly they arrive at the proper balance,so that they neither take up or giveoff moisture.

RegainThe absorption, and especially the

reabsportion of moisture by materialsis known as the "moisture regain,"This is of such importance to themanufacturers of certain productsthat a great deal of experimentalwork and study has been devoted toit. Regain curves have been devel-oped, especially in the rayon, silk,wool, paper, and cotton trades.

If, for instance, a manufacturer ofwoolen materials, placed the air con-ditioning system in operation late inthe winter, so that the relative hum-idity was raised from 40 to 50 percent, the wool would absorb 1.7 percent of its bone dry weight in addi-tional moisture. Paper, under similarconditions would absorb about 1.3per cent, while cotton would absorbabout 0.8 per cent in additionalmoisture. In production these addi-tional weights represent a consider-able loss if the materials are soldwithout regain.

Condensation on WindowsWhere the proper indoor relative

humidity is maintained in the wintermonths, condensation or frosting oc-curs on the windows. Windows that"steam up" are objected to, especiallyin homes, offices and factories, fornatural light is prevented from en-

tering and the windows are left spot-ted or streaked when dried. If thecondensation occurs in appreciableamounts over extended periods, itwill destroy the finish and create rustor rot. Usually the putty suffers andmay require attention every season.

Of course, condensation can beprevented by maintaining a lowerrelative humidity, but this is one ofthe objectives of the air conditioningsystem and in manufacturing formsone of the prime essentials in the pro-duction of the finished materials. Inhomes and offices, health and com-fort, require the higher relative hum-idity. Condensation, and incidentlythe load on the system can be cutdown or eliminated by the use ofdouble or triple windows.

The formation of moisture on win-dows is the same manifestation ofthe "dew point" mentioned before.

In the case of a single glass win-dow, the condensation appears likedrops of dew, just as it does on apitcher of ice water. If however, theoutdoor temperature is below thefreezing point, the condensation willfreeze and result in a frosted condi-tion.

Double and Triple WindowsDouble glass for windows, with an

air space between the panes, will re-sult in the inner glass being main-tained at a higher surface tempera-ture than where a single glass is em-ployed, so that no condensation willoccur under normal conditions, Inindustrial applications where highhumidities must be maintained tripleglass is used.

Manufacturers of store displaycases and counters have employeddouble and triple glass for a numberof years, realizing that the displaymust not be hindered by condensation.These manufacturers early learnedthat the space between the panesmust be sealed with an air tight andwaterproof material, otherwise mois-ture would enter and precipitation oc-cur in time.

The University of Illinois conducteda series of tests and evolved the chartgiven below, which lists the tempera-tures of the glass at which condensa-tion will take place. Inasmuch as the

ABC OF AIR

air within the air conditioned roomis usually in considerable motion, theglass surface is slightly warmed bythe warmed air flowing over it, sothat the temperatures and humiditiesgiven in the Chart can be assumed tobe the critical points, beyond whichcondensation will occur.

CHART 8

Percentage of Relative Humidity atwhich condensation forms.

Single Windows

OutdoorTempera-

ture

Temp. ofInner Surface

of glass

Relative humidityat which conden-sation forms on

glass-10 13 12

0 20 1810 28 2320 34 3030 42 3840 48 4850 55 6460 62 8070 69 99

Double Windows

OutdoorTempera-

ture

Temp. ofInner Surface

of glass

Relative Humidityat which Conden-sation forms on

glass-10 46 45

0 49 4910 52 5420 54 6030 57 6840 60 7550 63 8360 66 9170 69 99

Glass Door and Window CoefficientsThe values of K, expressed in B.

T.U. per hour per degree tempera-ture difference per square foot, aregiven below for all glass doors andwindows not exposed to the directrays of the sun.

CHART 9

Unexposed Windows and DoorsThickness of glass K

1

234

1.13.46.29.21

CONDITIONING 55

Exposed Windows and DoorsWhere windows have a south-east

or western exposure, they should beprovided with awnings or venetianblinds. Otherwise the direct rays ofthe sun will permit a large amount ofheat to enter the conditioned space-ranging from 20 B.T.U. per square ft.to 190 B.T.U. per square ft., besidesthe normal transfer of heat throughthe glass due to temperature differ-ences between the inside and outside.

Where awnings are used over win-dows and doors, the standard glasscoefficient as given in Chart 9 shouldbe used (which is for each degreedifference per square ft. of surface)and the result must be doubled orChart 10 may be used to determinethe amount that would pass throughwithout awnings, and reduce the totalamount that would pass through with-out awnings and reduce the totalamount by 75 per cent for 1st floorand 85 per cent for other than 1stfloor levels.

When calculating the heat load dueto solar radiation, it should be keptin mind that the sun's rays do notstrike the east, south and west win-dows at the same time. However,some means must be found to de-termine which side has the greatestload. Also determination must bemade as to the possibility of theseloads occurring at the peak load per-iod (as at 12 o'clock noon in a rest-aurant or 3 p.m. in an office).

To aid in selecting the load andtime of day, Table 10 has been de-veloped. This is by no means com-plete, as this particular factor in-volves pages of data from experi-ments for both windows and doors.

CHART 10Exposed Windows

ExposureB.T.U. Trans-

mitted perSq. Ft.

Time ofDay

Horizon -tal Sur-

faceEast 165 9 a.m. 180S. East 140 9 a.m. 180South 20 3 p.m. 180S. West 140 3 p.m. 180West 165 3 p.m. 180N. West 70 3 p.m. 180

This chart is given only to Illustratethe magnitude of sun effect and while


the B.T.U. transmitted for horizontalsurface is given as 180, it so hap-pens that for these two time settings,the B.T.U. figures are the same. Ac-tually, this factor varies from 35 at6 a.m. to 255 at 12 noon, then downto 20 at 6 p.m. for the locations at40 degrees north latitude, only.

From the above, it can be seen thatthis part of air conditioning heat gaincalculation is a study in itself anddoes not come within the scope ofthis book. It will, however, show thereader some of the intricate problemsencountered in scientifically figuringthe requirements for cooling and heat-ing for any given building.

In many cases awnings cannot beemployed due to the design of thebuilding. In such cases light coloredshades and other light impervious ma-terials may be used to cut down theeffect of solar radiation. Whereshades or screens are employed a re-duction of 50 per cent of the heatload of exposed glass areas may beused.

CHART 11

Solid Wooden Doors

Nominal thicknessinches

K

1 0.6911/4 0.591i/2 0.5212/4 0.51

0.4621/4 0.422Y2 0.3821Y4 0.353 0.33

The above coefficients are based ona wind exposure of 15 miles per hourand on 1 degree f. difference betweenthe outside and inside temperatures.

Ordinary office and residentialdoors consisting of thin panels orprovided with glass, should be esti-mated as having a coefficient of K=0.9 per sq. ft. per degree of tempera-ture difference per hour.

Motor Heats

All motors generate heat and whereinstalled or contemplated in air con-ditioned rooms must be included inestimating the total heat load.

CHART 12

Motor Heat Load

H. P. Motor B. T. U. Generatedper hour

1/20 4251/10 6801/8 7501/6 8171/4 10201/3 12901/2 18703/4 27501 3410

Electric Appliances

Electric lights dissipate approxi-mately 3.42 B.T.U. per hour for everywatt consumed and the heat load inevery room is easily determined by asurvey of the lamp sizes.

Many rooms only make use ofelectric lights on dark days. In suchcases the reduction in solar radiationcompensates for the heat generatedby the electric lights.

Electric toasters, waffle irons, hotplates and urns also dissipate con-siderable heat. In estimating the heatevolved through the use of these de-vices the watts ratings on each ofthe units should be noted and a studymade of the length of time each isemployed. Most of these devices willonly be in constant use during therush or peak load and may be usedbut little during the remainder of theday.

CHART 14

Heat Dissipated by Human Beings

Activity B.T.U. per hourSeated, at rest 400Standing, at rest 430Seated, light work 500Standing, light work 575Moderate work 800Heavy work 1,500Dancing 1,000Musician 1,000Carpenter 850Tailor 500Walking, 2 m.p.h. 700Walking, 3 mp.h. 1,050Walking, 4 m.p.h. 1,400Walking, 5 m.p.h. 2,500

ABCOF AIR CONDITIONING 57

Gas Heated DevicesMany of the heating devices used

in restaurant work, for example,make use of gas as a source of heat.There is a material difference whensuch devices are provided with ahood and are ventilated.

The following table refers to gasheated percolators. A good rule ofthumb to follow on gas heated appli-ances is to base the heat load on thenumber of cubic feet of gas burned.

For natural gas allow 1,000 B.T.U.per cubic foot and about 500 B.T.U.for manufactured gas. This allow-ance can be made for all gas heateddevices, including percolatox; waterheaters and steam plates. It is im-portant to obtain the hours of opera-tion, for in many cases where morethan one device of each kind may beused during the rush hours, only onemay be used during the remainder ofthe day.

CHAPTER 7

Definitions Used In Air Conditioning

THROUGHOUT this book, certainterms are used and are not ex-

plained in detail. We suggest thatreference be made to the followingpages for such information,

Air ConditioningThe science of controlling the

temperature, humidity, motion andcleanliness of the air, within an en-closure, to maintain conditions mostsuitable for health, comfort or com-mercial process work.

Atmospheric PressureAtmospheric pressure equals 14.7

lbs. per sq. in. at sea level, or 30 ins.of mercury which means that the airis exerting a pressure of 14.7 lbs.per sq. in. This will balance a col-umn of mercury 30 ins. high, pro-vided the vacuum is first created inthe top of the mercury tube. Toprove this, take a common tin canwith a small amount of water in it,and apply heat until steam is gen-erated. This will force the existingair out of the can, and if the heat isremoved and the can sealed, the steamwill soon condense into water, cre-ating a vacuum in the can. It is atthis point that we can prove the pres-ence of air pressure, by the fact thatthe can will collapse from the pres-sure of the surrounding air.

Barometric PressureSame as atmospheric pressure.B.T.U. (British Thermal Units)

Since heat is not a substance, itcannot be measured in pounds orpints, but, like energy, it may bemeasured by the work it performs.Therefore, a B.T.U. is a measure-ment of the amount of heat requiredto raise the temperature of 1 poundof water from 62 to 63 degrees. For

58

all practical purposes, the sameamount of heat will raise the tem-perature of 1 pound of water from180 to 181 degrees. Actually it takesslightly more heat to do this, fortemperature below 62 degrees re-quire a slightly smaller amount ofheat. Therefore, it is customary touse as a basis, one B.T.U. will raisethe temperature of one pound ofwater one degree F. and other sub-stances are raised a varying amountby one heat unit. For instance 4.2pounds, or approximately 55 cubicfeet, can be raised one degree by theapplication of one B.T.U.

Dew PointThe temperature at which moisture

will be condensed out of the air. Ifa mixture of air and humidity iscooled, it will ultimately reach apoint where it can no longer hold theamount of moisture present, and anyfurther lowering of the temperaturewill cause the moisture to be con-densed out. In air conditioning sys-tems, the cooling surface is at a tem-perature below the Dew point tem-perature of the air, so that air com-ing in contact with this surface iscooled to a temperature below thesaturation point, and moisture iscondensed out of the air, and findsits way to the drain pipe.

Dry BulbThe reading obtained from an or-

dinary thermometer. See "SensibleHeat."

FahrenheitMethod of calibrating or marking

off a mercury column to register thetemperature. This was named afterits inventor. Our ordinary thermom-eters are marked off on the Fahren-heit scale.


Grains of MoistureMoisture in the air is ordinarily

stated as being so many grains. Thismeans the weight of water vapor orhumidity in the air, at the conditionsmentioned. It requires 7,000 grainsto weigh 1 lb.

Heat GainThat heat which is transmitted

through the walls of a structure fromthe outside where the temperature ishigh to the conditioned space. Heatgain also applies to such heat generat-ing devices as electrical appliances,steam tables, human beings, etc.

Heat LossThe transfer of heat from inside an

enclosure to the surrounding outsideair. Heat always flows from an areaof high temperature to a low tem-perature area.

HumidityThis comes from the Latin word

humidus, meaning moist. Air at allconditions contains a certain amountof moisture, which is really steam orwater vapor. The presence of thismoisture in the air affects it in threeways. First, it increases its capacityfor heat. Second, it decreases itsweight per cubic ft. and makes itmore buoyant. Third, it reduces theamount of oxygen contained in acubic ft., thus imparting its value forpurposes of respiration. When theatmosphere contains the maximumquantity of steam or humidity thatcan exist at the temperature, the airis said to be saturated. Should theair temperature be lowered, moisturewill be condensed out of the air.

Latent HeatThe amount of heat required to

change a body or substance from onecondition to another without chang-ing its temperature. For example itrequires 144 B.T.U. to melt a poundof ice at 32 degrees, to water at thesame temperature. The pound ofwater so produced may be heated tothe boiling point, 212, by the addi-tion of 180 B.T.U., sensible heat. Tochange the water at 212 into steamat the same temperature requires971.7 B.T.U., latent heat which doesnot change the temperature but mere-

ly evaporates it to vapor steam. Steamso generated is mixed with the airand does not register on an ordinarythermometer.

RefrigerationThe process of cooling which is

really the removal of heat. It is theprocess by which the temperature ofa given space or substance is loweredbelow that of the atmosphere or sur-rounding materials. It is accomplishedby transferring the heat from onesubstance to another. When appliedto air conditioning, refrigeration gen-erally means the cooling of air orwater.

Relative HumidityThe amount of moisture that is in

the air at the condition given, ascompared to the amount the air couldhold if saturated at the same tem-perature. For example, if the relativehumidity is 50 per cent and the tem-perature if 80 degrees, the air is car-rying only half as much moisture asit is possible for it to carry. The airdoes not really hold moisture, or"carry" it. The moisture exists in avacuum space as well as in the at-mosphere.

Sensible HeatThe intensity, rather than the

amount-the more sensible heat abody possesses, the hotter it is, andthe more sensible heat that is takenaway from it, the colder it is. Thisis indicated by the word temperature.So if we raise the temperature, weincrease the sensible heat. It can,therefore, be recorded on an ordin-ary thermometer.

Sling PsychrometerAn instrument that has an ordin-

ary thermometer and a wet bulbthermometer attached to it, as illus-strated in Fig. 57. It is used to ob-tain the wet bulb temperature.

Specific HeatAll substances require a certain

amount of heat to change their tem-perature, and with the exception ofhydrogen, they require less heat toraise a pound one degree than doeswater. Therefore, the specific heatof water is taken as 1, while thespecific heat of air is .24 and mer-


Fig. 57This combined unit of wet and dry bulbthermometers is used in calculating air

conditioning needs and conditions.

cury is .033, which means that 1B.T.U. will raise the temperature of4.2 pounds of air one degree, or 30pounds of mercury 1 degree. Vari-our substances have definite specificheats and are always compared towater.

Ton of RefrigerationThe amount of heat which must be

abstracted from 2,000 pounds ofwater at 32 degrees F. to convert itinto ice at the same temperature, and,since the latent heat of the ice is 144B.T.U. per pound, the ton is equiva-lent to 144 times 2,000 pounds, or288,000 B.T.U. As an element oftime is considered for this absorp-tion, the 288,000 B.T.U. divided by24 hours gives a B.T.U. rating of12,000 per hour. A rated ton re-frigerant machine will absorb 12,000B.T.U. in one hour, or make one tonof ice in 24 hours.

Total HeatThe amount of sensible heat in the

air together with the amount oflatent heat at any given condition.

VaporA substance that at ordinary tem-

peratures is a liquid or a solid butwhen heat is applied, or the pressuresurrounding it is lowered, becomes agas. For example, mercury may bein all three conditions. At ordinarytemperatures, mercury is a liquid, at40 degrees below zero it becomes asolid by freezing, and it can be vap-orized to a gas at 600 degrees F.above zero.

VelocityThe speed at which air is moved

through a duct system. For example,a duct 12 ins. on each side has anarea of one sq. ft. or 144 sq. ins.,and air passing through at the rateof 1,000 ft. per minute (F.P.M.)would deliver 1,000 cubic ft. in aminute, expressed as cubic ft. perminute (C.F.M.). From anotherangle, assume the same 12 in. ductto be 1,000 ft. long. If we place asquare piston at one end and push itcompletely through in one minute, theair in the duct would travel at avelocity of 1,000 F.P.M. The volumeof the duct being 1,000 cubic feet, the


delivery would then be 1,000 cubicfeet in one minute. If we had aduct 24 ins. wide and 12 ins. high, ordeep, the area will be 2 sq. ft. Itis required to pass 6,000 cubic feet ofair through in one minute. The ac-tual air velocity inside the duct wouldthen be 3,000 F.P.M. If the duct isincreased to 24 ins. square, the sameamount of air could be delivered at avelocity of 1,500 F.P.M.

Volatile

Easily vaporized liquid at normalconditions, as associated with air con-ditioning or refrigeration.

VolumeSee velocity.

VentilationThe continuous removal of foul air

from a room, used for either habita-tion or manufacturing purposes, and

the constant introduction of fresh airto take its place.

Wet BulbThe reading obtained from an or-

dinary thermometer that has a mer-cury bulb enclosed in a moist clothsack, and whirled through the air for15 or 20 seconds, holding it awayfrom the influence of any externalheat. The final temperature will belower than a dry bulb thermometerif the air is not completely saturatedbecause moisture will be evaporatedout of the cloth and absorb heat fromthe mercury in the thermometer. Inthe event that the air is already satu-rated, no moisture will be evaporatedfrom the cloth and this reading wouldthen be the same as an ordinary drybulb thermometer. The drier the airis when the reading is taken, thegreater will be the depression of thewet bulb thermometer.

CHAPTER 8

Glossary of Air Conditioning Books

Alt, Harold L. Air conditioning sim-plified. 1934 Domestic Engineer-ing Co., Chicago, Ill.

Air Conditioning Engineers Hand-book. 1932.Contents:

1 What is Air Conditioningby E. V. Hill.

2 The Psychrometric Chart byE. V. Hill.

3 Cooling and Air Condi-tioning for Comfort by W.Goodman.

4 Notes on Refrigeration by0. W. Armspach.

5 How to Use the Anemo-meter by Professor LynnB. Davies.

6 The Pilot Tube and Mano-meter by P. J. Marschall.

7 Heating, Ventilating andA i r Conditioning, t h eHealthful Home.

Heating and Piping Contractors Na-tional Association. Air Condi-tioning for Heating Contractors;a series of lessons prepared andpublished under the auspices ofthe Committee on air condition-ing and edited by S. Lewis Land,1934. Heating and Piping Con-tractors Assoc., N. Y.

Hill, E. Vernon. Aerology for ama-teurs and others. 1930. Aerolo-gist Pub. Co., Chicago, Ill.

Lewis, Samuel R. Air Conditioningfor Comfort. 1932. EngineeringPublications. Chicago, Ill.

Mellish, A. J. First steps in air con-ditioning. 1933. Scott Publish-ing Co., N. Y.

Moyer, J. A. Air conditioning. 1933.McGraw-Hill Book Co., N. Y.

Official Air Conditioning Manual. Vol.1. Gernsback Publications, Inc.,N. Y.

Parks -Cramer Co. Air conditioningin printing and lithographicplants. Bulletin 1029. 1929.

62

Parks -Cramer Co., Boston, Mass.Haysbrand, E. Drying by means of

air and steam, 3 ed. 1924.

U. S. GOVERNMENT DOCUMENTS

Treasury DepartmentU. S. Public Health Service

Public Health Bulletin No. 207, July1933-Health of workers in atextile plant by R. H. Britten,J. J. Bloomfield and Jennie C.Goddard.

War DepartmentArmy Regulation No. 30-1660-Re-

frigeration. 1930.

PAMPHLETS

Hoffman, J. D. Insulation for HouseConstruction. Extension seriesNo. 31. Engineering BulletinPurdue University. July 1933.Engineering Extension Depart-ment. Lafayette, Indiana.

Poison, J. A. & Lowther, J. G. TheFlow of Air Through CircularOrifices in Thin Plates. Bulle-tin No. 240. University of Illi-nois Bulletin. January 29, 1932.Engineering Experiment Station.Univ. of Illinois, Urbana, Illi-nois.

Air Conditions and the Comfort ofWorkers. Industrial Health Ser-ies No. 5. Metropolitan Life In-surance Co., N. Y.

First Air -Conditioned Railroad Trainsintroduced by the Baltimore andOhio Railroad Company.

Marketing Electric Air Conditioning.National Electric Light Assoc.,420 Lexington Ave., N. Y. C.

Sales Manual for the Man Who Sells.Timken Airlux Humidifier.

U. S. GOVERNMENT DOCUMENTS

Department of CommerceBureau of the Census


Census of Manufactures, 1931,preliminary reports. Heating andcooking equipment (other thanelectrical).Machinery.Refrigerators a n d refrigeratorcabinets.

Bureau of Foreign nad Domestic Com-merceBibliography of information onair conditioning. 3rd ed., May -1934.

Bureau of StandardsElectric and gas refrigerators.(Letter circular 412.) 1934.1930.Heat transfer through buildingwalls. (Standards research pa-per 291.)Thermal insulation of buildings.(Circular 376.) 1929.

National Committee on Wood Utiliza-tionHouse insulation-its economiesand application. 1931.How to judge a house. 1931.Department of the Interior

Department of LaborMonthly Labor Review, April1932, p. 813-Effects of differ-ent temperatures on health andefficiency.

Navy DepartmentBureau of Engineering

Refrigerating plants. Instructionin operation, care, and repair ofrefrigerating plants. (Reprint ofChap. 17 of the Manual of En-gineering Instructions.) 1926.

U. S. PUBLIC HEALTH SERVICE

Public Health Report, March 7, 1919.Standards for measuring the ef-ficiency of exhaust systems inpolishing shops by C. E. A. Wins-low, L. Greenburg, and H. C.Angermyer.

Public Health Report, July 28, 1922.Efficiency of various kinds ofventilating ducts by C. E. A.Winslow and Leonard Greenburg.

Public Health Report, Oct. 18, 1929.A study of the efficiency of dust -removal systems in granite -cut-ting plants by J. J. Bloomfield.

REFRIGERATION, VENTILATION,ETC.

Althouse, A. D. & Trunquist, C. H.Modern Electric and Gas Refrig-eration. 1933. Goodheart & Wil-cox Co., Chicago.

American Blower Corporation, AirConditioning and Engineering, byEngineering Staff, Detroit, Mich-igan.

American Society of Heating andVentilating Engineers. 1934. An-nual Guide. 51 Madison Ave.,N. Y. C.

Brett, T. J. Engineer - CustodianManual. 1934. American Tech-nical Society, Chicago, Ill.

Carrier, Wilis H. Fan Engineering.Buffalo Forge Co., Buffalo, N. Y.1933.

Hull, H. B. Household Refrigera-tion. 1933. Nickerson & Collins,435 N. Waller Ave., Chicago, Ill.(4th ed.)

Macintyre, H. J. Handbook of Re-frigeration. 1928. Wiley, N. Y.

Motz, W. H. Principles of Refriger-ation. 1932. Nickerson & Col-lins, 435 N. Waller Ave., Chi-cago Ill.

Moyer, J. A. & Frittz, R. U. Re-frigeration. 2nd ed. 1933. Mc-Graw-Hill, N. Y.

Official Refrigeration Service Manual,Vol. 1 and 2, Gernsback Publica-tions, Inc., New York.

Refrigerating Data Book and Cata-log. 1933. American Society ofRefrigerating Engineers. 37 West39th St., N. Y. C.

Williams, Hal. Mechanical Refriger-ation. 4th ed. 1933.

Institute of Mechanical Heating andAir Conditioning. EngineeringBulletins.

Refrigeration directory and marketdata book. 1934. Business NewsPublishing Co., 5229 Cass Ave.,Detroit, Mich.


PERIODICALS

Aerologist.Domestic Engineering.Heating and Ventilating.Heating, Piping and Air Condition- Industrial Arts Index (index to tech-

ing.

Heating, Piping and Air ConditioningContractors National Association.Official Bulletin.

Sheet Metal Worker.

nical periodicals).

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THE idea of electricians, radio ser-vice men and other mechanicallyinclined men, servicing refrigeration

units is self-evident and the thoughthas occurred to perhaps untold thou-sands ever since electric refrigerationstarted. Yet nothing was done, becausethe average service man knows littleor nothing about refrigeration. Com-pared with servicing a radio set or wir-ing a home for electricity, the servicingof a refrigerator is absurdly simple,once you get the hang of it.

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Introduction to the Refrigeration Servicing BusinessHistory of RefrigerationFundamentals of RefrigerationDescription of All Known Types of RefrigerationService Tools and Shop ,EquipmentMotorsTiouble ShootingUnit Parts, Valves and Automatic EquipmentMakes anti Specifications of UnitsManufacturers of CabinetsRefrigerants and Automatic Equipment

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List of Contents in the Second Volume of the"Official Refrigeration Service Manual"

History Evaporators and Cooling Units Servicing Expansion ValveFood Preservation SystemsService Tools. Equipment andTheory and Fundamental Laws Tool Manipulation Servicing Thermostatic ValveMethods of Refrigeration SystemsRefrigerants, Lubricants and Commercial Unit Specifications Servicing Restrictor andBrines and Service Capillary Tube SystemsHand inn. Testing and Storage Household Unit Specifications Charging Systems withof Refrigerants and Service RefrigerantCompression Systems of

Refrigeration Servicing Refrigeration Electrical Service; Motors.ligui i Throttle Devices and Apparatus Fuses. Hookups

Valves Servicing Low Side Float Service KinkaRefrigerating Systems Valve SystemsElectric Control DevicesCompressors, Types. Seals. Servicing High Side Float

Valves. Capacities, Service Valve Systems

Estimating Refrigeration Loads,Coll and Machine Sizes

Miscellaneous Data

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ABCE AIR - americanradiohistory.com · ABCE AIR cosVITION/4,6 An accurate simplified, tech-nical review of the fundamen-tals of this latest branch of engineering, including servi-cing