00 Customer Service · 2016-10-04 · The constant arc keeps the flame burning even if it is belching smoke, soot, and unburned oil. With interrupted ignition, a poor flame goes out

00 Customer Service

Ignition SystemsChapter 9

Chapter 9—Ignition Systems 9-3

IntroductionThe completely automatic electric

ignition system is an important part ofoilburner technology. There are twodifferent main components used forignition systems on oilburners: the ignitiontransformer and the solid state ignitor.

The ignition transformer is a step-uptransformer using copper windings aroundan iron core. It steps up the incomingvoltage of 120 volts to an output voltage of10,000 volts. This is accomplished by a 90to 1 primary to secondary winding ratioaround the iron core.

The solid state ignitor utilizes electron-ics to produce an output voltage of any-

where from 14,000 to 20,000 volts peak.

Both components supply this highvoltage electricity to the electrodes. Aspark jumps from the tip of one electrode tothe tip of the other. The electrical arc thenignites the atomized oil.

Let’s examine the various componentsof the ignition system shown in Figure 9-1.

The voltage travels from the transformeror ignitor through the ignition cables, bussbars, or spring clips to the electrodes whichare held in place by the ceramic insulators(porcelains). When it reaches the tips of theelectrodes it jumps the gap between them,creating our spark.

Figure 9-1:Ignition systemcomponents

IgnitionCable

ElectrodeBracket

IgnitionElectrode

CeramicInsulator

IgnitionTransformer

Chapter 9Ignition Systems

9-4 Ignition Systems

Oilburners use one of two types ofelectric ignition control systems:

Interrupted ignition: the ignition sparkremains on for only a short time at thebeginning of each burner operating cycle,and is turned off once flame is established.

Intermittent ignition: the spark thatignites the oil vapors remains on as long asthe burner runs. Intermittent ignition usedto be called “constant ignition,” and somemanufacturers call intermittent ignition“constant duty ignition.”

Interrupted ignitionis better

Over time, the industry has switchedbetween interrupted and intermittentignition. Interrupted ignition has provensuperior because having the spark onduring the entire burn cycle detracts fromperformance for several reasons:

• Electrode life is significantly reduced.

• Ignitor or ignition transformer life issignificantly reduced.

• Electrical consumption is increaseddramatically.

• Operational noise in increaseddramatically.

• Intermittent ignition may hidecombustion problems that can cause soot-plugged boilers and oil running saturation.The constant arc keeps the flame burningeven if it is belching smoke, soot, andunburned oil. With interrupted ignition, apoor flame goes out and the unit would goon safety.

• NOx (nitrogen oxide) emissions are

higher with intermittent ignition becausethe spark burns nitrogen, creating NOx.

A strong sparkThe spark across the electrode gap at the

tips of the electrodes must be strongenough to withstand the velocity of the airbeing blown through the air tube by theburner fan. The air being blown throughthe air tube forces the ignition spark toform an arc toward the oil spray. This arcextends into the spray causing the oilvapors to ignite, and the flame to establish.The ignition voltage must be high enoughto create a spark that is hot enough to ignitethe oil. In some cases, widening the sparkwill produce better ignition.

The transformerThe AC transformer is a device that

receives electricity at one voltage anddelivers it at another voltage, either higheror lower.

Essentially, the transformer consists oftwo separate coils of wire wound on aniron core. One winding receives theelectrical energy from the power sourceand is called the primary; and the otherdelivers electrical energy and is called thesecondary. If the secondary windingdelivers a voltage that is higher than theprimary, then it is known as a step-uptransformer. On the other hand, if thesecondary voltage is lower than the primaryvoltage, then it is known as a step-downtransformer.

The factor that determines whether atransformer is of the step-up or step-downvariety is the relative number of turns inthe primary and in the secondary windings.



Step-up transformers are used for ignitionpurposes on oilburners.

Generally, it will be found that ignitiontransformers are made up of 90 to 100turns of fine wire in the secondary coil toone turn of stout wire in the primary coil.In the example, you will note there are60,000 turns in the secondary and 690 turnsin the primary coil, a ratio of about 90 to1. In Figure 9-3 on following page, we cansee what the ignition transformer looks likewith its outer case removed.

As voltage increases,amps decrease

This is a good time to explain a mostimportant characteristic of transformers,see Figure 9-2. The rule: If the voltage (E)flowing out of a transformer is increased,the current, or amperage (I), is alwaysdecreased proportionately. For instance, ifthe voltage is doubled, the current will becut in half. In the case of the transformer inour example, the primary voltage of 115volts is increased 90 times to 10,000 voltsin the secondary coil, where the currentflow (I

2) is 23 milliamperes, which is 23/

1000ths of one ampere. Although notshown in the example, the current flowingin the primary coil can be determined bymultiplying .023 x 90, or about 2 amperes,which is average for ignition transformers.This can be proven in the field by checkingamperage in the primary circuit with anamperage meter.

Moisture proofingIt is important that both the primary and

secondary coils of the ignition transformer

Figure 9-2:Transformer wiring

Warning! All high voltage circuits, especially ACcircuits, are potentially hazardous. Depending on thesize of the person, contact area and time, and voltage

characteristics (magnitude, frequency, and path),electric shock can occur and cause bodily damage,

burns, or death. Use extreme caution at the input oroutput end of an ignition transformer!

Transformer Wiring

IronCore

PrimaryE1 = 115V1

MagneticField

SecondaryE2 = 10,000 VI2 = 23 ma



are covered with a tar-like compound,whereas solid state ignitors feature epoxieswhich serve the purpose of moistureproofing the device. Epoxy, by its verynature, is somewhat more resistant tomoisture and acts as an excellent corrosioninhibitor and heat conductor.

If you must replacea transformer

When ordering replacement transform-ers, several facts must be known:

1. The size of the mounting base andlocation of mounting holes

2. The position of high tensionterminals

3. The style of transformer high tensionclips

4. Secondary coil voltage

5. Primary coil voltage

6. Transformer body size

Wiring ignitiontransformers

Wire the ignition transformer into theburner circuit as follows:

For intermittent ignition, attach a wirefrom the transformer or ignitor to theneutral wire, and the other wire to theorange motor wire from the primarycontrol. See Figure 9-4 for wiring a

Figure 9-3:Constructionof an ignitiontransformer

SecondaryCoil No.1

PrimaryCoil No.1

Direction ofMagnetic Flux

Laminated SteelMagnetic Shunt

LaminatedSteel Core

PrimaryCoil No. 2

SecondaryCoil No. 2

Mid Point ofCoils GroundedHere

SecondaryLead

SecondaryLead



primary intermittent ignition(the spark is on whenever themotor is on).

For interruptedignition, you need a primarycontrol built for this purpose.

Attach one wire from thetransformer or ignitor to theneutral wire and the other wireto the ignition wire or terminalon the primary control.

See Figure 9-5 for wiring aprimary control interruptedignition (the spark shuts off onceflame is established).

Figure 9-4:Wiring a primaryintermittentigntion

Figure 9-5:Wiring a primary controlinterrupted ignition


ControlSwitch

ToggleSwitch

StairSwitch Thermostat Cad Cell

Cad Cell RelayPrimary Control

HighLimit

Switch

Low Water

Cutoff

Black

WhiteOrange

IgnitionTransformer

BurnerMotor

Fuse

Legend: Screw Terminal ¼" Quick Connect Terminal

Power Supply, Provide Disconnect Meansand Overload Protection as Required

Optional Feature on Selected Models

Refer to Device Label for Wire Color Code

Valve is Optional on Specific Models

See Figure 2ToRemoteAlarmCircuit

JunctionBox

CadCell

Jumper

Thermostat


Drawbacks to iron coreignition transformers

An ignition transformer does just what itclaims to do—it transforms voltage. Thereis a single copper winding on the primaryside for every 90 to 100 windings on thesecondary side and that is how it transformsvoltage. This becomes a problem wheninput voltage drops. For every one volt youremove from the primary side, you removeninety volts from the secondary side. Theignition of the atomized oil is not a resultof the spark, but rather the result of theheat generated from the spark.

Remember, the ability of an ignitor toignite oil depends on more than just highvoltage; it depends on arc output as well!Spark heat energy = voltage times current.You must provide between 600-700°Fahrenheit to ignite atomized No.2 fuel oil.

This translates to approximately 9,000 voltsand about 19 MA short circuit current. A10,000 volt 23 MA transformer only has asmall margin of error built into it, and canbe a problem.

A few facts• Ignition transformers are insulated

with tar. Tar can melt with heat and the taroozes from the transformer and typicallydeposits on the combustion head assembly,making for a nasty clean-up.

• An ignition transformer’s tar-coveredwindings are susceptible to moistureinfiltration. Moisture infiltration will causean immediate shorting of the component.

• Electrical consumption with anignition transformer is typically 80 to 100watts of electricity. This is the approximateequivalent to a 100 watt light bulb turnedon over the burner when the transformer isrunning.

• Finally, ignition transformers deterio-rate over time. During this deterioration,they cause delayed ignition problems thatworsen until, finally, the transformer can nolonger light the atomized oil.

Transformer testingOver the years, there have been many

and various methods of testing transform-ers. Regardless of the method used, onething must be kept in mind and that is to besure the transformer has the correct inputvoltage to the primary coil. This is veryimportant because the output of thetransformer is relative to the input voltage.In other words, if the input is down by10%, the output will also be 10% lower.

Note: 9,000 volts by itself is not whatis required to ignite oil; 9,000 volts isconsidered sufficient to create an arc

across the air gaps between theelectrode tips normally used in oil-

burners. The secondary currentflowing through the arc heats the air

and lights the oil. The important factorin creating an arc is voltage; the

important factor in igniting the oil iscurrent. This is why UnderwritersLaboratory (UL) requires 10,000 V

ignition transformers to have a shortcircuit current of at least 19.5 MA

(11.6 MA across a 1/8" air gap). Most10,000 V ignition transformers ourindustry uses are rated for 23 MA.


Several types of transformer testers areavailable, Figure 9-6. These testers aredependable and usually come in their owncarrying case with all the instructions. Theone shown will also act as a backuptransformer and can be left on the job as atemporary solution and this can be espe-cially helpful with older obsolete burners.When using any one of these testers, readthe instructions for that particular testerbecause competitive units will operatedifferently.

Resistance testingAnother test for iron-core transformers

is to check the quality of the windingsusing an ohmmeter. The following proce-dure is used:

1. Turn the power to the unit off.Disconnect the primary leads from thecircuit.

2. Test the resistance across the primarywinding. Attach the test leads from yourohmmeter to the primary leads of the

transformer. You should get areading of 3 ohms, plus orminus 10% (2.7 through 3.3ohms). If your reading ishigher or lower, you shouldreplace the transformer.

3. Test the secondary sideof the transformer. Touch oneof your ohmmeter leads to asecondary terminal and theother to a mounting screw orground. You should get areading of 12,000 ohms plus orminus 10% (10,800 through13,200).

Then perform the same test from the othersecondary terminal to a mounting screw orground; you should read approximately thesame. If you get a higher or lower readingthat varies widely, you should replace thetransformer.

The following table is used with thisprocedure for specific brands:

Solid state oilburnerignition systems,electronic ignitors

Manufacturers are now mostly usingsolid-state electronic ignitors. These unitsare known for their small size, lightweight, and starting power. They may befor dedicated use on a particular type ofburner and are also available in generic

Figure 9-6: One ofseveral transformertesters available

Trade Brand Primary Leads Secondary Posts(each post to ground)

Allanson 2.4 ohms 9,200 ohmsDongan 3 ohms 12,000 ohmsFrance 3 ohms 12,000 ohms



versions for retrofit applications,depending on the mounting plateused. Output voltages of between14,000 volts and 20,000 voltspeak with amperages between 16MA to 45 MA respectively, on thesecondary coil, are considerednormal, Figure 9-7.

A solid state ignitor is a radicaldeparture from the traditionalignition transformers commonlyused on oilburners. Solid stateignitors eliminate transformerdesign shortcomings. Ignitorsutilize a solid state printed circuit boardwith what is called a ‘tank mechanism.’This technology allows the ignitor to havea more constant output if the input voltagedecreases. Therefore, we have fewerproblems with voltage drops.

Ignitors are insulated with epoxy, nottar. Epoxy is virtually resistant to heat andwill not melt on the combustion headassembly. This same epoxy makes theignitor virtually impervious to moisture.Electrical consumption from an ignitor is30 to 50 watts, much less than the trans-former. Ignitors are made from solid stateelectronic components and are trulyignition control systems.

Testing electronicignitor systems

Since these units contain solid-statedevices such as transistors, their trouble-shooting and servicing should be done tomanufacturers’ recommendations. Do notuse a transformer tester to test electronicignitors. Doing so will give you an inaccu-

rate measurement and may harm the ignitorand tester. Testing electronic ignitorsystems is different from testing ignitiontransformers because ignitors utilize a highfrequency output. The cycling operationsof a solid state ignition system are 20,000times per second. Standard AC transformerscycle at 60 times per second. This is thereason you cannot test a solid state ignitorwith a standard ignition transformer tester.

The testing of electronic ignitors is morecomplicated than testing the iron-coretransformer. Before you perform any ofthese tests, make sure the manufacturerapproves of the test, and be extra carefulnot to directly short the terminals without aspark between them. In many cases, it willshort out the ignitor and destroy its internalcircuitry. Keep in mind that ignitors are notmerely a pair of coils, but rather a complexelectronic device made up of severalelectronic circuits and components.

The first basic test for ignitors is to placean ohmmeter across the ignitor outputterminals with the power off and measure

Figure 9-7:Ignitors



the resistance from each ignitor post toground, Figure 9-8. Normally, the ignitoris considered good if the resistance fromeach post to ground has no more than a10% difference between posts. Eachmanufacturer is different and they should

be consulted for the proper output rangeand differential. It’s also important that youverify continuity between the ignitor caseground and true ground.

Another test that is approved by mostmanufacturers is to bring the ignitor outputterminals to within ½ to ¾ of an inch apartand turn on the power, Figure 9-9. Astrong blue spark should be generated.Another trick is to let it spark for a fewminutes, five to ten in most cases, and seeif the spark changes from blue to orange;if it does change, replace it.

Finally, you can check both electronicignitors and iron-core transformers with acommon test. Bring the ignitor or trans-

former output terminals to within ½to ¾ of an inch apart. Place amilliammeter in series with the hotline going to the ignitor and turn iton, Figure 9-10. Again, the readingshould stay steady and not vary forat least five minutes with a strongblue spark throughout the test whilestaying within 10% of the ratedamperage draw for the device.

Cables, buss bars,spring clips

In order to transport the highvoltage from the secondary terminals of theignition transformer, an effective andefficient path must be provided to theignition electrodes. This path may be anignition cable, buss bars, or spring typeconductors.

Ignition cables are normally constructedof heavy stranded copper wire covered withspecial heavy insulation to insulate againstdampness, and ensuretransmission around,over, or under any otherconducting surfacebetween the transformerlocation and the elec-trodes. The outstandingfeature of ignition cablesis flexibility, permittingeasy handling, bendingand installation in anyburner. Some nozzleassemblies are equippedwith clips to hold theflexible cable off thebottom of the burner air

Figure 9-8: Ohmmeter test

Figure 9-9:Spark test

Figure 9-10:Milliammeter



tube, especially when the air tube is long; ifthey are provided, use them.

Buss bars are non-insulated heavy gaugestrips of metal that are made by theoilburner manufacturer to the length andshape to fit a certain model of burner; theyare not interchangeable with other models.

Spring clips are similar to buss bars,except that contact with the transformer ismaintained by spring tension. After sometime, these clips can lose their tension andprevent proper and desired contact. Theyshould be checked whenever the burner isserviced.

ElectrodesElectrodes are metal rods made of

specialized steels, and partially coveredwith a ceramic (porcelain) insulator,Figure 9-11. These insulators are usuallymade in two major external diameters(7/16" and 9/16"). As we can see inFigure 9-13, these porcelains come invarious lengths. They may be ordered inindividual lengths 4" to 30", or they maybe sized on the job through the use of aspecial tool for cutting the porcelain

insulator.

The porcelains serve twopurposes: They securelyposition the electrode rods andthey serve as insulators,protecting the metal rodagainst shorting out to thenozzle assembly. Theseinsulators are center bored tofit the metal electrode rods,either 1/8" or 3/32" indiameter.

Electrode holders permitsecure and correct mounting

Figure 9-11:Electrodes

Figure 9-12:Electrode test

of the porcelains and electrodes so that,after adjustment, they cannot shift fromvibration or other causes and alter theirposition. In many cases, the electrodeholder is incorporated with the air spinneror turbulator.

Electrode testingand setting

Figure 9-12 shows one method fortesting the porcelain insulator of anelectrode for spark leakage. A neon testlamp, with one probe touching the ceramicinsulator, the other end of the test lampfree, is shown. By moving the one end ofthe test lamp over the surface of theporcelain, it can be easily determinedwhether or not the ceramic insulator is

cracked. If the insulator is defective, theneon test lamp will glow when the probereaches the defect.

Figure 9-13 is a setting for electrodeswhen one is not available from the manu-



Do Not Touch

Neon Test

Porcelains

Wire

facturer. The recommendationsof the burner manufacturershould be followed wheneverthey are available. Electrode tipsshould never be permitted totouch or extend into the oilspray, because a carbon bridgewill build up between them,ultimately causing ignitionfailure.

Ceramic insulators shouldalways be treated gently. Theyshould never be dropped orpacked loosely in service kits.In field servicing, they should always bewiped clean with a cloth, or cleaned with asolvent. If they show signs of aging orcracking, they should be replaced immedi-ately.

Ignition service problemsCorrecting faulty ignition is important.

Delayed or faulty ignition is the primecause of puffback. Puffback is the mostdisagreeable of all burner problems. Itoccurs when ignition is delayed. Due tosome fault in the ignition system, the oilvapor does not ignite until after the burnerhas run for some time. Then the accumu-lated vapors all ignite at once, creatingmore combustion products than the ventingsystem can handle. Delayed ignition cancause soot to blow out of the draft regula-tor, and in severe cases—called puffbacks—it can knock down the flue pipe.

Ignition problems are usually the easiestto recognize and solve. In most cases, wefind it necessary to merely clean theelectrodes and cables, and be certain that allconnections are tight and that the spark gapis in proper adjustment. We must makecertain that the electrode porcelains and the

transformer terminal porcelain insulatorsare not crazed (small cracks on surface),cracked, or oil soaked.

It is important that all exposed metalliccomponents of the ignition system be a safedistance away from any other metallic partof the burner, since it is grounded. Theshortest metal-to-metal distance throughoutthe entire ignition system should be thatdistance between the two electrode tips.Common sense tells us that any otherarrangement would cause the spark to shortout before the spark bridges the electrodetips. The best way to avoid this problem isto strictly adhere to the recommendedelectrode tip settings as shown in themanufacturer’s recommendations.

Troubleshootingignition problems

1. Connections at transformerjunction box loose. Always check linevoltage connections from the neutral wireof the primary control and the orange wireof the primary control (for intermittentignition) and the ignition wire of theprimary (interrupted ignition) to determineif there are loose connections at this

Figure 9-13:Typical genericsetting

5/32" Gap

5/16" AboveCenter

1/16" In Front ofNozzle



electrode tips are permitted to operatewhile extending into the oil spray, it willpromote a carbon bridge between theelectrode tips, thus shorting out the sparkand ultimately causing ignition failure.Clean the electrode tips and set themproperly.

7. Electrodes too close to the nozzle.It has already been outlined that theelectrodes set too close to the nozzle willpromote spark shorting out from theelectrode tip to the nozzle, thus creating adelayed ignition or ignition failure. Setelectrode tips according to prescribedprocedure.

8. Spark gap too wide. If the sparkgap is too wide, either there will be nospark at all, or the spark will short out atsome other point along the ignition system.Again, set tips as instructed previously.However, we are learning that in manyapplications today, and due to the changesin fuel oil, a slightly wider than normal gapmay result in smoother ignition. Ignition offuel is not an exact science and so a coupleof settings may have to be tried to find thebest results.

9. Insulators not held securely. In theevent the electrode support bracket is loose,or the porcelains do not fit properly in thebracket, it is possible that the electrodesmay move out of adjustment because ofburner vibrations. Set electrodes andtighten the electrode support bracketsecurely, but do not overtighten becausethat may crack the ceramic insulators.

10. Puffbacks may be caused by lackof draft. If it is discovered that the ceramicinsulators are heavily sooted and/orcarbonized and the electrode tips areproperly gapped and properly set, then it is

Correcting faultyignition isimportant.

Delayed or faultyignition is the

prime cause ofpuffback.


junction box. If they areloose, tighten themsecurely. Also check forloose connections at allterminals and make surethat wire nuts are tight.

2. Test the trans-former. If the trans-

former is defective, replace it.

3. Loose connections ateither the secondary terminalsof the transformer, or loose

connections where the high tension leadsor buss bars are fastened to the elec-trodes. If these connections are found to beloose, attempt to tighten them. If this failsto solve the problem, replace the connec-tors. Also clean out any dust or dirt thatmay have accumulated in or around thesecondary terminals of the transformer. Aspreviously outlined, check the high voltageleads to determine if the insulation hasbecome defective.

4. Remove the porcelain insulatorsfrom the electrode holder to determinewhether they are cracked. In many casesthe porcelains will crack beneath the clampof the electrode holder. Replace cracked orcrazed porcelains, even though they are stillfunctioning properly.

5. Carbonized insulator. Carbonaccumulations on the ceramic insulatorswill conduct electricity, thus causing thespark to short out against either the nozzleadapter, nozzle line, or the electrode holder.The carbon must be removed with a solventor cleaner. Then the insulators must bedried and checked for cracks and/or sparkleakage. The procedure for checking forspark leakage has been outlined.

6. Electrodes in oil spray. If the


a good possibility that lack of overfire draftis causing the trouble. Refer to Chapter 6—‘Chimneys & Draft.’ Puffbacks and carbonmay be caused by a partially cloggednozzle. See Chapter 5 on Nozzles.

11. Ignition “on” time should bechecked. This, of course, concerns inter-rupted ignition primary controls. Theignition “on” time is easily checked byconnecting one lead of a 40-watt test lightto the ignition wire of the primary, andconnecting the other lead to neutral or thewhite wire. Start the burner while watchingthe bulb time to determine the length oftime it remains “on.” With cad cell typecontrols, it should remain on for the lengthof time specified by the manufacturer.

Ignition ControlMost burner manufacturers today use

interrupted ignition. On commercial/industrial burners, ignition “on” times ofgreater than 10-20 seconds are seldomfound. The purpose of interrupted ignitionis to ignite the fuel and shut off the system,prolonging ignition system component life.For example, let us say that a residentialburner that consumes 1,000 gallons peryear is operating with a 1 GPH nozzle. Forthis example, let us assume the burner willstart 3,000 times per year.


Example 1Intermittent ignition = ignition is on

when burner runs. 1000 gallons / 1 GPH =1000 hours of ignition on time.

Example 2Interrupted ignition = timed

or sequenced ignition.

Cad-cell type relays3000 starts x 45 seconds = 37.5hours ignition on time

3000 starts x 30 seconds = 25 hours

3000 starts x 15 seconds = 12.5 hours

3000 starts x 8/10 seconds = 40minutes ignition on time

As we can see, we can dramaticallylower ignition on-time and prolong theuseful life of our ignition systems andreduce service calls.

Delayed ignition is one of the frus-trating ignition problems we encoun-ter. Some solutions are covered in thefollowing charts provided by BeckettCorp., Figure 9-14: Ignition ServiceHelp Chart and Figure 9-15: DelayedIgnition Problem Solving, on follow-ing pages.


Designation Description Service Hints

1. 120V ac input wires Brings 120 volt to primary coil Wires must not be pinched against housingwhen transformer is closed

2. Primary coil Current in this coil generates amagnetic field

3. Iron core Transfers magnetic field intosecondary coil

4. Secondary coil Magnetic field from core inducesvoltage in this coil

5. Insulating compound Keeps moisture out, conducts heat Should not be leaking out

6. Metal cover Protects internal of transformer Should not be punctured or severely dented

7. Mounting base plate Mounts transformer to Must not be bent and cause air to leakburner housing from around transformer

8. Transformer output Insulates high voltage from ground 1. Must not be crackedceramic insulator and opposing terminal. Holds 2. Must be totally clean

ignition spring dimensions

9. Ignition spring terminals Transmits high voltage to 1. Must make good, clean contact toelectrode rods electrode rods

10. Electrode rods Transfers high voltage to electrode tips Must be clean

11. Electrode insulators Mounts electrodes and insulates Must be clean and not crackedeach electrode from ground

12. Arc gap and electrodes Specified gap (1/8” - 5/32”) allows arc 1. Too close causes delayed ignitionto jump to other terminal and ignite 2. Too wide results in no ignition and

possible damage to secondary3. Clean and properly adjust


Figure 9-14:Ignition servicehelp chart




Figure 9-15

Documents

00 Customer Service · 2016-10-04 · The constant arc keeps the flame burning even if it is belching smoke, soot, and unburned oil. With interrupted ignition, a poor flame goes out