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Chapter 9
Ignition Systems

Chapter 9

Ignition Systems

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

The completely automatic electric
Both components supply this high
ignition system is an important part of
voltage electricity to the electrodes. A
oilburner technology. There are two
spark jumps from the tip of one electrode to
different main components used for
the tip of the other. The electrical arc then
ignition systems on oilburners: the ignition
transformer and the solid state ignitor. ignites the atomized oil.

The ignition transformer is a step-up Let’s examine the various components

transformer using copper windings around of the ignition system shown in Figure 9-1.
an iron core. It steps up the incoming The voltage travels from the transformer
voltage of 120 volts to an output voltage of or ignitor through the ignition cables, buss
10,000 volts. This is accomplished by a 90 bars, or spring clips to the electrodes which
to 1 primary to secondary winding ratio are held in place by the ceramic insulators
around the iron core. (porcelains). When it reaches the tips of the
The solid state ignitor utilizes electron- electrodes it jumps the gap between them,
Figure 9-1:
ics to produce an output voltage of any- creating our spark. Ignition system
components

Ignition Electrode Ignition

Cable Bracket Electrode

Ceramic
Insulator

Ignition
Transformer

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Ignition Systems

Oilburners use one of two types of higher with intermittent ignition because
electric ignition control systems: the spark burns nitrogen, creating NOx.
Interrupted ignition: the ignition spark
remains on for only a short time at the A strong spark
beginning of each burner operating cycle, The spark across the electrode gap at the
and is turned off once flame is established. tips of the electrodes must be strong
enough to withstand the velocity of the air
Intermittent ignition: the spark that
being blown through the air tube by the
ignites the oil vapors remains on as long as
burner fan. The air being blown through
the burner runs. Intermittent ignition used
the air tube forces the ignition spark to
to be called “constant ignition,” and some
form an arc toward the oil spray. This arc
manufacturers call intermittent ignition
extends into the spray causing the oil
“constant duty ignition.”
vapors to ignite, and the flame to establish.
The ignition voltage must be high enough
Interrupted ignition to create a spark that is hot enough to ignite
is better the oil. In some cases, widening the spark
Over time, the industry has switched will produce better ignition.
between interrupted and intermittent
ignition. Interrupted ignition has proven The transformer
superior because having the spark on The AC transformer is a device that
during the entire burn cycle detracts from receives electricity at one voltage and
performance for several reasons: delivers it at another voltage, either higher
• Electrode life is significantly reduced. or lower.

• Ignitor or ignition transformer life is Essentially, the transformer consists of

significantly reduced. two separate coils of wire wound on an
iron core. One winding receives the
• Electrical consumption is increased electrical energy from the power source
dramatically. and is called the primary; and the other
• Operational noise in increased delivers electrical energy and is called the
dramatically. secondary. If the secondary winding
delivers a voltage that is higher than the
• Intermittent ignition may hide primary, then it is known as a step-up
combustion problems that can cause soot- transformer. On the other hand, if the
plugged boilers and oil running saturation. secondary voltage is lower than the primary
The constant arc keeps the flame burning voltage, then it is known as a step-down
even if it is belching smoke, soot, and transformer.
unburned oil. With interrupted ignition, a
The factor that determines whether a
poor flame goes out and the unit would go
transformer is of the step-up or step-down
on safety.
variety is the relative number of turns in
• NOx (nitrogen oxide) emissions are the primary and in the secondary windings.

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Figure 9-2:
Step-up transformers are used for ignition Transformer wiring
purposes on oilburners.
Generally, it will be found that ignition
transformers are made up of 90 to 100
Iron Magnetic
turns of fine wire in the secondary coil to Core Field
one turn of stout wire in the primary coil.
In the example, you will note there are
60,000 turns in the secondary and 690 turns
in the primary coil, a ratio of about 90 to
1. In Figure 9-3 on following page, we can Primary
Secondary
see what the ignition transformer looks like E = 115V
1 1
Transformer Wiring
E = 10,000 V
2
with its outer case removed. I = 23 ma
2

As voltage increases,
amps decrease
This is a good time to explain a most
important 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 always
decreased proportionately. For instance, if
the voltage is doubled, the current will be
cut in half. In the case of the transformer in
our example, the primary voltage of 115
volts is increased 90 times to 10,000 volts
in the secondary coil, where the current
flow (I2) is 23 milliamperes, which is 23/
1000ths of one ampere. Although not
shown in the example, the current flowing
in the primary coil can be determined by
multiplying .023 x 90, or about 2 amperes,
which is average for ignition transformers. Warning! All high voltage circuits, especially AC
This can be proven in the field by checking circuits, are potentially hazardous. Depending on the
amperage in the primary circuit with an size of the person, contact area and time, and voltage
amperage meter. characteristics (magnitude, frequency, and path),
electric shock can occur and cause bodily damage,
Moisture proofing burns, or death. Use extreme caution at the input or
It is important that both the primary and output end of an ignition transformer!
secondary coils of the ignition transformer

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Ignition Systems

Secondary Primary
Coil No.1 Coil No.1

Secondary
Lead Direction of
Magnetic Flux

Laminated Steel
Magnetic Shunt

Secondary
Lead
Laminated
Steel Core

Mid Point of
Coils Grounded Secondary Primary
Here Coil No. 2 Coil No. 2

Figure 9-3:
Construction
of an ignition
transformer are covered with a tar-like compound, 3. The style of transformer high tension
whereas solid state ignitors feature epoxies clips
which serve the purpose of moisture 4. Secondary coil voltage
proofing the device. Epoxy, by its very
nature, is somewhat more resistant to 5. Primary coil voltage
moisture and acts as an excellent corrosion 6. Transformer body size
inhibitor and heat conductor.

Wiring ignition
If you must replace transformers
a transformer Wire the ignition transformer into the
When ordering replacement transform- burner circuit as follows:
ers, several facts must be known:
For intermittent ignition, attach a wire
1. The size of the mounting base and from the transformer or ignitor to the
location of mounting holes neutral wire, and the other wire to the
2. The position of high tension orange motor wire from the primary
terminals control. See Figure 9-4 for wiring a

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Ignition Systems

Figure 9-4:
Wiring a primary
intermittent
igntion

Control Toggle Stair

Switch Switch Switch
Thermostat Cad Cell
primary intermittent ignition
(the spark is on whenever the
Fuse
motor is on).
High
For interrupted Limit
Switch
ignition, you need a primary
control built for this purpose.
Attach one wire from the
transformer or ignitor to the Low
Water
neutral wire and the other wire Cutoff
to the ignition wire or terminal Cad Cell Relay
Primary Control
on the primary control. Black
See Figure 9-5 for wiring a White
primary control interrupted Orange

ignition (the spark shuts off once

flame is established). Burner Ignition
Motor Transformer

Figure 9-5:
Wiring a primary control
interrupted ignition

Thermostat

Jumper

Legend: Screw Terminal ¼" Quick Connect Terminal

Power Supply, Provide Disconnect Means

and 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 2
To
Remote
Cad
Alarm
Cell
Circuit
Junction
Box

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Ignition Systems

Drawbacks to iron core This translates to approximately 9,000 volts

ignition transformers and about 19 MA short circuit current. A
An ignition transformer does just what it 10,000 volt 23 MA transformer only has a
claims to do—it transforms voltage. There small margin of error built into it, and can
is a single copper winding on the primary be a problem.
side for every 90 to 100 windings on the
secondary side and that is how it transforms A few facts
voltage. This becomes a problem when • Ignition transformers are insulated
input voltage drops. For every one volt you with tar. Tar can melt with heat and the tar
remove from the primary side, you remove oozes from the transformer and typically
ninety volts from the secondary side. The deposits on the combustion head assembly,
ignition of the atomized oil is not a result making for a nasty clean-up.
of the spark, but rather the result of the
heat generated from the spark. • An ignition transformer’s tar-covered
windings are susceptible to moisture
Remember, the ability of an ignitor to infiltration. Moisture infiltration will cause
ignite oil depends on more than just high an immediate shorting of the component.
voltage; it depends on arc output as well!
Spark heat energy = voltage times current. • Electrical consumption with an
You must provide between 600-700° ignition transformer is typically 80 to 100
Fahrenheit to ignite atomized No.2 fuel oil. watts of electricity. This is the approximate
equivalent to a 100 watt light bulb turned
on over the burner when the transformer is
running.
Note: 9,000 volts by itself is not what
is required to ignite oil; 9,000 volts is • Finally, ignition transformers deterio-
considered sufficient to create an arc rate over time. During this deterioration,
across the air gaps between the they cause delayed ignition problems that
electrode tips normally used in oil- worsen until, finally, the transformer can no
burners. The secondary current longer light the atomized oil.
flowing through the arc heats the air
and lights the oil. The important factor Transformer testing
in creating an arc is voltage; the
Over the years, there have been many
important factor in igniting the oil is
and various methods of testing transform-
current. This is why Underwriters
ers. Regardless of the method used, one
Laboratory (UL) requires 10,000 V
thing must be kept in mind and that is to be
ignition transformers to have a short
sure the transformer has the correct input
circuit current of at least 19.5 MA
voltage to the primary coil. This is very
(11.6 MA across a 1/8" air gap). Most
important because the output of the
10,000 V ignition transformers our
transformer is relative to the input voltage.
industry uses are rated for 23 MA.
In other words, if the input is down by
10%, the output will also be 10% lower.

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Ignition Systems

transformer. You should get a

Figure 9-6: One of reading of 3 ohms, plus or
several transformer minus 10% (2.7 through 3.3
testers available ohms). If your reading is
higher or lower, you should
replace the transformer.
3. Test the secondary side
of the transformer. Touch one
of your ohmmeter leads to a
secondary terminal and the
other to a mounting screw or
ground. You should get a
reading of 12,000 ohms plus or
minus 10% (10,800 through
13,200).
Several types of transformer testers are Then perform the same test from the other
available, Figure 9-6. These testers are secondary terminal to a mounting screw or
dependable and usually come in their own ground; you should read approximately the
carrying case with all the instructions. The same. If you get a higher or lower reading
one shown will also act as a backup that varies widely, you should replace the
transformer and can be left on the job as a transformer.
temporary solution and this can be espe- The following table is used with this
cially helpful with older obsolete burners. procedure for specific brands:
When using any one of these testers, read
the instructions for that particular tester
Trade Brand Primary Leads Secondary Posts
because competitive units will operate (each post to ground)
differently.
Allanson 2.4 ohms 9,200 ohms
Dongan 3 ohms 12,000 ohms
Resistance testing France 3 ohms 12,000 ohms

Another test for iron-core transformers

is to check the quality of the windings
using an ohmmeter. The following proce- Solid state oilburner
dure is used: ignition systems,
1. Turn the power to the unit off.
electronic ignitors
Manufacturers are now mostly using
Disconnect the primary leads from the
solid-state electronic ignitors. These units
circuit.
are known for their small size, light
2. Test the resistance across the primary weight, and starting power. They may be
winding. Attach the test leads from your for dedicated use on a particular type of
ohmmeter to the primary leads of the burner and are also available in generic

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Chapter 9
Ignition Systems

versions for retrofit applications,

depending on the mounting plate
Figure 9-7:
used. Output voltages of between Ignitors
14,000 volts and 20,000 volts
peak with amperages between 16
MA to 45 MA respectively, on the
secondary coil, are considered
normal, Figure 9-7.
A solid state ignitor is a radical
departure from the traditional
ignition transformers commonly
used on oilburners. Solid state
ignitors eliminate transformer
design shortcomings. Ignitors
utilize a solid state printed circuit board rate measurement and may harm the ignitor
with what is called a ‘tank mechanism.’ and tester. Testing electronic ignitor
This technology allows the ignitor to have systems is different from testing ignition
a more constant output if the input voltage transformers because ignitors utilize a high
decreases. Therefore, we have fewer frequency output. The cycling operations
problems with voltage drops. of a solid state ignition system are 20,000
Ignitors are insulated with epoxy, not times per second. Standard AC transformers
tar. Epoxy is virtually resistant to heat and cycle at 60 times per second. This is the
will not melt on the combustion head reason you cannot test a solid state ignitor
assembly. This same epoxy makes the with a standard ignition transformer tester.
ignitor virtually impervious to moisture. The testing of electronic ignitors is more
Electrical consumption from an ignitor is complicated than testing the iron-core
30 to 50 watts, much less than the trans- transformer. Before you perform any of
former. Ignitors are made from solid state these tests, make sure the manufacturer
electronic components and are truly approves of the test, and be extra careful
ignition control systems. not to directly short the terminals without a
spark between them. In many cases, it will
short out the ignitor and destroy its internal
Testing electronic
circuitry. Keep in mind that ignitors are not
ignitor systems merely a pair of coils, but rather a complex
Since these units contain solid-state
electronic device made up of several
devices such as transistors, their trouble-
electronic circuits and components.
shooting and servicing should be done to
manufacturers’ recommendations. Do not The first basic test for ignitors is to place
use a transformer tester to test electronic an ohmmeter across the ignitor output
ignitors. Doing so will give you an inaccu- terminals with the power off and measure

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the resistance from each ignitor post to former output terminals to within ½
ground, Figure 9-8. Normally, the ignitor to ¾ of an inch apart. Place a
is considered good if the resistance from milliammeter in series with the hot
each post to ground has no more than a line going to the ignitor and turn it
10% difference between posts. Each on, Figure 9-10. Again, the reading
manufacturer is different and they should should stay steady and not vary for
at least five minutes with a strong
blue spark throughout the test while
Figure 9-8: Ohmmeter test
staying within 10% of the rated
amperage draw for the device.

Cables, buss bars,

spring clips
In order to transport the high Figure 9-9:
voltage from the secondary terminals of the Spark test
ignition transformer, an effective and
efficient path must be provided to the
ignition electrodes. This path may be an
ignition cable, buss bars, or spring type
conductors.
Ignition cables are normally constructed
of heavy stranded copper wire covered with Figure 9-10:
be consulted for the proper output range special heavy insulation to insulate against Milliammeter
and differential. It’s also important that you dampness, and ensure
verify continuity between the ignitor case transmission around,
ground and true ground. over, or under any other
conducting surface
Another test that is approved by most
between the transformer
manufacturers is to bring the ignitor output
location and the elec-
terminals to within ½ to ¾ of an inch apart
trodes. The outstanding
and turn on the power, Figure 9-9. A
feature of ignition cables
strong blue spark should be generated.
is flexibility, permitting
Another trick is to let it spark for a few
easy handling, bending
minutes, five to ten in most cases, and see
and installation in any
if the spark changes from blue to orange;
burner. Some nozzle
if it does change, replace it.
assemblies are equipped
Finally, you can check both electronic with clips to hold the
ignitors and iron-core transformers with a flexible cable off the
common test. Bring the ignitor or trans- bottom of the burner air

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Ignition Systems

tube, especially when the air tube is long; if of the porcelains and electrodes so that,
they are provided, use them. after adjustment, they cannot shift from
vibration or other causes and alter their
Buss bars are non-insulated heavy gauge
strips of metal that are made by the position. In many cases, the electrode
oilburner manufacturer to the length and holder is incorporated with the air spinner
shape to fit a certain model of burner; they or turbulator.
are not interchangeable with other models.
Spring clips are similar to buss bars, Electrode testing
except that contact with the transformer is and setting
maintained by spring tension. After some Figure 9-12 shows one method for
time, these clips can lose their tension and testing the porcelain insulator of an
prevent proper and desired contact. They electrode for spark leakage. A neon test
should be checked whenever the burner is lamp, with one probe touching the ceramic
serviced. insulator, the other end of the test lamp
free, is shown. By moving the one end of
Electrodes the test lamp over the surface of the
porcelain, it can be easily determined
Electrodes are metal rods made of
whether or not the ceramic insulator is
specialized steels, and partially covered
with a ceramic (porcelain) insulator,
Figure 9-11. These insulators are usually Figure 9-12:
made in two major external diameters Electrode test
(7/16" and 9/16"). As we can see in Do Not Touch
Figure 9-13, these porcelains come in
various lengths. They may be ordered in
individual lengths 4" to 30", or they may
be sized on the job through the use of a
special tool for cutting the porcelain
Figure 9-11: insulator. Neon Test
Electrodes
The porcelains serve two
purposes: They securely
position the electrode rods and Porcelains
they serve as insulators, Wire
protecting the metal rod
against shorting out to the
nozzle assembly. These
insulators are center bored to
fit the metal electrode rods, cracked. If the insulator is defective, the
either 1/8" or 3/32" in neon test lamp will glow when the probe
diameter. reaches the defect.
Electrode holders permit Figure 9-13 is a setting for electrodes
secure and correct mounting when one is not available from the manu-

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facturer. The recommendations

of the burner manufacturer 5/32" Gap
should be followed whenever
they are available. Electrode tips
5/16" Above
should never be permitted to Center
touch or extend into the oil
spray, because a carbon bridge
will build up between them,
ultimately causing ignition
failure.
Ceramic insulators should 1/16" In Front of
always be treated gently. They Nozzle
should never be dropped or
packed loosely in service kits. Figure 9-13:
In field servicing, they should always be transformer terminal porcelain insulators Typical generic
wiped clean with a cloth, or cleaned with a are not crazed (small cracks on surface), setting
solvent. If they show signs of aging or cracked, or oil soaked.
cracking, they should be replaced immedi- It is important that all exposed metallic
ately. components of the ignition system be a safe
distance away from any other metallic part
Ignition service problems of the burner, since it is grounded. The
Correcting faulty ignition is important. shortest metal-to-metal distance throughout
Delayed or faulty ignition is the prime the entire ignition system should be that
cause of puffback. Puffback is the most distance between the two electrode tips.
disagreeable of all burner problems. It Common sense tells us that any other
occurs when ignition is delayed. Due to arrangement would cause the spark to short
out before the spark bridges the electrode
some fault in the ignition system, the oil
tips. The best way to avoid this problem is
vapor does not ignite until after the burner
to strictly adhere to the recommended
has run for some time. Then the accumu-
electrode tip settings as shown in the
lated vapors all ignite at once, creating
manufacturer’s recommendations.
more combustion products than the venting
system can handle. Delayed ignition can
cause soot to blow out of the draft regula-
tor, and in severe cases—called puff
Troubleshooting
backs—it can knock down the flue pipe.
ignition problems
1. Connections at transformer
Ignition problems are usually the easiest junction box loose. Always check line
to recognize and solve. In most cases, we voltage connections from the neutral wire
find it necessary to merely clean the of the primary control and the orange wire
electrodes and cables, and be certain that all of the primary control (for intermittent
connections are tight and that the spark gap ignition) and the ignition wire of the
is in proper adjustment. We must make primary (interrupted ignition) to determine
certain that the electrode porcelains and the if there are loose connections at this

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Ignition Systems

Correcting faulty junction box. If they are electrode tips are permitted to operate
ignition is loose, tighten them while extending into the oil spray, it will
important. securely. Also check for promote a carbon bridge between the
Delayed or faulty loose connections at all electrode tips, thus shorting out the spark
ignition is the terminals and make sure and ultimately causing ignition failure.
prime cause of
that wire nuts are tight. Clean the electrode tips and set them
puffback.
2. Test the trans- properly.
former. If the trans- 7. Electrodes too close to the nozzle.
former is defective, replace it. It has already been outlined that the
3. Loose connections at electrodes set too close to the nozzle will
either the secondary terminals promote spark shorting out from the
of the transformer, or loose electrode tip to the nozzle, thus creating a
connections where the high tension leads delayed ignition or ignition failure. Set
or buss bars are fastened to the elec- electrode tips according to prescribed
trodes. If these connections are found to be procedure.
loose, attempt to tighten them. If this fails 8. Spark gap too wide. If the spark
to solve the problem, replace the connec- gap is too wide, either there will be no
tors. Also clean out any dust or dirt that spark at all, or the spark will short out at
may have accumulated in or around the some other point along the ignition system.
secondary terminals of the transformer. As Again, set tips as instructed previously.
previously outlined, check the high voltage However, we are learning that in many
leads to determine if the insulation has applications today, and due to the changes
become defective. in fuel oil, a slightly wider than normal gap
4. Remove the porcelain insulators may result in smoother ignition. Ignition of
from the electrode holder to determine fuel is not an exact science and so a couple
whether they are cracked. In many cases of settings may have to be tried to find the
the porcelains will crack beneath the clamp best results.
of the electrode holder. Replace cracked or 9. Insulators not held securely. In the
crazed porcelains, even though they are still event the electrode support bracket is loose,
functioning properly. or the porcelains do not fit properly in the
5. Carbonized insulator. Carbon bracket, it is possible that the electrodes
accumulations on the ceramic insulators may move out of adjustment because of
will conduct electricity, thus causing the burner vibrations. Set electrodes and
spark to short out against either the nozzle tighten the electrode support bracket
adapter, nozzle line, or the electrode holder. securely, but do not overtighten because
The carbon must be removed with a solvent that may crack the ceramic insulators.
or cleaner. Then the insulators must be
10. Puffbacks may be caused by lack
dried and checked for cracks and/or spark
of draft. If it is discovered that the ceramic
leakage. The procedure for checking for
insulators are heavily sooted and/or
spark leakage has been outlined.
carbonized and the electrode tips are
6. Electrodes in oil spray. If the properly gapped and properly set, then it is

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Ignition Systems

a good possibility that lack of overfire draft Example 1

is causing the trouble. Refer to Chapter 6— Intermittent ignition = ignition is on
‘Chimneys & Draft.’ Puffbacks and carbon when burner runs. 1000 gallons / 1 GPH =
may be caused by a partially clogged 1000 hours of ignition on time.
nozzle. See Chapter 5 on Nozzles.
11. Ignition “on” time should be
Example 2
checked. This, of course, concerns inter- Interrupted ignition = timed
rupted ignition primary controls. The or sequenced ignition.
ignition “on” time is easily checked by
connecting one lead of a 40-watt test light Cad-cell type relays
to the ignition wire of the primary, and 3000 starts x 45 seconds = 37.5
connecting the other lead to neutral or the hours ignition on time
white wire. Start the burner while watching 3000 starts x 30 seconds = 25 hours
the bulb time to determine the length of
time it remains “on.” With cad cell type 3000 starts x 15 seconds = 12.5 hours
controls, it should remain on for the length 3000 starts x 8/10 seconds = 40
of time specified by the manufacturer. minutes ignition on time
As we can see, we can dramatically
Ignition Control lower ignition on-time and prolong the
Most burner manufacturers today use useful life of our ignition systems and
interrupted ignition. On commercial/ reduce service calls.
industrial burners, ignition “on” times of
greater than 10-20 seconds are seldom Delayed ignition is one of the frus-
found. The purpose of interrupted ignition trating ignition problems we encoun-
is to ignite the fuel and shut off the system, ter. Some solutions are covered in the
prolonging ignition system component life. following charts provided by Beckett
For example, let us say that a residential Corp., Figure 9-14: Ignition Service
burner that consumes 1,000 gallons per Help Chart and Figure 9-15: Delayed
year is operating with a 1 GPH nozzle. For Ignition Problem Solving, on follow-
this example, let us assume the burner will ing pages.
start 3,000 times per year.

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Ignition Systems

Figure 9-14:
Ignition service
help chart

Designation Description Service Hints

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

2. Primary coil Current in this coil generates a

magnetic field

3. Iron core Transfers magnetic field into

secondary coil

4. Secondary coil Magnetic field from core induces

voltage 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 leak
burner housing from around transformer

8. Transformer output Insulates high voltage from ground 1. Must not be cracked
ceramic 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 to
electrode 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 cracked
each electrode from ground

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

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Figure 9-15 Chapter 9
Ignition Systems

Chapter 9—Ignition Systems 9-17