Lennox KGA Series Service Literature page 22

9-Spark Electrode Figure 13
An electrode assembly is used for ignition spark. The elec­
trode is inserted through holes under the left-most burner.
The electrode tip protrudes into the flame envelope of the
adjacent burner. The electrode assembly is fastened to
burner supports and can be removed for service without re­
moving any part of the burners.
During ignition, spark travels through the spark electrode
(figure 13) and ignites the left burner. Flame travels from
burner to burner until all are lit.
The spark electrode is connected to the ignition control by
an 8 mm silicone‐insulated, stranded, high-voltage wire.
The wire uses a 1/4" (6.35 mm) female quick connect on
both ends of the wire.
NOTE - If the electrode wire is replaced, wire and sup­
pression must be same type of cable. See repair parts
listing for correct replacement.
The spark electrode assembly can be removed for inspec­
tion by removing the screw securing the electrode assem­
bly and sliding it out of unit.
For proper unit operation, electrodes must be positioned
and gapped correctly.
Spark gap may be checked with appropriately sized twist
drills or feeler gauges. Disconnect power to the unit and re­
move electrode assembly. The gap should be between
0.125" + 0.015" (3.2 mm + .4 mm). See figure 13.
NOTE - IN ORDER TO MAXIMIZE SPARK ENERGY
TO ELECTRODE, HIGH-VOLTAGE WIRE SHOULD
TOUCH UNIT CABINET AS LITTLE AS POSSIBLE.
SPARK GAP
SHOULD BE 1/8"
(3mm)
FIGURE 13
10-Flame Sensor Figure 14
A flame sensor is located under the right-most burner. The
sensor is inserted through a hole in the burner support and
the tip protrudes into the flame envelope of the right-most burn­
er. The sensor assembly is fastened to burner supports and
can be removed for service without removing any part of the
burners.
When flame is sensed by the flame sensor (indicated by
microamp signal through the flame) sparking stops imme­
diately or after the eight-second trial for ignition. During
operation, flame is sensed by current passed along the
IGNITOR
ground electrode (located on the spark electrode),
through the flame, and into the sensing electrode. The ig­
nition control allows the gas valve to stay open as long as a
flame signal (current passed through the flame) is sensed.
SIDE VIEW SENSOR
Gas Flow
INTEGRATED CONTROL BOARD A3
11-Burner Control A3
Shock hazard. Spark related compo­
nents contain high voltage which can
cause personal injury or death. Discon­
nect power before servicing. Control is
not field repairable. Unsafe operation
will result. If control is inoperable, sim­
ply replace the entire control.
The burner control A3 is located in the gas heat section. See
figures 16 and 15.
The ignition control provides four main functions: gas
valve control, blower control, ignition and flame sensing.
The control has a green LED to show control status (table
4). The unit will usually ignite on the first trial and A3 allows
three trials for ignition before locking out. The lockout time is
1 hour. After lockout, the ignition control automatically resets
and provides three more attempts at ignition. Manual reset
after lockout requires removing power from the control for
more than 1 second or removing the thermostat call for heat
for more than 1 second but no more than 20 seconds. 24 volt
thermostat connections (P2) and heating component con­
nections (J1) are made through separate jackplugs. See ta­
ble 5 for thermostat terminations and table 6 for heating
component terminations.
LED
Slow Flash
Fast Flash
Internal Control Fault, No Power To Board
Steady Off
Steady On
2 Flashes Lockout. Failed to detect or sustain flame.
Page 22
1-3/4"
(45mm)
3/8"
(10mm)
FIGURE 14
WARNING
TABLE 4
STATUS
Normal operation. No call for heat.
Normal operation. Call for heat.
or Gas Valve Relay Fault
Control Internal Failure.