Lennox LGT Series Unit Information page 28

TABLE 7
GAS VALVE REGULATION FOR LGT UNITS
Operating Pressure "W.C.
Max Inlet
(outlet) Factory Setting
Pressure
Natural
"W.C.
Low
13.0 1.6+0.2. 3.7+0.3
WHITE RODGERS 36H54 GAS VALVE
Outlet Pressure
Tap
Low Fire Adjustment
High Fire Adjustment
(under cap)
GAS VALVE SWITCH SHOWN IN ON POSITION.
FIGURE 20
11-Spark Electrodes
An electrode assembly is used for ignition spark. Two iden-
tical electrodes are used (one for each gas heat section).
The electrode is mounted through holes on the left-most
end of the burner support. The electrode tip protrudes into
the flame envelope of the adjacent burner. The electrode
assembly is fastened to burner supports and can be re-
moved for service without removing any part of the burn-
ers.
During ignition, spark travels through the spark electrode
(figure 21) 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 a 8 mm silicone-insulated stranded high voltage wire.
The wire uses 1/4" (6.35 mm)female quick connect on the
electrode end and female spark plug-type terminal on the
ignition control end
L.P. Propane
High Low High
5.5+0.3 0.5+0.5
Two-Stage
Inlet Pressure Tap
(under cap)
NOTE-IN ORDER TO MAXIMIZE SPARK ENERGY TO
ELECTRODE, HIGH VOLTAGE WIRE SHOULD
TOUCH UNIT CABINET AS LITTLE AS POSSIBLE.
.125" ± .015"
(3.2 mm ± .4 mm)
GROUND
ELECTRODE
12-Flame Sensors
A flame sensor is located on the right side of each burn-
er support. The sensor is mounted through a hole in the
burner support and the tip protrudes into the flame enve-
lope of the right most burner. The sensor assembly is fas-
tened 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.
During operation, flame is sensed by current passed along
the ground electrode (located on the spark electrode),
through the flame and into the sensing electrode. The igni-
tion control allows the gas valve to stay open as long as a
flame signal (current passed through the flame) is sensed.
Page 28
ELECTRODE
FIGURE 21
SENSOR
FIGURE 22
GROUND