Lennox G50UHi Unit Information page 9

INTEGRATED IGNITION CONTROL 97L48
FIGURE 6
TABLE 1
IGNITION CONTROL 97L48 TERMINAL DESIGNATIONS
ACB COOL blower − cooling speed (line voltage)
ACB HEAT blower − heating speed (line voltage)
PARK
ACB LOW
ACC
accessory terminal (line voltage)
TX
line voltage to transformer
HOT
HTG ACC
heat only accessory (line voltage)
NEUTRAL
24VAC HOT 24vac return from transformer
24VAC RTN
FLAME SENSE
J156
J58
alternate blower speeds
continuous low speed
120vac hot
120vac neutral
24vac from transformer
flame sense terminal
IGNITION CONTROL 97L48 J156 TERMINAL
PIN #
1
2
3
4
5
6
IGNITION CONTROL 97L48 J58 TERMINAL
PIN #
1
2
3
4
5
6
7
8
9
a−Electronic Ignition (See Figure 8)
On a call for heat the SureLight
bustion air inducer prove switch. The control will not begin
the heating cycle if the prove switch is closed (by−passed).
Once the proving switch is determined to be open, the com-
bustion air inducer is energized. When the differential in the
prove switch is great enough, the prove switch closes and a
15−second pre−purge begins. If the prove switch is not
proven within 2−1/2 minutes, the control goes into Watch-
guard−Pressure Switch mode for a 5−minute re−set period.
After the 15−second pre−purge period, the SureLight ignitor
warms up for 20 seconds during which the gas valve opens
at 19 seconds for a 4−second trial for ignition. The ignitor
stays energized during the 4−second ignition trial until
flame is sensed. If ignition is not proved during the 4−sec-
ond period, the control will try four more times with an inter
purge and warm−up time between trials of 35 seconds. Af-
ter a total of five trials for ignition (including the initial trial),
the control goes into Watchguard−Flame Failure mode. Af-
ter a 60−minute reset period, the control will begin the igni-
tion sequence again.
The SureLight control board has an added feature that pro-
longs the life of the ignitor. After a successful ignition, the
SureLight control utilizes less power to energize the ignitor
on successive calls for heat. The control continues to ramp
down the voltage to the ignitor until it finds the lowest
amount of power that will provide a successful ignition. This
amount of power is used for 255 cycles. On the 256th call
for heat, the control will again ramp down until the lowest
power is determined and the cycle begins again.
Page 9
TABLE 2
DESIGNATIONS
FUNCTION
Ignitor
Not Used
Ignitor Neutral
Combustion Air Inducer Line Voltage
Not Used
Combustion Air Inducer Neutral
TABLE 3
DESIGNATIONS
FUNCTION
Primary Limit In
Gas Valve Common
Roll Out Switch Out
Gas Valve 24V
Pressure Switch In
Pressure Switch and Primary Limit Out
Not Used
Roll Out Switch In
Ground
®
control monitors the com-