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A−Sequence of Operation
Ignitor operation will vary between SureLight boards. Board
63K89, 56L83 and 24L85 will energize ignitor for the first
second of the 4 second ignition trial. Board 97L48, will en-
ergize ignitor during the entire trial until flame is sense.
1 − When there is a call for heat, W1 of the thermostat en-
ergizes W of the furnace control with 24VAC.
2 − SureLight control runs self−check for S10 primary limit
switch normally closed contacts. The control also
checks S128 combustion air prove switch and S102
high fire prove switch normally open contacts. Follow
steps 4 through 8 per respective thermostat.
Single−stage Mode, Single−stage Thermostat
3 − SureLight control energizes combustion air inducer B6
on high speed. Combustion air blower runs until S102
high fire prove switch closes (switch will close within
2−1/2 minutes or control goes into Watchguard−
PROVE Switch mode). A 15−second pre−purge follows
after S102 closes.
4 − SureLight control energizes ignitor. A 20−second
warm−up period begins.
5 − Gas valve is energized on first stage heat (low). Gas
valve opens for a 4 second trial for ignition.
6 − Flame is sensed. After 8 seconds from when gas valve
opens, valve energizes on second stage (high heat).
7 − After 45−second delay, indoor blower B3 is energized
on heating speed.
Two−stage Mode, Single−stage Thermostat
1 − SureLight control energizes combustion air inducer B6
on low speed. Combustion air inducer runs until com-
bustion air prove switch S102 (or S128 onG32V3−75
units) closes (switch will close within 2−1/2 minutes or
control goes into Watchguard−PROVE Switch mode).
A 15−second pre−purge follows once S102 closes.
2 − SureLight control energizes ignitor. A 20−second
warm−up period begins.
3 − Gas valve is energized on first stage. Gas valve opens
for a 4−second trial for ignition. Signal is sent from con-
trol module to two−stage control board to begin W2
(second−stage) ON delay.
4 − Flame is sensed, gas valve remains open for the heat
call.
5 − After 45−second delay, indoor blower B3 is energized
on low speed.
6 − Second stage time on delay complete (8, 12, or 15 min-
utes). Combustion air inducer B6 switches to high
speed, indoor blower B3 switches to heating speed
and gas valve opens on high fire (second stage.)
Two−stage Mode, Two−stage Thermostat
1 − SureLight control energizes combustion air inducer B6
on low speed. Combustion air inducer runs until com-
bustion air prove switch S102 closes (or S128 on
G32V3−75 units. Switch will close within 2−1/2 minutes
or control goes into Watchguard−PROVE Switch
mode). A 15−second pre−purge follows once S102
closes.
2 − SureLight control energizes ignitor. A 20−second
warm−up period begins.
3 − Gas valve is energized on first stage only. Gas valve
opens for a 4−second trial for ignition.
4 − Flame is sensed, gas valve remains open for the heat
call.
5 − After 45−second delay, indoor blower B3 is energized
on low speed.
6 − Call for second stage heat comes from indoor thermo-
stat (W2).
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