Lennox 80MGF Series Manual page 35

80MGF WITH SURELIGHT IGNITION CONTROL
1 − When there is a call for heat, W1 of the thermostat en-
ergizes W of the furnace control with 24VAC.
2 − S10 primary limit switch and S47 rollout switch are
closed. Call for heat can continue.
3 − SureLight control energizes combustion air blower
B6. Combustion air blower runs until S18 combustion
air prove switch closes (switch must close within 2−1/2
minutes or control goes into 5 minute Watchguard
Pressure Switch delay). Once S18 closes, a 15−sec-
ond pre−purge follows.
4 − SureLight control energizes ignitor. A 20−second
warm−up period begins.
5 − Gas valve opens for a 4−second trial for ignition.
6 − Flame is sensed, gas valve remains open for the heat
call.
7 − After 45−second delay, SureLight control energizes
indoor blower B3.
8 − When heat demand is satisfied, W1 of the indoor ther-
mostat de−energizes W of the SureLight control which
de−energizes the gas valve. Combustion air blower
B6 continues a 5−second post−purge period, and in-
door blower B3 completes a selected OFF time delay.
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