Page 24
80UHG-2 MODEL WITH SURELIGHT CONTROL
1 - When there is a call for heat, W1 of the thermostat
energizes 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 blowĆ
er B6. Combustion air inducer runs until S18 comĆ
bustion 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-second 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
(ignitor will remain energized for the first second).
6 - Flame is sensed, gas valve remains open for the
heat call.
7 - After 45-second delay, SureLight control enerĆ
gizes indoor blower B3.
8 - When heat demand is satisfied, W1 of the indoor
thermostat de-energizes W of the SureLight conĆ
trol which de-energizes the gas valve. CombusĆ
tion air inducer B6 continues a 5-second post-
purge period, and indoor blower B3 completes a
selected OFF time delay.
