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1 -
Line voltage is applied to L1 and N. the T1 low voltage transformer is energized, and line voltage is applied to B3 indoor blower.
2 -
S47 rollout switch(es) must be closed in order for 24V from transformer to be output on integrated control ”R” to power thermo
stat.
3 -
When there is a call for heat, W1 of the thermostat energizes W of the furnace control with 24VAC.
4 -
A92 integrated control runs a self-check. S10 primary limit and S21 secondary limit contacts are found to be closed. Call for
heat can continue.
5 -
A92 integrated control energizes B6 combustion air inducer. S18 combustion air pressure switch closes . Once S18 closes, a
15-second pre-purge follows.
6 -
A92 integrated control energizes R33 ignitor. A 20-second warm-up period begins.
7 -
GV1 gas valve opens for a 4-second trial for ignition
8 -
Flame is sensed, gas valve remains open for the heat call.
9 -
After 30-second delay (from flame sensed), A92 integrated control applies 24VAC to Heat speed of B3 indoor blower.
10 - When heat demand is satisfied, W1 of the indoor thermostat de-energizes W of A92ignition control which de-energizes GV1
gas valve.
B6 combustion air inducer continues a 5-second post-purge period, and B3 indoor blower completes a selected OFF time
delay.
EL180UHNE040 Schematic
