Fig. 45 — IGC Operating Sequence
Call for heat:
W terminal is energized
Pre-purge: Induced draft motor
starts and runs for 30 seconds at
ignition speed, Speed 1
Ignition: Gas valve and
igniter energize for 2
seconds
Rectification: Flame
sensor activates for
2 seconds after
ignition period
Is flame
sensed after
ignition trial?
Do any limit switches
trip after 90 second
fan off-delay time?
Gas valve and igniter
de-energerized
Unit locks-out for 1 hour
(1 hour auto reset)
Post-purge: Induced draft
motor runs for 30 seconds.
Indoor fan off-delay time
starts for 90 seconds.
Call-off for heat:
W terminal is
de-energized.
Warm-up: Indoor fan on-delay
time starts for 30 seconds.
Inducer motor automatically
ramps up to second speed
with 100 rpm/s rate and then
to steady state rpm/s (third
speed) with 10 rpm/s rate.
Is it the
fourth trial?
15 seconds is added to
fan off-delay time up to a
maximum of 3 minutes.
Normal operation,
no error.
Yes
No
No
No
Yes
Yes
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