Goodman ACS series Service Instructions Manual page 78

PRODUCT DESIGN
NORMAL SEQUENCE OF OPERATION
Amana Brand Two-Stage 80% and 90% Furnaces
®
White-Rodgers 50V61 Integrated Ignition Control
P U
OWER P
The normal power up sequence is as follows:
1. 115 VAC power applied to furnace.
2. Integrated control module performs internal checks.
3. Integrated control module LED will light.
4. Integrated control module monitors safety circuits con-
tinuously.
5. Furnace awaits call from thermostat.
H M
EATING ODE
The normal operational sequence in heating mode is as
follows:
1. R and W1 (or R and W1/W2) thermostat contacts close,
initiating a call for heat.
2. Integrated control module performs safety circuit
checks.
3. Induced draft blower is energized on high speed for a
15-second prepurge. Humidifier terminals are energized
with induced draft blower.
4. Induced draft blower steps to low speed following
prepurge. Low stage pressure switch contacts are
closed.
5. Igniter warm up begins upon step to low speed and
presence of closed low stage pressure switch contacts.
6. Gas valve opens at end of igniter warm up period, deliv-
ering gas to burners and establishing flame.
7. Integrated control module monitors flame presence. Gas
valve will remain open only if flame is detected.
8. If the thermostat call is for low heat, gas valve and in-
duced draft blower will continue on low stage. If the call
is for high heat, the gas valve and induced draft blower
will change to high stage.
9. Circulator blower is energized on heat speed following
a fixed thirty (30) second blower on delay. The circula-
tor blower requires thirty (30) seconds to ramp up to full
speed. Electronic air cleaner terminals are energized
with circulator blower.
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10. Furnace is now operating on the specified stage called
for by the two-stage thermostat.
11. Furnace runs, integrated control module monitors safety
circuits continuously.
12. If the two-stage thermostat changes the call from low
heat to high heat, the integrated control module will im-
mediately switch the induced draft blower, gas valve,
and circulator blower to their high stage settings.
13. If the two-stage thermostat changes the call from high
heat to low heat, the control will immediately switch the
induced draft blower and gas valve to their low stage
settings. The circulator blower will remain on high heat-
ing speed for thirty (30) seconds before switching to the
low heat circulating speed.
14. R and W1 (or R and W1/W2) thermostat contacts open,
allowing the gas valve to cycle off.
15. Induced draft blower is de-energized following a fifteen
(15) second post purge. Humidifier terminals are de-
energized.
16. Circulator blower continues running for the selected heat
off delay period (90, 120, 150 or 180 seconds). The
speed run during this period depends on the last heat
call provided by the thermostat.
If the last call for heat was a call for low heat, the air
circulator motor will run on low heat speed for the dura-
tion of the heat off delay period (90, 120, 150 or 180
seconds).
If the last call for heat was a call for high heat, the air
circulating motor will run on the high heating speed for
thirty (30) seconds
17. Circulator blower and electronic air cleaner terminals
are de-energized.
18. Circulator blower ramps down to OFF during the 30 sec-
onds following the heat off delay period.
19. Furnace awaits next call from thermostat.