Amana GUIA Series Service Instructions Manual page 87

SYSTEM OPERATION
NORMAL SEQUENCE OF OPERATION
(80% Two-Stage Models with White-Rodgers 50A51-215
Integrated Ignition Control)
Power Up
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 flashes LED one time.
4. Integrated control module monitors safety circuits con-
tinuously.
5. Furnace awaits call from thermostat.
Heating Mode
The normal operational sequence in heating mode is as fol-
lows:
1. R and W1 (or R and W1 and W2) thermostat contacts
close, initiating a call for heat.
2. The induced draft blower is energized on high speed for
a 10 second prepurge. Humidifier terminals are energized
with induced draft blower.
3. The induced draft blower steps to low speed following
prepurge. Low stage pressure switch contacts are closed.
4. The ignitor is energized and is allowed to preheat for 17
seconds.
5. The gas valve is energized delivering gas to the burners
at the low stage heat flow rate.
6. The control checks for a signal from the flame sensor
within seven seconds after the gas valve is energized
(opens). Gas will only continue to flow if a signal is
present.
7. The control checks the thermostat to see whether the
call for heat is for low stage heat or high stage heat. If
the call is for high stage heat, the induced draft blower
is switched to high speed and the gas valve is ener-
gized on high flow rate.
8. The control waits 30 seconds and turns on the air circu-
lator blower to the appropriate speed (high heat speed
for high heat or low heat speed for low heat). Electronic
air cleaner terminals are energized with the circulator
blower.
On some Amana models, the high heat air circulator
speed may be the same as the low heat circulator speed.
These models are factory shipped to be within the rise
range on both stages with the same air circulator speed.
9. The furnace is now operating on the specified stage called
out by the two stage thermostat.
10. If the two stage thermostat changes the call from low
heat to high heat, the control will immediately switch the
vent blower motor, gas valve, and air circulating speed to
their high stage setting.
11. If the two stage thermostat changes the call from high
heat to low heat, the control will immediately switch the
induced draft blower motor to low speed and switch the
flow rate on the gas valve to low. The air circulator blower
will remain on high heating speed for thirty seconds be-
fore switching to the low heat circulating speed. The 30
second delay feature on the circulator speed eliminates
the possibility of tripping the high (primary) limit when
the high stage flue products are traveling through the
heat exchanger upon a call for low stage heat.
12. R and W1 (or R and W1 and W2) thermostat contacts
open, completing the call for heat.
13. The control turns the gas valve off, extingushing flame.
14. After a five second delay while flue products are purged
from the heat exchanger, the induced draft blower motor
is turned off (the induced draft blower is on low speed
during the five second post purge.) Humidifier termi-
nals are de-energized.
15. The air circulator blower has an adjustable delay-off tim-
ing of 60, 90, 120, or 180 seconds (starting from the
time the gas valve closes). The speed(s) run during this
period depend on the last heat call seen by the thermo-
stat.
If the last call for heat was a call for low heat, the air
circulator blower will run on the low heat speed for the
duration of the adjusted delay-off timing (60, 90, 120, or
180 seconds).
If the last call for heat was a call for high heat, the air
circulating blower run on the high heating speed for thirty
seconds and then switch to the low heating speed for
the balance of the adjusted delay-off timing (30, 60,
90, or 150 seconds).
16. Electronic air cleaner terminals are de-energized.
17. Furnace awaits next call from thermostat.
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