35
•
Gas valve opens at end of igniter warm up period, delivering
gas to burners and establishing flame.
•
Integrated control module monitors flame presence. Gas
valve will remain open only if flame is detected.
•
If the thermostat call is for low heat, gas valve and induced
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.
•
Circulator blower is energized on heat speed following a
thirty (30) second blower on delay. The circulator blower
requires thirty seconds to ramp up to full speed.
Electronic air cleaner terminal is energized with circulator
blower.
•
Furnace is now operating on the specified stage called
for by the two-stage thermostat.
•
Furnace runs, integrated control module monitors safety
circuits continuously.
•
If the two-stage thermostat changes the call from low
heat to high heat, the integrated control module will
immediately switch the induced draft blower, gas valve,
and circulator blower to their high stage settings.
•
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
heating speed for thirty (30) seconds before switching to
the low heat circulating speed.
•
R and W1 (or R and W1/W2) thermostat contacts open,
completing the call for heat.
•
Gas valve closes, extinguishing flame.
•
Induced draft blower is de-energized following a fifteen
second post purge. Humidifier terminals are de-energized.
•
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 duration
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 and then switch to the low heating
speed for the
balance
of the heat off delay period (60,
90, 120 or 150 seconds).
•
Circulator blower and electronic air cleaner terminal is
de-energized.
•
Circulator blower ramps down to OFF during the 30
seconds following the heat off delay period.
•
Furnace awaits next call from thermostat.
C
OOLING
M
ODE
The normal operational sequence in cooling mode is as fol-
lows:
•
R and Y1/G or Y2/G thermostat contacts close, initiating
a call for cool.
•
Integrated control module performs safety circuit checks.
•
Outdoor fan and compressor are energized to their
appropriate speed.
•
Circulator blower is energized on the appropriate cool
speed at the level and time determined by the selected
ramping profile. Electronic air cleaner terminal is
energized with circulator blower.
•
Furnace circulator blower and outdoor cooling unit run
their appropriate speeds, integrated control module
monitors safety circuits continuously.
•
R and Y1/G or Y2/G thermostat contacts open,
completing the call for cool.
•
Outdoor fan and compressor are de-energized.
•
Circulator blower continues running during a cool off delay
period. The OFF delay time and airflow level are
determined by the selected ramping profile.
•
Electronic air cleaner terminal and circulator blower are
de-energized.
•
Furnace awaits next call from thermostat.
F
AN
O
NLY
M
ODE
The normal operational sequence in fan only mode is as fol-
lows:
•
R and G thermostat contacts close, initiating a call for
fan.
•
Integrated control module performs safety circuit checks.
•
Circulator blower is energized on continuous fan speed
(25% of the furnace’s maximum airflow capability)
following a five (5) second delay. Electronic air cleaner
terminal is energized.
•
Circulator blower runs, integrated control module
monitors safety circuits continuously.
•
R and G thermostat contacts open, completing the call
for fan.
•
Circulator blower is de-energized. Electronic air cleaner
terminal is de-energized.
•
Furnace awaits next call from thermostat.
O
PERATIONAL
C
HECKS
The burner flames should be inspected with the burner com-
partment door installed. Flames should be stable, quiet, soft,
and blue (dust may cause orange tips but they must not be
yellow). Flames should extend directly outward from the burn-
ers without curling, floating, or lifting off. Flames must not
impinge on the sides of the heat exchanger firing tubes.
