27
Blower Heat Off Delay Timings
The integrated control module provides a selectable heat-off
delay function. The heat off delay period may be set to 90, 120,
150 or 180 seconds using the DIP switches or jumper provided
on the control module. The delay is factory-shipped at
150 seconds, but may be changed to suit the installation
requirements and/or homeowner preference. Refer to the
following chart for DIP switch positions and corresponding delay
times.
NORMAL SEQUENCE OF OPERATION
Power Up
The normal power up sequence is as follows:
■
115 VAC power applied to furnace.
■
Integrated control module performs internal checks.
■
Integrated control module displays “88” on the dual
7-segment LED display.
■
Integrated control module monitors safety circuits
continuously.
■
Furnace awaits call from thermostat. Displays “OP” on the
dual 7-segment LED display.
Heating Mode
The normal operational sequence in heating mode is as follows:
■
R and W1 (or R and W1/W2) thermostat contacts close,
initiating a call for heat.
■
Integrated control module performs safety circuit checks.
■
Induced draft blower is energized on high speed for a
15-second prepurge. Humidifier terminal is energized with
induced draft blower.
■
Induced draft blower steps to low speed following prepurge.
Low-stage pressure switch contacts are closed.
■
Igniter warm-up begins upon step to low speed and presence
of closed low-stage pressure switch contacts.
■
Gas control valve opens at the end of the igniter warm-up
period, delivering gas to the burners and establishing a flame.
■
Integrated control module monitors flame presence. Gas
control valve will remain open only if flame is detected.
■
If the thermostat call is for low heat, the gas control valve and
induced draft blower will continue on low stage. If the call is
for high heat, the gas control valve and induced draft blower
will change to high stage.
■
Circulator blower is energized on heat speed following a fixed
30-second blower-on delay. The circulator blower requires
30 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 2-stage thermostat.
■
Furnace runs, integrated control module monitors safety
circuits continuously.
■
If the 2-stage thermostat changes the call from low heat to
high heat, the integrated control module will immediately
switch the induced draft blower, gas control valve and
circulator blower to their high-stage settings.
■
If the 2-stage thermostat changes the call from high heat to
low heat, the integrated control module will immediately
switch the induced draft blower and gas control valve to their
low-stage settings. The circulator blower will remain on
high-heating speed for 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 control valve closes, extinguishing flame.
■
Induced draft blower is de-energized following a 15-second
post purge. Humidifier terminal is 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
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 terminals are de-
energized.
■
Circulator blower ramps down to Off during the 30 seconds
following the heat-off delay period.
■
Furnace awaits next call from thermostat.
Cooling Mode
The normal operational sequence in cooling mode is as follows:
■
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 speeds.
■
Circulator blower is energized on the appropriate cool speed
at the level and time determined by the selected ramping
profile. Electronic air cleaner terminals are energized with
circulator blower.
■
Furnace circulator blower and outdoor cooling unit run their
appropriate speed; 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.
Switch Bank: S1
DIP Switch Number
Heat-Off Delay
1
2
90 seconds
Off
Off
120 seconds
On
Off
150 seconds*
Off
On
180 seconds
On
On
*Indicates factory setting
