SYSTEM OPERATION
47
Rev. 0
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 flashes LED one time.
•
Integrated control module monitors safety circuits
continuously.
•
Furnace awaits call from thermostat.
Heating Mode
The normal operational sequence in heating mode is as
follows:
•
R and W thermostat contacts close, initiating a call
for heat.
•
Integrated control module performs safety circuit
checks.
•
Induced draft blower is energized causing pressure
switch contacts to close. Humidifier terminals are en-
ergized with induced draft blower.
•
Igniter warm up begins upon close of pressure switch
contacts.
•
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 sensed.
•
Circulator blower is energized on heat speed follow-
ing a fixed thirty second blower on delay. Electronic
air cleaner terminals are energized with circulator
blower.
•
Furnace runs, integrated control module monitors
safety circuits continuously.
•
R and W thermostat contacts open, completing the
call for heat.
•
Gas valve closes, extinguishing flame.
•
Induced draft blower is de-energized following a fif-
teen second post purge. Humidifier terminals are de-
energized.
•
Circulator blower is de-energized following a select-
able heat off delay period (60, 90, 120, or 180 sec-
onds). Electronic air cleaner terminals are de-ener-
gized.
•
Furnace awaits next call from thermostat.
Cooling Mode
The normal operational sequence in cooling mode is as
follows:
•
R and Y thermostat contacts close, initiating a call
for cool.
•
Integrated control module performs safety circuit
checks.
•
Outdoor fan and compressor are energized.
•
Circulator blower is energized on cool speed follow-
ing a fixed five second on delay. Electronic air cleaner
terminals are energized with circulator blower.
•
Furnace circulator blower and outdoor cooling unit
run, integrated control module monitors safety cir-
cuits continuously.
•
R and Y thermostat contacts open, completing the
call for cool.
•
Outdoor fan and compressor are de-energized.
•
Circulator blower is de-energized following a fixed
forty five second cool off delay period. Electronic air
cleaner terminals are de-energized.
•
Furnace awaits next call from thermostat.
Fan Only Mode
The normal operational sequence in fan only mode is as
follows:
•
R and G thermostat contacts close, initiating a call
for fan.
•
Integrated control module performs safety circuit
checks.
•
Circulator blower is energized on cool speed. Elec-
tronic air cleaner terminals are 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 terminals are de-energized.
•
Furnace awaits next call from thermostat.
