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G60UH Series
Heating Sequence of Operation
NOTE − The thermostat selection DIP switch on the integrated
control is factory−set in the TWO−STAGE" position.
Applications Using a Two−Stage Thermostat
A − Heating Sequence −− Integrated Control Thermostat
Selection DIP switch in Two−Stage" Position (Factory
Setting)
1 − On a call for heat, thermostat first−stage contacts close
sending a signal to the integrated control. The inte-
grated control runs a self-diagnostic program and
checks high temperature limit switches for normally
closed contacts and pressure switches for normally
open contacts.The combustion air inducer is ener-
gized at low speed and the humidifier terminal is ener-
gized.
2 − Once the control receives a signal that the low pres-
sure switch has closed, the combustion air inducer be-
gins a 15−second pre−purge in low speed.
3 − After the pre−purge is complete, a 20−second initial ig-
nitor warm−up period begins. The combustion air in-
ducer continues to operate at low speed.
4 − After the 20−second warm−up period has ended, the gas
valve is energized on low fire (first stage) and ignition oc-
curs. At the same time, the control module sends a sig-
nal to begin an indoor blower 45−second ON−delay.
When the delay ends, the indoor blower motor is ener-
gized on the low fire heating speed. The furnace will
continue this operation as long as the thermostat has
a first−stage heating demand.
5 − If second−stage heat is required, the thermostat sec-
ond−stage heat contacts close and send a signal to the
integrated control. The integrated control initiates a
30−second second−stage recognition delay.
6 − At the end of the recognition delay, the integrated con-
trol energizes the combustion air inducer at high
speed. The control also checks the high−fire (second
stage) pressure switch to make sure it is closed.The
high−fire (second stage) gas valve is energized and
the indoor blower motor is energized for operation at
the high−fire heating speed.
7 − When the demand for high−fire (second stage) heat is
satisfied, the combustion air inducer is switched to the
low−fire heating speed and the high−fire (second
stage) gas valve is de−energized. The low−fire (first
stage) gas valve continues operation. The indoor
blower motor is switched to the low−fire heating speed.
8 − When the thermostat demand for low−fire (first stage)
heat is satisfied, the gas valve is de−energized and the
field−selected indoor blower−off delay begins. The
combustion air inducer begins a 5−second post−purge
period.
9 − When the combustion air post−purge period is com-
plete, the inducer and humidifier terminal are de−ener-
gized. The indoor blower is de−energized at the end of
the off delay.
Applications Using A Single−Stage Thermostat
B − Heating Sequence −− Integrated Control Thermostat
Selection DIP switch in Single−Stage" Position
NOTE − In these applications, two−stage heat will be initi-
ated by the integrated control if heating demand has not
been satisfied after the field adjustable period (10 or 15
minutes).
1 − On a call for heat, thermostat first−stage contacts close
sending a signal to the integrated control. The inte-
grated control runs a self-diagnostic program and
checks high temperature limit switches for normally
closed contacts and pressure switches for normally
open contacts.The combustion air inducer is ener-
gized at low speed and the humidifier terminal is ener-
gized.
2 − Once the control receives a signal that the low pres-
sure switch has closed, the combustion air inducer be-
gins a 15−second pre−purge in low speed.
3 − After the pre−purge is complete, a 20−second initial ig-
nitor warm−up period begins. The combustion air in-
ducer continues to operate at low speed.
4 − After the 20−second warm−up period has ended, the gas
valve is energized on low fire (first stage) and ignition oc-
curs. At the same time, the control module sends a sig-
nal to begin an indoor blower 45−second ON−delay.
When the delay ends, the indoor blower motor is ener-
gized on the low−fire heating speed. The integrated
control also initiates a second−stage on delay (factory−
set at 10 minutes; adjustable to 15 minutes).
5 − If the heating demand continues beyond the second−
stage on delay, the integrated control energizes the
combustion air inducer at high speed. The control also
checks the high−fire (second stage) pressure switch to
make sure it is closed.The high−fire (second stage)
gas valve is energized and the indoor blower motor is
energized for operation at the high−fire heating speed.
6 − When the thermostat heating demand is satisfied, the-
combustion air inducer begins a 5−second post−purge.
The field−selected indoor blower−off delay begins.
7 − When the combustion air post−purge period is com-
plete, the inducer and humidifier terminal are de−ener-
gized. The indoor blower is de−energized at the end of
the off delay.
Service
WARNING
Disconnect power before servicing unit.
CAUTION
Label all wires prior to disconnection when servicing
controls. Wiring errors can cause improper and dan-
gerous operation. Verify proper operation after ser-
vicing.
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