GC9C80 Installation Manual
17
• The furnace is setup by default to use a two-stage
heating thermostat.
• The menu may be accessed by pressing the Left or Right
menu switches to get to theAHSmenu.
• The menu will display these options: no10203060
AUt
• Select no.
• Press the center switch to save the selection.
• In this mode only a W2 signal on the control board will
bring on 2nd stage heat.
This furnace can be used in conjunction with a heat pump
in a fossil fuel application. A fossil fuel application refers to
a combined gas furnace and heat pump installation which
uses an outdoor temperature sensor to determine the most
A heat pump thermostat with three stages of heat is required
to properly use a two-stage furnace in conjunction with a
heat pump. Refer to the fossil fuel kit installation instructions
for additional thermostat requirements.
Strictly follow the wiring guidelines in the fossil fuel kit instal-
lation instructions. All furnace connections must be made
to the furnace two-stage integrated control module and the
Two furnaces of the same model may be twinned. The in-
tegrated control board has a 3/16” terminal labeled “TWIN”
located beside the low voltage thermostat connection strip.
Twinning allows simultaneous operation of two furnaces and
forces the indoor blower motors of each furnace to operate
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external kits or parts. The staging and speed tap options
must be set the same on both furnaces.
power supply. The L1 connection to each furnace must be in
service panel phase leg). To verify that the furnaces are in
phase, check from L1 to L1 on each furnace with a voltme-
ter. If the furnaces are in phase, the voltage between both
furnaces will be .
ROOM THERMOSTAT
Y2
Y/Y1
C
G
R
W/W1
W2
Y2
Y/Y1
C
G
R
W/W1
W2
Y2
Y/Y1
C
G
R
W/W1
W2
TWIN
TWIN
COND UNIT
CONTACTOR
COND UNIT
CONTACTOR
FURNACE 1
FURNACE 2
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The furnace integrated control module is equipped with line
voltage accessory terminals for controlling power to an op-
below:
Humidifier
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structions for locating, mounting, grounding, and controlling
these accessories. Accessory wiring connections are to be
made through the 1/4” quick connect terminals provided on
as shown.
If it is necessary for the installer to supply additional line
voltage wiring to the inside of the furnace, the wiring must
conform to all local codes, and have a minimum temperature
inside the furnace junction box.
H) is energized with 115 volts whenever the induced draft
blower is energized. The integrated control module electron-
whenever the circulator blower is energized. This terminal
transformer. The remaining primary transformer wire would
be connected to the Line N on the control board.