GM9S96 Service Manual
SYSTEM OPERATION
23
2. Remove and save the two screws securing the junc-
tion box to the side panel.
3. Relocate junction box and associated plugs and
grommets to opposite side panel. Secure with screws
removed in step.
Wire routing must not interfere
with circulator blower operation, filter removal or routine
maintenance.
To ensure proper unit grounding, the ground wire should run
from the furnace ground screw located inside the furnace
junction box all the way back to the electrical panel.
Do not use gas piping as an electrical ground. To
and perform the following check.
1. Measure resistance between the neutral (white) con-
nection and one of the burners. Resistance should
measure 10 ohms or less.
This furnace is equipped with a blower door interlock switch
which interrupts unit voltage when the blower door is opened
for servicing. Do not defeat this switch.
Wiring routing must not interfere with cir-
Low voltage connections can be made through either the
right or left side panel. Thermostat wiring entrance holes
shows connections for a “heat/cool system”.
This furnace is equipped with a 40 VA transformer to facili-
tate use with most cooling equipment. Consult the wiring di-
agram, located on the blower compartment door, for further
details of 115 Volt and 24 Volt wiring.
Y
C
Y
C
G
R
W
Y2
Y/Y1
C
G
R
W
ROOM THERMOSTAT
INTEGRATED FURNACE
CONTROL MODULE
REMOTE COOLING UNIT
(SINGLE STAGE)
Thermostat - Single-Stage Heating with Single-Stage Cooling
Y1
C
Y1C
G
R
W
Y2
Y/Y1
C
G
R
W
ROOM THERMOSTAT
INTEGRATED FURNACE
CONTROL MODULE
REMOTE COOLING UNIT
(TWO STAGE)
Y2
Y2
Thermostat - Single-Stage Heating with Two-Stage Cooling
WARNING
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 is required to properly use a sin-
gle-stage furnace in conjunction with a heat pump. Refer to
the fossil fuel kit installation instructions for additional ther-
mostat 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 “FUR-
NACE” terminal strip on the fossil fuel control board.
Two furnaces of the same model may be twinned. The in-
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
synchronously into a common duct system. Using the twin-
-
ternal kits or parts. The staging and speed tap options must
be set the same on both furnaces.
Each furnace must be connected to it’s own 115
VAC power supply. The L1 connection to each furnace must
be in phase (connected to circuit breakers on the same 115
VAC service panel phase leg). To verify that the furnaces
are in phase, check from L1 to L1 on each furnace with a
voltmeter. If the furnaces are in phase, the voltage between
both furnaces will be ZERO.