GM9S96 Service Manual
SYSTEM OPERATION
24
ROOM THERMOSTAT
Y2
Y/Y1
C
G
R
W
Y2
Y/Y1
C
G
R
W
Y2
Y/Y1
C
G
R
W
TWIN
TWIN
COND UNIT
CONTACTOR
COND UNIT
CONTACTOR
FURNACE 1
FURNACE 2
WARNING
Natural Gas Minimum: 4.5" w.c. Maximum: 10.0" w.c.
Propane Gas Minimum: 11.0" w.c. Maximum: 13.0" w.c.
The furnace rating plate includes the approved furnace gas
input rating and gas types. The furnace must be equipped to
operate on the type of gas applied. This includes any con-
version kits required for alternate fuels and/or high altitude.
Inlet gas supply pressures must be maintained within the
must be constant and available with all other household gas
-
sure must be maintained to prevent unreliable ignition. The
WARNING
1.
furnace.
2.
3. Set the room thermostat to the lowest possible setting.
4. Remove the burner compartment door.
This furnace is equipped with an ignition device
which automatically lights the burner. Do not try to light the
burner by hand.
5. Move the furnace gas valve manual control to the OFF
position.
6.
air.
7.
the safety instructions in the Safety Considerations on
minutes, move the furnace gas valve manual control
to the ON position.
8. Replace the burner compartment door.
9.
furnace.
10. Turn on the electrical power to the furnace.
11. Adjust the thermostat to a setting above room tem-
perature.
12. After the burners are lit, set the thermostat to desired
temperature.
• On a call for heat, the thermostat contacts close & the
control board receives 24 VAC on the W terminal.
• The control board microcomputer runs its self-check
routine.
•
on Pin 8 of the 12 Pin connector).
•
(0 VAC on Pin 5).
• The control module performs a gas valve circuitry
check to verify gas valve relay state and presence of
voltage at the valve.
• The system will energize the Induced draft blower.
• The pre-purge period begins once the pressure switch
is detected closed (24 VAC on Pin 5).
• After the completion of pre-purge, the control will
energize the igniter.
• After completion of the ignitor warm-up period:
• The gas valve is energized.
•
• After 30 seconds the indoor blower is energized on
heating speed.
•