GM9S80 Service Manual
SYSTEM OPERATION
8
24 VOLT HUM. &
HUMIDISTAT
W R G C Y
24V HUM Terminal is
energized when pressure
switch is closed
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
temperature.
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.
•
• The gas valve is de-energized.
• The inducer remains energized for the post purge
period (15 seconds).
•
(90 seconds by default, adjustable from 30 – 180
seconds).
To change the main blower speed in HEATING mode, follow
the following steps:
1.
single stage HEATING). Press center button and LED
Blower speed number).
2. The control shall rotate available speed number ev-
ery time Left/Right switches are pressed. Table be-
low shows the available speeds for Low & High heat
mode.
3. When the center switch is pressed, the current dis-
played speed shall be selected, and control shall
Always refer to the Heating Chart to choose
from available heating speeds
THERMOSTAT CALL AVAILABLE SPEEDS
W/W1
F01
F03
F04
F02 (DEFAULT)
To change the main blower speed in circulation mode, follow
the following steps:
1.
Press the center switch and LED will display the select-
from 1 to 9). F01 is the default speed for circulation.
2. The control will rotate available speed number every
time left/right switches are pressed. All 9 speeds are
available for circulation.