SYSTEM OPERATION
9
W2 W/W1 R GC Y/Y1 Y2
24V HUM
Terminal is
energized when
pressure switch
is closed
24 VOLT HUM.
& HUMIDISTAT
24 Volt Humidifier Connection
Gas Heat Sequence of Operation
Call for 1st Stage Heat
•
On a call for heat, the thermostat contacts close & the
control board receives 24 VAC on the W1 terminal.
•
The control board microcomputer runs its self-check
routine.
•
The control verifies the limit switch is closed (24 VAC on
Pin 8 of the 12 Pin connector).
•
The control verifies that pressure switch circuit is open
(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 low fire 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.
•
The ignitor is de-energized as soon as flame is sensed.
•
After 30 seconds the indoor blower is energized on
heating speed.
•
When using a single-stage heating thermostat, the
furnace will transition to 2nd stage gas heat by either a
fixed time or auto mode depending on menu selections
made by the installer.
•
The inducer motor is enabled at high speed.
•
Closure of the 2nd stage pressure switch will energize
the high fire stage of the gas valve.
•
The 2nd stage gas heat speed of the indoor blower is
energized
•
When the thermostat is satisfied:
•
The gas valve is de-energized.
•
The inducer remains energized for the post purge period
(15 seconds).
•
The indoor blower runs for the selected off delay period
(90 seconds by default, adjustable from 30 – 180
seconds).
Call for 2nd Stage Heat During 1st Stage Heat Operation
•
The control board receives a 24 VAC signal on the W2
terminal.
•
The inducer motor is enabled at high speed.
•
Closure of the 2nd stage pressure switch will energize
the high fire stage of the gas valve.
•
The 2nd stage gas heat speed of the indoor blower is
energized.
Heating Mode Speed Selection
To change the main blower speed in HEATING mode, follow
the following steps:
Press the left or right switch until LED displays “gA1”
(for single-stage HEATING) or “gA2” (for two-stage
HEATING). Press the center switch and LED will display
the selected speed number as Fxx (xx: Blower speed
number).
The control will rotate available speed number every time
left / right switches are pressed. The table below shows
the available speeds for low & high heat mode.
Press the center switch to save the selection.
NOTE:
Always refer to the Heating Chart to choose from
available heating speeds
THERMOSTAT
CALL
AVAILABLE
SPEEDS
W/W1
F01
(DEFAULT)
F03
F04
W2
F02
(DEFAULT)
F04
F05
One and Two-Stage Heating Speed Table for 2 Stage IFC
Continuous Fan Mode Speed Selection
To change the main blower speed in circulation mode, follow
the following steps:
Press the left or right switch until LED displays “FSd”. Press
the center switch and LED will display the selected speed
number as Fxx (xx: Blower speed number from 1 to 9).
F03 is the default speed for circulation.
