5322625-UIM-A-0417
22 Johnson Controls Unitary Products
GAS VALVE FAULT
If the main valve output is sensed to be energized for more than 1 sec-
ond when commanded to be off, the control de-energizes the induced
draft motor (if flame is not present) to attempt to open the pressure
switch to de-energize the gas valve. If the main gas valve still senses
being energized after the inducer has been off for 10 seconds, the con-
trol re-energizes the inducer to vent the unburned gas. The control
enters a hard lockout flashing a sequence of “10” times on the LED.
The only way to recover from a hard lockout is to remove and reapply
24VAC power to the control board.
Safety Controls
The control circuit includes the following safety controls:
1. Limit Switch (LS) - This control is located inside the blower compart-
ment and protrudes into the heat exchanger compartment and is set
to open at the temperature indicated in the Temperature Controls
Table of the unit wiring diagram. It resets automatically. The limit
switch operates when a high temperature condition occurs, thus
shutting down the ignition control, closing the main gas valve and
energizing the blower.
2. Pressure Switch (PS) - If the draft motor should fail, the pressure
switch prevents the ignition control and gas valve from being ener-
gized.
3. Flame Sensor - The flame sensor is located on the left-most burner.
If an ignition control fails to detect a signal from the flame sensor
indicating the flame is properly ignited, then the main gas valve
closes.
4. Rollout Switch (RS) - This switch is located on the burner assembly.
In the event of a sustained main burner flame rollout, the control
closes the main gas valve. This is a manual reset type switch.
NOTICE
The manual reset Rollout Switch (RS) must be reset before allowing
furnace operation.
Table 18: Ignition Control Board Fault Codes
Flash Code Description
Normal Operation
Green Heartbeat Standby mode
Amber Heartbeat Call for furnace heat active
Operational Faults
Steady ON (any color) Control failure
Rapid Amber Flashes Low flame current
1 Red Flash Flame sensed with gas valve off
2 Red Flashes Pressure switch closed with inducer off
3 Red Flashes Pressure switch open with inducer on
4 Red Flashes Limit switch or rollout switch open
5 Red Flashes
Limit switch or rollout switch open greater than
15 minutes
6 Red Flashes Pressure switch cycle lockout
7 Red Flashes Lockout due to failed ignition
8 Red Flashes Lockout due to too many flame dropouts
10 Red Flashes Gas valve fault code
11 Red Flashes
Limit/Rollout switch open between 5 and 15
minutes
12 Red Flashes Model ID plug not inserted
Wiring Related Faults
9 Red Flashes Incorrect low voltage polarity
4 Amber Flashes Y1 or Y2 thermostat demand without a G
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