1101790-UIM-C-0414
28
Johnson Controls Unitary Products
Lockout
While in lockout, the control board keeps the pilot gas valve,
main gas valve and induced draft motor de-energized.
Lockouts due to failed ignition or flame losses may be reset by
removing the call for heat (W1) for more than 1 second, but less
than 20 seconds, or by removing power from the control for
over 0.25 seconds. The control will automatically reset lockout
after 60 minutes.
Lockouts due to detected internal control faults will reset after
60 minutes or power interruption.
High Temperature Limit Switch
Any time the high temperature limit switch is open the control
board will run the indoor blower motor on heat speed, the
inducer (on high speed for 2 stage models), de-energize the
gas valve, and flash “6” on the LED. When the high temperature
switch closes, the control will restart the ignition sequence
beginning with pre-purge.
Rollout Switch
If the rollout switch opens for more than 0.25 seconds, the
control board will run the inducer (on high speed for 2 stage
models) for a post-purge period, immediately de-energize the
gas valve, and flash “7” on the LED. The blower output will be
energized during an open rollout condition.
If the rollout switch closes, the control shall remain locked out
until power removed or “W” is removed.
Rollout switch lockout shall not reset automatically.
Power Interruptions
Power interruptions of any duration shall not cause lockout or
any operation requiring manual intervention.
Flame present with Gas off
If flame is sensed for longer than 4.0 seconds during a period
when the gas valve should be closed, the control will enter
lockout flashing “8” on the LED. The control will turn on the
inducer blower while the flame is present.
Gas Valve Stuck Open or Closed
If either or both Pilot and Main Gas valve outputs are sensed to
be off for more than 1 second when commanded to be on, the
control board shuts off all outputs and enters a hard lockout
flashing "9" on the LED.
If the Pilot valve or Main valve output is sensed to be energized
for more than 1 second 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 pilot or main gas valve is still sensed as energized
after the inducer has been off for 5 seconds, the control re-
energizes the inducer to attempt to vent the unburned gas. In
either case, the control enters a hard lockout flashing "9" on the
LED. If the pilot or main valve becomes Un-Welded the inducer
will de-energize, but the control will remain in a hard lockout
and not respond to any thermostat demands.
The only way to recover from a hard lockout is to remove and
then reapply 24VAC power to the control board.
Flame Sense Circuit Failure
If the control detects an internal hardware failure in the flame
sense circuit, it shuts off all outputs and enters a hard lockout
flashing "10" on the LED. The control will not respond to
thermostat demands during a hard lockout.
The only way to recover from a hard lockout is to remove and
then reapply 24VAC power to the control. If problem persist
after removal and reapplication of 24VAC power, the board may
need to be replaced.
Safety Controls
The control circuit includes the following safety controls:
1.
Limit Switch (LS)
- This control is located inside 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 caused by inadequate
supply air flow occurs, thus shutting down the ignition control
and 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 controls and gas
valves from being energized.
3.
Flame Sensor
- The flame sensor and controls are located
per Proper Flame Adjustment Figure 14. If an ignition
control fails to detect a signal from the flame sensor
indicating the pilot flame is properly ignited, then the main
gas valve will not open.
4.
Rollout Switch (RS)
- This switch is located in the burner
vestibule. In the event of a sustained main burner flame
rollout, it shuts off the ignition control and closes the main
gas valve.
NOTE:
The manual reset
Rollout Switch (RS)
must be reset
before allowing furnace operation.
5.
Auxiliary Limit Switch (ALS)
- This control is located
inside the heat exchanger compartment and is set to open
at 160°F. It is a manual reset switch. If ALS trips, then the
primary limit (LS) has not functioned correctly. Replace the
primary limit LS.
Table 18: Ignition Control Board Flash Codes
Flash Code
Description
Heart Beat
Normal Operation
2 Flashes
Pressure switch open with inducer on
3 Flashes
Pressure switch closed with inducer off
4 Flashes
Not Used
5 Flashes
Lockout from too many flame losses
6 Flashes
High temperature switch open
7 Flashes
Rollout switch open
8 Flashes
Flame present with gas off
9 Flashes
Gas valve stuck OFF or ON
10 Flashes
Flame sense circuit failure
