A127_F - Flame Present with Gas Valve Off - UL
Status
This is an extremely critical fault and should rarely (if ever) be seen in the field.
Description
Flame has been detected when the gas valve has no signal to be open.
Expected Operation
Flame sense is monitored at all times. If flame is somehow sensed for more than four seconds when it is not expected (including standby, cooling and continuous fan operation), the unit will respond as follows:
1. Gas valve and igniter are turned off (if not already turned off).
2. Inducer is immediately energized at high speed (if not already at high speed).
3. Indoor blower (IBM) is energized at the high heat speed unless there is another call also present – in which case the higher speed shall be used.
4. "A127_F Flame Present with Gas Valve Off - UL" and “A014_F Flame Present with Gas Valve Off” alarms are logged.
These states will remain as described above until the undesired flame is gone.
Once the undesired flame is no longer present, the control clears alarm "A014_F Flame Present with Gas Valve Off", completes inducer post-purge and the user set heat blower off delay. Alarm "A127_F Flame Present with Gas Valve Off - UL" will remain set. The control then proceeds to a one-hour "soft" lockout with alarm "A116_F One-hour Lockout: Flame Presence Alarm" declared throughout the duration. Upon completion of the lockout, control clears alarm "A116_F One-hour Lockout: Flame Presence Alarm". UL safety alarm "A127_F Flame Present with Gas Valve Off - UL" remains logged until power is cycled or a clear alarms command is used to clear the fault. The control then resumes normal operation.
Cause
1. Field mis-wiring of gas valve.
2. Faulty gas valve relay that is stuck or sticking.
3. Faulty furnace control that is sensing flame when no flame is present.
4. Flame sense wire is grounded.
5. 24VDC for blower control on the IFC is grounded, check if removing blower harness fixes the fault.
Solution
1. Wire properly.
2. Replace furnace control (IFC).
3. Flame sense wire should be properly connected to flame sense rod and should not be grounded.
4. Replace indoor blower motor if blower motor control is grounding 24VDC on the IFC board.
