A126_F - Flame Not Sensed with Gas Valve On - UL
Status
This is an extremely critical fault and should rarely (if ever) be seen in the field.
Description
Gas valve relay is energized but flame is not sensed.
Expected Operation
If the relay is welded shut and the alarm active, the unit will respond as follows:
1. Gas valve and igniter shall be turned off (if not already turned off).
2. Inducer will immediately be energized at high speed (if not already at high speed).
3. Indoor blower (IBM) will immediately turn on. This will normally energize at the high heat speed unless there is another call also present – in which case the higher speed shall be used.
4. Alarms "A126_F Flame not Sensed with Gas Valve On - UL", "A093_F Internal Control Fault Detected", and "A225_F Internal Fault: Gas Vlv 1 Rly Welded Shut” or "A227_F Internal Fault: Gas Vlv 2 Rly Welded Shut” (as appropriate for the relay) shall be logged.
These states will remain as described above until the condition is gone.
Once this condition is no longer present, the furnace shall clear the alarm "A225_F Internal Fault: Gas Vlv 1 Rly Welded Shut” or "A225_F Internal Fault: Gas Vlv 1 Rly Welded Shut"and "A093_F Internal Control Fault Detected", complete the inducer post-purge and the user set heat blower off delay. The control will then proceed to a one-hour "soft" lockout with the alarm "A115_F One-hour Lockout: Gas Valve Stuck Closed" declared throughout the duration. Upon completion of the lockout, alarm "A115_F One-hour Lockout: Gas Valve Stuck Closed" is cleared. Alarm "A126_F Flame not Sensed with Gas Valve On - UL" will remain logged until power is cycled to the unit or a clear alarms command is used to clear the fault. The control then resumes normal operation.
Cause
Faulty furnace control - relay malfunction
Solution
Replace furnace control (IFC)
