A055_F: Combustion Pressure Switch Closed When Should Be Open
Status
This is a critical fault. The furnace will not operate in gas heat modes but all other modes (e.g. cooling) should function if present simultaneously with a heating call (e.g. defrost call in dual-fuel mode).
Description
The combustion pressure switch should not be closed when the inducer is not running. If it is this is a sign of a serious condition. The switch may be welded closed or purposely bypassed in the field. Before any heat cycle can begin the pressure switch is tested to make sure that it is open. The switch is ignored except in gas heating modes.
Expected Operation
There will be no other operation than displaying of the fault code and diagnostic messages to the homeowner and technician. The fault code is only present during a heat call before pre-purge or calibration begins.
Cause
1. Faulty Switch
2. Pressure switch physically bypassed in the field.
3. Loose or faulty wiring.
4. Abnormally high negative pressure present on vent system without inducer running.
Solution
1. Replace combustion pressure control (switch).
2. Remove bypass and restore correct operation. Determine reason for bypass (e.g. vent length too long) and correct issue. Notify homeowner and proper authorities of illegal tampering if necessary.
3. Check wiring and connections. Replace and/or repair as necessary.
4. Check for proper venting and terminations as defined in the furnace installation instructions.
