A high pressure alarm indicates the controller has received an open signal from the normally closed high pressure switch circuit. Three active alarms within one hour will trigger a compressor lockout to protect the refrigerant circuit. The lockout can be cleared by power cycling the controller.
Troubleshooting
| Possible Cause | Component to Check | Recommended Action |
| Condenser coil blockage | Condenser coil | Wash/Clean condenser coil. Remove any blockage. |
| Loose/incorrect alarm wiring | High Pressure Alarm Wiring (see diagram below ) | If the high pressure switch is closed but the controller is receiving an open signal between ID4 and IDC1, verify/tighten alarm wiring according to the High Pressure Alarm Wiring diagram. |
| Condenser fan wiring | Condenser fan wiring (see diagram below) | If condenser fan does not receive power across wires 120 and 400, verify/tighten condenser fan wiring according to the Condenser Fan Wiring diagram. |
| Faulty condenser fan switch | High pressure switch for condenser fan (HP1) | If high pressure switch for condenser fan does not close properly, replace the switch. |
| Condenser fan relay (not present in Cat 5 models) | condenser fan cycle relay (KA2 for 2.5/3.5 Ton model, KA1 for 5 Ton model) | If the fan cycling relay does not close when the coil is energized, replace the relay. |
| High Pressure Alarm Switch defective | High pressure alarm switch (HP) HP Switch Spec: R407C: 420/360 ±10psi* R410A: 600/450 ±10psi *Some switches intended for outside of CA/AZ areas are 390/330 ±10psi. These switches are labeled 2.7/2.25MPa | If switch is open when high side pressure is in normal range, replace the switch |
| Condenser fan failure | Power at Condenser fan (240V across wire 120 and wire 400) | If condenser fan receives power but does not run, replace the condenser fan. |
Condenser Fan Wiring
High Pressure Alarm Wiring
