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.
|Component to Check
|Condenser coil blockage
|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