The High Temp Alarm is triggered when the indoor temperature exceeds temperature setpoint + high temp alarm trigger (default = 16°F). This alarm has a built in 1-minute delay, which can be changed at F35 under L05 Menu if using the PLD or at P8 in the User Menu if using the PGD.


Possible Cause
Component to Check
Recommended Action
Reduced cooling capacity
Filter, condenser coil, low side pressure.
Clean/wash filter and condenser. Remove blockage if appropriate. Leak check/ repair if low on refrigerant. 
Improper value set for high temp alarm trigger
Ht under E menu or other thermostat used to monitor high temperature
If using the pGD, this parameter can be accessed from User Menu – P8
Default = 18°F above the main setpoint.
Undersized unit
Check if the heat load of the site exceeds sensible capacity of the AC units
Add/Upgrade AC or reduce heat load by turning off unused equipment
Cooling command not given by controller
Check for other alarms present on controller.
Use D52/D57 under C Menu to view current compressor command for unit1/unit2 respectively
Correct other alarms that would prevent compressor start up, such as high/low pressure lockout and smoke/fire alarm.
Improper value set for compressor turn on
Lead compressor turn on: C02 under E menu
Lag compressor turn on: F38 under L05

If using the pGD, these parameter can be accessed under User Menu.
Correct compressor settings.
Compressor circuit failure
Compressor contactor (KM1)
Compressor run caps (C)
Compressor circuit wiring
Replace failed component.
Correct/tighten wiring according to the Compressor Circuit diagram.

Indoor temperature sensor
Indoor temp sensor (ST1)
Indoor temp sensor calibration (N2A under C menu)
Backup Indoor temp sensor (ST2)
Backup indoor temp sensor calibration (N42 under C Menu)
If using the pGD, calibrations can be accessed in Maintenance Menu
Verify sensor operation.
Correct calibration.

Compressor Circuit