Low Temp Alarm is triggered when the indoor temperature drops below temperature setpoint - low temp alarm trigger (default = 34°F). This alarm has built-in 1 minute delay. AIRSYS WPUs are designed for equipment sites where they are usually unoccupied. As such, the heater turns on 29 degrees below the main setpoint by default. Comfort mode is recommended if equipment site is temporarily occupied. 


Possible Cause
Component to Check
Recommended Action
Improper value set for low temp alarm trigger
Lt under E menu or other thermostat used to monitor site temperature.
Default = 34°F below the main setpoint.
Improper value set for heater turn on
Lead compressor turn on: H02 under E menu.
Lag compressor turn on: F38 under L05 Menu
If using the pGD, these parameters can be accessed from the User Menu.
Correct heater settings.
Heating command not given by controller
Other alarms in the system
Use D53/D58 under C Menu to view current heater command for unit1/unit2 respectively.
If using the pGD, use Input/Output Menu to view current commands.
Correct other alarms that would prevent heater start up, such as fan overload.
Heater circuit failure
Heater contactor (KM2)
Heater protection device (fused, located behind supply grill)
Heater circuit wiring
Replace failed component.
Correct/tighten wiring according to the Heater Wiring diagram.
Indoor temperature sensor calibration
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)
Verify sensor operation.
Correct calibration.

Heater Wiring