The controller receives a normally closed signal (can be changed to normally open at SFT under D Menu or Manufacturer Menu – C2a) from the smoke/fire detector on terminal 41 and 5. When the controller receives an active smoke/fire alarm, all components on both units will shut to minimize airflow within the site: outside air damper, heater, compressor, and supply fan. This alarm is reset automatically when alarm is no longer active.

Note: The normally open or normally closed signal must be isolated relay contacts. Piggybacking with other devices may cause false alarms.


Possible Cause

Component to Check

Recommended Action

Incorrect input signal setting

SFT parameter in D Menu and input signal on terminal 41 and 5Adjust SFT in D Menu to switch between normally open and normally closed alarm input. If using the pGD, this parameter can be accessed under Manufacturer Menu – C2a.
Loose/incorrect alarm wire

Smoke/Fire alarm wiring (see diagram below)

If the detector relay is closed but the controller is receiving an open signal between ID4 and IDC1, verify/tighten alarm wiring according to the Smoke Fire Alarm Wiring diagram below.

Note: Switch on smoke detector must be a form C contact (no voltage on smoke detector contacts when signal wire is not connected).
Smoke/Fire detector is falsely triggered

Smoke/Fire detector

If defective, replace detector.

Smoke/Fire Alarm Wiring