To: Service Contractors responsible for PM Service and Repair

Subject: Increasing alarm tolerance for temperature differential
Product: AIRSYS WPUs (all models); ASLLC (all models) with software revision prior to Rev. 13B47

Background: A24 and A25 are damper actuator alarms for HVAC1 and HVAC 2, respectively. These are minor alarms added in later software revisions to make sure the damper is not stuck open or stuck closed. The damper actuator alarm works by accessing the temperature difference across the damper to make sure the damper closes and opens completely.  Here are the two scenarios:

  1. When the damper is completely open, the supply air temperature should be equal to the outside temperature within a tolerance.
  2. When the damper is completely close, the supply air temperature should be equal to the inside temperature within a tolerance.

Factors such as opening shelter door may cause the temperature to exceed the tolerance and unnecessarily trigger this alarm.  In some environments, it may be necessary to increase the alarm tolerance to avoid recurring nuisance alarms. 


From the Main Menu (Room Temp will be displayed):

Press UP until the screen display Set, then press DOWN and Sel at the same time.

If done correctly the screen should display 0; if not, return to previous step.

Change 0 to 3 and press Sel. The screen should display stp.  

Press UP until you get to FC3 and press Sel.

Change the default 3.6 to 20 and press Sel.

Press UP for FC2 and press Sel. Change 3.6 to 20 and press Sel.