Emergency wiring allows AIRSYS WPUs to run temporary mechanical cooling in the event that the controller is unavailable. Emergency wiring bypasses internal protection mechanisms and should never be used as a long-term solution.


All Emergency wiring must be by performed by professional technicians.


Note: Emergency wiring should ONLY be used if instructed by AIRSYS Support (855-874-5380) or if AIRSYS Support cannot be reached and immediate mechanical cooling is needed to prevent equipment failure.


Note: When emergency wiring is implemented, the supply fan(s) will run at full speed until the wiring is removed. The compressor will do the same unless a thermostat is used to provide a call for cooling.


DANGER! Risk of electric shock can cause serious injury or death. Switch the breakers off to both HVAC units AND the controller before adding OR removing emergency wiring.


There are three cooling options available for emergency wiring:

  1. Emergency MC Without Thermostat. The compressor will stay on until wiring is removed.
  2. Emergency MC With Thermostat. A simple line voltage thermostat is used to provide a call for cooling.
  3. Emergency Free Cooling. The economizer will open and the supply fan will run at full speed until wiring is removed. Suitable if outdoor temperature will remain under 65°F until controller functionality is restored.


Wiring instructions for each option can be found below. A PDF containing the same information is attached in this article. 


Note: A line voltage thermostat (230VAC) must be used for wiring if Option 2 is selected.


Instructions for Emergency MC Without Thermostat (ASLLC.2 Controller Bypass)


Add 4 Jumper Wires at the Unit:

  1. Between 400 and 1
  2. Between 400 and 2
  3. Between L and 4
  4. Between +10V and 11


Instructions for Emergency MC With Thermostat (ASLLC.2 Controller Bypass)


Add 5 Jumper Wires at the Unit:

  1. Between 400 and 1
  2. Between 400 and 2
  3. Between L and Rc
    1. Rc (voltage for cooling) is found on thermostat
  4. Between Y and 4
    • Y (switch the cooling) is found on thermostat
  5. Between +10V and 11

Instructions for Emergency Free Cooling (ASLLC.2 Controller Bypass)


Add 3 Jumper Wires at the Unit:

  1. Between 400 and 2
  2. Between L and 4
  3. Between +10V and 11


Manually Open the Damper:

  1. Remove the damper inspection panel
  2. Depress the manual override button
  3. Manually move the damper to the open position while holding the override
  4. Release the manual override



Instructions for Emergency MC Without Thermostat (ASLLC.2A Controller Bypass)


Add 2 Jumper Wires at the Unit:

Note: Leave Existing Wires in Place

  1. Between Rc and A2
    • A2 is on the KM1 contactor, existing wire on A2 is #72
  2. Between +10V and 11


Instructions for Emergency MC With Thermostat (ASLLC.2A Controller Bypass)


Add 3 Jumper Wires at the Unit

Note: Leave existing wires in place

  1. Between L and Y
    • Y (switch for cooling) is found on thermostat
  2. Between Rc and A2
    • Rc (voltage for cooling) is found on thermostat
    • A2 is on the KM1 contactor, existing wire on A2 is #72
  3. Between +10V and 11


Instructions for Emergency Free Cooling (ASLLC.2A Controller Bypass)


Add 1 Jumper Wire at the unit between +10V and 11

Note: Leave existing wires in place


Disconnect the T2 ethernet cable at the unit


Manually Open the Damper

  1. Remove the damper inspection panel
  2. Depress the manual override button
  3. Manually move the damper to the open position while holding the override
  4. Release the manual override