To: Site Technicians responsible for verifying system operation.

Subject: Verifying the operation of the AIRSYS Air Filter Protection Device (AFPD)

Related Products: All ASLLC Series Controllers (ASLLC.2, ASLLC.2.48, ASLLC.2A, ASLLC.2A.48)

Background: The AIRSYS AFPD senses dust or other particulates in the air and will automatically close the free cooling damper when the concentration reaches a preset amount. This bulletin provides instructions for verifying that the sensor is installed and operating correctly. This bulletin is only applicable when the unit is actively free cooling.


Note: A particulate source must be provided to verify system operation. Sources include canned smoke, cigarette smoke, and dirt.

Note: Verification must be conducted when the outdoor temperature is < 65°F. This will help ensure that free cooling conditions are met.

I. Verifying AFPD Installation

Before verifying operation, verify that the AFPD has been installed at the site. An AFPD may not be installed on all units, but at least one per controller should be present. To access it, the front-bottom panel of the HVAC must be removed by taking off the four screws securing it. The AFPD is a white box that should be mounted below the filters. If it is not present in the first of a lead/lag pair then check the second unit.  If neither unit has an AFPD mounted, then verification is not necessary.

II. Verifying AFPD Operation 

Caution: When testing use short bursts/small amounts of smoke to avoid setting off fire suppression systems within the shelter. It is best practice to have the fire suppression system in bypass or test mode to avoid any chance of accidental discharge.

  1. The system should be free cooling upon arrival at the site if the outdoor temperature is <65°F. Free cooling operation can be verified in one of two ways:
  2. Shutting off the lights at the site and looking into the return (top) hole of the unit from the inside. If free cooling is active (damper is open), it should be possible indirect sunlight.
  3. Looking above the filter and checking the damper position (see below for pictures):
  4. If free cooling is not active, open the controller box and reset the QF1 breaker inside. Free cooling should start soon after the controller reboots and displays the indoor temperature.
  5. Introduce a particulate source near the AFPD to simulate a protection event.
  6. The dampers of the unit and any other units connected to the same controller should begin closing. If this is not the case, proceed to Section III.
  7. Once all dampers on units connected to the same controller have closed, verification is complete, and the panels can be replaced on the unit.

III. Troubleshooting

Use the instructions below to verify that the controller settings are correct, then re-attempt the verification process outlined in Section II. If free cooling is still unavailable and AFPD is present on the units, contact a service contractor to verify hardware installation.

  1. Press Up and Down buttons together to reach indoor temperature display.
  2. Press Up until Set is displayed.
  3. Press the Up and Select buttons together. The screen should display teS (if unit off) or SFT (if unit on). If unsuccessful, return to step 1.
  4. Press Up until AFP is displayed and then press Sel.
  5. Press Up to change No to Yes and then press Sel, the screen should be back to AFP.
  6. Press Up and Down together to return to indoor temperature display.
  7. Press Up until Set is displayed.
  8. Press Down and Sel together, the screen should display 0 (if unsuccessful, return to step 6).
  9. Press Up until 6 is displayed, press Sel. The screen should display L01.
  10. Press Up until L05 is displayed, press Sel. The screen should display F01.
  11. Press Down until F03 is displayed, press Sel. The screen should display Yes. If this is not the case, press Up to change No to Yes. Press Sel to confirm.
  12. Press Down until F04 is displayed, press Sel. The screen should display Yes.
  13. Press Down until No is displayed, press Sel. The screen should display F04.
  14. Press Down until F23 is displayed, press Sel. The screen should display 10.
  15. Press Down until 0 is displayed, press Sel.
  16. Press Up and Down together to return to the L menu and Up and Down together a second time to return to the indoor temperature display.