To: Service Contractors responsible for PM Service and Repair

Subject: Resolving high indoor humidity issues in cell sites

Product: AIRSYS WPUs (all models); ASLLC (all models) with software revision prior to Rev. 13B47

Background: Some cell sites can have higher indoor humidity due to their lower heat load. In these sites, the compressor does not run long enough for de-humidification and the computer equipment does not generate enough heat to control the relative humidity. In the extreme cases one can observe water on the floor!  A few factory settings can be adjusted to control the higher humidity for these sites.

Controller Setting Changes (see below for step-by step instructions):

· Decrease maximum humidity allowed for free cooling.

· Decrease maximum outside temperature allowed for free cooling:

· Increase minimum compressor runtime

Additional steps for service contractors:

· Verify evaporator drain holes are clear and flow freely.

· Verify humidity sensor is responding by going to humidity display (HU) and breathing on the sensor.

· Verify the Free Cooling dampers are working correctly by using the step test.

Step-by-Step Instructions:

       Enter L Menu:

1. Press UP and DOWN together to return to main menu (indoor temperature displayed)

2. Press UP until Set is displayed

3. Press DOWN and SEL at the same time, the screen should display 0 if done correctly. Otherwise return to step 1.

4. Change to 6 and press SEL, the screen should display L01

      Decrease maximum humidity for free cooling

1. Go to L04 and press SEL, the screen should display U01

2. Press DOWN until you find U04 and press SEL, the screen should display the current setting (default: 85)

3. Change to 75 (or 65 in extreme conditions) and hit SEL, the screen should be back at U04

4. Press UP and DOWN together to return L01

    Decrease maximum outdoor temperature for free cooling

1. Go to L04 and press SEL, the screen should display U01

2. Press DOWN until U06 is displayed. U06 is the minimum temperature difference

between indoor and outdoor temperature for free cooling.

3. Press SEL, the screen should display the current setting (default: 3.6)

4. Change to 5 (or 7 in extreme conditions) and press SEL, the screen should display U06

5. Press UP and DOWN together to return L01

     Increase minimum compressor run-time:

1. From L01 Go to L05 and press SEL, the screen should display F01

2. Press DOWN until you find F21 and press SEL, the screen should display current setting in seconds (default: 60)

3.  Change to 600 and press SEL, the screen should be back at F21 (Now set to 10 minutes)

4. Press UP and DOWN together twice to return to the main menu.