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System checklist
We strongly recommend that you hook-up and run a simple bench test before installing the thermostat. Not
only will this save you time in system checkout, but will also make you familiar with the thermostat’s
operation.
Thermostat bench test
To bench test the thermostat, do the following:
1. Connect the WDU to the control unit with a short (12 to 24 in.) four-wire cable.
2. Before power up, set the control unit DIP switch, SW1 to ALL OFF.
3. Connect power to the control unit.
4. Verify the control unit status LED is blinking.
5. Verify the WDU display comes on and shows the current temperature:
• If no display and backlights are not on, check your wiring to the control unit.
• If a CommFailure display is shown on the WDU, check your wiring to the control unit.
• Do not proceed until the current temperature is displayed on the WDU.
With the current temperature displayed on the WDU, you have verified communication between the
WDU and the control unit. Any communication problems will result in a CommFailure
(communications failure) display on the WDU and must be fixed before proceeding.
6. Press the Fan button on the WDU until Fan On is displayed. The control unit’s fan LED and relay
should turn on. Press the Fan button again and the fan LED and relay should turn off.
7. Press the Mode button on the WDU until Heat Mode is displayed.
8. Press the setpoint Up button until the setpoint is above the current temperature. The heat LED and
relay should come on. If they don’t come on, make sure the status LED is not flashing twice indicating
minimum off delay. Wait until the LED stops flashing twice before proceeding.
9. Press the Mode button on the WDU until Off Mode is displayed. The heat LED and relay will turn off.
10. Wait six minutes for the minimum off delay to expire. The status LED will stop flashing twice.
11. Press the Mode button on the WDU until Cool Mode is displayed.
12. Press the setpoint Down button until the setpoint is below the current temperature. The compressor and
fan LEDs and relays should turn on.
13. Press the Mode button on the WDU until Off Mode is displayed. The cool LED and relay should turn
off.
When you have successfully completed this process, you have verified that the thermostat is working correctly.