Problem Recommended Troubleshooting Steps
Fan does not run
with ventilation
activated.
Compressor runs
briefly but cycles on
& off with humidity
control turned to
ON.
1. Loose connection in fan circuit.
2. Obstruction prevents fan rotation.
3. Defective fan.
4. Defective fan relay.
5. Defective fan capacitor.
Evaporator
coil frosted
continuously, low
de-humidifying
capacity.
1. Defrost thermostat loose or defective.
2. Low refrigerant charge.
3. Dirty air filter(s) or airflow restricted.
Unit not providing
ventilation.
1. Check control wire connections (check connections at fresh air damper also).
2. Defective fresh air damper.
3. Dirty air intake. Clean outside intake hood.
Unit removes some
water, but not as
much as expected.
1. Air temperature and/or humidity have dropped.
2. Humidity meter and or thermometer used are out of calibration.
3. Unit has entered defrost cycle.
4. Dirty air filter.
5. Defective defrost thermostat.
6. Low refrigerant charge.
7. Air leak such as loose cover or ducting leaks.
8. Defective compressor.
9. Restrictive ducting.
10. Optional Condensate Pump Safety Switch open.
Unit Test to
determine problem:
1. Detach field control wiring connections from main unit.
2. Connect the R and FAN contacts from the main unit together; only the impeller
fan should run. Disconnect the wires.
3. Connect the R and DHUM contacts from the main unit together; the compressor
and impeller fan should run.
4. If these tests work, the main unit is working properly. You should check the
control panel and field control wiring for problems next.
5. Remove the control panel from the mounting box and detach it from the field
installed control wiring. Connect the blue, yellow, and green wires from the
control panel directly to the corresponding colored pigtails on the main unit.
Leave the violet, white, and red wires disconnected!
6. Turn on the humidity control. The compressor and impeller fan should run.
7. If these tests work, the problem is most likely in the field control wiring.
DR90/DR120A3000 Dehumidification System 33-00298EFS—01 13
Troubleshooting (continued)
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