Troubleshooting (continued)
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. Air filter dirty.
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.
Refrigerant Charging
If the refrigerant charge is lost due to service or a leak, a new charge must be accurately weighed in. If any
of the old charge is left in the system, it must be recovered before weighing in the new charge. Refer to the
unit nameplate for the correct charge weight and refrigerant type.
Compressor/Capacitor Replacement
This compressor is equipped with a two terminal external overload and a run capacitor, but no start
capacitor or relay.
TrueDry DR90 Dehumidification System 69-2407—01
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