No dehumidification, compressor does not run but impeller fan
runs with fan switch and ventilation timer OFF and humidity
control turned to ON.
1. Defective compressor run capacitor (Sec. 5.6).
2. Bad connection in compressor circuit
(See Fig. 4).
3. Defective compressor overload (Sec. 5.6A).
4. Defective compressor (Sec. 5.6).
5. Defrost thermostat open (Sec. 5.8).
Impeller fan runs with fan switch and ventilation timer OFF, but
compressor cycles on & off.
1. Low ambient temperature and/or humidity causing unit to
cycle through defrost mode.
2. Defective compressor overload (Sec. 5.6A).
3. Defective compressor (Sec. 5.6).
4. Defrost thermostat defective (Sec. 5.8).
5. Dirty air filter(s) or airflow restricted.
6. Low refrigerant charge, causing defrost control to cycle.
7. Bad connection in compressor circuit.
Impeller fan does not run with fan switch in either position.
Impeller fan does not run with ventilation timer activated.
Compressor runs briefly but cycles on & off with humidity
control turned to ON.
1. Loose connection in impeller fan circuit (See Fig. 4).
2. Obstruction prevents impeller fan rotation.
3. Defective impeller fan.
4. Defective impeller fan relay.
5. Defective impeller fan capacitor.
Impeller fan runs with fan switch ON. Impeller fan does not run
with ventilation timer activated.
1. Defective ventilation timer.
2. Time not correct on ventilation timer.
3. Ventilation timer set to manual & switched OFF.
4. Defective fan switch.
Evaporator coil frosted continuously, low dehumidifying
capacity.
1. Defrost thermostat loose or defective (Sec. 5.8).
2. Low refrigerant charge
3. Dirty air filter(s) or airflow restricted.
4. Excessively restrictive ducting connected to unit.
Unit not providing ventilation. Ventilation timer not operating
correctly.
1. If timer is not functioning correctly reset timer and reprogram
(Sec. 3.5).
2. Check control wire connections (check
connections at fresh air damper also).
3. Defective fresh air damper (Sec. 5.9).
4. Defective fan switch.
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 (Sec. 5.8).
4. Air filter dirty (Sec. 4.1 & 4.2).
5. Defective defrost thermostat (Sec 5.8).
6. Low refrigerant charge (Sec. 5.4).
7. Air leak such as loose cover or ducting leaks.
8. Defective compressor (Sec. 5.6).
9. Restrictive ducting (Sec. 2.4).
10. Optional Condensate Pump Safety Switch open (Sec 5.11).
Unit Test to determine problem:
1. Detach field control wiring connections from main unit.
2. Connect the yellow and green pigtails from the main unit
together; only the impeller fan should run. Disconnect the
wires.
3. Connect the yellow and blue pigtails 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 fan switch; the impeller fan should run. Turn off
the fan switch.
7. Turn on the humidity control; the compressor and impeller fan
should run.
8. If these tests work, the problem is most likely in the field
control wiring.
7.4 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.
7.5 Impeller Fan Replacement
The motorized impeller fan is a unitary assembly consisting of the
motor and impeller fan. If defective, the complete assembly must
be replaced.
1. Unplug the power cord.
2. Remove the cabinet access panel.
3. Remove the screw attaching the impeller fan support bracket
to the base.
4. Disconnect the impeller fan leads inside the electric box.
FOR HVAC INSTALLER ONLY
13
Ultra-Aire XT150H Installer’s & Owner’s Manual
