Evaporator coil frosted continuously, low dehumidifying capacity.
1.Defrost thermostat loose or defective (Sec. 2.10 and 4.7).
2.Defrost timer incorrectly set or defective (Sec. 2.10 and 4.7).
2.Low refrigerant charge (Sec. 4.4).
3.Dirty air filter or air flow restricted. (Sec. 3.1).
Compressor runs with power switch OFF.
1.Defective relay (Sec. 4.10).
2.Defective power switch (Sec. 2.6)
4.4 Refrigerant Charging
If the refrigerant charge is lost, a new charge must be accurately weighed in. If any of the old charge is left in the system, it must be removed before weighing in the new charge. Refer to the unit nameplate for the correct charge weight and refrigerant type.
4.5 Blower Replacement
The centrifugal blower has a PSC motor and internal thermal overload protection. If defective, the complete assembly must be replaced.
1.Unplug the power cord.
2.Remove the cabinet front (6 screws).
3.Disconnect the blower leads.
4.Pull the oil tubes out of the motor.
5.Tip the unit on its back. From the bottom, remove the 2 screws that fasten the blower housing to the base.
6.Remove the four screws holding the blower outlet flange to the cabinet end.
7.Remove the blower. Use care to avoid hooking wiring, tubing or electrical components.
8.Reassembling with the new blower is the above procedure reversed.
4.6 Compressor/Capacitor Replacement
This compressor is equipped with a two terminal external overload, run capacitor, but no start capacitor or relay (see Fig. 3).
4.6A Checking Compressor Motor Circuits
Perform the following tests if the blower runs but the compressor does not with the power switch ON.
1.Turn the power switch OFF and unplug the unit, remove the cabinet front (6 screws).
2.Plug in the unit and turn the power switch ON. Use a voltmeter to check for 110 to 120 volts between
(a) the relay terminal that the black wire from the compressor connects to and (b) the capacitor terminal with the (3) white wires and (1) red wire connected.
If voltage is present, go to step 3. If no voltage, the low pressure control, the time delay or the relay are open or there is a loose connection in the compressor circuit. Test each component for continuity; see the appropriate section if a defect is suspected.
3.Turn the power switch OFF and unplug the unit, then disconnect the red and yellow wires from compressor terminals R and S. Using an ohmmeter, check continuity between the points listed below.
4.Compressor terminals C and S: No continuity indicates an open start winding; the compressor must be replaced.
5.Compressor terminals C and R: No continuity indicates an open run winding; the compressor must be replaced.
6.Compressor terminal C and overload terminal 1: No continuity indicates a defective overload lead.
7.Overload terminals 1 and 3: If there is no continuity, the overload may be tripped; wait 10 minutes and try again. If there is still no continuity, it is defective and must be replaced.
8.Compressor terminal C and compressor case: Continuity indicates a grounded motor; the compressor must be replaced.
9.Disconnect the wires from the capacitor. Set the ohmmeter to the Rx1 scale; the capacitor is shorted and must be replaced if continuity exists across its terminals. If there is no needle movement with the meter set on the Rx100000 scale, the capacitor is open and must be replaced.
10.Reconnect the wires to the compressor and capacitor; plug in and turn on the unit. If the compressor fails to start, replace the run capacitor.
11.If the unit still does not start, adding a
4.6B Replacing a Burned Out Compressor
The refrigerant and oil mixture in a compressor is chemically very stable under normal operating conditions. However, when an electrical short occurs in the compressor motor, the resulting high temperature arc causes a portion of the refrigerant oil mixture to break down into carbonaceous sludge, a very corrosive acid,
www.thermastor.com • sales@thermastor.com |
