Therma-Stor Products Group 300 - Manual (Page 6)

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Evaporator coil frosted continuously, low dehumidifying
capacity.
. Defrost thermostat loose or defective
(Sec. 2.0 and 4.7).
2. Defrost timer incorrectly set or defective
(Sec. 2.0 and 4.7).
2. Low refrigerant charge (Sec. 4.4).
3. Dirty air filter or air flow restricted. (Sec. 3.).
Compressor runs with power switch OFF.
. Defective relay (Sec. 4.0).
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.
. 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).
CAUTION-ELECTRICAL SHOCK HAZARD: Electrical power
must be present to perform some tests; these tests should
be performed by a qualified service person.
4.6A Checking Compressor Motor Circuits
Perform the following tests if the blower runs but the
compressor does not with the power switch ON.
. 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 0 to 20 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 () 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 : No
continuity indicates a defective overload lead.
7. Overload terminals and 3: If there is no continuity,
the overload may be tripped; wait 0 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 Rx 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 Rx00000 scale, the capacitor is
open and must be replaced.
0. 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.
. If the unit still does not start, adding a hard-start kit
will provide greater starting torque. If this does not
work, the compressor has an internal mechanical
defect and must be replaced.
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,