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and water. These contaminants must be carefully removed
otherwise even small residues will attack replacement
compressor motors and cause failures.
The following procedure is effective only if the system is
monitored after replacing the compressor to insure that
the clean up was complete.
1. This procedure assumes that the previously listed
compressor motor circuit tests revealed a shorted or
open winding. If so, cautiously smell the refrigerant
from the compressor service port for the acid odor of
a burn out.
WARNING: The gas could be toxic and highly acidic. If no
acid odor is present, skip down to the section on changing
a non-burn out compressor.
2. Remove and properly dispose of the system charge.
DO NOT vent the refrigerant or allow it to contact your
eyes or skin.
3. Remove the burned out compressor. Use rubber gloves
if there is any possibility of coming in contact with the
oil or sludge.
4. To facilitate subsequent steps, determine the type of
burn out that occurred. If the discharge line shows no
evidence of sludge and the suction line is also clean
or perhaps has some light carbon deposits, the burn
out occurred while the compressor was not rotating.
Contaminants are therefore largely confined to the
compressor housing. A single installation of liquid
and suction line filter/driers will probably clean up the
system.
If sludge is evident in the discharge line, it will
likely be found in the suction line; this indicates the
compressor burned out will running. Sludge and acid
have been pumped throughout the system. Several
changes of the liquid and suction filter/driers will
probably be necessary to cleanse the system.
5. Correct the system fault that caused the burn out.
Consult the factory for advice.
6. Install the replacement compressor with a new
capacitor and an oversized liquid line filter.
In a running burn out, install an oversized suction line
filter/drier between the accumulator and compressor.
Thoroughly flush the accumulator with refrigerant to
remove all trapped sludge and to prevent the oil hole
from becoming plugged. A standing burn out does not
require a suction line filter/drier.
7. Evacuate the system with a good vacuum pump and
accurate vacuum gauge. Leave the pump on the
system for at least an hour.
8. Operate the system for a short period of time,
monitoring the suction pressure to determine that the
suction filter is not becoming plugged. Replace the
suction filter/drier if pressure drop occurs. If a severe
running burn out has occurred, several filter/driers
may have to be replaced to remove all of the acid and
moisture.
NOTE: NEVER use the compressor to evacuate the system
or any part of it.
4.6C Replacing a Compressor- Non-Burn Out
Remove the refrigerant from the system. Replace the
compressor and liquid line filter/drier. Charge the system
to 50 PSIG and check for leaks. Remove the charge and
weigh in the refrigerant quantity listed on the nameplate.
Operate the system to verify performance.
4.7 Defrost Thermostat and Timer
The defrost thermostat is attached to the refrigerant
suction tube between the accumulator and compressor.
If the low side refrigerant temperature drops due to
excessive frost formation on the evaporator coil, the
thermostat opens. The compressor is then cycled off and
on by the defrost timer. The blower will continue to run,
causing air to flow through the evaporator coil and melt the
ice when the compressor is off. When the air temperature
and/or humidity increase, the evaporator temperature will
rise and the thermostat will close to end the defrost cycle.
To improve performance in low temperatures, see Sec. 2.9
for defrost timer adjustment.
4.8 Condensate Pump
Condensate is automatically pumped when the water level
in the pump’s reservoir rises to close the float switch or if
the pump purge switch is held in.
If the pump is unable to empty its reservoir due to a
pump failure or blocked condensate hose, a pump safety
float switch is triggered before the reservoir overflows.
The switch turns on the pump fail light and turns off the
compressor via its relay.
To replace the condensate pump:
1. Unplug the unit and remove the front cover.
2. Disconnect the 2 hoses from the pump.
3. Cut the pump lead wires near the old pump.
4. Remove the 4 screws from the unit bottom that hold
the pump to the base.
5. Attach the new pump with 4 screws.
6. Connect the new pump wiring. It may be easier to
splice the new and old gray leads together with a wire
nut, and splice the new and old yellow leads together,
rather than route the new ones to the pump purge
switch and pump fail light.
7. Connect the hoses to the new pump. Carefully
route the hoses so they do not contact the copper
refrigerant lines or the compressor shell.