Honeywell TRUEDRY DH150 - Manual (Page 17)

TrueDRY DH150
15 69-2271EFS—01
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 por-
tion of the refrigerant oil mixture to break down into carbonaceous sludge, a very corrosive acid, 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.
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 contacting 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.
Replacing a Compressor, Non-Burnout
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.
Defrost Thermostat
The defrost thermostat is attached to the refrigerant suction tube between the accumulator and the compressor. It
will automatically shut the compressor off if the low side refrigerant temperature drops due to excessive frost for-
mation on the evaporator coil. The impeller fan will continue to run, causing air to flow through the evaporator coil
and melt the ice. When the ice has melted, the evaporator temperature will rise and the thermostat will restart the
compressor.
Troubleshooting