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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, 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 (standing
burn out). 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 while running
(running burn out). 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.
5.6C Replacing a Compressor, Nonburn
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.
5.7 Remote Controls
Devices mounted on a panel that is remote from the
unit control the DHV-150H. You may or may not have
the devices listed below depending on the model of
the remote control panel that you purchased. If the
DHV-150H fails to operate as desired, always check
the settings of the controls to insure that they are
correct. Check that the controls are receiving 24Vac
from the DHV-150H. Check the connections between
the DHV-150H, the control panel, and the field control
wiring.
5.7A Humidity Control
The humidity control is an adjustable switch that closes
when the relative humidity of the air in which it is
located rises to the dial set point. It opens when the
RH drops 4 to 6% below the set point. If the DHV-
150H does not run, try turning the humidity control
clockwise until it reaches the stop and the knob pointer
points at “Max Dry” (see back of control panel cover.)
The DHV-150H is equipped with an automatic defrost
mechanism. If the DHV-150H operates in conditions
that develop frost on the evaporator, it will sense the
frost build-up and automatically defrost the evaporator.
The DHV-150H may not appear to be operating
correctly during the defrost sequence, but once the
defrost sequence is completed, the DHV-150H will
resume dehumidifying.