| Meier
Supply
Company, Inc.
HVACR Specialists
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Handling Hermetic Compressor Burnouts
Using these simple procedures should prevent additional compressor failures and result in
a satisfied customer.
A common cause of compressor failures is the burnout of the motor in hermetically sealed
compressors. This failure is generally the result of a reduction in the
dielectric integrity (resistance) of the motor winding insulations.
In air conditioning systems, when excessively high temperatures occur in the refrigerant
system, the thermal stability point of the refrigerant may be reached. When this happens,
the refrigerant may break down and , as HCFC R-22 has Chlorine and Fluorine in its chemical makeup,
Hydrochloric and Hydrofluoric acids may be produced. These acids are corrosive and will
damage the compressor motor winding insulation. The resulting reduction in insulation
resistance will create an increase of electron flow (amperage) through the conductive refrigerant
surrounding the motor to ground. Due to this loss of amperage to ground, the amperage
requirement of the motor is increased. The more severe the contamination, the greater
is the increase in amperage draw. When the amperage draw exceeds the rated load amps of
the motor, heat builds up in the motor windings, causing the eventual burnout of the motor.
The correct handling of system cleanup and compressor replacement after a burnout is of the utmost importance.
Before the prohibition on venting of Chlorinated Halocarbons, R-11 refrigerant was commonly
used to flush systems after burnouts. This was very effective because R-11 is a good solvent.
Since the prohibition, other system flushing products have been introduced. Great
care must be exercised when using these products because they may be trapped in the system and may be difficult
to remove.
The best method to protect the replacement compressor and insure against additional failures is to install
an oversized liquid line filter drier and a properly sized suction line filter drier. Filter
drier desiccants clean the refrigerant and oil of acids that may remain in the system. The oil
can be tested after some run time of the replacement compressor to verify that no acids are presents.
Also, a megohm meter can be used to test the dielectric strength of the winding insulation to verify
that it is free of contamination.
The suction line filter drier should be removed after cleanup is complete and replaced with a suction filter
with a bypass feature. If this is not done, the filter drier may become restricted, causing
excessive suction line pressure drop. This pressure drop has a direct impact on compressor
performance causing an increase in compression ratio, power consumption, and a reduction in
system capacity.
Using these simple procedures should prevent additional compressor failures and result in a
satisfied customer.
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