Troubleshooting - Emerson Copeland Scroll ZR24KRE Application Manuallines

7

Troubleshooting

Most in-warranty electrical failures are a result of mechanical problems (particles in the oil, liquid
refrigerant in the oil, etc.) and most mechanical problems are a result of system problems. Unless
the reason for the failure is found, replacing the compressor will probably lead to another compressor
failure.
If the compressor fails to start and run properly, it is important that the compressor be tested to
determine its condition. It is possible that electrical components may be defective, the protector may
be open, or a safety device may have tripped. Here is a list of the most common compressor
problems encountered in the field.
WARNING
Electrical cables! Electrical shock! Before attempting any electrical
troubleshooting, make sure all grounds are connected and secure and there
is ground continuity throughout the compressor system. Also ensure the
compressor system is correctly grounded to the power supply. If you are not
a qualified service person familiar with electrical troubleshooting techniques,
DO NOT PROCEED until a qualified service person is available.
Condition Cause
Wired
incorrectly
Low supply
voltage
Shorted or
grounded
motor
windings
The scroll
compressor does
not run, instead a
buzz sound can
be heard
Internal
compressor
mechanical
damage
30
Corrective action
Check the power supply on the compressor terminals if there is
voltage measured. Trace the wiring diagram to see where the
circuit is interrupted.
If the voltage falls below 90% of the nameplate voltage, the motor
may develop insufficient torque. Make sure the compressor is
supplied with rated nominal voltage.
Check the motor for ground by means of a continuity check
between the terminals. If grounded replace compressor.
Refrigeration migration: When the compressor is switched off
for a long period, refrigerant can condense in the crankcase. If
the compressor body is colder than the evaporator, refrigerant
will move from the evaporator to the compressor crankcase.
Refrigerant migration normally occurs when the compressor is
installed in a cold area. A crankcase heater and/or a pump-
down cycle provide good protection against refrigerant
migration.
Acid formation: Acid forms in the presence of moisture, oxygen,
metal, salts, metal oxides and/or high discharge temperatures.
The chemical reactions are accelerated at higher temperatures.
Oil and acid react with each other. Acid formation leads to
damage of the moving parts and in extreme cases to motor
burnout. Several different test methods can be used to test for
acid formation. If acid is present a complete oil change
(including the oil in the oil separator) will help. A suction filter
which removes acid should also be fitted. Check filter-drier
condition.
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