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C6.2.26/1013-1116/E
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 be tripped. The most common compressor problems
encountered in the field are listed below.
WARNING
Electrical connections! 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
Corrective action
The Scroll
compressor does
not run, instead a
buzz sound can be
heard
Wired
incorrectly
Check the power supply on the compressor terminals if
there is voltage measured. Trace the wiring diagram to
see where the circuit is interrupted.
Low supply
voltage
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.
Defective
capacitor or
relay
For a single-phase motor, a defective capacitor or relay
may prevent the compressor from starting. Check these
components by substituting “a known-to-be-good”
component if available. Make sure that the capacitors
are electrically discharged before checking.
Shorted or
grounded
motor windings
Check the motor for ground by means of a continuity
check between the terminals. If grounded replace
compressor.
Internal
compressor
mechanical
damage
Refrigerant 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.
