MODEL PCA090480WH
CHAPTER 3
TROUBLESHOOTING
Section 5: Helpful Troubleshooting information
3-5
March 2013
Page 92
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© 2013 Twist, Inc.
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NOTE:
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Reciprocating compressors are often pumped into a
vacuum to check if the valves are defective. Since the
scroll compressor does not have valves, there is no need
to apply this test to a scroll compressor.
12.
Compressor Motor Megging
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CAUTION:
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DO NOT UNDER ANY CIRCUMSTANCES USE A MEGOHM
METER OR APPLY POWER TO THE WINDINGS OF A
COMPRESSOR WHILE IT IS IN A VACUUM. MOTOR
WINDINGS DAMAGE WILL RESULT.
Typical acceptable megohm readings considered safe to start a compressor
should not be less than 1,000 ohms per volt of the nominal motor voltage.
Example:
380 volt compressor - 380,000 ohms
460
volt
compressor
-
460,000
ohms
Generally, a 500 volt DC megohm insulation tester is recommended for
testing the compressor motor windings. The use of a megger with a voltage of
more than 500 volts is not recommended for insulation systems of 600 volts or
less because of the potential for damage to the insulation system.
If readings below these values are measured, evacuate the compressor to
insure complete dehydration, bring it back up to a positive pressure with
refrigerant and remeg. It may be necessary to clean the terminal plate before
re-megging.
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WARNING
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: SINCE THE MOTOR ACTS LIKE A CAPACITOR WHEN
VOLTAGE IS APPLIED, GROUND THE MOTOR WINDING
TERMINAL STUDS TO THE MOTOR FRAME AFTER
COMPLETING TEST. THIS WILL DECREASE ANY RESIDUAL
VOLTAGE IN THE MOTOR THAT COULD RESULT IN A
SEVERE ELECTRICAL SHOCK.
13.
Overcharge of Refrigerant
An overcharge of refrigerant will cause high condensing pressure. Liquid will
back-up in the condenser and decrease the amount of surface available for
condensing. As a result, the condensing pressure will rise. In extreme cases,
it may rise to a point where the high-pressure cutout will stop the compressor.
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