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© 2015 Emerson Climate Technologies, Inc.
AE4-1331 R7
motors partially submerged in oil and refrigerant.
When Copeland Scroll compressors are hipot tested
with liquid refrigerant in the shell, they can show higher
levels of leakage current than compressors with the
motor on top. This phenomenon can occur with any
compressor when the motor is immersed in refrigerant.
The level of current leakage does not present any
safety issue. To lower the current leakage reading,
the system should be operated for a brief period of
time to redistribute the refrigerant to a more normal
configuration and the system hipot tested again. See
AE4-1294
for megohm testing recommendations.
Under no circumstances should the hipot test
be performed while the compressor is under a
vacuum.
Final Run Test
Customers that use a nitrogen final run test must be
careful to not overheat the compressor. Nitrogen is not
a good medium for removing heat from the compressor,
and the scroll tips can be easily damaged with high
compression ratios and/or long test times. Copeland
Scroll compressors are designed for use with refrigerant,
and testing with nitrogen may result in a situation where
the compressor does not develop a pressure differential
(no pump condition). When testing with nitrogen, the
compressor must be allowed to cool for several minutes
between tests.
Single phase scrolls with an electrical nomenclature of
“PFV” (208-230 volt, 1Ø, 60 Hertz) at the end of the
model number are guaranteed to start at 187 volts or
higher and must have a voltage no lower than 197 volts
once the compressor is running under load. All other
compressor voltages, both single and three phase, 50 &
60 Hertz are guaranteed to start and run at 10% below
the lowest voltage shown on the nameplate.
Variable transformers used on assembly lines are
often incapable of maintaining the starting voltage
when larger compressors are tested. To test for
voltage sag during starting, the first compressor in a
production run should be used to preset the voltage.
Remove the start wire from the compressor and apply
200 volts to the compressor. With the start winding
removed, the compressor will remain on locked
rotor long enough to read the supply voltage. If the
voltage sags below the minimum guaranteed starting
voltage, the variable transformer must be reset
to a higher voltage. When discussing this starting
amperage it should be noted that “inrush current” and
locked rotor amps (LRA) are one and the same. The
nameplate LRA is determined by physically locking
a compressor and applying the highest nameplate
voltage to the motor. The amperage that the motor
draws after four seconds is the value that is used on
the nameplate. Since there is a direct ratio between
voltage and locked rotor amperage, the lower the line
voltage used to start the compressor, the lower the
locked rotor amperage will be.
Unbrazing System Components
WARNING
Before attempting to braze, it is important to
recover all refrigerant from both the high and low
side of the system.
If the refrigerant charge is removed from a scroll-
equipped unit by recovering one side only, it is very
possible that either the high or low side of the system
remains pressurized. If a brazing torch is then used
to disconnect tubing, the pressurized refrigerant and
oil mixture could ignite when it escapes and contacts
the brazing flame. Instructions should be provided
in appropriate product literature and assembly (line
repair) areas. If compressor removal is required, the
compressor should be cut out of the system rather than
unbrazed. See
Figure 8
for proper compressor removal
procedure.
SERVICE PROCEDURES
Copeland Scroll Compressor Functional Check
A functional compressor test during which the suction
service valve is closed to check how low the compressor
will pull the suction pressure is not a good indication
of how well a compressor is performing.
Such a test
will damage a scroll compressor in a few seconds.
The following diagnostic procedure should be used
to evaluate whether a Copeland Scroll compressor is
functioning properly:
1.
Proper voltage to the unit should be verified.
2. Determine if the internal motor overload has
opened or if an internal motor short or ground
fault has developed. If the internal overload has
opened, the compressor must be allowed to cool
sufficiently to allow it to reset.
3. Check that the compressor is correctly wired.
4. Proper indoor and outdoor blower/fan operation
should be verified.
5. With service gauges connected to suction and
discharge pressure fittings, turn on the compressor.
If suction pressure falls below normal levels the
system is either low on charge or there is a flow
blockage in the system.
