Emerson Copeland Scroll ZP K3 Series - Pressure Testing; Assembly Line System Charging Procedure; Final Run Test

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© 2015 Emerson Climate Technologies, Inc.
AE4-1365 R4
The rst step in the tandem assembly process is to
securely mount both compressors to the rails using
the appropriate mounting hardware listed in Table 4.
After both compressors are mounted to the rails, the
suction, discharge, and gas equalization manifolds
can be brazed to the appropriate stub tubes of each
compressor using standard brazing practices with
a nitrogen purge. Special consideration needs to
be given to the oil equalization line that connects
the oil sumps of the two compressors. The ZP92-
122KCcompressorshaveoilttingsthataredifferent
than other compressors in this family. For tandem
applications the 1/4" Schrader tting should be
removedfromtheoilttingssotheoilequalizationline
can be attached via rotalock connection or brazing. The
oil in the single, tandem ready compressor is located
at the center of the oil equalization tting.After both
compressors are mounted to the compressor rails and
prior to removing the rubber plug in the oil equalization
stubs, the assembly should be tilted back a minimum
of 12° from horizontal (see Figure 6) to move the oil
levelawayfromtheoilequalizationttingforbrazing.
The oil equalization stubs of both compressors should
be wiped clean with a lint free towel to remove any oil
residue before brazing.
Pressure Testing
WARNING
Never pressurize the compressor to more than
475 psig (33 bar) for leak checking purposes.
Never pressurize the compressor from a nitrogen
cylinder or other pressure source without an
appropriately sized pressure regulating and relief
valve.
The pressure used on the line to meet the UL burst
pressure requirement must not be higher than 475
psig (33 Bar). Higher pressure may result in permanent
deformation of the compressor shell and possible
misalignment or bottom cover distortion.
Assembly Line System Charging Procedure
Systems should be charged with liquid on the high side
to the extent possible. The majority of the charge should
be pumped in the high side of the system to prevent low
voltage starting difculties, hipot failures, and bearing
washoutduringtherst-timestartontheassemblyline.
If additional charge is needed, it should be added as
liquid to the low side of the system with the compressor
operating. Pre-charging on the high side and adding
liquid on the low side of the system are both meant to
protect the compressor from operating with abnormally
low suction pressures during charging. NOTICE Do not
operate the compressor without enough system
charge to maintain at least 55 psig (3.8 bar) suction
pressure. Do not operate the compressor with
the low pressure cut-out disabled. Do no operate
with a restricted suction or liquid line. Depending
on the discharge pressure, allowing pressure to drop
below 55 psig (3.8 bar) for more than a few seconds
may overheat the scrolls and cause early drive bearing
damage. NOTICE Do not use the compressor to test
the opening set point of a high pressure cutout.
Bearings are susceptible to damage before they have
had several hours of normal running for proper break in.
“Hipot” (AC High Potential) Testing
CAUTION
Use caution with high voltage and never hipot
when compressor is in a vacuum.
CopelandScrollcompressorsareconguredwiththe
motor down and the pumping components at the top
of the shell. As a result, the motor can be immersed
in refrigerant to a greater extent than hermetic
reciprocating compressors when liquid refrigerant is
present in the shell. In this respect, the scroll is more
like semi-hermetic compressors that have horizontal
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conguration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 nal 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.