CG-SVX17D-EN 159
Maintenance
Compressor Operational Pump Down
The operational pump down is used to manage the refrigerant charge and prevent liquid slugging
into the compressors, oil dilution and oil starvation. The pump down will be completed by the last
operating compressor in the refrigerant circuit and occurs during normal shutdown conditions.
The electronic expansion valve will close.
The operational pump down sequence will end when:
• Saturated evaporator temperature drops below the operational pump down set point
• Compressor pressure differential exceeds 348 psid (Condensing Pressure - (Evaporator
Pressure x 2.9)
• When the operational pump down time expires (60 x (100/circuit capacity %))
• An immediate shutdown diagnostic occurs
• A pressure transducer fails
Compressor Service Pump Down Procedure
The Service Pump down procedure is used to store the Model CGAM refrigerant in the condenser.
The condenser is sized to hold the entire refrigerant charge.
Procedure:
• Select compressor to use for pump down.
• All chiller safeties remain in effect.
• Evaporator water flow must be proven
• Condenser fans operate normally
• Manually close refrigerant liquid line service valve
Note: The service pumpdown algorithm expects the liquid line service valve to be closed during
service pumpdown. The EXV will open, allowing the refrigerant between the liquid line
service valve and EXV to be pumped out.
Service pump down is complete when:
• Service pump down time expires (60 x (100/circuit capacity %))
• Saturated evaporator pressure falls below Low Pressure Cutout x1.15 for one second
After pump down terminates, the MP automatically puts circuit into lockout. Pump down can also
be terminated by “Abort Pump down” in service tool, an immediate shutdown diagnostic occurs
or a pressure transducer fails.
Oil Equalizer Line
CSHN Compressors
The oil equalizer line is equipped with a Rotolock fitting for easy removal. Torque values for
tightening these fitting is 100 ft.-lbs, plus or minus 10 ft. lbs.
Drain the oil to a level below the oil equalizer tube fitting before removing the oil equalizer line. This
must be done on both compressors. Use the oil drain valve on the compressor. If the oil is drained
below the level of the oil level sight glass, it will be below the oil equalizer line level. Pressurize the
low side of the compressor using nitrogen to help drain the oil. No more than 10 psig of pressure
will be needed.
CSHD Compressors
CSHD compressors do not have an oil drain valve. Therefore, before removing the oil equalizer line,
the system refrigerant charge must be recovered before draining the oil. Use a catch pan to catch
the oil when the compressor oil equalizer line is loosened to ensure that oil does not spill out of
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