Emerson Liebert iCOM Manual De Usuario

Pump down is applicable to compressorized systems that are equipped for pump-down operation, 

which is set at the factory. This operation prevents the compressor oil from being diluted with liquid 

refrigerant to ensure that the compressor is properly lubricated for the next startup. Systems 

equipped with crankcase heaters and discharge line check valves may be set for pump down, however 

it is not required.
The pump down operation operates in the following manner:
Whenever the control determines that no more cooling is required and a compressor should be shut 

Off, the liquid line solenoid valve (LLSV) is closed (de-energized). The compressor will continue to 

operate until the low suction pressure device (LPS or LPT) opens, which shuts Off the compressor. If 

the LP device does not open within a specified time, the LLSV is turned On, then back Off (the 

assumption is that the LLSV is stuck). If, after three times, the LP device does not open, the 

compressor and LLSV are locked Off and an alarm “Pump Down not completed” will appear.
There is a re-pump down if the LP device opens again after the compressor has been already 

stopped—a maximum of six re-pump-down cycles per hour are allowed. At the seventh request of 

re-pump down, the alarm “Comp 1 Pumpdown Fail” or “Comp 2 Pumpdown Fail” will appear and the 

compressor will be locked out.
Pump down is always performed loaded (for compressors with unloaders: unloaders Off, digital scroll: 

control solenoid valve disabled).
For digital scroll only: when pump down has finished successfully (LP device opened), pump down will 

be continued for another half-second with the control solenoid valve energized.

When the compressor is initially activated, the system will be monitored for a high-pressure situation. 

When high-pressure is detected during the first 10 minutes of operation, the unit will attempt to 

correct the problem several times without notification. If the unit is unsuccessful in correcting the 

problem, an alarm will occur and the affected compressor will be locked Off. If high head pressure 

alarm trips three times in a rolling 12 hour period, the affected compressor will be locked Off.
After the compressor has been running for 10 minutes, if a high head pressure situation is detected, 

an alarm will occur and the affected compressor will be immediately locked Off without the unit 

trying to correct the problem.
Once the compressor is locked Off, it will not come back On until main power is reset or until the 

HP Alarm Counters (Service Menu, Diagnostics) are reset to 0.