Closing the liquid line service valve or solenoid while the compressor runs empties the low side, and the compressor stops on low pressure, leaving the charge stored on the high side. Techs do a manual pump-down to work on the low side without recovering the charge. Commercial refrigeration often uses automatic pump-down every cycle, so liquid cannot migrate to the compressor during the off cycle.
Do a pump down to 5 psi on the low side, front-seat the suction valve, and we can change the TXV without recovering.
Also heard as
- pumpdown
- pump it down
Related terms
Service valve
A manually operated valve on a condensing unit or receiver that isolates refrigerant and provides a gauge port.
Recovery
Removing refrigerant from a system into a recovery cylinder instead of venting it to the atmosphere.
Slugging
Liquid refrigerant or oil being drawn into a compressor's cylinders, where it can't be compressed and causes damage.
High side
The high-pressure half of a refrigeration system, from compressor discharge through condenser to the metering device.