Refrigerant Pumping Down

This procedure transfers the refrigerant circulating around the system from the liquid shut-off valve at the liquid receiver to the inlet of the compressor for storage in the condenser and the receiver, thereby making it possible for
other tasks to be performed.
The method is as follows:

1. Fit gauges, set the service valves to operating positions and operate the plant.
2. Close the liquid shut-off valve at the receiver.
3. Allow the compressor to operate until a pressure slightly above atmospheric pressure is registered on the compound gauge (3 psi or 0.2 bar). If the system employs a low pressure cut-out switch then the range will need to be altered; note the cut-out pressure beforehand. Modern switches have a small lever which can be moved to override the cut-out point, thus keeping the compressor running.
4. Stop the plant and front seat the suction service valve.

The system can now be worked on for a number of repairs.

When it is required to close down a plant for an extended period, the discharge service valve should also be front seated after the gauges have been removed.

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