Where water-cooled refrigeration and air-conditioning systems are not operated in the winter, it is necessary to service them before discontinuing their operation. They should be pumped down, water drained from the condensers and piping, belts loosened, and motors oiled. The compressor should be thoroughly tested for leaks, and any found should be corrected.
To pump down and discontinue service, attach head and suction gages, and close the liquid shutoff valve at the receiver. Run the compressor until a suction pressure of from 2 to 5 psig is obtained. If, on stopping the compressor, the suction pressure rises, repeat until this pressure is steady. Close the suction and discharge shutoff valves to confine the refrigerant charge in the receiver. Open the main switch and be sure to tag it with a warning not to start the compressor without first opening the discharge and suction stop valves, because damage to the compressor may result. Tighten all packing nuts on valve stems. Cap all valve stems tightly.
The condenser is usually of sufficient capacity to hold the complete charge. However, if it is not, the overcharge must be pumped into an empty drum. Never fill a receiver completely with a liquid refrigerant (indicated by a rise in head-gage pressure above the safety cutout pressure) so that no gas space exists. If the compressor room temperature increases, there is danger of rupturing the receiver. Shut off the water supply to the compressor, and disconnect the outlet water line from the condenser. This will allow the water to drain from the condenser. After the water has all drained out, connect the air line or an automobile tire pump to the blowout plug, and proceed to force the remaining water (if any) out of the condenser. Condensers with removable heads can be effectively drained by shutting off the waste supply and removing the condenser heads, thus allowing all the water to drain.
On compressors of large capacity, it will be necessary to arrange for a connection to accommodate the airline, or pump. After all water has been forced from the condenser, it is recommended that all water lines be disconnected from the condenser and the water valves drained by removing the drain plug from the bottom of the water valves. For frequent and quick draining, it is suggested that a tee and drain valve be installed between the water-regulating valve and condenser inlet. The safest, surest way to prepare condensers for winter shutdown is to flush them out with an antifreeze solution. After the condenser has been treated with the antifreeze solution and drained, the condenser inlet and outlet water connections should be plugged in order to maintain the remaining antifreeze solution in the condenser. Remove the belts from the compressor motor, but not from the flywheel, so that they will not take a permanent set. It is also advisable to oil the motor to protect the bearings from corrosion.