Why Should a Vapor-Compression Cooling System with a Compressor Be Vacuumed Before Charging with Refrigerant?

The vacuuming process involves completely removing air and water vapor from the refrigeration cycle. The reasons for this are:

۱. Removal of Moisture (Water Vapor):

If moisture remains in the system:

a) It will freeze at the low temperature of the evaporator and block the piping.

b) It will react with the compressor oil and produce acid, which can damage the compressor.

c) It will cause internal corrosion and clog the expansion valve or other control valves.

۲. Removal of Non-Condensable Gases:

The remaining air (oxygen, nitrogen, etc.) is non-condensable and:

a) Increases the condenser pressure.

b) Reduces the cooling capacity.

c) Disrupts compressor operation and decreases system efficiency.

۳. Detection of Potential Leaks:

If the system pressure rises after vacuuming, it may indicate a leak in the connections or piping.

The image shows a vacuum pump from the Gilson brand, made in the USA.