Why is refrigerant vapor reintroduced to the refrigeration system before refrigerant liquid after system servicing?

The correct answer is that refrigerant vapor is reintroduced to the refrigeration system before refrigerant liquid to prevent overheating of the compressor. When servicing a refrigeration system, introducing vapor allows for the gradual equalization of pressure and helps to ensure that there is sufficient refrigerant moving through the system. This is essential because the compressor is designed to compress vapor; if liquid refrigerant were introduced directly into the compressor, it could lead to liquid slugging, which can damage the compressor.

Additionally, reintroducing vapor first ensures that the compressor has an adequate supply of lubricant, as the vapor can aid in circulating oil throughout the system, maintaining lubrication for the compressor's moving parts. Therefore, the primary concern is preventing compressor damage and ensuring proper functioning after servicing, making this practice pivotal for the system's longevity and efficiency.