How does air get into the cooling system?

The residual air in the refrigeration system can cause a lot of harm, so how does the air get into the refrigeration system? The main approaches are as follows:

• 1. Before charging the refrigerant, the vacuuming operation is not thoroughly carried out, so that the air remains in the system.

• 2. When the refrigeration system is supplemented with refrigerant oil, it is brought into the air.

• 3. When the refrigeration system works under negative pressure, the air penetrates into the place where the refrigeration system is not tightly sealed.