First-stage oil returen: There is a built-in oil separator in the compressor. After compression, the mixture of oil and refrigerant can be separated when going through the built-in oil separator. Only a small amount of oil can be brought out of the compressor.
Second-stage oil return: The refrigerant discharged from the compressor will pass through the second-stage oil separator built inside the condenser for secondary operation. The majority of the lubricating oil will return the compressor through the oil return pipe at the bottom of the oil separator.
Third-stage oil return: A very small amount of lubricating oil enters the refrigerant system along with the refrigerant and then remains in the evaporator. At this point, the third-stage injection oil return will pump the lubricating oil back to the compressor completely.
