The lubricant in refrigeration and air conditioning systems has many important functions. Even though the circulated refrigerant is the working fluid required for cooling, the lubricant or oil is needed for lubrication of the compressor’s moving mechanical parts.
Oil minimizes mechanical wear by reducing friction. Oil also maintains a seal between the high and low side of the compressor. Without proper lubrication, the compressor’s valves, mating scrolls, screws, and vanes would not properly seal. The results would be high-side refrigerant pressures entering the low side of the refrigeration system. Piston rings in a reciprocating compressor and rotating vanes in centrifugal compressors rely on the lubricating oil to prevent blow-by around the pistons and vanes. Oil also acts as a noise dampener within the compressor and transfers heat away from moving and rotating parts within the compressor.