Getting compressor oil that circulates with the refrigerant back to the compressor.
Some oil always leaves the compressor with the discharge gas. It returns by travelling with refrigerant, which depends on miscibility (oil and refrigerant mixing), pipe pitch and vapour velocity. Good practice includes pitching horizontal suction lines toward the compressor, sizing risers for velocity, and using the oil type the refrigerant requires: most HFCs need POE oil rather than mineral oil.
Exam work areas
C · Planning installs and retrofits D · Installing systems and controls