Superheat generally does not affect actual oil return to the compressor crankcase unless the superheat is set so high that it causes a starved condition resulting in low return gas velocity or evaporator icing. Low superheat at the compressor results in liquid refrigerant being present in the oil sump. The violent action of liquid refrigerant boiling in the crankcase will cause oil to be blown out into the system resulting in low oil levels. Liquid refrigerant in the compressor’s pressurized lubrication system will result in a loss of net oil pressure resulting in an oil failure trip, bearing damage due to the loss of lubrication to bearing surfaces and possible valve damage due to liquid slugging caused by the returning oil.
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