Subcooling

A diagnostic measurement showing how much liquid refrigerant cools below its condensing temperature in the outdoor unit — paired with superheat to verify proper system operation.

What Is a Subcooling?

Subcooling is the opposite of superheat, measured at the condenser (outdoor unit). It's the difference between the liquid refrigerant temperature and its condensing (saturation) temperature. Typical subcooling ranges from 10-18°F depending on the system. Low subcooling often indicates a low refrigerant charge. High subcooling can indicate an overcharge or a restriction in the liquid line. Together with superheat, subcooling gives a complete picture of how the refrigerant is behaving throughout the system.