Excessive ________, caused by a low refrigerant charge, is an indication of a leak in a high-pressure system.

• A. Subcooling
• B. Temperature
• C. Pressure
• D. Superheat

Answer: (D)

Superheat is the temperature rise of refrigerant vapor above its saturation temperature at the evaporating pressure. In a normally charged system, the evaporator leaves with vapor close to saturation, so superheat stays within the expected range. If the refrigerant charge is low because of a leak, there isn’t enough liquid to absorb the heat in the evaporator. The liquid-vapor mixture boils off more completely, and the vapor leaving the evaporator gets much hotter than the saturation temperature, creating excessive superheat. This condition strongly points to a low charge caused by a leak in a high-pressure system. Temperature or pressure alone don’t reliably indicate charge state, and subcooling relates to the liquid line after the condenser rather than the evaporator. So excessive superheat is the clearest indicator of a leak-induced low charge.