NATE Low Global Warming Potential (GWP) Practice Test

Superheat is the amount by which the suction gas temperature exceeds the saturated vapor temperature at the evaporator (suction) pressure. To calculate it, read the suction line temperature, determine the saturated vapor temperature for the system’s suction pressure, and subtract that saturation temperature from the measured suction temperature. The result shows how much the refrigerant vapor has heated above its phase-change point, which is the essential measure used to assess proper evaporator operation and compressor protection. The other methods don’t reflect the refrigerant’s pressure-enthalpy state: ambient temperature has no relation to the refrigerant’s pressure, subtracting suction from liquid line temperature mixes phases and isn’t a correct superheat measure, and comparing suction temperature to the saturated liquid temperature would relate to subcooling rather than superheat.