How do you calculate superheat in an HVAC system?

To calculate superheat in an HVAC system, you find the difference between the saturation temperature of the refrigerant at a given pressure and the actual temperature of the refrigerant vapor in the suction line. This process is crucial for ensuring that the refrigerant is adequately vaporized when it returns to the compressor, which protects the compressor from damage caused by liquid refrigerant.

Saturation temperature corresponds to the pressure of the refrigerant in the evaporator. By subtracting the suction line temperature from this saturation temperature, you determine how much heat has been added to the refrigerant vapor since it left the evaporator. This value tells you if the refrigerant is reaching the compressor in the required vapor state, indicating the efficiency of the cooling process.

The other methods outlined do not correctly reflect the process of determining superheat and do not provide usable information about the efficiency or state of the refrigerant in the system. Hence, the correct calculation involves this specific subtraction, leading to accurate superheat values essential for proper HVAC function.