Refrigerant Charge Calculator — Superheat and Subcooling
Determine refrigerant charge status by calculating actual superheat and subcooling values, then comparing them to target ranges. Supports both TXV/EEV and fixed-orifice metering device systems.
System Configuration
Superheat Method (Fixed Orifice / Piston)
Target Superheat Inputs (Fixed Orifice Systems)
Formulas
Actual Superheat (Fixed Orifice Systems):
Superheat (°F) = Tsuction line − Tsat @ suction pressure
Where Tsat @ suction pressure is the saturation (boiling) temperature of the refrigerant at the measured suction line gauge pressure, obtained from refrigerant pressure-temperature tables.
Target Superheat (Fixed Orifice Systems):
Determined by bilinear interpolation of the AHRI/manufacturer superheat charging chart using: outdoor ambient dry-bulb temperature and indoor return air wet-bulb temperature. The chart encodes the relationship between heat load, airflow, and required evaporator performance.
Actual Subcooling (TXV / EEV Systems):
Subcooling (°F) = Tsat @ liquid line pressure − Tliquid line
Where Tsat @ liquid line pressure is the condensing saturation temperature at the measured liquid line gauge pressure. Subcooling confirms all refrigerant has condensed to liquid before the metering device.
Saturation Temperature Interpolation:
Tsat(P) = T0 + (P − P0) × (T1 − T0) / (P1 − P0)
Linear interpolation between adjacent data points in the refrigerant P-T table.