HVAC Subcooling & Superheat Charging Diagnostic Calculator
Calculate HVAC refrigerant subcooling and superheat from high/low-side gauge pressures (R-410A, R-22), evaluate TXV charging, and diagnose leaks or overcharging.
Calculated Results
Frequently Asked Questions
What is the difference between Subcooling and Superheat in HVAC?
Subcooling measures how much liquid refrigerant has cooled below its condensing saturation temperature in the outdoor condenser coil. Superheat measures how much refrigerant vapor has warmed above its boiling evaporation temperature in the indoor evaporator coil.
When do you charge an AC system by Subcooling vs. Superheat?
Systems with a Thermal Expansion Valve (TXV) regulate superheat automatically, so they MUST be charged by measuring Subcooling. Systems with a fixed orifice (piston) cannot adjust refrigerant flow and MUST be charged using a targeted Superheat chart.
What does low subcooling with high superheat indicate?
Low subcooling combined with high superheat is the classic symptom of an Undercharged system (refrigerant leak). There is insufficient liquid in the condenser and the evaporator is starved of refrigerant.
Why is excessive superheat dangerous for an AC compressor?
Compressors rely on cold returning suction gas to cool their internal electric motor windings. High superheat means hot suction gas enters the compressor, triggering thermal overload trips and oil breakdown.