Superheat and Subcooling Calculator
Use this refrigerant charge calculator to find saturation temperature, superheat, and subcooling for R-410A and R-22 systems.
Verify readings before making a charging decision
Gauge PT scales and the equipment manufacturer data are the authority. Sanity-check this calculator against your gauge scale, verify airflow first, and use the equipment nameplate target.
System Readings
PT table range for R-410A: 50 to 450 PSIG
Target Superheat Helper
TXV systems are charged by subcooling to the nameplate value instead.
Typical Reference Range
Fixed-orifice superheat is often 8 to 15°F at target conditions. Compare the actual reading with the calculated target and manufacturer procedure.
A dirty filter, dirty coil, blower problem, or incorrect airflow can imitate a charge problem and invalidate the diagnosis.
What Superheat and Subcooling Indicate
Superheat shows how far suction vapor is above its saturation temperature. Subcooling shows how far liquid refrigerant is below its saturation temperature. Low or high readings can point toward undercharge, overcharge, a metering problem, or an airflow problem, but no single reading proves the cause.
Fixed Orifice
Use superheat with indoor wet-bulb and outdoor dry-bulb conditions. Compare measured superheat with the target only after the system stabilizes and airflow is verified.
TXV
Charge a TXV system by subcooling to the equipment nameplate value. The TXV regulates evaporator superheat, so superheat alone is not the charging target.
When Readings Are Unreliable
Do not rely on ordinary cooling-mode charge readings with incorrect airflow, dirty coils, unstable operation, active low-ambient controls, or outdoor temperature below about 55°F unless the manufacturer provides an approved charging procedure. Verify gauge accuracy and temperature clamp contact.
Superheat and Subcooling Questions
Document the completed service call
Plenum Invoicing keeps approved work, line items, and customer records together after the system is diagnosed.
See Invoicing