Superheat and Subcooling Calculator

Superheat is the suction line temperature minus the saturation temperature at the suction pressure (from the PT chart). Subcooling is the saturation temperature at the liquid line pressure minus the liquid line temperature. Both require a manifold and an accurate pipe-clamp thermometer.

Read the suction line pressure on your manifold and look up the saturation temperature on a PT chart for your refrigerant (R-410A, R-32, R-454B, R-22). Then take the actual suction line temperature with a pipe-clamp thermometer about 6 inches from the compressor. Subtract the saturation temperature from the line temperature. Example: 118 psig R-410A = 40 degF saturation; suction line at 52 degF gives 12 degF superheat.

Read the liquid line (high-side) pressure and look up the saturation temperature on the PT chart for your refrigerant. Take the actual liquid line temperature with a pipe-clamp thermometer near the condenser outlet. Subtract the line temperature from the saturation temperature. Example: 365 psig R-410A = 110 degF saturation; liquid line at 100 degF gives 10 degF subcooling.

For TXV and EEV systems, target 8 to 12 degF superheat measured at the evaporator outlet or near the compressor. Fixed-orifice systems vary with conditions and typically run 5 to 25 degF based on the manufacturer charge chart.

Most TXV systems target 8 to 12 degF subcooling. Some manufacturers specify 6 to 14 degF on the data plate. Subcooling under 5 degF usually means undercharged; over 15 degF often indicates overcharge or condenser restriction.

That combination almost always points to an undercharged system. There is not enough refrigerant to fully condense in the condenser (low SC) and not enough liquid feeding the evaporator to fully boil (high SH). Add refrigerant slowly and recheck.

Charge TXV and EEV systems to subcooling first, then verify superheat is in target range. Charge fixed-orifice systems to superheat using the manufacturer chart based on indoor wet-bulb and outdoor dry-bulb temperatures.

Yes. The math is refrigerant-agnostic. Look up the saturation temperature for your specific refrigerant on its PT chart, enter the temperatures here, and the calculator returns superheat and subcooling. R-410A, R-32, R-454B, R-22, and others all use the same formulas.

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