Support

Frequently Asked Questions

How do I read the PT Chart?

Pick a refrigerant, then enter either a pressure or a temperature — the other value updates instantly. For blend refrigerants (e.g. R-407C, R-454BA2L), both the bubble point (saturated liquid) and dew point (saturated vapor) are shown, along with the glide between them.

What's the difference between bubble point and dew point?

For blends, the liquid and vapor don't boil/condense at exactly the same temperature for a given pressure. Bubble point is the saturated-liquid line (used for subcooling); dew point is the saturated-vapor line (used for superheat). For single-component or azeotropic refrigerants the two are equal.

How is Superheat calculated?

Superheat = suction line temperature − saturation (dew point) temperature at the measured low-side pressure.

How is Subcooling calculated?

Subcooling = saturation (bubble point) temperature at the measured high-side pressure − liquid line temperature.

Gauge vs. absolute pressure — which do I enter?

By default RefCalc expects gauge pressure (psig), matching your manifold gauges. You can switch to absolute pressure (psia) in Settings if that's what your instrument reads.

My result looks wrong / negative superheat or subcooling

This is usually a sign of a gauge/absolute pressure mismatch, or a measurement taken at the wrong point in the system. Double-check your pressure reference setting and probe location. RefCalc provides the math — always confirm final charge against the equipment nameplate or OEM charging chart.

Does RefCalc need an internet connection?

No. RefCalc works 100% offline — all refrigerant data and calculations are stored and run on your device.

Which refrigerants are supported?

R-410A, R-32, R-454B, R-452B, R-22, R-134a, R-404A, R-407C, R-448A/R-449A, R-290, R-1234yf, and R-513A, including the newer A2L mildly-flammable refrigerants used in current residential and light-commercial systems.

Can I change units and language?

Yes — go to Settings to switch pressure unit (psi / bar / kPa / MPa), gauge vs. absolute reference, temperature unit (°F/°C), and app language.

Report a Data Issue

Refrigerant PT data is sourced from NIST REFPROP and OEM/ASHRAE published charts. If you find a value that doesn't match your manufacturer's chart, please email us the refrigerant, temperature or pressure point, and expected value so we can verify and correct it.