Refrigerant PT charts
Each chart gives saturation pressure from -40°F up to 160°F (or the critical point, if lower). The refrigerant PT chart index has a lookup for any refrigerant and an overview at 40°F and 100°F. For example, R-410A reads 118.8 psig at 40°F and R-22 reads 68.6 psig. The groups below follow ASHRAE's refrigerant numbering, where the 400 series are zeotropic blends and the 500 series are azeotropic blends.
Charging calculators
Each calculator takes gauge pressure and line temperature and does the PT lookup for you. ASHRAE defines superheat against the dew point and subcooling against the bubble point, so the calculators use the dew point for suction readings and the bubble point for liquid readings.
- Superheat calculator: suction line temperature minus the saturation temperature at suction pressure.
- Subcooling calculator: saturation temperature at liquid line pressure minus liquid line temperature.
- Line-set charge calculator: extra charge for a longer liquid line, from tube volume and liquid density.
- AC pressure chart: estimated low and high side pressures by outdoor temperature for home central AC and heat pumps.
Refrigerant comparisons
Side-by-side pressures, safety class, GWP, glide and US regulatory status:
Guides
- How to read a PT chart, including gauge vs absolute pressure and altitude.
- Bubble point, dew point and glide: which column to use for blends.
- How to measure superheat and subcooling: where to put the gauges and clamps.
- A2L refrigerants: what the class means and where to read the rules.
Where the numbers come from
Saturation pressures are computed with CoolProp 8.0.0, an open-source thermophysical property library, at whole degrees Fahrenheit. Pressures are gauge pressures referenced to the standard sea-level atmosphere of 14.696 psi. The methodology page explains the calculation and the checks against manufacturer charts, and every page lists its sources.
The U.S. Department of Energy's Building America diagnostics guide says manufacturers' installation instructions should be strictly followed for refrigerant charging. Where an equipment manufacturer publishes a charging chart, target or line-set adjustment, use that number over any general rule here.