Refrigerant Pressure-Temperature Converter

Refrigerant pressure and temperature have a direct relationship: at a given pressure, a refrigerant boils (or condenses) at a specific temperature. This relationship is essential for HVAC technicians to diagnose system performance and charge systems correctly.

Common refrigerants:

• R-22 (Freon): Older residential AC systems. Being phased out due to ozone depletion. No longer manufactured, only recycled supplies available.
• R-410A (Puron): The standard replacement for R-22 in new residential systems since 2010. Operates at significantly higher pressures than R-22.
• R-134a: Used primarily in automotive air conditioning and small commercial refrigeration. Also common in household refrigerators.

Pressure-Temperature chart (saturated, psig). These are the exact rows the calculator above reads, interpolating between them, so the two cannot drift apart:

That negative R-134a figure is not a typo. R-134a boils at about -15F at atmospheric pressure, so anywhere below that it sits in a vacuum and a compound gauge reads on the inches-of-mercury side. The -7.3 psig at -40F is the same reading a gauge shows as roughly 14.8 in Hg of vacuum, and confusing those two scales is the usual reason a low-side reading looks impossible. R-22 and R-410A both stay above atmospheric across this whole range.

Key diagnostic concepts:

• Superheat: The temperature above the saturated boiling point at the suction line. Normal range is 10-20F (5-11C). Too high means not enough refrigerant; too low means too much.
• Subcooling: The temperature below the saturated condensing point at the liquid line. Normal range is 10-15F (5-8C).
• Measuring both superheat and subcooling helps determine whether a system is properly charged.

Important safety notes:

• R-410A operates at approximately 1.6 times the pressure of R-22. Never use R-22 equipment for R-410A.
• All refrigerants must be recovered and recycled by EPA-certified technicians. Venting refrigerant is illegal in most countries.
• Always wear safety glasses and gloves when working with refrigerants, as they can cause frostbite on contact.