R-22 PT Chart (Pressure-Temperature)

How do you use an R-22 PT chart on an older system?

Convert each gauge pressure to its saturation temperature and compare it with the pipe temperature. Because R-22 is a single compound, the same chart column works on both sides of the system: suction pressure gives the evaporator's boiling temperature, and liquid-line pressure gives the condensing temperature.

At the cold end, R-22 is close to atmospheric pressure: the table shows 0.6 psig at −40°F. Low-temperature R-22 equipment can pull the suction side into a vacuum, which a compound gauge shows in inches of mercury. Air-conditioning evaporators run far above that range.

Is R-22 still legal to use?

Yes, in existing equipment. EPA's homeowner fact sheet says U.S. production and import of HCFC-22 ended on January 1, 2020, "but you may continue to use HCFC-22 in your existing system for as long as necessary" (EPA-430-FR-20001). No federal rule requires an owner to replace a working R-22 system.

• Venting is illegal. Under Section 608 of the Clean Air Act, it's illegal to knowingly vent or release refrigerant while servicing, repairing or disposing of AC equipment. Recover it.
• Supply is finite. With no new production, every pound used for service comes out of recovered, reclaimed or pre-2020 stock. Leak repair is the cheapest way to keep an R-22 system running.
• Watch for fakes. EPA warns that "R-22a" has been falsely marketed as R-22 or an R-22 replacement. It's a hydrocarbon blend whose main components include propane and butane, highly flammable, and not an acceptable alternative for residential AC.

What about converting an R-22 system to another refrigerant?

EPA's SNAP program lists non-ozone-depleting alternatives for residential AC. EPA's fact sheet notes that some are for new systems only, while others are listed for both new and retrofitted systems. We don't call any of them a "drop-in": EPA's guidance for a retrofit is that the technician recovers all remaining R-22, follows the manufacturer's handling and installation guidelines for that specific alternative, and explains how the conversion may change the system's performance and energy use.

• Check the replacement refrigerant manufacturer's retrofit guide for oil, seals, metering device and charge instructions before quoting a conversion.
• Never put R-410A, R-32 or R-454B in an R-22 system. They run at much higher pressures and are listed for new equipment designed for them.
• Never mix a replacement refrigerant with leftover R-22. Recover first, then charge the new refrigerant to its own PT chart.
• Label the system with the new refrigerant so the next tech doesn't read the wrong chart.

How this table was made and checked

We compute the table with CoolProp 8.0.0 using its equation of state for pure R-22, converted to gauge pressure relative to 14.696 psia. Our tests compare 20 temperatures against the Daikin A1 vs. A2L chart and 10 against the Arkema Forane wall chart (NIST REFPROP 9.0). Every point matches within 0.1 psi; at 100°F all three read 195.9 psig.