R-507A PT Chart and Refrigerant Profile

Where you will find R-507A

R-507A is an R-125/R-143a azeotrope used in low- and medium-temperature commercial refrigeration: display cases, cold storage, ice machines and transport units (Arkema Forane Technical Digest). Like R-404A it replaced R-502 and R-22 in low-temperature work, and the two often sit side by side in the same store or warehouse.

Techs and supply houses usually call it R-507. Chemours sells it as Freon 507, and Honeywell’s original name was Genetron AZ-50; the ASHRAE designation is R-507A. Whether the AZ-50 brand is still sold in the US was not confirmed.

R-507A and R-404A run close but not identical pressures. At a 40°F dew point the computed charts give 89.2 psig for R-507A and 85.4 psig for R-404A; at -20°F, 17.6 and 16.0 psig. That is enough to throw off a superheat reading, so confirm the refrigerant on the nameplate and the cylinder label before you use the chart.

Charging R-507A

R-507A is an azeotrope. The computed bubble and dew pressures differ by 0.25 psi or less across the chart (glide about 0.04°F at 40°F), so in practice one pressure applies at each temperature. That is why the at-a-glance table above says it can be charged as vapor or liquid.

Arkema’s guidance is stricter: R-507A should be charged in the liquid phase, and if vapor feed into the system is needed, the liquid should be flashed through a metering valve.

Either column of the PT chart works for superheat and subcooling. On TXV and EEV systems, charge to the manufacturer’s subcooling or charging instructions and check with the subcooling calculator. Capillary-tube self-contained units are charged by weight to the nameplate. The target superheat calculator uses the CEC table for fixed-metering comfort air conditioners and is not meant for refrigeration.

There is no single normal suction pressure for an R-507A freezer or cooler. Suction pressure follows the design saturated evaporating temperature, which comes from the case or unit maker: at -20°F the chart gives 17.6 psig, at 20°F 58.2 psig. This chart was spot-checked against the Chemours pressure-temperature guide with differences of 0.03 psi or less.

Oil and compatibility

R-507A uses POE oil. When converting an R-502 system, Arkema says to reduce the residual mineral oil to 5% or less. BITZER lists POE or PVE, with alkylbenzene only of limited use. Use the oil grade on the compressor label.

Moving an R-507A system on to R-449A or R-448A keeps the existing POE, according to Chemours and Solstice. See the oil types guide.

Safety, handling and recovery

R-507A is class A1: lower toxicity, no flame propagation. Standard tools and a recovery machine certified to Appendix B3 (AHRI 740) apply.

It is a high-pressure appliance refrigerant under 40 CFR 82.152 (liquid saturation pressure 170–355 psia at 104°F). Section 608 Type II or Universal certification is required, and sales are restricted to certified technicians. Recover to 0 in Hg on systems under 200 lb and to 10 in Hg on 200 lb or more (equipment made after November 15, 1993, 40 CFR 82.156).

Since January 1, 2026, appliances with 15 lb or more of HFC fall under the leak repair rules of 40 CFR 84.106, and commercial refrigeration with 1,500 lb or more needs automatic leak detection (84.108).

The legacy color for R-507A is blue-green (teal). New containers since January 1, 2020 are light green-gray (RAL 7044) under AHRI Guideline N-2017, with the legacy color only on the label, so a teal cylinder is older stock. See cylinder colors.

Status and replacements

Servicing existing R-507A equipment is legal. Supply shrinks with the AIM Act allowance cuts (40 CFR 84.7): 60% of baseline in 2024–2028, 30% in 2029–2033.

For new equipment, 40 CFR 84.54 names R-507A as restricted in new road and marine transport units from January 1, 2025, and in new large ice machines and refrigerated food processing and dispensing equipment from 2027. Its GWP is above the 1,400 limit the May 2026 final rule (91 FR 31284) set for new remote condensing units from July 27, 2026 and new supermarket systems from January 1, 2027, and above the 700 limit for new cold storage from July 27, 2026; lower 150/300 limits follow on January 1, 2032. EPA SNAP had already listed R-507A as unacceptable in new cold storage warehouses from January 1, 2023.

From January 1, 2029, servicing supermarket systems, refrigerated transport and automatic commercial ice makers must use reclaimed refrigerant (40 CFR 84.112(e)).

Chemours’ suggested retrofit for R-507A is R-449A (Opteon XP40); R-448A is the other common A1 option. New equipment uses A2L blends such as R-454A, R-454C and R-455A, or CO2 (R-744). Compare in R-404A vs R-507A and R-404A replacement.

Common questions

Is R-507 the same as R-507A?

In practice, yes. R-507A is the ASHRAE designation for the 50/50 R-125/R-143a azeotrope; Chemours sells it as Freon 507, and “R-507” is how most techs and wholesalers write it.

Can R-507A be charged as vapor?

As an azeotrope it barely fractionates, but Arkema still says to charge it as liquid and flash it through a metering valve when vapor feed is needed. Follow that guidance.