What R-507A is and where it is used
R-507A is a 50/50 blend of R-125 and R-143a by weight. Honeywell sold it as Genetron AZ-50, and Chemours sells it as Freon 507. It is an azeotrope, so it boils and condenses at one temperature for a given pressure, like a single-component refrigerant. It carries an ASHRAE A1 rating.
Chemours describes R-507A as a zero-ODP HFC and a long-term replacement for R-502 that works over the entire R-502 operating range, in commercial refrigeration such as supermarket and transport systems. EPA lists R-507A, along with R-404A and R-407A, among the refrigerants most often found in supermarket rack systems, and also in some condensing units.
How to read the R-507A chart
Because R-507A is azeotropic, its bubble and dew pressures are effectively the same, so the chart shows one column. In the computed table the two values differ by a few tenths of a psi at most, too little to change a superheat or subcooling reading. Use the same column for both readings:
- Superheat: at 50 psig suction the saturation temperature is 13.6°F. Subtract it from the suction line temperature, or use the superheat calculator.
- Subcooling: at 250 psig liquid pressure the saturation temperature is 102.2°F. Subtract the liquid line temperature, or use the subcooling calculator.
Do not swap in an R-404A chart. The two are close but not identical: at 40°F, R-507A is 89.3 psig and R-404A is 86.9 psig bubble. See how to read a PT chart.
Typical R-507A pressures
Chemours' R-404A/R-507 retrofit guide compares refrigerants at a 104°F condensing temperature, a 14°F medium-temperature evaporator and a -22°F low-temperature evaporator. At those saturation temperatures R-507A reads:
- Low-temperature suction at -22°F: 16.2 psig
- Medium-temperature suction at 14°F: 50.5 psig
- Condensing at 104°F: 256.4 psig
These are saturation pressures at the stated temperatures, not service targets. Check the equipment's installation manual for operating pressures and set points.
Service notes
- Oil. Chemours says equipment makers recommend POE with R-507A. Arkema rates both of its components, R-125 and R-143a, as poorly soluble in mineral oil and alkylbenzene.
- Charging. Arkema notes that fractionation from leaks is small with an azeotrope, and Chemours says R-507A does not separate when it leaks. Arkema still advises charging all blends as liquid.
- Flammability. Arkema lists R-143a alone as A2L (mildly flammable), but the R-507A blend is rated A1. Chemours warns that no HFC-containing blend should be mixed with air to check for leaks. Pressure test with dry nitrogen.
- Converting. Chemours publishes a procedure for moving R-507 systems to R-449A, keeping the existing POE in most systems. Suction pressure changes: at a 14°F saturation temperature R-507A reads 50.5 psig and R-449A reads 37.6 psig dew. Chemours says set points and cutouts may need resetting.
Status and replacements
R-507A's GWP of 3,985 is far above EPA's Technology Transitions limits for new equipment. New stand-alone units have been capped at 150 since 2025. The current limits also bar it from new remote condensing units and cold storage warehouses installed from July 27, 2026, and from new supermarket systems installed from Jan 1, 2027. EPA says existing systems may be serviced and repaired throughout their useful life. HFC supply is limited by the AIM Act phasedown, which drops allowed production and consumption to 30% of the historic baseline in 2029. Chemours (R-449A) and Honeywell (R-448A) both market blends to replace R-507 in low- and medium-temperature systems, new or retrofit. EPA lists R-744 (CO2) as acceptable in retail food refrigeration, and transcritical CO2 racks are in use in US supermarkets.