R507A is an azeotropic blend consisting of 50% R125 and 50% R143a by weight; like a pure substance it evaporates and condenses at a single temperature. It came onto the market in the same period as R404A, to replace R502, and is used in the same applications: frozen storage rooms, blast freezing tunnels, ice machines, industrial low-temperature plants. It is in safety class A1 and works with POE oil. It boils at −47 °C at atmospheric pressure; its saturation pressure at 0 °C is about 5.2 bar g.
Its difference from R404A is small: its pressures and capacity are some 2–3% higher and its glide is zero. Because it has no glide it has been preferred in industrial plants with pumped and flooded evaporators; in this kind of evaporator zeotropic blends can separate into their components. Superheat and subcooling are measured from a single saturation column, it can be charged as gas or as liquid, and its composition is not upset after a leak. From the service point of view it is one of the most trouble-free blends. On gauge dials, too, it mostly appears side by side with R404A.
Its problem is the same as that of R404A, and even a little more serious: its GWP is 3,985, far above the 2,500 limit. The F-gas regulation has banned this refrigerant in new commercial refrigeration systems since 2020 and has also restricted servicing with virgin gas in systems exceeding 40 tonnes CO₂ equivalent (a charge of about 10 kg with R507A). The 5 tonnes CO₂e threshold is exceeded with a charge of only 1.25 kg; that is, almost every R507A system is subject to at least one leak check a year. Its price is rising and its availability is decreasing.
Existing plants can go on running; however, a major repair such as a compressor replacement is the right time for a retrofit. In direct expansion systems R448A or R449A can be used with the same compressor and oil; the expansion valve setting and the discharge temperature are reviewed. In flooded and pumped plants the retrofit is not so easy; because of the glide it is assessed project by project. You can compare the saturation pressures of R507A with R404A in our refrigerant pressure–temperature chart. Before deciding, the compressor manufacturer’s list of approved refrigerants should be consulted.