R513A

For anyone who wants to move away from R134a in an above-zero room or a chiller, this is the gas most often suggested. Slightly more than half of it is R1234yf, the rest R134a. At this ratio the two form an azeotrope, so it boils at a single temperature like a pure gas, and the flammability of R1234yf disappears. Its greenhouse effect is less than half that of R134a. Its pressure is about one tenth higher, and its capacity and efficiency are almost the same. Its boiling point is −29 °C.

In a retrofit the compressor and oil stay, and the expansion valve usually does too; checking the superheat is enough. The old gas is recovered, the drier is renewed, the circuit is evacuated and then charged, and the label is corrected. It is never added on top of R134a left in the system. It is not chosen for frozen rooms or blast freezing: below −20 °C the suction falls to atmospheric pressure and capacity melts away. It is common in the upper circuit of CO₂ cascade systems and in milk and beverage cooling.