R448A

This gas is often the shortest way to take an old R404A plant out of the reach of the bans. The compressor and the POE oil are left alone, and no extra safety equipment goes into the machine room. Besides R32, R125 and R134a it contains two HFOs: R1234yf and R1234ze. Its greenhouse effect is about one third of R404A’s, so the CO₂ equivalent of the same charge falls and leak checks may become less frequent. Its trade name is Solstice N40.

A retrofit quotation lists a new filter drier, resetting of the expansion valve and pressure switches, and a complete new charge. On the suction side the gauge reads lower than with R404A; the discharge side is almost the same. The real risk is a discharge temperature 10–15 K higher; in frozen rooms below −30 °C, liquid injection or a head fan is allowed for. Superheat is read from the dew pressure, subcooling from the bubble pressure. It is an equivalent of R449A, yet the two are never put in the same circuit together.