R449A is a zeotropic blend of R32, R125, R1234yf and R134a. It works at almost the same capacity and pressures as R404A and is compatible with POE oil and existing compressors; this is why it has become the most common choice both in new systems and in retrofits from R404A. It is in safety class A1: non-flammable, low toxicity.
With a GWP of 1,397 it is 36% of R404A and stays below the F-gas limits. Its discharge temperature is a few degrees higher than R404A (watch compressor cooling in low-temperature applications), while its efficiency is generally equal or slightly better.
The one point to watch is glide: the blend evaporates and condenses not at a single temperature but over a range of 4–5 K in the evaporator and condenser. Superheat is calculated from the "dew" (vapour) point, subcooling from the "bubble" (liquid) point. The system is charged as liquid (cylinder inverted). Our refrigerant P–T chart gives bubble and dew values separately for R449A.