R454C is a zeotropic blend containing 21.5% R32 and 78.5% R1234yf by weight. Its importance comes from its GWP value: at 148 it stays just below the 150 limit of the F-gas regulation. Thanks to this it is not affected by the restrictions placed on refrigerants with a GWP above 150, and a condensing unit installed today is expected to have no gas availability problem throughout its life. It is used at low and medium temperature in condensing units, monoblock units and supermarket systems. It is also known on the market as Opteon XL20.
Its pressures are lower than those of R404A: about 2 bar g at the dew point at −10 °C and 14–15 bar g at 40 °C condensing. Its volumetric capacity is also lower; the same compressor delivers 15–20% less capacity than with R404A, so a compressor one size larger is selected. Its efficiency is equal to or better than that of R404A, while its discharge temperature is close to it; the high discharge temperature problem seen with R448A and R449A is milder here. Its glide is 6–8 K.
Its safety class is A2L: it is hard to ignite and its flame spreads slowly, but it is flammable. For this reason it is not charged into an existing system running on R404A or R449A; the electrical panel, fans, valves and compressor must be A2L approved. The EN 378 standard limits the allowable charge according to room volume; with large charges a gas detector, ventilation and emergency shut-off valves are required. Because the evaporator is inside the cold room, the calculation is made according to the volume of the smallest room served.
In service both the A2L and the glide rules apply: a spark-free recovery unit, purging with nitrogen before brazing, charging as liquid from the cylinder, and calculating superheat from the dew column and subcooling from the bubble column. Because of the high glide the mean evaporating temperature is taken as the basis in evaporator selection; the colder tubes at the inlet frost up a little more. It is often compared with R455A, which serves a similar purpose. If you are considering a new investment you can ask about the refrigerant options of the condensing units in our catalog.