R1234yf is an HFO (hydrofluoroolefin): its molecule has a double bond between carbons. This bond breaks quickly in the atmosphere; the lifetime of the refrigerant in air is about 11 days, whereas for R134a it is 13–14 years. This is the reason its greenhouse effect is so low: its GWP is 4, against 1,430 for R134a. Because it contains no chlorine it does no harm to ozone. Its safety class is A2L, that is, not toxic but mildly flammable. It is colourless and almost odourless; a leak is noticed only with a detector.
Its thermodynamic behaviour is very similar to that of R134a: it boils at −29.5 °C at atmospheric pressure, and its saturation pressure is about 2.1 bar g at 0 °C and 9.2 bar g at 40 °C. Its capacity is some 5% lower than that of R134a. Thanks to this closeness the air conditioning of new cars produced in Europe has been charged with R1234yf since 2017; in vehicle air conditioning service a charging station dedicated to this refrigerant, a separate coupling and PAG (polyalkylene glycol) oil are used. It is also compatible with POE oil; this oil is used in stationary systems.
In stationary refrigeration it is seen less on its own: chillers, small plug-in cabinets and some heat pumps. Its truly widespread role is as a blend component. About a quarter of R449A, a fifth of R448A, 56% of R513A and 78.5% of R454C is R1234yf; it is the component that lowers the GWP of these blends. A cold room owner sees R1234yf not on a cylinder but in the list of contents of the blend being used. Its close relative R1234ze, for its part, is used mostly in large chillers.
Points to watch: its price is several times that of R134a, so a leak is a direct cost. Because it is flammable it is not charged directly into an R134a system; the equipment has to be designed for A2L. In service, spark-free equipment and ventilation are essential. When it breaks down at very high temperature, for example in a brazing flame, it gives off toxic and corrosive gases; this is why no brazing is done until the circuit has been emptied and purged with nitrogen. For pressure–temperature values you can consult our refrigerant chart. In the chart it can be compared side by side with R134a.