When a new split air conditioner model is launched on the market, the refrigerant used is usually R32 – difluoromethane (CH2F2). Although this is a fresh solution – pioneers decided to design and sell devices with this refrigerator only in 2013 – R32 split air conditioners may nowadays constitute even half of the European market of such devices. In 2019, it was 37% and it will be over 80% by 2023 (assessments and forecasts by the British consultancy agency BSRIA).
R32 would not enjoy its present amazing popularity as the working medium for new air conditioners had it not been for the gradual withdrawal of high GWP (Global Warming Potential) refrigerants from the market in accordance with the Kigali Amendment to the Montreal Protocol and the timetable presented in Regulation EU 517/2014 (called the F-Gas Regulation). New small split air conditioners (with refrigerant filling levels up to 3 kg for a single air conditioning system) that will be first introduced after 1 January 2025 would need to be filled with a refrigerant with a GWP no higher that 750. The recent leader in the air conditioning refrigerants market until recently, R410A, has a GWP of as much as 2088, while R32 – approx. 675–677.
Currently, the European Commission is reviewing the F-Gas Regulation within the scope of achieving its goals, i.e. decreasing F-gas emissions by two thirds until 2030 in comparison to 2014. Draft regulation amendments include a complete ban on using refrigerants with a GWP >750 in stationary air conditioners and heat pumps. In practice, this would mean that using R410A would be restricted to larger VRF systems where R32 cannot be used, because its flammability limits the filling level.
It is exactly due to flammability or rather “slight flammability”, as R32 is qualified as a refrigerant with slight flammability (class A2L* in accordance with the EN 378 standard) – a maximum filling level also applies for split air conditioners. This is derived from LFL (Low Flammable Limit), which for R32 is 0.306 kg/m3 (i.e. 3.5% of the refrigerant volume in the air). For split air conditioners, the maximum device filling level depends on the room floor area (A) and the device installation height (h) in accordance with the following formula:
maximum filling level [kg] = 2.5 x LFL x 1.25 x h x √A
That is why the manufacturers of R32 air conditioners should provide information on the maximum floor area and installation height admissible for the specific air conditioner model. Rooms fitted with such devices should have good ventilation and must not contain any open fire sources, while the floor level should be lowered locally (R32 is heavier than air, so in the case of a leakage it will accumulate in floor cavities).
As R32 is “slightly flammable”, it does not affect safety during normal operation. Problems start when there is a leakage and in the presence of an ignition source. For most devices, however, the lower flammability limit of 0.306 kg/m3 will not be exceeded even if the entire refrigerant leaks out from the device. There might be a greater risk with carelessness during servicing or repair works, when the released refrigerant may mix with oxygen. That is why extra attention should be paid to avoid aspiration of air during repairs. In itself the refrigerant is not toxic, but its thermal decomposition products (which occurs at the temperature of 300–400ºC) are. That is why the system should be emptied and flushed with nitrogen before soldering during repairs. When inspecting the room for leakage, the detector should be placed near the floor (R32 is heavier than air).
Good news for users and fitters is that, except for its flammability, clean R32 is a better solution than R410A (of which it is a component). It is more efficient – a device filling level may be even up to 30% lower than with R410A – and energy-efficient because of better heat conductivity and lower viscosity. As a homogeneous refrigerant, it may be used for servicing works (e.g. working medium refills) both in liquid and gaseous state. The R32 refrigerant is also approx. 20% cheaper than R410A, although it requires the fitter to have appropriate equipment: dedicated pressure gauges, leakage detector and refrigerant recovery station.
What is the future of R32 then? It will surely play a major role in new split air conditioners. Due to its slight flammability, it is not a substitute for R410A in existing devices – it cannot be used for retrofitting. The second important application of R32 will be its inclusion in new refrigerants (mixtures) which are to ensure ever lower GWP values, preferably without flammability. Such solutions are already under development…
* Class A2L was introduced into the EN 378-1+A1 standard in 2017 because of the growing significance of refrigerants with low GWP and low flammability. An A2L class refrigerant is characterized by flame propagation under test conditions in air at 60°C and 101.3 kPa, at max combustion speed ≤10 cm/s under the test conditions of 23°C and 101.3 kPa.