R466A: in search of a substitute for R410A

Withdrawal of refrigerants with high GWP values and introduction of synthetic refrigerant alternatives does not always progress smoothly. This is mostly related to the flammability of the new refrigerants. As slightly flammable fluids (class A2L in accordance with the EN 378-1+A1 standard), refrigerants such as R32 or R1234ze(E) cannot be used for retrofitting existing devices working with nonflammable refrigerants (class A1). System size is the second issue – it is limited because of the relation between the maximum system filling limit and the lower flammability limit of the particular refrigerant.
Such problem occurs in current R410A refrigerant applications (GWP = 2088). A good alternative for new split or even multi-split air conditioners is the R32 refrigerant. However, a slightly flammable refrigerant cannot be used for large systems with variable refrigerant flow (VRF/VRV). It is assumed that, in the absence of special safety precautions (leakage detection system, isolation valves, ventilation), the maximum air conditioning system R32 filling level is 12 kg.
That is why creating a refrigerant with characteristics similar to those of R410A in terms of thermal properties and efficiency, but nonflammable and with a GWP value of below 750, as this is the GWP limit value for refrigerants to be used in small air-conditioning devices, has become an important goal for chemical companies manufacturing refrigerants.
In 2018, Honeywell announced that it developed such a refrigerant. In accordance with the ASHRAE classification, it is called R466A. It is nonflammable (class A1 in accordance with the EN 378 standard) and has a GWP of 737. A combination of these two characteristics was achieved through the untypical mixture composition. The mixture consists of 49% of R32, 11.5% of R125 and the remaining 39.5% is CF3I (trifluoroiodomethane) which had not been previously used in the cooling technology industry. This compound is used in firefighting as an extinguishing agent, constituting a substitute for halons and sulfur fluoride (SF6) due to, among others, its very low GWP values (0.4). It was exactly the inclusion of hits new substance that allowed to decrease the GWP of the new solution and ensure its nonflammability. At the same time, it was highlighted that the new refrigerant offers the same energy efficiency as R410A and can replace it without any detriment to the essential technical parameters.
Once the development of the new refrigerant has been announced, official information about tests performed by the device manufacturers (Midea and Toshiba, where the latter described the new refrigerant as “promising”) and cooling components manufacturers (Sanhua and Parker Hannifin) started to appear.

In 2019, the refrigerant was classified by ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) as nonflammable and having lower toxicity. A moment later the Japanese association with a similar profile classified the refrigerant as “inert”.
R466A (which is supposed to be sold under the brand name Solstice N41) was supposed to be introduced into the market in 2020, there have however been no official announcements in this matter so far. In response to inquiries from journalists and the industry, Honeywell informs that the refrigerant is still being tested by device manufacturers and its commercialization is “advanced”. There is still however no specific release date. Comments have been made that there may be problems related to the stability of the new refrigerant in relation to using CF3I, which by itself is a labile substance. Honeywell denies such opinions and emphasizes pending extensive tests with 15 manufacturers of both cooling devices and compressors.

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