R427A as a substitute for R22
This refrigerant blend was introduced some years ago under the trade name Forane® FX100 (Arkema) and is now listed in the ASHRAE nomenclature as R427A.
The R22 substitute is offered for the conversion of existing R22 systems for which a "zero ODP" solution is requested. It is an HFC mixture with base components R32/R125/R143a/R134a.
In spite of the blend composition based on pure HFC refrigerants, the manufacturer states that a simplified conversion procedure is possible.
This is facilitated by the R143a proportion. Accordingly, when converting from R22 to R427A, all it takes is a replacement of the original oil charge with ester oil. Additional flushing sequences are not required, as proportions of up to 15% of mineral oil and/or alkyl benzene have no significant effect on oil circulation in the system.
However, it must be taken into account that the highly polarized mixture of ester oil and HFC will lead to increased dissolving of decomposition products and dirt in the pipework. Therefore, generously dimensioned suction clean-up filters must be provided.
Regarding refrigerating capacity, pressure levels, mass flow and vapor density, R427A is relatively close to R22. During retrofit, essential components such as expansion valves can remain in the system. Due to the high proportion of blend components with low adiabatic exponent, the discharge gas temperature is considerably lower than with R22, which has a positive effect at high compression ratios.
It must be taken into account that this is also a zeotropic blend with a distinct temperature glide. Therefore the criteria described for R407C apply here as well.
R427A meets the requirement of the EU F-Gas Regulation, which only allows refrigerants with GWP < 2500 since 2020. However, the quantity limitation due to the "phase-down" will also lead to significantly restricted availability.