R417A/417B/422D/438A as substitutes for R22
Similar to the development of R422A (R422A as substitute for R22 and R502), one aim of developing these blends was to provide chlorine-free refrigerants (ODP = 0) for the simple conversion of existing R22 plants.
R417A was introduced to the market years ago, and is also offered under the trade name ISCEON® MO59 (Chemours). This substitute for R22 contains the blend components R125/R134a/R600 and therefore differs considerably from e.g. R407C with a correspondingly high proportion of R32.
Meanwhile, a further refrigerant based on identical components, but with a higher R125 content, has been offered under the ASHRAE designation R417B. Due to its lower R134a content, its volumetric refrigerating capacity and pressure levels are higher than for R417A. This results in different performance parameters and a different focus within the application range.
The same applies to a further blend with the same main components, but R600a as hydrocarbon additive. It is offered under the trade name ISCEON® MO29 (Chemours) and listed as R422D in the ASHRAE nomenclature.
Another refrigerant belonging to the category of HFC/HC blends was introduced in 2009 under the trade name ISCEON® MO99 (Chemours) – ASHRAE classification R438A. This formulation was designed especially for a higher critical temperature for applications in hot climate areas. The base components are R32, R125, R134a, R600 and R601a.
Like R407C, all four substitute refrigerants are zeotropic blends with a more or less significant temperature glide. In this respect, the criteria described for R407C also apply here.
Apart from a similar refrigeration capacity, there are nevertheless fundamental differences in thermodynamic properties and in oil transport behaviour. The high proportion of R125 causes a higher mass flow with R417A/B and R422D than with R407C, a lower discharge gas temperature and a relatively high superheating enthalpy. These properties indicate that there are differences in the optimization of system components, and a heat exchanger between liquid and suction lines is of advantage.
Despite the predominant proportion of HFC refrigerants, conventional lubricants can be used to some extent because of the good solubility of the hydrocarbon constituent. However, in systems with a high oil circulation rate and/or a large volume of liquid in the receiver, oil migration may result. In such cases, additional measures are necessary. For further information on oil return and lubricants: R422A as substitute for R22 and R502.
Due to the high global warming potential (GWP ≥ 2500), R417B and R422D are no longer allowed for new installations in the EU since 2020. The requirements and restrictions are specified in the F-Gas Regulation 517/2014. However, the "phase-down" quantity limitation will also lead to significantly restricted availability of R417A and R438A.