R407C as substitute for R22
Mixtures of HFC refrigerants R32, R125 and R134a were considered to be the preferred candidates for short-term substitutes for R22 in the EU in view of the early ban of R22. Performance values and efficiency are very similar (Comparison of performance data). At first, two blends of the same composition have been introduced under the trade names AC9000* (DuPont) and KLEA® 66* (ICI). They are listed in the ASHRAE nomenclature as R407C. There are further blend varieties (e.g. R407A/R407F/R407H) with somewhat differing compositions, whose properties have been optimized for particular applications (R407A/B/F/H as substitutes).
Unlike the substitutes for R22 in refrigeration systems with identical blend components (R407A/B/F/H as substitutes and R422A as substitute), the substitutes for R22 in air conditioning systems and heat pumps contain higher proportions of R32 and R134a. A good correspondence with the properties of R22 in terms of pressure levels, mass flow, vapour density and volumetric refrigerating capacity is thus achieved. In addition, the global warming potential is relatively low (GWP = 1774).
Thus, R407C also complies with the requirement of the new EU F-Gas Regulation which from 2020 onwards only allows refrigerants with GWP < 2500. However, the quantity limitation through the "phase-down" will also lead to significantly restricted availability.
The high temperature glide is a disadvantage for usual applications which requires appropriate system design and can have a negative influence on the efficiency of the heat exchangers (Characteristics of zeotropic blends).
Due to the properties mentioned, R407C is preferably an R22 substitute for air conditioning and heat pump systems and (within certain limitations) also for medium temperature refrigeration. In low temperature refrigeration, because of the high proportion of R134a, a significant drop in refrigerating capacity and COP is to be expected. There is also the danger of an increased R134a concentration in the blend in evaporators, with reduced performance and malfunctioning of the expansion valve (e.g. insufficient suction gas superheat).
Material compatibility is similar to that of the blends discussed previously; the same applies to lubricants.
* Previous trade names are not used any more.
