R404A and R507A as substitutes for R22 and R502
These blends are chlorine free substitutes (ODP = 0) for R22 as well as for R502 in medium and low temperature ranges.
A composition which was already launched at the beginning of 1992 is known under the trade name Suva® HP62 (DuPont). Long term use has shown good results. Further blends were traded as Forane® FX70 (Arkema) and Genetron® AZ50 (Allied Signal/ Honeywell) or Solkane® 507 (Solvay). HP62 and FX70 have been listed in the ASHRAE nomenclature as R404A and AZ50 as R507A.
The basic components belong to the HFC group, where R143a belongs to the flammable category. Due to the combination with a relatively high proportion of R125 the flammability is effectively counteracted, even in the case of leakage.
A feature of all ingredients is the very low isentropic compression exponent which results in a similar, with even a tendency to be lower, discharge gas temperature to R502 (Comparison of discharge gas temperatures). The efficient application of single stage compressors with low evaporating temperatures is therefore guaranteed.
Due to the similar boiling points for R143a and R125, with a relatively low proportion of R134a, the temperature glide with the ternary blend R404A within the relevant application range is less than one Kelvin. The characteristics within the heat exchangers are therefore not very different than with azeotropes. The results obtained from heat transfer measurements show favourable conditions, too.
R507A is a binary pairing of substances which even forms an azeotropic blend over a relatively wide range. The conditions therefore tend to be even better.
The performance (Comparison of performance data) shows hardly any difference between the various substances and is very similar to R502. This also explains the high market penetration of these refrigerants. With regard to the thermodynamic properties, they are particularly suitable for commercial medium and low temperature systems.
Typical metallic materials are compatible with HFC refrigerants. Elastomers, however, must be adapted to the changed characteristics. Suitable lubricants are polyol esters (Lubricants for compressors).
The relatively high global warming potential (GWP = 3922 .. 3985), which is mainly determined by R143a and R125, is something of a hitch. However, it is better than R502 and with regard to the favourable energy demand also leads to a reduction of the TEWI value. Other improvements are possible in this respect due to further developed system control.
Nevertheless, due to their high global warming potential (GWP), the use of R404A and R507A is no longer allowed in the EU in new installations since 2020. This has been settled in the F-Gas Regulation No. 517/2014 to be applied since 2015. However, the current requirement of phase-down in connection with a strict quota system has led to an earlier phase-out in many applications. For more detailed information, please refer to BITZER brochure A-510.
In the USA, Canada and Australia there are also requirements to phase out R404A and R507A. For an international phase-down (starting in 2019) of HCFC and HFC refrigerants, the so-called Kigali Amendment was agreed upon in 2016 as part of the Montreal Protocol.
Alternatives with lower GWP are the HFC blends explained below, as well as the newly developed HFO/HFC blends ("Low GWP" HFOs and HFO/HFC blends as alternatives to HFCs).
Halogen free refrigerants or cascade systems using different refrigerants are also an option for specific applications (Halogen free (natural) refrigerants).
