Service blends with the basic component R22* as substitutes for R502
As a result of the continued refurbishment of older installations, the importance of these refrigerants is clearly on the decline. For some of them, production has already been discontinued. However, because of the development history of service blends, these refrigerants will continue to be covered in this Report.
These refrigerants belong to the group of "Service blends" and have been offered under the designations R402A/R402B* (HP80/ HP81 – DuPont), R403A/R403B* (formerly ISCEON® 69S/69L) and R408A* (“Forane®” FX10 – Arkema).
The basic component is in each case R22, the high discharge gas temperature of which is significantly reduced by the addition of chlorine free substances with low isentropic compression exponent (e.g. R125, R143a, R218). A characteristic feature of these additives is an extraordinarily high mass flow, which enables the mixture to achieve a great similarity to R502.
R290 (Propane) is added as the third component to R402A/B and R403A/B to improve miscibility with traditional lubricants as hydrocarbons have especially good solubility characteristics.
For these blends two variations are offered in each case. When optimizing the blend variations with regard to identical refrigerating capacity as for R502 the laboratory measurements showed a significantly increased discharge gas temperature (Effect upon the dischargegas temperature), which above all, with higher suction gas superheat (e.g. supermarket use) leads to limitations in the application range.
On the other hand a higher proportion of R125 or R218, which has the effect of reducing the discharge gas temperature to the level of R502, results in somewhat higher refrigerating capacity (Comparison of performance data).
With regard to material compatibility the blends can be judged similarly to (H)CFC refrigerants. The use of conventional refrigeration oil (semi or completely synthetic) is also possible due to the proportion of R22 and R290.
Apart from these positive aspects there are also some disadvantages. These substances are alternatives only for a limited time. The R22 proportion has an (although low) ozone depletion potential. Furthermore, the additional components R125, R143a and R218 have a high global warming potential (GWP).
* When using blends containing R22, legal regulations are to be observed (R22 as transitional refrigerant).
