Which refrigerant is a suitable interim replacement for R-12?

R-409A is recognized as a suitable interim replacement for R-12 because it is a blended refrigerant specifically designed to operate in existing R-12 systems with minimal modifications. R-12, a chlorofluorocarbon (CFC), was phased out due to its ozone-depleting properties. R-409A contains a mixture of non-ozone-depleting alternatives, allowing for compatibility with the materials and lubricating oils used in systems originally designed for R-12. This replacement helps maintain efficiency and performance while adhering to environmental regulations.

In contrast, while R-134A can also be used as an alternative to R-12, it typically requires more extensive modifications to systems, particularly those that were not originally designed for it. R-404A and R-422B, on the other hand, are intended for different applications and may not perform as effectively in R-12 systems, making R-409A the most appropriate interim choice.