Which refrigerant serves as a drop-in replacement for R502?

R408A is recognized as a drop-in replacement for R502 due to its similar thermodynamic properties, which allow it to be used in existing systems designed for R502 with minimal modifications. R502 is a refrigerant that was commonly used in commercial refrigeration applications, particularly in low and medium temperature systems. When R502 was phased out due to environmental concerns, R408A emerged as a suitable alternative because it contains a blend of substances (primarily R22, R125, and R134A) that offer comparable performance characteristics.

In contrast, while R22, R404A, and R134A may have their own uses in refrigeration, they do not provide the same compatibility with systems originally designed for R502. R22 is often used in residential applications, R404A is more commonly utilized for commercial refrigeration, particularly in low-temperature applications but with different pressure characteristics, and R134A, which is primarily used in automotive and some commercial refrigeration applications, lacks the desired properties to effectively replace R502 without significant system modifications. Hence, R408A is the most appropriate choice for replacing R502 with minimal impact on system efficiency and functionality.