Which refrigerant would you convert a walk-in freezer to when replacing the condensing unit on an R502 system?

Choosing R404A as the refrigerant for converting a walk-in freezer initially designed for R502 is appropriate because R404A is a low-temperature refrigerant that closely aligns with the operational requirements of systems originally using R502. R502, which is no longer manufactured due to environmental regulations, has similar thermodynamic properties to R404A, making it a suitable direct replacement for maintaining the efficiency and performance of the refrigeration system.

R404A is also a blend of several refrigerants, including R125, R134A, and R143A, which enhances its physical properties and stability at lower temperatures. As a result, it can achieve the necessary cooling effect needed for walk-in freezers without requiring significant modifications to the overall system design.

In terms of compatibility, R404A can be used in existing system components designed for R502, provided that the system has been adequately retrofitted and checked for any necessary adjustments. This ensures a smoother transition when upgrading systems for compliance with modern refrigerant standards while maintaining operational effectiveness.

Other refrigerants listed would not be suitable for use in this scenario due to their differing temperature glide characteristics and operational efficiencies, making them less effective substitutes for walk-in freezer applications.