A refrigeration system which was originally designed using R502 as refrigerant was rebuilt to adapt the special
requirements of R404A. The experiments, both for R502 and R404A, on this system were done and some
parameters such as evaporating temperature, condensing temperature, discharge temperature, compressor input
power and so on were measured under different working conditions. Then the operating characteristics and the
performances were compared between R404A and R502. The influences of R404A as refrigerant on refrigeration
system were further analyzed. Some recommendations for existing R502 refrigeration systems to use R404A as
refrigerants were put forward in the end of this paper.