Servicing of refrigeration systems. Substitution of R502 for R404A or R507

• Substitution of R12 for R134a
• Substitution of R502 for R404A or R507
• Substitution of R12 for R401A, R409A, R401B. Substitution of R500 for R401B.
• Substitution of R502 for R402A, R408A, R402B
• Substitution of R22 for R407C

R404A refrigerant is accepted as an alternative to R502 in the new equipment. It can be used also for charging of some systems operating on R502, such as commercial refrigeration equipment of big universal shops, refrigeration facilities of food industry factories, transport refrigeration facilities. As to its characteristics, R404A, as it has been stated before in chapter 7, is the best to correspond to R502 refrigerant of all CFC, and it can be used within all the working range of temperatures and pressures characteristic for R502. Discharge temperatures of the compressor operating on R404A, is lower than while using R502, which contributes to increasing of reliability and service life of the compressor.

R507 refrigerant also serves as an alternative to R502 refrigerant in the new equipment, and it can be used for retrofit of the systems operating on R502. Characteristics of R507 are also close to characteristics of R502, their working ranges coincide. Discharge temperatures of the compressor where R507 serves as a refrigerant is lower than that in the compressors with R502.

Composition of vapors of R404A and R507, contained in the ballon, slightly differ from the composition of the liquid refrigerant. These insignificant differences can effect operational efficiency of the systems with flooded evaporators.

As practical experience shows, in some systems, where R502 is substituted for R404A or R507, the level of leakage can become higher due to using of sealing made of elastomers. But substitution of elastomers can lead to additional costs and cause time waste for re-equipment.

Methods of retrofit of refrigeration systems during transfer from R502 to R404A or R507 are analogous to the methods of substitution of R12 refrigerant for R134a.

R404A and R507 refrigerants have good compatibility with polyester oils. When charging of the liquid refrigerant into the system, it is necessary to be poured out of the charging ballon only. Ballons are provided with immersion legs with the help of which it's possible to drain liquid out of the ballon being in vertical position. Proper position of the ballon at liquid drainage is shown by arrows on the ballon and on the box for the ballon. Refrigerant can be charged into the system either in the state of liquid or in the gaseous state. If it's necessary to transfer the liquid into tyhe gaseous state, there is used a valve of collecting pressure gage or throttling device. Disposable ballons with R507 do not have immersion leg, and therefore they have to be turned for liquid drainage.

Usually for charging of the refrigeration system there is required less (mass) of refrigerant R404A or R507, than that of R502. Optimal mass of the charging dose depends on the system structure and its operational conditions. For the majority of ystems optimal mass of the alternative refrigerant when charging constitutes 75-90 % of mass of the initial one.

When starting the system, they correct the volume of the refrigerant being charged. For comparison of pressures and temperatures of the initial refrigerant and alternative refrigerants it is necessary to use the table.

Expected values of operational parameters of the refrigeration system after substitution of R502 for R404A or R507 are given in the table.