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used to replace high GWP HFCs in existing equipment. When retrofitting refrigerants in existing equipment, it is recommended to consult with the refrigerant and equipment manufacturers as well as appropriate safety standards and building codes. The newer lower GWP HFC/HFO blends also exhibit “glide”. Therefore, it is important to make sure that the system design can accommodate this glide. It is also important to follow manufacturer recommended guidelines to adjust superheat and subcooling setpoints for optimum performance. For stand-alone equipment, there is no real incentive to change the refrigerant because the refrigeration circuit is totally brazed and hermetic, and this type of equipment will be changed based on its current lifetime, if no heavy leaks occur. However, a few options for stand-alone equipment are: R-448A, R-449A or R-452A as replacements for R-404A; R-450A and R-513A for HFC-134a. These replacement refrigerants are classified as A1 and can be used for retrofit. This list can be expected to grow as more manufacturers release alternates for existing refrigerants and equipment. The R-407 series of refrigerants like R-407A, R-407F and R-407H are now used in many countries as retrofit refrigerants for R-404A depending on individual manufacturers’ approvals. These refrigerants, including R-407C, are commercially available and are also formulated to replace HCFC-22. Newer HFC/HFO blends with GWP close to or lower than 2000, such as R- 448A, R-449A, R-452A, etc., are also commercially available and are candidates to replace HCFC-22 and R-404A. In fact, the most important issue for the replacement of HCFC-22 in Article 5 countries will be to find replacement options at acceptable costs, given the fact that Article 5 countries will lag the non-Article 5 ones in adopting these changes; the cost of these changes can be expected to be better when Article 5 countries are ready to make the change. Depending on the lifetime of refrigeration systems, the retrofit option is part of the refrigerant management plan required to follow the phase-down schedule. Recovery and recycling of existing refrigerants represent a strong option in order to smooth the transition from present day refrigerants to a series of lower GWP options. 4.4.1 Energy efficiency in existing equipment Retrofit refrigerants are approved by equipment manufacturers to be as close in performance to the ones that are being replaced and therefore, energy efficiency is often not looked at closely when making a choice. Existing equipment, however, makes up the bulk of the energy consuming devices and it is important that steps are taken to ensure that the energy consumed is not significantly higher. Fortunately, the refrigerants mentioned thus far all have as good or better performance than ones being replaced, especially when equipment manufacturers make these recommendations. Additional steps that can and should be taken at the time of retrofit are well documented in best practices documents and some of them are listed below. It is important to note that flammable refrigerants cannot be used as a retrofit refrigerant in an existing system designed for an A1 refrigerant. Proper retrofit process: Selecting the right refrigerant is the most important first step. The right retrofit refrigerant should deliver the same refrigerating capacity as the original and the energy consumption should be equal or less. Matching the refrigerant to the compressor and the expansion valve is an equally important second step in the process. Finally, if a refrigerant exhibits temperature glide, then adjusting the refrigerant charge, superheat and subcooling taking this glide into account is critical to the retrofit success. Proper refrigerant charge: A retrofit is a good time to confirm that leaks, if any, are identified and repaired. Filling the manufacturer recommended refrigerant charge is important for the performance of the system and its reliability. Too much or too little refrigerant charge will lead to poor performance and efficiency losses. 2018 TOC Refrigeration, A/C and Heat Pumps Assessment Report 91PDF Image | Heat Pumps Technical Options
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