Section 01 Alternatives to HCFCs in the Refrigeration and Air Conditioning Sector 38 Before refrigerant change A “Performance Inspection” or at least a careful status 01. check of the old system will document if there are components that are not functional and should be changed during the retrofit process. For systems that are old and/or in poor shape, it might be more cost effective to replace them than spend money when the remaining life time is short and the energy efficiency is poor. A leak inspection will make it possible to correct leaks at 02. the lowest possible cost during the retrofit procedure to decrease emissions and cost after the retrofit. It will be necessary to check with suppliers about 03. the list of components to determine if there are any incompatibilities between the components and the new refrigerant and oil. This inspection should include validating that the pressure vessels are compatible with the new pressures of the system. This is particularly true if there is a change from R-22 to R-404A, which has a higher pressure level than R-22 in the condenser. Each pressure vessel should have a label stating maximum allowed pressure. A failure to ensure a compatible pressure level can be dangerous. Plan the change and consider what measures to reduce 04. leaks and improve efficiency are cost effective in connection with a change of refrigerant. If a retrofit (e.g. an oil change) is the preferred route, 05. select the method of oil change and set a target for the remaining content of the old oil remaining in the system (e.g. 1-5°C). If a service blend will be used, check what the refrigerant and compressor suppliers recommend with respect to the oil. Refrigerant change Change the oil either with repeated oil changes or by 06. “flushing” if this was the route chosen (see the section on oil change). Correct problems and leaks, if any.07. Replace the drier and any incompatible or defective 08. components. Evacuate the system carefully, using the dry nitrogen and 09. double vacuum method. Start up with care.10. After the refrigerant change Measure the performance/behaviour and adjust the 11. system to optimize the performance and reliability Document all relevant parameters of the operation so they 12. are available for reference before future servicing. Label the system with correct refrigerant, charge and oil 13. type and content. It can advisable to take oil sample after approximately 14. 100 hours of operation. This sample can be analysed later if a problem occurs or it can be sent for analysis at once. Keep a sample of the oil can: if there is an indication of a problem, it is important to validate that the retrofit was performed to an acceptable standard. Fig. 1.12 R-22 plant in a warm climate might not have pressure vessels with sufficient design pressure to be used with R-404A. In those cases these vessels should be changed if a retrofit to R-404A is to be done. All pressure vessels should have a plate stating the maximum allowed pressure as shown above. MaMa ny se r vice journals are not useful for evaluating how a system works since they lack information on how the values were taken and provide no information on the stability of the system’s operation. There are options to do the evaluation with a more detailed commissioning sheet or in more detailed way with a “Performance Analyser” so that the pre- and post-retrofit status of the system can be documented. 1.6.1 Documentation of status and performanceThis can be done manually with a protocol like the one below, or - as presented in some of the case studies of conversions/retrofits - with a computerised “Performance Analyser” that measures the pressures and temperatures in the system and analyse them on-line, so (for example) cooling capacity, COP, compressor efficiency and adjustment parameters are documented before and after the retrofit.