Section 01 Alternatives to HCFCs in the Refrigeration and Air Conditioning Sector 40 Th e main technical challenge is neither to recover the old refrigerant nor to charge the new refrigerant. The issues the technicians and end-users need to deal with are the evaluation of the best option for a particular system and how to cost effectively go through the required steps. The main question is often whether the existing oil can be used or if it has to be removed. If an oil change is necessary or preferred, the challenge is how to remove the old oil. The complexity and cost of replacing the old oil is often the main factor in the decision whether the “standard” refrigerants commonly used in new systems of the same type (e.g. R-407C or R-404A) could be used, or if a “service” refrigerant blend should be used. From the point of view of service availability, it is an advantage to move directly to the same refrigerants that are used in new systems if it can be done at an acceptable cost. Also, some of the uncertainties with oil transport in connection with service blends are avoided. The oil in an RAC system will mainly be in the compressor, but a significant amount will be distributed around the system. In larger systems there are frequently oil plugs or valves, but even in those cases 20 to 50% of the oil will often remain after the oil has been drained through these ports. For hermetic compressors there are rarely any possibilities to drain any oil. Some components such as oil separators and receivers can sometimes contain more oil than in the compressor and frequently there are no possibilities to drain them without application of special methods. The maximum level of mineral oil for safe operation, when changing from HCFCs to HFCs, is system-dependent and affected by the status of the oil remaining in the system. “The cleaner the better” rule is valid, 1% is considered as a preferred level whereas 5% is often deemed acceptable if the old oil is not heavily contaminated with acid, moisture or wear particles. For a retrofit to a standard HFC refrigerant, the refrigerant manufacturers recommend that 95- 99% of the old oil should be replaced, by using polyolester oil, e.g. only 1-5% of mineral oil should remain after the retrofit. Oil changes can be performed through one of the following methods: R Repeated oil change. The number of changes are determined by the targeted maximum content of the old oil. A. Typically the number of oil changes vary between three and eight, depending on configuration of system. Flushing with the old refrigerant using a “flushing unit” designed for this purpose. This method requires that B. the technicians have access to equipment and are specially trained to apply it. The advantage with this method against the one described below is that no cleaning solvent is introduced and that the waste is separated in a recycled HCFC fraction and an oil fraction on site. The HCFC can then be re-used after validation of the quality. Flushing with solvent using a flushing unit designed for this purpose requires that technicians have access to the equipment and are properly trained on this procedure. The solvents often contain HFC (and/or HCFC) and need to be handled in a responsible way after use. National and international regulations apply for the use and transports of different solvents. Some of the solvents can be reprocessed by the manufacturer. The responsible use must be ensured in each market to make this option an acceptable solution. The service company and/or equipment owner should verify the compatibility of any solvent used with all components, refrigerant and oil. Some proposals to flush with nitrogen have been made but no documentation of this method have been found by the author. Additionally, since nitrogen will be injected as vapor it cannot be expected to move much of the oil out of the systems unless there are small diameter tubes where a sufficient velocity can be created. Moreover, it cannot be used to move oil or contaminants that have accumulated below the drainage points which is the benefit of flushing. Obviously nitrogen can be used in connection with oil change to speed up the oil drain.