S R C C Alternatives to H F s in the efrigeration and Air Conditioning Sector ection 01 43 I t is possible to calculate the number of oil changes required to achieve a targeted level of remaining mineral oil. The number of oil changes or flushes required to achieve the target level can be calculated based on two sets of information: The amount of oil in the system. A. How much oil that can be removed during one oil change B. or flush. The lower the target of remaining mineral oil is set the safer the system will be for future problems but the cost to achieve the target will increase. Factors affecting the selection of target level are how much acidity, moisture and other contaminants there is in the old oil and how high temperatures the system will work on. This together with the age and value of the equipment and cost to achieve a certain level of remaining mineral oil will define the cost effective target. The relative quantity of oil that can be removed will depend on: The oil plug position.■■ The evaporator design and suction line length and size.■■ Whether oil separators/receivers and suction ■■accumulators are used. A maximum level of 1% is by most sources considered a ideal level. A level of 5% is considered acceptable by several compressor manufacturers if the old oil is of acceptable quality, e.g. it does not contain too many contaminants that can trigger chemical reactions in system after retrofit. Two clean oils in a dry system under normal temperatures are not expected to cause chemical stability problems, so the level of contaminants in the old system is an important factor. If properly done, the repeated oil changes should then lead to < 1 to 5 % remaining mineral oil (based on the target set). More precisely, the required number of oil changes or number of flushes with refrigerant or solvent is a function of the amount of the total oil volume that can be removed in each change/flush. 1.6.6 Number of oil changes required Su mmary Number of repeated oil changes or flushes required It is possible to calculate the number of oil changes required to achieve a targeted level of remaining mineral oil. The lower the target of remaining mineral oil is set, the more the system will be protected from future problems but the cost to achieve the target will increase. Factors affecting the selection of the target level include how much acidity, moisture and other contaminants there are in the old oil, and how high the temperatures will be for the system’s operation. This, together with the age and value of the equipment and cost to achieve a certain level remaining mineral oil, will define the cost effective target. A level of maximum 1% is by most sources considered an ideal level. A level of 5% is considered acceptable by several compressor manufacturers if the old oil is of acceptable quality, e.g. it does not contain too many contaminants that can trigger chemical reactions in the system after retrofit. Two clean oils in a dry system under normal temperatures are not expected to cause chemical stability problems, so the level of contaminants in the old system is an important factor. REMOVEDEMOVEDEMOVEDEMOVED %OF OILOILOIL CHARGE REQUIRED NO.CHANGESNGESNGESNGES/FLUSHESES TOTO REACH 1% TYTY P IC AL INSTINSTALLATIONS 50 % 7 Supermarket direct expansion with oil separators 60 % 5 L arge chillers and heat pumps 70 % 4 Small chillers and condensing units 90 % 2 Flushing large direct expansion systems with oil separators 99 % 1 Flushing compact systems (unitary/split/chillers)