Alternatives to HCFCs in the Refrigeration and Air Conditioning Sector 55 S ection 02 Th is cold storarage is operated by one of the major cold store/transport companies in Sweden and located in Jordbro, a suburb of Stockholm. The system was cooled by an installation with semi hermetic screw compressors chillers and a secondary fluid to cool the storage areas. The chiller had been moved to this site and retrofitted from R-22 to R-404A in 2001. The maximum cooling demand is approximately 350 kW. They operated with R-404A for several years but there were significant leakage rates due to leaks around the electrical connection of the motor. The local authorities required the operator to take action to reduce the leaks of the high-GWP refrigerant R-404A. When it turned out to be difficult to fix this problem, the company decided to install a new refrigeration plant. To achieve a redundancy and capacity for potential changes in the future, it was decided that two chillers would be installed. After evaluating several options, a solution with a combination of several relatively new but commercially available and proven technologies was selected. It was desired to use a low-GWP refrigerant in line with the A. policies of the companies to minimize their environmental impact, so ammonia was selected. As there was also a concern for the risk associated with B. ammonia, it was decided to minimize the charge in the chillers by using welded plate heat exchangers with dry expansion technology, with electronic expansion valves. The charge reduction is significant compared to the flooded evaporators traditionally used with ammonia. To do this, it is necessary to use a soluble oil that can be transported back to the compressor automatically. The charge and associated risks of using ammonia could thus be minimized. The oil used is a PAG oil. These chillers have each a total charge of 30 kg while for a direct evaporation system the ammonia charge could be around 1000 kg on 2.4 Cold store with low charge ammonia chillers Fig. 2.12 The cold store. The “dry” coolers are on the roof and the low charge anmmonia chillers inside. Fig. 2.13 Low charge ammonia chiller with dry expansion, welded plate heat exchangers and a variable speed drive on the compressor. Su mmary A large cold store company selected two low charge ammonia chillers to replace two old R-22 chillers that had been retrofitted to R-404A six years earlier. A key factor in the company’s decision to change to ammonia was the high leakage rates of the old retrofitted R-22 chillers. In cold stores, HCFCs has been extensively used in some markets, whereas ammonia has remained a preferred alternative in others. The use of ammonia requires special training and in some markets, there is a lack of trained staff and training facilities, which can limit the possibility of a transition to ammonia unless the training capability is initiated or strengthened. New developments in this sector include minimum charge chillers with compact design. In the case presented here, the low ammonia charges minimized the risks. The charges could be minimized with plate heat exchangers and dry expansion (use of expansion valves and soluble oils). This case also shows how variable motor speed was applied to optimise performance and allow stable control of the cooling process. Background data/information given for this installation comes from Kenneth Weber, from the contractor ETM Kylteknik, (ETM Kylteknik AB). The description is based on the data received from the contractor, but as regards the selection of information and interpretation, the responsibility is with the author of this report.