In this paper, the performances of a vapour compression refrigeration plant using as working fluids R22 and its substitute R417A (R125/R134a/R600, 46.6/50/3.4% in mass) are experimentally studied. This type of plant is applied to a commercially available cold store, generally adopted for preservation of foodstuff. Its working is regulated by on/off cycles of the compressor, operating at the nominal frequency of 50 Hz, imposed by the classical thermostatic control. The problems related to the replacement of the fully halogenated chlorofluorcarbons (CFCs) and of the partially halogenated (HCFCs) have been only partially solved. As for R22, there is no unanimous solution for its substitution. In this paper, the refrigerant fluid experimentally tested as a substitute for R22 is the non-azeotropic mixture R417A. R417A is a non-ozone depleting long term replacement for R22, which can be used in new and existing direct expansion systems using traditional R22 lubricants. R417A provides an easy solution to the legislation requirement, since it presents an ozone depletion potential equal to zero, and it does not require a change of lubricant type, equipment redesign or significant modifications. The experimental analysis has allowed the determination of the best energetic performances of R22 in comparison with those of R417A in terms of the coefficient of performance, exergetic efficiency, exergy destroyed in the plant components and other variables characterizing the refrigeration plant performance. (C) 2003 Elsevier Ltd. All rights reserved.