The problem of HCFC22 phase-out in refrigeration plants is analysed, A comparison is performed between R22 and R407C, The latter seems a promising drop-in substitute. Indeed, its use in existing plants would only require discharge of mineral oil and refilling with a compatible polyolester oil. The experimental tests are performed in a plant consisting in a water-cooled vapor-compression circuit employed for cooling a water-glycol mixture in a closed-loop system. Both the thermodynamic properties and general performance of R407C are comparable with those of R22. The COP, however, is 5-17% lower, As a consequence, in order to provide the same refrigerating load, a plant working with R407C requires higher electric-power consumption. The operational behaviour of R407C is increasingly better with increasing condensation and evaporation temperature. Therefore, R407C is a good R22 substitute in all applications requiring high evaporation temperatures, such as air-conditioning plants. (C) 1997 by John Wiley & Sons, Ltd.