Abstract: A refrigeration/heat pump system comprises a compressor, condenser, evaporator and expansion valve all of which are mounted within a rectangular housing for convenient layout and accessibility. The condenser, evaporator and expansion valve are all oversized relative to the compressor so as to obtain modifications in the operating parameters and particularly a compression ratio of the compressor which is less than 4.5:1. This mismatch of the components surprisingly provides an enhanced efficiency of operations in tons/hp. The components are arranged in the housing with the compressor centrally of the housing, the evaporator along one side, the condenser along the opposed side and with the system connections in the rear wall. The electrical components are provided in a vertical compartment on one side of the front wall which can be accessed by an opening door. A removable panel in the front wall and in the rear wall allows access to the components.