An efficient refrigeration system for mounting on the wall of a food storage structure, includes cooling coils and heat exchange vanes, and a lower inlet and an upper outlet. A centrifugal fan and motor are removably mounted as a sub-unit on mating tracks, on the sub-unit and the housing, and are held in place by quick release arrangements, for ease in repair and/or replacement of the sub-unit. An expansion valve for the refrigeration system is mounted near the inlet. An additional fan for cooling the electric motor forms part of the sub-unit.