Abstract: A modular refrigeration unit comprising a condenser assembly and an evaporator assembly is bottom-mounted inside a merchandising display cooler such that cool air emerging from the evaporator assembly rises in a plenum defined between an insulated back wall of the cooler and an interior back panel. The cold air passage is centrally disposed between return warm air passages for returning air from the inside of the cabinet into the evaporator assembly. Air inlet and outlet openings are provided at selected locations on the interior back panel. The evaporator assembly is disposed above an evaporator pan which is integrally formed with a well for collecting condensed water vapor and discharging the collected moisture on the other side of a bulkhead insulating the evaporator assembly from a condenser assembly exposed to the ambient atmosphere.