A refrigeration system includes a core comprising a stack of core plates. The core defines a condenser, an evaporator and a refrigerant reservoir. The condenser has a plurality of refrigerant flow passages and a plurality of first coolant flow passages in alternating arrangement. The evaporator has a plurality of refrigerant flow passages and a plurality of second coolant flow passages in alternating arrangement. The condenser has a refrigerant outlet in flow communication with the refrigerant inlet of the refrigerant reservoir, where the refrigerant side of at least one of said core plates includes a refrigerant communication passage providing flow communication between the refrigerant outlet of the condenser section and the refrigerant inlet of the reservoir section.