A refrigeration system with a multi-function heat exchanger has a first heat exchanger with an internal partition defining a condenser, a subcooler and an evaporator. An expansion device is located external of the heat exchanger and receives condensed refrigerant from the subcooler and provides expanded refrigerant to the evaporator. A compressor circulates the refrigerant through the condenser, the subcooler, and the evaporator. A secondary coolant circulates through the subcooler, the evaporator and the loads. A control system receives refrigerant temperature and pressure signals, and provides a control signal to the expansion device to maintain a temperature of the refrigerant within a predetermined range. A second heat exchanger cools a condensing fluid circulating through the condenser to condense the refrigerant.