Refrigeration systems are provided which include a first refrigeration system and a second refrigeration system that share a common heat exchanger. The heat exchanger includes a vessel that operates as a condenser for the second refrigeration system. A coil disposed in the vessel operates as an evaporator for the first refrigeration system. A method of operating a refrigeration system is also provided that includes exchanging energy between the refrigerant of the first refrigeration system and the refrigerant of the second refrigeration system.