CO2 refrigeration system with external coolant control

A refrigeration system comprising:

• an evaporator within which a refrigerant absorbs heat;
• a gas cooler/condenser within which the refrigerant rejects heat;
• a fluid conduit attached to an inlet of the gas cooler/condenser or an outlet of the gas cooler/condenser to direct the refrigerant into the gas cooler/condenser or out of the gas cooler/condenser;
• a heat exchanger coupled to the fluid conduit and within which heat is transferred from the refrigerant in the fluid conduit to an external coolant when the external coolant flows through the heat exchanger, the external coolant circulated from a source external to the refrigeration system and circulated back to the source external to the refrigeration system after flowing through the heat exchanger, the source external to the refrigeration system comprising a building water supply line;
• a control valve fluidly coupled to the heat exchanger;
• and
• a controller configured to operate the control valve to control a flow of at least one of the refrigerant or the external coolant through the heat exchanger based on a temperature of the external coolant relative to a temperature of the refrigerant within the fluid conduit.

A method for operating a refrigeration system, the method comprising:

• circulating a refrigerant between an evaporator within which the refrigerant absorbs heat and a gas cooler/condenser within which the refrigerant rejects heat to provide cooling to a temperature-controlled space;
• directing the refrigerant into the gas cooler/condenser or out of the gas cooler/condenser via a fluid conduit;
• operating a control valve to control a flow of at least one of the refrigerant or an external coolant through a heat exchanger coupled to the fluid conduit based on a temperature of the external coolant relative to a temperature of the refrigerant within the fluid conduit;
• circulating the external coolant from a building liquid source in which the refrigeration system is installed through the heat exchanger;
• circulating the external coolant back to the building liquid source in which the refrigeration system is installed after flowing through the heat exchanger;
• and
• transferring heat from the refrigerant in the fluid conduit to the external coolant within the heat exchanger when the external coolant flows through the heat exchanger.