Fluid defrost system and method for secondary refrigeration systems

A fluid defrost system for defrosting the cooling coil of a product fixture normally cooled by circulating cold secondary liquid coolant therethrough in a cooling loop refrigerated by a primary vapor compression system having compressor, condenser and evaporator means;

• the defrost system comprising a defrosting loop constructed and arranged for circulating warm secondary liquid coolant through the cooling coil, said defrosting loop including warm heat exchanger means constructed and arranged downstream of the condenser means for receiving heat therefrom, and control means for controlling the flow of warm liquid coolant in the defrosting loop and cooling coil including valve means in the cooling and defrost loop inputs to the fixture cooling coil for establishing refrigerating and defrosting cycles, and other flow control means constructed and arranged for determining the nature and timing of the defrost cycle.

The method of defrosting the cooling coil of a product fixture normally cooled in a refrigerating phase by circulating cold secondary coolant liquid cooled by a primary vapor compression system having compressor, condenser and evaporator means, comprising the steps of:

• circulating secondary coolant liquid to the cooling coil in a heating loop having a warming heat exchanger downstream of the condenser means, and
• controlling the circulation of warm coolant liquid through the warm heat exchanger and cooling coil during a defrost cycle.

The method of defrosting the cooling coil of a commercial product fixture comprising the steps of discontinuing the normal refrigerating phase of the cooling coil and initiating a defrost cycle by circulating warm coolant liquid through the cooling coil, and interrupting the circulation of warm coolant liquid and establishing a static charge thereof in the cooling coil for completing the defrost cycle.