A fluid chiller system supplying cold fluid to a therapeutic wrap, in which a minimum level of fluid flow is provided through the heat exchange coils to insure that the fluid in the coils does not freeze. A fluid flow meter or pressure sensor connected inline with the inlet port of the chiller unit measures a level of fluid flow. A controller is connected to the flow meter or pressure sensor and a bypass valve, wherein based on a signal from the flow meter or pressure sensor, the controller adjusts the bypass valve to provide a predetermined level of fluid flow into the inlet port of the chiller unit, in order to prevent the heat exchange coils from freezing, if the flow through the wrap is blocked.