A refrigeration system includes a primary loop that cools a secondary loop that circulates a coolant through a refrigeration load. The secondary loop includes a suction header to receive the coolant from the load, and a discharge header to direct the coolant to the heat exchanger, and a pump to pump the coolant from the suction to the discharge header. A charging loop maintains a pressure of the coolant in the supply header within a predetermined range, and includes an inlet from the discharge header and an outlet to the suction header. A flow nozzle and a valve are located between the inlet and the outlet, and a reservoir of make-up coolant communicates with the flow nozzle. Upon a low pressure condition in the suction header, the valve opens to permit flow of coolant through the flow nozzle to draw in make-up coolant from the reservoir.