In general, the brine freezing point should be run about 5° F (3° C) colder than the operating temperature of the brine. In other words, if you are running your brine at 25° F (-4° C), you should have your salt solution mixed to give you a freezing point of 20° F (-7°C) (10.5% salt) or lower.

As a direct measure to prevent freezing of the brine solution in the heat exchanger, the freezing point for the brine solution should be lower than the suction temperature of the refrigeration control system.