System for the refrigeration of a liquid and method for controlling said system

A system for the refrigeration of a liquid suitable for circulating between at least one inlet (1) and at least one outlet (2) of a primary liquid cooling circuit (3), comprises at least a first air-cooled refrigeration unit (4) having at least a first air-cooled cooling coil (6) inserted on the primary liquid cooling circuit (3), at least a second refrigeration unit (5) with a cooling cycle having at least one evaporator (7) inserted on the primary liquid cooling circuit (3) in cascade with the first air-cooled cooling coil (6), means for shutting off the first air-cooled cooling coil (6) from the primary liquid cooling circuit (3), forced air ventilation means suitable for acting on at least the first air-cooled cooling coil (6) and on at least a second air-cooled cooling coil (10) provided for at least one condenser of the second refrigeration unit (5) for condensing the refrigerant fluid operating in the cooling cycle, there being further provided a secondary liquid circuit (13) on which at least the first air-cooled cooling coil (6) and at least one secondary exchanger (14) for subcooling the refrigerant fluid leaving the second air-cooled cooling coil are inserted.