Refrigeration plant with multiple evaporation levels and method of managing such a plant

A refrigeration plant with multiple evaporation levels, operating according to a vapour compression cycle, the refrigeration plant comprising:

• a circuit comprising:
• a high-pressure branch, wherein is arranged at least one heat exchanger, which functions as a condenser or gas cooler, and
• two or more low-pressure branches, each of which operates at a different evaporation level to serve users having different refrigeration requirements, each low-pressure branch of the two or more low-pressure branches of said refrigeration plant comprising an expansion device, at least one evaporator, and a compressor group, each of the two or more low-pressure branches having at least one evaporator connected directly to said high-pressure branch,
• wherein a first low-pressure branch of the two or more low-pressure branches operating at a first evaporation level comprising a liquid separator that is fluidically connected:
• to an evaporator outlet of said first low-pressure branch to collect a liquid exiting the at least one evaporator of the first low-pressure branch when the at least one evaporator of the first low-pressure branch is operating in overfeeding conditions;
• and
• to an intake of the compressor group of said first low-pressure branch;
• wherein said liquid separator of the first low-pressure branch is not fluidically connected to an inlet of the at least one evaporator of said first low-pressure branch, but is fluidically connected to a second low-pressure branch of the two or more low-pressure branches operating at a second evaporation level lower than the first evaporation level upstream of the expansion device of the second low-pressure branch through a first connection duct, and
• wherein said circuit comprises first valve means comprising one or more valves that are installed in the first connection duct and in the second low-pressure branch and are controllable in such a way that said second low-pressure branch is alternately fed by the high-pressure branch or by said liquid separator of the first low-pressure branch through said first connection duct, said first valve means being actuated to allow feeding the at least one evaporator of the second low-pressure branch with liquid coming from the liquid separator of the first low-pressure branch when the at least one evaporator of the first low-pressure branch is made to operate in overfeeding conditions so as to discharge the liquid that collects in said liquid separator of the first low-pressure branch.