Refrigeration device and related operating method

Refrigeration device (100) having a closed circuit (C) within which a refrigerant fluid circulates, said closed circuit comprising at least one compressor (101), at least one condenser (102), expansion means (103) of said refrigerant fluid, at least one evaporator (104) to thermally condition, directly or indirectly, at least one user (UT), and at least one shut-off valve (105) operable between an open position and a closed position to regulate the flow of refrigerant fluid through said at least one evaporator depending on the temperature required by said at least one user, said closed circuit further comprising at least one secondary by-pass branch (200) having an inlet section (201) and an outlet section (202) respectively arranged downstream (D) and upstream (U) of said at least one compressor (101) for the passage of said refrigerant fluid, said secondary by-pass branch (200) comprising at least one passage valve (204) operable between an open position, to allow the fluid to recirculate between said secondary by-pass branch (200) and said at least one compressor (101), and a closed position, to prevent the passage of fluid through said secondary by-pass branch, characterized in that said closed circuit (C) comprises means (106) to prevent the backflow of said refrigerant fluid from said condenser to said compressor, at least when said passage valve (204) is open, said means to prevent the backflow of said refrigerant fluid being arranged between said condenser and said inlet section (201) of said secondary by-pass branch (200).