Abstract: A self-enclosed modular refrigeration unit for refrigeration system comprises compressor adapted to compress a refrigerant. A heat exchanger is connected to a cooling water network to condense the refrigerant with cooling water. A suction line is connected to a suction side of the compressor and adapted to provide a feed of refrigerant to the compressor. A discharge line is connected to a discharge side of the compressor and to the heat exchanger to direct compressed refrigerant to the heat exchanger. A head pressure control valve is in the discharge line downstream of the heat exchanger to control an upstream pressure. A casing encloses the compressor, the heat exchanger, the head pressure control valve. An outlet line has an outlet end downstream of the head pressure control valve adapted to output cooling refrigerant having passed through the head pressure control valve. An inlet end is upstream of the suction line to provide a feed of refrigerant to the compressor.