Refrigerant compressor

A refrigerant compressor for refrigeration systems, comprising an electric motor, at least two cylinder banks, each of which has at least one cylinder unit having in each case at least one cylinder housing and at least one reciprocating-movement piston driven by the electric motor, and a cylinder head that is associated with each cylinder bank and has an inlet chamber, through which an inlet stream flows, and an outlet chamber, through which an outlet stream flows, and a mechanical performance control unit for activating and deactivating at least one of the cylinder banks in order to activate or deactivate its refrigerant output, wherein, for the purpose of operation in a primary partial performance condition, the refrigerant compressor is operable in at least two different operating modes, of which each provides an activation or deactivation of the cylinder banks that is different from another of the at least two different operating modes, wherein associated with the refrigerant compressor is a frequency converter for controlling the speed of the electric motor, wherein associated with the refrigerant compressor is an operating condition controller that, in accordance with a performance request signal supplied to it for operation of the refrigerant compressor in the primary partial performance condition corresponding to this performance request signal, operates the refrigerant compressor in the operating mode that is selected from the at least two different operating modes and at a speed of the electric motor adapted to the selected operating mode, for the purpose of achieving the primary partial performance condition;

• wherein, in order to determine the quality grade or COP value of the at least two different operating modes, partial performance conditions, including the primary partial performance condition, to be achieved are divided into partial performance conditions that are above a boundary value and those below a boundary value, and wherein, in the case of the partial performance conditions above the boundary value in any of the at least two different operating modes that requires a higher speed of the electric motor than other operating modes, the assumption is made of a high quality grade or COP value or a low electrical power consumption, and thus these operating modes are selected, and in the case of the partial performance conditions below the boundary value in any of the at least two different operating modes that require a lower speed of the electric motor than the other operating modes, the assumption is made of a high quality grade or COP value or a low electrical power consumption and thus these operating modes are selected.