Fully submersible, multistage submersible pump as a centrifugal pump in sectional construction with integrated non-return valve for pumping process water. A corrosion-free, encapsulated permanent magnet motor with water-glycol filling and integrated frequency converter is used as the drive. The permanent magnet motor is hermetically sealed with enamel-insulated windings, resin-impregnated and with self-lubricating bearings. The integrated frequency converter allows operation using either direct current or alternating current power sources. The Actun OPTI-MS pump is therefore especially suitable for operation with solar power. In applications with solar modules, the integrated software algorithm MPPT (“Maximum Power Point Tracking”) allows the available power to be matched in order to maximise the pumped volume flow (dynamic MPPT). The unit can be installed in a vertical or horizontal position. The motor is cooled by the pumped fluid. Therefore, the unit must always be operated immersed. The limit values for maximum fluid temperature, minimum flow velocity and voltage ranges must be adhered to. Vertical installation is possible, depending on the design with or without cooling shroud. In cases of horizontal installation, a cooling shroud must always be provided. Scope of delivery *Submersible pump with connection cable *Casting resin cable connector with integrated water level sensor *Installation and operating instructions