A heating installation or cooling installation mixing device has a valve housing (14) including a first flow path from a first connection (A-B) to a second connection (A), and a second flow path from the first connection (A-B) to a third connection (B). A movable valve element (24), arranged inside the valve housing (14) in the flow paths, is configured to vary a ratio of cross sections of the flow paths. A valve element drive (36) is arranged on the valve housing (14) and includes an internal control device (38) for movement control of the drive (36) and includes a first communication interface (44) for external control device (40) communication and a second communication interface (46). An internal sensor (48, 50) is arranged in or on the valve housing (14) and is connected to the first communication interface (44) for transmitting a sensor signal to the external control device (40).
