GOB-217H is a part of the Russell range of mechanical heating controls manufactured by Danfoss. It is a pre-assembled, three-port, diverting valve and actuator pack, designed for use within domestic central heating systems. It consists of a motorised switching valve, surrounded by an insulation pack, which responds to thermostat signal when used within the appropriate control environment. When used as part of a two-port (on/off) system, the GOB-217H takes the place of two manual valves, or three in the three-port configuration, allowing for precise and automatic switching and temperature control. The range also features an energy-saving mode, allowing for further reduction in energy usage.