Honeywell V4073A 3 Port Motorised Mid Position Valve 22mm has been designed to control the flow of water in domestic central heating systems, where both radiator and hot water cylinder circuits are pumped. It enables independent control of the heating and hot water. It should be used in conjunction with a room thermostat and cylinder thermostat to provide full temperature control. It has a manual lever for filling and draining down the system and operates quietly with minimal power consumption.