Motor driven control valve

摘要

A motor driven control valve for controlling a hot water and central heating system comprises a valve member (20) able to selectively take up one of three positions by the operation of an electric motor 68. The motor can be driven, braked by d.c. current through a diode D2 or demagnetised by a low a.c. current through a resistor R4, so that a spring repositions the valve. A control circuit 130 for the electric motor 68 includes two switches S1 and S2a whose position is determined by the position of the valve member (20). Power is applied to terminals 56, 62 and 46 of the control circuit depending on the demand from room thermostat 26 and hot water thermostat 28. The applied power is fed to the motor by the switches S1 and S2a so that the valve is driven to the appropriate position to a blow heated water flow to the hot water cylinder, the central heating, or both. The thermostats 26, 28 also apply power when required to the pump 2 and boiler 4. It is stated that the control circuit 130 arrangement prevents the unwanted feed of power from terminal 56 to the pump 2 and boiler 4 when there is no demand from the thermostats.