The VDE valve is designed for use in combined home boilers with instant and semi-rapid production of domestic hot water. It is designed to shunt the flow of water away from the primary boiler circuit to the secondary heat exchanger, excluding the heating circuit (priority to hot water) . It can be used in boilers that employ series VDP series VDPIM valves without changing the layout of the boiler fittings and by merely inserting the control unit.