Hi, I have a fully pumped central heating system with a 3 way valve. When the heating switches on via the timer, the water tank heats up and the heating comes on. But as soon as the water reaches the temperature set by the cylinder stat, the pump switches off. Even though the room stat is still asking for hot water for the radiators. I have replaced both stats and the motorised valve is only 18 months old, it is a Sunvic valve. If the room stat temperature is reached the pump continues to operate ane the valve closes the valve to stop the water supply from the heating, as you would expect. But when the stat asks for more water for the radiators, the valve does not open. If you bang the motor, the valve opens. The fact that the pump goes off after the temperature has been reached on the cylinder stat, does this mean that the motorised valve is faulty or could there be a fault with the way the wiring has been set up. Or could it be related to something else!
