After 3 Way Motorised Valve was replaced, now only getting hot water, but no heating


Hello, I have a smart thermostat, extension kit and internet bridge, connected to a Worcester Greenstar. Heating system is a Y plan, in a new build house, c23 yrs old

Previously we had a problem where calls on the boiler for hot water (after 2 people had a shower, f.e.) caused all the radiators to get hot on a warm day, when temp in the room with the thermostat was well above the heating level and therefore heating not requested. Research online suggested the motorised valve was faulty, and so I called up a plumber, who agreed. Today he called around and replaced the valve, and showed me before he left that with hot water on, the hot water feed to the tank was hot and water was no longer being pumped around the rads… all good.

However this evening, it was a bit cool so we turned the heating up, it was then I worked out that the calls for heating on the app were not firing up the boiler. By turning off the heating to all rooms, and turning up the hot water cylinder thermostat, I was able to prove that the app is able to communicate via the bridge and the extension unit, because with the hot water ON, the boiler fires, I heard the motorised valve whirring and the circuit delivers hot water to the cylinder. If I then turned off the Hot Water on the app, the boiler and pump both stopped.

However, the boiler / pump / valve do absolutely nothing when I bump up the heating to 25 degrees. I hear the relay clicking in the extension unit and the app shows as if the heating is called for, but the boiler doesn’t fire.

Most online sources suggest that the motorised valve is at fault in such cases, but I know it has just been replaced, so it can’t be that. Could it be that the plumber has wired the valve up incorrectly?

BTW even whilst we had the problem with the rads warming up on Hot Water only, the heating was still working when called for


  • wateroakley
    wateroakley ✭✭✭

    The symptoms point to either a faulty 3-way valve or a wiring problem. Can you check that the CH or HW NO terminals have a live 240V feed when calling for CH or HW?