Hot water = hot radiators, but three way valve is ok

[lifechooser]

Now that the warmer weather is here, I've discovered that our radiators still get hot for no apparent reason. Presumably when the hot water is heated.

A plumber replaced our three way valve over the winter at my request, but couldn't see a problem with it.

Does anyone know what the issue might be. AFAIK, this is a typical boiler / hot water tank system. I looked at the valve this morning and all three pipes were hot, but the valve was pointing at W.

Could it be a programmer issue?

 

[oilhead]

If the 3 way valve is at W, and has been for the selected time, then the pipework configuration needs to be checked. Is the heating flow pipe hot after a distance away from the valve? You will get some conduction.
You may be getting reverse circulation from the hot water return. Seek the advice of your plumber who knows and has already worked on the system.