Hi, we have noticed the boiler running when CH / underfloor heating are not "on" Had the same problem a year ago....engineer said boiler was ok (2yrs old).. but a problem with Honeywell diverter valve....he showed me the spring which is slack when "On"...then spring activates when "off". I don't know what he did but it sorted it out he did not install any new component. Seems that the D Valve controlling the underfloor heating allows the boiler to work when stat is in off position.
Does this make sense?....what might he have done? thanks .
Does this make sense?....what might he have done? thanks .