Combi boiler issue Help and information on all topics relating to your central heating, air conditioning and ventilation issues.

[paulus22]

Looking for help. I have recently moved into a 3 storey house with a combi boiler on the ground floor. The basin on the third floor has plenty of pressure and flow but the flow does not fire the boiler (a Vaillant). If I turn a kitchen tap on low then boiler fires and the water upstairs is hot.

I am baffled, since the flow is good, why the boiler does not fire. Any ideas? Is the flow switch adjustable? It beats me.

paulus22

[htg engineer]

Possible the diaphragm in the diverter has split or become stretched - replacing this - and maybe the fulcrum arm - will solve the problems.

htg

[paulus22]

Thanks for the advice, just a couple of questions. Are these readily available parts - swapped on a diy basis, or are they part of a replaceable unit. Since it is in the water system, presumably you don't need to be Corgi registered to do this kind of thing - just an amateur plumber?

paulus22