Vaillant Turbomax - 3 Diverter Valves In 3 Years???

[Whitespirit66]

My elderly parents have a 3 year old Vaillant Turbomax Plus 824/2E combi. They're just about to have their third diverter valve fitted.

These valves are OK for the first ten months. After this, if you have the heating on, and you open a hot tap, there is a really loud bang from the boiler as the diverter valve operates. The fault doesn't happen when the heating is off. This noise travels throughout the whole house via the heating pipes and radiators, and wakes you up.
I think that the diverter is partially sticking, and suddenly frees itelf with a jolt - hence the loud bang.

Has anyone heard of a problem with these boilers?
What is causing the diverter to start jamming after only 10 months?
Is corrosion or scale in the heating circuit a likely cause?
If the inhibitor in the system was too weak, would this cause the failure?

I would appreciate any advice on this, including anything we can do to prevent more valves failing. This could start getting expensive!

 

[cross thread]

i think vaillant alterd the pcb for that problem, a slight time delay

 

[ChrisR]

They did.
It's not usually loud enough to cause a real problem, though.

 

[mark.neale]

 

[Whitespirit66]

Thanks for the advice given. Much appreciated.

Yes it really is a loud bang. Imagine giving a good hard whack with a hammer to the heating pipes. The radiators amplify the noise, you can hear it in every room.

One thing that occurred to me, is that if it is the pcb, why does replacing the diverter valve rectify the fault for the first 10 months?