combination boiler

[neil parcs]

I was wondering if you could help i have a vokera excell combi boiler the pilot is lit but the bioler does not operate what is the likley fault cheers

[John Stumbles]

It's too warm and the room thermostat is not calling for heat, and nobody's turned on a hot tap so there's no need to fire for DHW. Or it's powered off at the FCU.

If that doesn't fix it perhaps you'd better arrange for members of this group to come round to your house and fix it for free. Or provide more information for people here to have a snowball's hope of helping you diagnose it.

[matthew.larkin]

Just as a peculiarity, we have a combi that had problems a while back

- would produce DHW fine, but wouldn't fire for the central heating. The common factor every time that it happened was that someone had left the hot tap for the bath dripping slightly (and dripping cold water, as the drip wasn't enough to fire the boiler!).

Now, I've no idea why this would stop the combi firing for the central heating, but once the dripping tap was turned fully closed the central heating fired up straight away. Any ideas why this might have happened?

So that's one bizarre thing to check. But as John says, I think people might need more info. But the best answer is "call a plumber".

Matt

[Ed Sirett]

This fault is almost unique to the Pott. Puma combi. It arises from the unique way that the HW/CH diverter valve is driven. Google archive for mor details.

[John Stumbles]

Beat me to it!

Also (known as?) the Combi 100. You wouldn't know it's a Puma from the outside. (And presumably there's a Combi 80 as well.)

[matthew.larkin]

Blimey, you're good!! Yes, I have a Potterton Combi 100. When I did have the problem I googled extensively but couldn't find an answer (though at the time I didn't know that there was a dripping tap).

I'll track it down. Thanks!

Matt