really loud boiler vibration

30 Dec 2011
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United Kingdom
My boiler makes a really really loud vibration (like a trombone) when the flame is heating. it is not like kettling or knocking, it is a faster vibration like a 2nd WW bomber.
It starts the noise when dhw is flowing through at half flow (tap only opened a little) and when the water temperature of the boiler is set low. Changing the water temperature output to high or opening the tap to max stops the vibration.
It recently started vibrating also in central heating mode. Here vibration occurs at 55-60 degrees. Lower temperatures are OK and 65-70 it seems to stop also (although see below).

I had a couple of engineers round to have a look through. One said that it might be limescale in the main heat exchanger and that it needed replacing. At the time of his visit the vibration only occured in dhw mode, not in ch mode.

I called for a second opinion, and this guy swore it wasn't limescale and was probably due to make of boiler (it is a heatline solaris pc30 boiler) but could not suggest what the problem was for sure, maybe loose fan housing or something twisted.

I read through the manual and fiddled with some settings:
The boiler range had been set to minimum even though factory preset should have been about 80%, so I adjusted this back to 80%. This reduced the vibration significantly.

I also adjusted the max fan speed up to 90%. This almost entirely solved the vibration. It now only vibrated in dhw mode when the water temperature is set to low.

I have yet to see whether the problem starts up in its favourite time which was at 5am when the heating was firing up for the day (oh yes).

Any ideas as to what the problem is - is it limescale? what can I do to solve it? If someone can give me an idea then at least I will be able to tell if the next engineer who comes round knows what they're talking about.
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You tell us all that information (some of which is useless) but forget to give the most important bit of info. I'll leave you to guess. :evil:
apologies for the long post - was just trying to get all the info across.

what more can I say. The system was installed by a pro. Inhibitor was added to the system. The heating system was all new so no old sludge to wash out. The system has been running for 3 years. The problem started about a year and a half ago and has got steadily worse. We do live in a hard water area.

I have had the system looked at but the engineer was not convinced he knew what the problem was, thought it might be limescale but another engineer has categorically told me it is not, so..?

in case people don't spot the make buried in the middle of my post it is a:
HEATLINE SOLARIS 30PC combi boiler
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Sounds very much like the fan or possibly the pump but most likely the fan.
Seems incredible that two engineers couldn't identify what was causing the vibration.
Sometimes the fan causes other metallic bits to vibrate.
I don't suppose you could take the cover off and have a look? It's not rocket science or maybe just wait for another "engineer".
45 yr :LOL: :LOL: :LOL: :LOL: :LOL: :LOL:

I knew what you were getting at, in such a long post it should have been mentioned earlier to keep us interested.

I would suggest crud in the heat exchanger if as above (Gaswizzards post) checks out ok.

If co2% ratings are correct then the way to think of it is -
Boil a kettle that is open to expand the bubbles into atmosphere and you get a bubbling noise,
boil a heat exchanger under pressure and the bubbling prodeces pangs and pops within the water ways causing noises, normally only happens when the boiler cant get enough cooler water to compensate the heat load.

So if co2% is ok as gaswizzard suggest's i would also be supecting main heat exchanger and also possibly a sytem clean.

Unfortunatly cheaper boiler being installed normally mean corners being cut.
How did you choose these two engineers to "come for a look" ?

Could they be coming with you expecting a free diagnosis? If they sussed that was what you were expecting then it does not surprise me that they did not want to tell you what was wrong or use their test equipment.

I always charge to diagnose boiler faults which is probably why you would not have called me! I have seen boilers before so I know what they look like.

Something you get for free usually has no value! ( Charles Dickens ! )


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