Boiler Noise

[RJH]

After 3 component failures in the past few months (heat engine, water pressure sensor, pressure gauge), it's looking like my Ideal Logic + is on to its 4th.

On starting heat or water and for about 5 minutes, the boiler makes a loud resonating sound, a bit like a bearing on its very last throes. It's difficult to tell where it's coming from with the cover on, centre up. I don't think it's the fan - the noise stops once the boiler stops firing. Once it settles down after 5 minutes or so the noise more or less goes, maybe fades in/out for a few seconds every so often. Recording clips at:

(After 5 minutes - noise more or less gone, normal sound) (First 5 minutes - new noise, boiler from cold, stops after about 5 minutes)

Internet searches tend to suggest gas valve, although this sound can't be heard outside, and the reports I've read suggest it doesn't stop after a few minutes. Replacement looks relatively straightforward - 5 minute job. Any comments please?

[Tim+]

Surely that?s when the fan stops too?

My money would be on the fan motor bearing. Having said that, we once had a boiler that howled due to kettling. This was down to a low static head of pressure and a pump that wasn?t removing heat fast enough.

Tim

[RJH]

I think the fan carries on for a short while after the burner switches off. The noise certainly sounds like more than I'd expect from just the pump.

Yes, thanks, could be. This is a sealed system and the pressure's fine, but I did post a while back about the burner switching off and the pump running during heating. So maybe there's a bit of runaway and a failed sensor somewhere. It's certainly not the sort of sound I'd expect a valve to make.

[nothanks]

If it's yours, and you consider yourself competent, removing the cover should help you track-down the source. If you're asking out of interest and will get someone else to fix it then an image search for "ideal logic boiler parts diagram" should give you an idea of the probable cause.

[RJH]

Thanks - I've got a decent manual, and I'm quite familiar with the workings. Just I'm having trouble diagnosing this problem. That said, you're right - I could almost certainly diagnose it more accurately with the cover off, but I'm not sure about doing that with the boiler running.

[alan_m]

Water being heated too fast - turn down the gas pressure/turn down the flame??? The fins on the heat exchanger resonating with the speed of gas/flame passing over them???

On my very old boiler I had a similar noise, but when the water in the system was up to temperature. The cure was to turn down the gas to the burners slightly - an adjustment on the gas valve. My problem only started when the gas pipe to the boiler was changed from 15mm to 22mm so possibly marginally increasing the gas pressure as it entered the boiler.

[Fredxx]

With most conventional modern boilers no combustion gases will flow into the boiler casing and so safe to run with the casing off.

I would be tempted to shut off a couple of rads during the first 5 mins and check if there is a change in volume or tone.

With the cover off I expect you'll be able to detect the issue by feeling the vibration from the offending component. Pump / fan / gas valve. I have known heat exchangers amplify noise by hitting a harmonic.

[Harry Bloomfield, Esq.]

RJH expressed precisely :

Its the fan, or rather its bearings.

[Clive Arthur]

At about 10s on 'first five minutes' there's briefly a higher pitched note changing to a lower pitch. It sounds like a 3:2 ratio, so I'd be looking for something resonating - it starts off with 1.5 cycles between it's fixed ends and and settles on 1. It then gets louder and starts distorting producing a slightly lower fundamental frequency.

Could be a length of pipe, or maybe a panel. Try pressing on various bits to see if you can damp it. Could be as simple as a loose clamp.

Why does it stop? Expansion? Dunno.

[RJH]

I'd have thought so - just that the installation manual expressly says not to.

Yes, tried that - no change. But the whole cacophony is over within a few minutes, so it's difficult to tell with certainty.

The fan housing seems to be vibrating a fair bit, and insofar as I can tell, the noise seems to be coming from there. So I'll try the fan first (fairly low risk at £20 for a 'pull'). Wouldn't surprise me if it was the gas valve, though.

[RJH]

Yes, could be. Diagnosing to that level is beyond my pay grade though :-) I'l try to keep the thing running through the winter and get somebody in to check calibration etc. It's had a few components changed recently - but none could be adjusted in any way.

[RJH]

Whatever's causing it does seem to excite various pipes etc - as mentioned above, I'm going to swap out the fan and see if that helps. A google search suggests that it's not uncommon to diagnose this sort of fault incorrectly for this boiler.

[Mathew Newton]

I don't half feel old... Friday night and here I am sitting here listening to recordings of someone else's boiler... ;-)

Still, I suppose even the youth aren't doing much at the moment so perhaps this counts as fun afterall!

[Paul]

If a fan is going, it might last about a week.

If I was you, I'd order in something just to take its place. If you can get the item cheaply, you'll look positively heroic when it blows. With item in hand, ready to go.

Fans wear. It's an item guaranteed to need replacement. If you think the device is a keeper, then keeping a spare fan next to the machine might make sense.

The only reason for me mentioning this, is when I needed a fan, it wasn't a stock item. I should have been more proactive.

My fan was *designed* to make a noise as it was failing. If the motor had been ordinary, it would have been quiet, until the instant it stalled. Whereas what they did, was use materials so it could "clang together for quite a while before stalling". The noise is supposed to make you "call someone immediately".

Paul

[RJH]

In my last place it rattled away for 2 years, then failed.

I have, thanks. But just a 'pull' from ebay for £20 (but with a 3 month warranty, and tested by a 5000+ seller). I'm still not 100% it's the fan, but figured trying a swap would be no great hardship.

[Thomas Prufer]

... or try to oil the fan bearings. Probably a temporary fix at best --sintered bearings are picky about lube, and a drop of oil isn't enough once they are gone-- but if you oil them and the problem goes away, you've found the problem.

(And you might get in touch with Geoff (formerly of this parish) at Cet Ltd...)

Thomas Prufer

[RJH]

I did have a look for any sign of an aperture/lubrication point. But it's all encased, and at £20 for a s/h part, I can wait the couple of days it'll take to get here.

Thanks - interesting, and I'll certainly take a look, especially when the PCB inevitably fails :-) These boilers seem to have a ready supply of s/h spares. I dread to think how many have been replaced after an easily replaced component failure

Small update - the noise changes noticeably and instantly when the CH temperature's adjusted. Suggests to me the valve - so I've ordered one of those too.

[RJH]

FWIW, replaced both the valve and the fan with 'pulls', about £20 each from ebay. Pretty much exactly the same. Went over the whole boiler, checked connections and joins. Nothing out of place, a cracked plastic flue to case locator (I think) superglued and refitted. On firing up, still a noise, but slightly quieter. Then, while I had a rest from it all for a few days, the noise got quieter and has now gone. No idea what is was all about.