Oh no... another boiler noise question!

[Larches]

We have a Vaillant Ecotec 415 system boiler, about 11 years old. It has been serviced annually (most recently in Sept 2021) and we've had a couple of issues with odd noises in the past (once just after servicing), but these have been resolved by a heating engineer tweaking something or other - otherwise it has behaved perfectly and when I asked the engineer not long ago about its likely lifespan, he said it's a good boiler, working well and should have a good bit of life left in it.

The boiler is usually reasonably quiet, but in the past few days, it's become noticeably noisier and sounds a bit rough. The odd noises that were resolved previously were quite different and higher-pitched. This time it seems more like excess vibration causing an uneven low hum, which can be heard in other parts of the house, especially the room above. I've attached a couple of audio clips but unfortunately the recording isn't very good (probably needs volume right up). I know there's a thing called kettling and I'm not exactly sure what that sounds like, but I would guess it's not what's going on here as it sounds more like something causing vibration.

Apart from the noise, the boiler is (dare I say it) doing its job as normal so far. To be honest, we can live with the noise as it's not too loud, but I wouldn't want to ignore it if there's a safety risk or if the boiler could be damaged by whatever is the cause of the excess noise. We're really hoping it's nothing major as these are not the easiest of times and we're looking to sell the house soon, so having to replace the boiler now would not be a welcome development. Anyway, I expect the answer is that we'll need to get a heating engineer out to look at it, but before I fork out a callout fee I thought it wouldn't hurt to ask on here in case anyone has other suggestions. I was shown previously how to adjust the output (part load / range rate) which is what one engineer did before to resolve noise, but I think we have a different issue on this occasion. Any ideas before I call someone out?

Thanks.

 

[EvilDrPorkChop]

Sounds like a noisy fan to me, but you need someone to take a look as you've said.

 

[Larches]

Sounds like a noisy fan to me, but you need someone to take a look as you've said.

Thanks. I was thinking fan or pump may be the most likely source from what I'd read, but I'll just have to get it checked out and hope there's not a big bill at the end.

 

[Larches]

Well, not sure what's going on here. I found a local (Vaillant-approved) heating engineer and he reckoned it could be a problem with the heat exchanger and that getting a Vaillant fixed-price repair might be the best option if we're not keen to consider replacing the boiler anytime soon (which we're not, especially with a house move coming up). He wasn't sure though, and said one thing worth trying would be scale reducer and inhibitor. So I drained the header tank plus a bit more from the system, added a bottle of 'boiler noise reducer' and a bottle of inhibitor, and refilled the tank. Though not before cleaning the tank, as I found it had some odd pale-coloured scum of some sort floating around and around the edges (not a lot, but enough to warrant cleaning up).

That was nearly 2 weeks ago. Since then, things definitely changed in that the noise from the boiler seemed to reduce very gradually, to the point where it wasn't that noticeable (though still not quite back to normal). However, just as that improved, we started hearing much more noise coming from (I'm fairly sure) the pump in the airing cupboard. Enough to send a bit of vibration around the house. That was last week, but now, for the past couple of days, they seem to have swapped over again - i.e. pump back to normal, but the boiler has this really noisy pulsing hum/vibration all the time it's running (sound clip attached). So I'm wondering if there's some kind of junk in the system that is circulating around and causing problems in more than one place.

The question now is, has the chemical treatment had long enough to do its stuff (opinions seem to vary between 1-4 weeks... this is an 11-rad system / 4 bed house)? The noise is getting a bit alarming (the last thing we want is boiler breakdown or damage to the system) so I could give in and cough up the hefty £285 for a Vaillant repair (£99 if it's not repairable) - or find another engineer to take a look - but should I hold off a bit longer? Or would the chems have worked by now if they were ever going to? I'd appreciate your views.

 

[Larches]

Aaaand it's all changed again. The worrying noise that sounds like a sort of pulsating droning/vibrating has eased off again and now it's sounding a bit more normal. Well, still sounds a bit rough and louder than usual but not anything like as bad. Really not sure what's causing it to fluctuate like this.

 

[Steve Gas Man]

Well, not sure what's going on here. I found a local (Vaillant-approved) heating engineer and he reckoned it could be a problem with the heat exchanger and that getting a Vaillant fixed-price repair might be the best option if we're not keen to consider replacing the boiler anytime soon (which we're not, especially with a house move coming up). He wasn't sure though, and said one thing worth trying would be scale reducer and inhibitor. So I drained the header tank plus a bit more from the system, added a bottle of 'boiler noise reducer' and a bottle of inhibitor, and refilled the tank. Though not before cleaning the tank, as I found it had some odd pale-coloured scum of some sort floating around and around the edges (not a lot, but enough to warrant cleaning up).

That was nearly 2 weeks ago. Since then, things definitely changed in that the noise from the boiler seemed to reduce very gradually, to the point where it wasn't that noticeable (though still not quite back to normal). However, just as that improved, we started hearing much more noise coming from (I'm fairly sure) the pump in the airing cupboard. Enough to send a bit of vibration around the house. That was last week, but now, for the past couple of days, they seem to have swapped over again - i.e. pump back to normal, but the boiler has this really noisy pulsing hum/vibration all the time it's running (sound clip attached). So I'm wondering if there's some kind of junk in the system that is circulating around and causing problems in more than one place.

The question now is, has the chemical treatment had long enough to do its stuff (opinions seem to vary between 1-4 weeks... this is an 11-rad system / 4 bed house)? The noise is getting a bit alarming (the last thing we want is boiler breakdown or damage to the system) so I could give in and cough up the hefty £285 for a Vaillant repair (£99 if it's not repairable) - or find another engineer to take a look - but should I hold off a bit longer? Or would the chems have worked by now if they were ever going to? I'd appreciate your views.

Firstly the Vaillant 415 is not a system boiler its a heat only boiler and will have a separate pump (system boilers have an internal pump). I would say your problem lies with the pump or system filter (if you have one). Remove the pump (and filter if fitted) and check for debris. This is the most common problem with older open vented systems.

 

[Larches]

Firstly the Vaillant 415 is not a system boiler its a heat only boiler and will have a separate pump (system boilers have an internal pump). I would say your problem lies with the pump or system filter (if you have one). Remove the pump (and filter if fitted) and check for debris. This is the most common problem with older open vented systems.

Whoops, yes, well spotted. Getting my systems and my heat onlys mixed up. The last engineer I spoke to said he's come across this quite a few times with this boiler and he has a method of cleaning out the heat exchanger, which often works... but not always. So his recommendation in view of the boiler's age was actually to do nothing while it isn't too bad (which it isn't, just now). Maybe you're right about the pump though, so that might be worth investigating too - thanks for the suggestion.