Vaillant Ecotec 831 noisy heat exchanger

[treytrey]

We had a Vaillant Ecotec 831 installed about nine months ago and have had no problems until a couple of months ago.

Since then, the heat exchanger has been making loud clicking/clunking/popping/cracking/clanging noises as it heats up and cools down. It's loud enough to be heard through the house where previously it was very quiet. It sounds like a thirty year old ascot rather than a modern boiler.

Can anyone offer any suggestions as to where the problem is? I've read that the nuts on the heating exchanger need to be slackened off and retightened, or that there's a allen bolt on a heating element though a insulation pad that needs to be tightened.

I'm not planning on doing the work myself (the boiler came with a couple of years of BG callout service), but I want to be able to point the engineer in the right direction if he wants to claim it's normal that after seven months the boiler goes from silent to noisy.

Thanks for any advice.

 

[Garfeild]

Call Vaillant they'll sort it.

 

[mickyg]

its a simple fix but needs an RGI, call them out.

 

[treytrey]

I've got a British Gas guy coming tomorrow as they support the whole system, not just the boiler. I'm glad it's a simple fix, but can you tell me what I should say to him if he claims it's just supposed to be that noisy? Apparently some Vaillant service guys have been telling that to customers with the same problem.

I just want to be able to say "the problem is in the <whatever>, that's what you need to look at". It wouldn't be the first time I've had a BG engineer cry off a job because it was too difficult or because they'd rather be off home early, so I like to pin them down...

 

[gaswizzard]

what I should say to him if he claims it's just supposed to be that noisy? Apparently some Vaillant service guys have been telling that to customers with the same problem.

I doubt it.

I just want to be able to say "the problem is in the <whatever>, that's what you need to look at". It wouldn't be the first time I've had a BG engineer cry off a job because it was too difficult or because they'd rather be off home early, so I like to pin them down...

Just make him a brew.

 

[bell824]

if it's during the heat up and cool down period then vaillant engineers would not be saying it is supposed to be that noisey.

we would not want to advise you on how to advise another engineer where the problem lies,

He will have it in his little black box of tricks how to solve the issue (his laptop)!

 

[treytrey]

Out of interest, could this have been caused by changing our old lead water mains (51 years of limescale) to a shiny blue plastic pipe? Would the increase in the water flow rate mean the boiler needs to be rebalanced for it?

 

[mickyg]

nope its to do with metal expansion/contraction. Two different metals expanding at different rates.

 

[treytrey]

Well so much for the easy fix!

BG man turned up and said it was too quiet to be sludge in the system. He called Vaillant who disagreed and said it was sludge just starting to build up in the heat exchanger. BG man has to come back to do a water test to see if the repair or the heating team has to come back and reflush it, so that'll be another ten days to do the test and get the results. He didn't even take the front cover off the boiler even though he agreed that it sounded like metal expansion.

Given the system it was flushed/cleansed by BG eight months back and had a spirotrap and descaler fitted, along with all the old bits removed and replaced, it's a bit annoying they now have to argue amongst themselves as to who comes back and fixes it.

Unfortunately I couldn't say anything more than "guys on the internet said it would be a quick and simple fix but wouldn't tell me more in case I decided to dismantle my new boiler and blow up the house"

At least I've still got heating and hot water, but I'm afraid they are going to do a water test, then a reflush, and find that nothing is different, and they need to finally start looking at the heat exchanger.

 

[gaswizzard]

"guys on the internet said it would be a quick and simple fix"

What did he say? , don't worry I can imagine.

 

[treytrey]

"guys on the internet said it would be a quick and simple fix"

What did he say? , don't worry I can imagine.

Well he was a young bloke and open to suggestions, so he didn't just instantly discount it. He claimed not to have ever heard a boiler making the noises mine is making as he was expecting the much louder banging you get on a sludged up boiler. He did say it sounded like the noise old rads make as they expand, but he was happy to put the "metal expansion" aside in favour of "sludge in the exchanger" as soon as the spoke to Vaillant on the phone, so the diagnosis was pretty much made by someone who wasn't on site.

However, he did seem unwilling to do anything more than make phone calls and listen to the boiler clunking away, rather than get the lid off and have a look at it. I guess with no error codes showing, he didn't think it necessary to actually do any... you know... fixing...

BG have to order the water test kits, so he's got to come back for 10 mins next week to do the test, instead of just taking some water now and sending it off straight away. If they do have to come back and reflush, it won't cost me anything, and they get the test done by Furnox with recommendations as to what inhibitors and how much need to go in my particular water. I would have thought that would have all been sorted by the BG man who put my boiler in eight months back.

 

[bell824]

Lets just say he will be coming back with some copper paste to place between the metals that are expanding at different rates, surprised this wasn't in his little black box of tricks to be honest.

 

[Bunnyman]

They don't tell em the useful repairs just the traditional fault finding charts yawn!

 

[treytrey]

Lets just say he will be coming back with some copper paste to place between the metals that are expanding at different rates, surprised this wasn't in his little black box of tricks to be honest.

No he won't - he'll be doing a water test and then no doubt trying to get someone else to powerflush the system again in a couple of weeks time.

Would have been useful to have known about copper paste before he turned up so I could have at least suggested that to him.

Still he did call Vaillant, and they told him it was sludge over the phone, and he accepted that even though it was six months after a full power cleanse with big parts of the system replaced. It's a shame that Vaillant didn't suggest paste instead of making a load of work for someone else and weeks of delay for me to get it sorted.

 

[bell824]

My question is this, did he explain the right symptoms to vaillant on the phone? Because the noises you describe are also caused by a blocked heat exchanger, though this predominatly happens on domestic water demand when the boiler is at it's fullest gas rate.
But as you have mentioned it is durring the heat up and cool down period then that suggest's the two metals moving at different rates therefor the copper paste between them cures this.
It is all in the explanation and questioning of a customer, you have explained the fault really well and most engineers that have replied know exactly what the fault is and probably 90% of those who know, know how to cure it.