Vaillant 637 Ecotec plus - air bubbles in system

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General question to Vaillant engineers - is it possible for the boiler to create air bubbles in a sealed system. Reason I ask is i'm bleeding air from the same radiator every night for the last 2 weeks. It's a new vertical radiator on the floor directly above boiler. Wondering if installing spirovent aerator would solve the problem.
 
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iateyoubutler

I don`t know the answer to your question but I`m glad that somebody else has experienced this with Vaillant.....

I don`t have a sealed system, mine is vented, but I used to have an Ecotec 415 (I gave up on it 9 months ago - heap of ****) and had the exact same issue as you. The Vaillant replaced the original Ideal Concord boiler that was in the house when I moved in, the Ideal worked without fault. Had the Vaillant fitted, and then battled with air problems with it non-stop until I had it ripped out 9 years later because I was sick of it. Basically, during the winter months I was bleeding two of my rads every other day and every time they were completely empty of water, or if I had the hot water on the noise was terrible.

I proved it was the boiler because if I ran the pump on its own without anything being heated, then everything would settle down and run quietly. As soon as the boiler was fired up, all hell would break loose yet again........

Had it replaced back in the spring and all is perfect once again. I haven`t needed to bleed anything since the system was initially filled up, and the hot water is so quiet that I don`t even realise that it`s on.

I don`t know why it was happening, I couldn`t find anything on it, but I`m glad I`m not alone!

I hope you manage to get to the bottom of it
 
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thank you for the replies.
iateyoubutler - I put in a new boiler 2 years ago and have been having this issue. Went from vented to unvented and renewed mains pipe into house. Put in 3 new vertical radiators as a part of an extension on the first floor. Plumber originally thought boiler was oversized (even though he put it in) so it's set to 14kw and produces decent heat. Plumber wasn't sure what to do so I called in Vaillant engineer who thought I needed an external by pass as I was having banging issues when the boiler went into pump over run. So had external by pass put in. Vaillant engineer also didn't like the way flue was fitted and shut boiler down as he said it was too dangerous. Had flue fixed. Plumber not sure what to do so I'm going through a process of elimination - bleed radiators, balance system, check TRV flow direction, check pressure on a regular basis for any leaks.
RayCaister - Plumber did powerflush system when boiler installed so I assume he added inhibitor - although he forgot to bleed and balance system. I did that so will ask him about inhibitor just to make sure
 
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Non engineering onion:

How can a boiler generate air?
It's just a boiler.

Sounds to me like poor installation in both cases.

I'd also be wondering about leaks and accelerated corrosion.

If its being regularly bled, does this also mean you have to keep topping it up?
 
I

iateyoubutler

Non engineering onion:

How can a boiler generate air?
It's just a boiler.

Sounds to me like poor installation in both cases.

I'd also be wondering about leaks and accelerated corrosion.

If its being regularly bled, does this also mean you have to keep topping it up?

Perhaps some sort of reaction then? But I am not going to be swayed from my conclusion that the boiler was at fault. There were no issues of this type for the 35 years that the original boiler in the house was in use, and there are once again no problems whatsoever since I got rid of the Vaillant. Anyhow mine only had issues when the boiler was actually heating, so I`m sorry - that Vaillant boiler was bang to rights at fault. It also hissed and kettled from brand new, where the other two boilers never did - but that was another issue
 
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Perhaps some sort of reaction then? But I am not going to be swayed from my conclusion that the boiler was at fault. There were no issues of this type for the 35 years that the original boiler in the house was in use, and there are once again no problems whatsoever since I got rid of the Vaillant. Anyhow mine only had issues when the boiler was actually heating, so I`m sorry - that Vaillant boiler was bang to rights at fault. It also hissed and kettled from brand new, where the other two boilers never did - but that was another issue

This sub is absolutely rammed with posts that are ultimately, the result of incompetence in the install.

The industry is an utter sham.

I replumbed my system to stop this very thing and its worked fantastic since.

My growing approach to any queries on this sub is "start from scratch, assume nothing is right"

In your case, "Oh hai, yea, you've no bypass lol". from the OEM is astounding. I'd be livid with the "plumber" who did that. I'd also check everything else he did.
 
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Thank you again for you replies. I never had this issue with my previous two boilers and I have lived in this house with the same pipework for almost 25 years. There is a possibility the boiler is the issue. I have just got my guarantee through after two years - plumber forgot to register the boiler so kicked up a fuss and finally got it a few months ago and was able to get a Vaillant engineer out but he refused to touch boiler because flue was incorrectly installed.

I agree with you BlueLoo- not sure how boiler can generate air that's why I was asking some expert engineer on here. I don't keep topping up because not much water escapes when I bleed radiator each night. I keep an eye on the pressure and it is always around 1-1.1 KBar when cold.

Corrosion is a possibility. As you said I am starting from scratch to try to figure air and banging problem (in other pipes/radiator) as the plumber not sure what to do and although he is a nice guy his performance hasn't been great. Someone on this site mentioned a device to remove air bubbles in system (Spirovent) but trying to understand how system generates air in first place. Maybe it is just corrosion in which case system needs a proper clean.
 
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I'm no plumber so take my posts accordingly.

Have you done the hydrogen-match-glass-poof! Thingy? :p

Is your expansion tank leaking? (Diaphragm?)

I'm sure someone better qualified may comment soon enough
 
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Not tested gas for hydrogen. Will try this. Expansion vessel for the hot water is ok but didn't think this was linked to central heating.
 
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Here is a possibility. When water is heated, it cannot hold as much dissolved air, so it drives the air out of the water and makes bubbles. Depending on how your system is piped, there may be many places where air can be trapped, and can dissolve into the water over time. Colder water can hold more air, and this effect is amplified by pressure. So the air pockets dissolve slowly into the water, get transported to the boiler, and then released. If this is what is causing your issue, keep bleeding the radiator, topping it up when required (which will introduce more air) and it should eventually go away.

https://www.engineeringtoolbox.com/air-solubility-water-d_639.html
 
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General question to Vaillant engineers - is it possible for the boiler to create air bubbles in a sealed system. Reason I ask is i'm bleeding air from the same radiator every night for the last 2 weeks. It's a new vertical radiator on the floor directly above boiler. Wondering if installing spirovent aerator would solve the problem.

Open vented system, with a Vaillant boiler installed and this is the third boiler installed on my system. When ever anything is done which has involved any draining, it has always needed several weeks until all air has been bled out of my system. Usually the air collects in the upstairs rads and mostly in the bathroom radiator. So I would suggest to stick at it, bleeding regularly for a while longer and see if the amount of air decreases.
 
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Thank you sirocosm and Harry Bloomfield.

I have noticed the amount of air released each time is less after 3 weeks so you both might be right. I'm trying to figure out of this issue is related to loud banging in the pipes near my other upstairs bathroom radiator, particularly in the mornings. Never had this issue before the installation of new boiler.
 
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Here is a possibility. When water is heated, it cannot hold as much dissolved air, so it drives the air out of the water and makes bubbles. Depending on how your system is piped, there may be many places where air can be trapped, and can dissolve into the water over time. Colder water can hold more air, and this effect is amplified by pressure. So the air pockets dissolve slowly into the water, get transported to the boiler, and then released. If this is what is causing your issue, keep bleeding the radiator, topping it up when required (which will introduce more air) and it should eventually go away.

https://www.engineeringtoolbox.com/air-solubility-water-d_639.html

Interesting article - looks like adding a deaerating device to the heating system could make sense
 

DP

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I suspect radiator creating that issue. Have come across this problem many times.

your boiler is a sealed system. Electrolytic reaction breaks the water down. Check if it is hydrogen ( search how to check if gas is hydrogen)
 
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