Vaillant ecoTec plus 637 'Kettling' noises

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emailalantaylor

I had a new heat exchanger fitted to my Vaillant 637 boiler.
I had a powerflush done just before that.
When we start the boiler it performs ok at lower temperatures, but when we turn up the heat it starts making loud knocking noises- I beleive this is called kettling , and we have to turn off the boiler.
Vaillant engineer tells me there is a blockage. We checked all pipes into and out of boiler and primaries with vacuum - everything seems fine. Powerful pull on ends away from vacuum pump. Vaillant engineer says air is not water and there is a blockage in the pipe system somewhere.
Someone has told me that what I have got tis an air lock. Possible, because when the flame goes off we canhear something noisy going on in the boiler. But how do we get rid of this air if it is? Plumber worked three hours on this the other day and got no where. Slight improvement when internal by pass adjusted- but thats not the answer.
Suggestion is to disconnect all pipework and rig up new pipes to boiler from heating cylinder- this will prove if boiler is still malfunctioning or if the problem is within the pipework- although why suddenly the pipes should block goodness knows.

Any ideas guys. I am being sent round the twist with this heating system Started with dirt in system, but now have alledgedly clean system and new boiler interior and still the thing doesn't work.
 
Is it an open or sealed system?

I'd try sticking a new pump in it if it's sealed mate.

If it's open then I'd be looking to drain it and fit aav's on the highest points on the flow and returns,refill&vent and see how it goes
 
Well I would agree with you that it is the pump- but there is no fault reported by the boiler that the pump has a problem. Plumber checked it and seems like its working - as in impeller turning I am told..

Sorry- its a sealed system.

Also the primary pipe out of the boiler is getting hot but heat doesn't seem to be going through to rads..
 
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just cos the impellor turns doesnt mean the pumps ok, it my be slightly stiff and not working at full power. it needs to be able to spin freely and easily.
 
emailalantaylor said:
Well I would agree with you that it is the pump- but there is no fault reported by the boiler that the pump has a problem. Plumber checked it and seems like its working - as in impeller turning I am told..

Sorry- its a sealed system.

Also the primary pipe out of the boiler is getting hot but heat doesn't seem to be going through to rads..
Click to expand...

change the pumphead mate, in my experience boilers will only indicate 'boiler overheat', they won't say the pumps goosed.

It could just be air but it's very unlikely as it's a sealed system.
 
Hi, Possibly if pump running slow or weakly it may need speeding up
This if I remember rightly is done by accessing second diagnostic level
Check with your Vaillant techie

Regards 😀
 
You haven't told us why a new heat exchanger was required in the first place ?

When commissioning you need to run "mode 0" on these boilers, ideally a couple of times. This clears any air from the main heat exchanger prior to exposure to heat.
If the heat exchanger overheats it will blow the fuse link at the top. If this happens it is not replaceable & you are looking at another new heat exchanger.
Also as this is a powerful boiler it could be that it needs range rating. Easy enough to do electronically on these boilers using the D0 command.
 
The new heat exchanger was required because there was dirt in it. The system was powerflushed and certain radiators flushed individually and then the new heat exchanger installed. I would hope that the Vaillant engineer knows to run mode 0 when re setting up the boiler. The fact it was flushed is why we are as certain as can be that a blockage could not have just appeared. There are four 'circuits' fed by a manifold from the primary in/outs and controlled individually by thermostats.
I suspect the pump and/or the AAV because there can be no other obvious reason we can figure... I also get F75 message now and again which indicates pump and aav problem. Unless you have any other suggestion..

A
 
On Wednesday we changed the pump and AAV . Guess what. Sysytem now running what seems to be perfectly. No blockage was there. No kettleing now. All is well (I hope.)

THANK YOU ALL FOR YOUR ADVICE AND PARTICULARLY THOSE WHO URGED ME TO CHANGE THE PUMP. Never mind the advice I was getting - you were right!
 
emailalantaylor said:
On Wednesday we changed the pump and AAV . Guess what. Sysytem now running what seems to be perfectly. No blockage was there. No kettleing now. All is well (I hope.)

THANK YOU ALL FOR YOUR ADVICE AND PARTICULARLY THOSE WHO URGED ME TO CHANGE THE PUMP. Never mind the advice I was getting - you were right!
Click to expand...

I'm please Myself and a few others convinced u.
in these occasions, I'm changing the pumphead as one of my first port of calls. None of this suspect block h/e's nonsense. U change the pump first and if it's still doin it then u 'may' be looking at blockages etc. At least you'll know it's not the pump as it'll be brand new.

For me a kettling boiler needs a new pump, end of
 
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