Banging noise in central heating system

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I'm hoping someone can help. I don't know much about central heating systems.

I've just installed a new boiler (Vaillant Ecotec 637) and new hot water cylinder. Previous system was vented whilst the new system is unvented.

Problem I have is when the boiler cycles to heat the radiators I hear loud banging noises in the pipes and radiators. My boiler seems to cycle 4/5 times a hour and the noise is a problem particularly when the heating goes on before I get up in the morning - no need for an alarm clock!.

I suspect the boiler is more powerful than it should be. The previous boiler was a Vaillant 28KW and it worked fine. I've added some underfloor heating in one room and increased the size of the hot water cylinder but not sure that justifies the increase to 37KW. I've played around with the power settings taking it down to 24KW but doesn't seem to make any difference. Some of the loudest radiators are the closest the the boiler so I'm wondering whether there is a flow speed issue that maybe fixed through balancing the radiators.

Any thoughts/ideas welcome.

Thanks
 
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If I’m reading this right, I can only imagine the replies you are going to get to this one.......
 
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If I’m reading this right, I can only imagine the replies you are going to get to this one.......

What you mean like, "get someone in who knows what the hell they are doing and able to do it safely and legally." Something along those lines???
 
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Looks like I've opened up a can of worms with my post. But you are right - I wouldn't get the same guys to do the work again although they did have the all the credentials.

So can anything be done to resolve my issue or do I just live with it?
 
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TBH, I'd be getting them back in and get them to sort it. You shouldn't really be on a forum trying to remote fix your new boiler and cylinder installation.

Even if your boiler is too large for the system, all it should do is short cycle but it certainly shouldn't be banging.
 
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Thanks - you are right. Boiler was short cycling. Have got them back and they changed power setting and increased pump speed but that hasn't done very much. I have asked them to come back but confidence in my plumbers is not the highest right now.
 
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Is it banging at the radiators, it almost sounds like the TRV's are directional, they will clunk if the flow isn't the correct direction. Did they change the rads and do they have old TRV's on them?
 
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Banging at the radiators and in the pipes when the boiler cycles very 10 minutes. Checked TRVs - arrows going in both directions. They didn't change the rads or TRVs. They did perform Powerflush.
 
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Remove the sensor heads from the TRVs and see if that stops the banging, I have seen Bi-Directional ones still banging, post a pic of what TRVs you have some you have to set the direction, it could be that when they fitted the new boiler they have reversed the flow and return, happens all the time
 
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Thanks - good idea. Will post a pic of TRV when I get home.
some makes, even though they are indeed Bi-directional, you have to manually set the valve to the correct orientation , takes literally seconds to do and you dont need any tools
 
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The Danfoss RA / RAS - C2's spring to mind
th
 
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After looking at my TRVs I seem to have two types

First TRV doesn't have arrows in both directions - see two pics below:
Top of TRV 1
https://www.dropbox.com/s/3ld1h2qxojo0u4n/2020-12-22 16.48.47.jpg?raw=1

Side of TRV1
https://www.dropbox.com/s/znp39ejtmvtk2ww/2020-12-22 16.48.39.jpg?raw=1

Second TRV has arrows in both directions - see two pics below:

Top of TRV2

https://www.dropbox.com/s/1fbdrkghq9lg25b/2020-12-22 16.49.08.jpg?raw=1

Side of TRV2

https://www.dropbox.com/s/1tyb7knge90atch/2020-12-22 16.47.14.jpg?raw=1
 
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1st valve isn't a TRV, its a screw down/lockshield valve. The 2nd is though it shouldn't need any adjustment as it is a native 2 way valve. What happens when you shut that TRV valve to off, does that stop the banging?
 
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Thanks - thought first one was trv as the otherside of the radiator is a lockshield valve I've used to adjust flow and all my rads were upgraded to TRVs. Now after 14yrs I just found out that wasn't true. When I do switch off the TRV valve banging isn't so bad - for the loudest radiator near the bedroom I do switch off the TRV and it did make a difference,
 
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