Banging Central Heating pipes

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Before I ask my question some background on my heating system. Installed Vaillant 637 Ecotec boiler two years ago when I had my garage converted into a room. Had underfloor heating installed into garage and a new vertical radiator installed in room above. Went from a vented to unvented system and installed new mains pipe from street to my house.

So the issue I have is around banging pipes which only began after the new system was installed. There a two types of banging - one when the boiler cycles and usually occurs between the pump over run mode just before the burner mode when cycle starts again. This isn't so bad now after playing around with the boiler settings - thanks to the help from guys on this website. The second banging is limited to a radiator in an upstairs bathroom. I've put this down to air in the pipes - it could also be pipes rubbing against floor boards but not sure what would have caused this as these pipes have not been touched.

I've bled the air in all the radiators but for the last 7 days when the heating switches off and cools down I've been bleeding the new vertical radiator as there always seems to air in it.

Is it normal to keep bleeding the same radiator even though the previous times it seemed like all the air was taken out?
 
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Thank you for your reply. Yes has thermostatic valves. I have already tried that but made no difference.
 
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Is the thermostatic valve (TRV) quite old, see if there is an arrow marked on it.

If the install of new boiler has switched the flow and return around you may now have a directional TRV banging. If so it will need reversed or replaced.
 
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I've bled the air in all the radiators but for the last 7 days when the heating switches off and cools down I've been bleeding the new vertical radiator as there always seems to air in it.

Is it normal to keep bleeding the same radiator even though the previous times it seemed like all the air was taken out?


I fitted a Spirovent deaereator to my sealed system and it got, and kept, every drop of air out of the system.

https://www.spirotech.com/products/spirovent/
 
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Madrab - All the TRVs are bi-directional- was first thing I checked
Mottie - Spirovent deaerator does look interesting
 
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Ticking and clicking would usually be from pipes expanding/contracting in the floor.

Air in the pipework would usually give you gurgling and bubbling sounds

Is it an actually a banging?? If you put a largish screwdriver against the valve when there's banging you will be able to hear if it is the valve itself or from the pipework. A soft thump/knock would usually be a sticky valve
 
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Ticking and clicking is what I would normally expect - had it with last system but was not a big deal.

My issue is definitely banging - it's so loud in the morning have to switch offending radiator off. Still hear some banging but not so bad.
Will try placing screwdriver against valve when I hear the banging.

Had Vaillant engineer come over a few months ago. He said the way pipes plumbed into boiler meant I needed an external bypass valve. My plumber agreed and put in external by-pass ( even though I thought Ecotec 637 had internal bypass). Still get the banging though
 
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