Discuss Air in heating g system - Already had two plumbers fail to diagnose. in the USA area at PlumbersForums.net

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Hi all,

Hoping you can help me out.

We had building work last summer and added a few radiators on both ground first floor. We also replaced our vented hot water system with an unvented hot water system but the heating remains open with a small F&E tank in the loft.

Since the works, when the radiators come on (they are on smart Honeywell Evohome TRVs so open and close on demand) there's a lot of gargling noises from the radiator even on the ground floor. There is also a lot of annoying tapping of pipes around the house that we never had prior to the works. Finally, there is a lot of air in the radiators but I've addressed that by adding the automatic bleed valves although I'm well aware I'm only masking the problem.

I have attached two videos. One is of the F&E tank in the loft showing air coming into it. The other is the recording of the gurgling noise from a ground floor radiator when the TRV opens.

One plumber just suggested the obvious that the radiators need bleeding which I'd already done. I've put automatic bleed valves on all the radiators since I was having to bleed them every other day.

The second plumber was more thorough. He noticed a problem with the installation of the new unvented tank that meant a valve that should be open would close when the boiler overran which he thought could be the cause of the problem. We fixed that but the problem remains. He also tested the water for any contaminants which came back negative (although it did confirm the system has no inhibitor which I need to address) . Finally, he pressure tested it to make sure there are no leaks.

I put a camera on the F&E tank and noticed that every time the boiler fires up (assume also the pump) there is air being pushed into the tank. I have attached a recording if it helps. On the plus side, over 3 days no water was required to top up the tank so hopefully, that means there's no leak.

I'm not sure if it's relevant but one of the new radiators on the ground floor never really heats up. There's no air in it and I removed the TRV to eliminate the possibility of it being locked. The pipe supplying the water get's hot but the pipe exiting the radiator remains lukewarm at best. I've tried opening it all the way up and then closed it slightly each day but it makes no difference. I'm wondering if the is a blockage on the return and I'm wondering if that could be related to the air in the system. My logic is the pump fires up and is immediately met with resistance which causes the burp in the F&E tank. There's no science to my logic so may be complete nonsense.

Lastly, the condensate pipe on the boiler (Worcester bosch 32 CDI about 18 months old) does seem to be dripping constantly when running. My understanding is that it should fill to a specific level and dump the entire lot rather than have a slow drip. Again, not sure if it's related but thought I’d mention it.



Any thoughts?

Thanks in advance
 

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Sounds like the might of messed around with the feed and vent position
 
Yeah I would have done. Especially with the extension etc.

Surprised many don't fit a system boiler these days on replacing a Heat only. I hardly do any Heat onlys these days...

normally the same price tbh I like heat onlys as I can size my expansion vessel correctly and there’s no special parts eg prv or pump block etc
 
It looks like there is something wrong there for a long time judging by the condition of the F&E tank.
Can you post a photo of your vent and cold feed arrangement as sometimes a simple modification can cure the problem.
Also sometime your pump model and settings.
 
normally the same price tbh I like heat onlys as I can size my expansion vessel correctly and there’s no special parts eg prv or pump block etc
The way I look at it, that's all covered under the manufactures warranty if anything fails. Usually for 10 years these days. And as you say they're usually the same price nearly.

Agree with the expansion though, I usually add on additional.
 
Thanks for the replies. Here are some photos of the unvented tank and components around it. I have also attached a vid up in the loft showing the feed and vent pipes and a few photos. At the end of the video, the pipes drop down to the airing cupboard (hot water tank).

I considered sealing the heating system when we replaced the vented tank, but it was spending money on something that to my knowledge at the time provided no additional benefits. The heat-only boiler was replaced before we considered the extension, so we never considered an alternative (the old one died on us so we just needed a new one asap). We also have very high water pressure coming into the house (6 bar which I assume you’d have to limit) which is great for showers but scares me a little connected to a 25-year-old heating system. If I was to replace the open system with a sealed system am I not just masking the underlying problem? Would the air currently going into the F&E tank instead just trigger the pressure release valve?

John.g – you said it looks like there’s been something wrong for a long time based on the condition of f&e. Can you elaborate a little? There’s a thin layer of sludge at the bottom but other than that it looks ok to me.

Thanks again.
 

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