Air in heating g system - Already had two plumbers fail to diagnose.

[Quinla01]

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

 

[EvilDrPorkChop]

Photo of the Unvented? With a picture of the pump and motorised valves etc. I assume they're all in the airing cupboard?

 

[ShaunCorbs]

Sounds like the might of messed around with the feed and vent position

 

[EvilDrPorkChop]

Sounds like the might of messed around with the feed and vent position

That was my thoughts too.

 

[ShaunCorbs]

That was my thoughts too.

im surprised they didn’t seal it tbh

 

[EvilDrPorkChop]

im surprised they didn’t seal it tbh

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...

 

[ShaunCorbs]

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

 

[John.g]

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.

 

[EvilDrPorkChop]

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.

 

[Quinla01]

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.

 

[Quinla01]

Photo of the Unvented? With a picture of the pump and motorised valves etc. I assume they're all in the airing cupboard?

Thanks, See the latest post.

 

[ShaunCorbs]

The air is being sucked in via the vent so if you seal it the air wouldn’t get in also you would run it at a pressure of 1 bar not 6

you’ve said you had it pressure tested for leaks so in theory the system would be ok sealed

try turning the pump speed down to 2 it’s on 3 atm

 

[Quinla01]

The air is being sucked in via the vent so if you seal it the air wouldn’t get in also you would run it at a pressure of 1 bar not 6

you’ve said you had it pressure tested for leaks so in theory the system would be ok sealed

try turning the pump speed down to 2 it’s on 3 atm

The guy pressure tested it at 2 bar. He said he didn't want to go any higher just in case.

I already turned the pump down to 2 and it made no difference. I turned it up to 3 hoping it would address the cold radiator issue I mentioned in my original post. It didn't.

 

[ShaunCorbs]

You would be fine sealing it then

 

[Quinla01]

You would be fine sealing it then

Yes. I never knew they run at 1 bar. But is that really the solution? And again, is it not just masking an underlying issue that may come back to bite me even with a sealed system?

 

[ShaunCorbs]

If it’s sealed no air can get in

 

[John.g]

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.

There should be no sludge of any description in that tank.
I had a look at your attachments but you can inform easier on your set up, Is the pump on the flow from the boiler and if so the accepted way of installing the vent and feed is (from the boiler) vent, cold feed then pump with the vent and cold feed no more than 150MM apart, if not like this you might show where the cold feed tees into the system.
Another way and better IMO is to have a combined vent and cold feed like my > 40 year old system which is spotless.
You can convert to a sealed system obviously or convert to the combined vent & cold feed which only needs a few litres of water drained down and almost guaranteed success, just ensure the vent is clear, the insulation looks kinked on it but I presume the actual vent isn't.

 

[ShaunCorbs]

Think it’s combined feed and vent atm pipe off the top of the h

 

[John.g]

Could be, and if so then points to some blockage somewhere but far better to combine high up like mine as the cold feed "can't" have a blockage and as long as the vent is absolutely clear cannot vent or pump back.

 

[Quinla01]

Getting a bit over my head now but I think it is combined if this (attached photo) is what you mean. The tank has never moved and we never had any problem prior to the installation of new radiators and replacement of the vented cylinder.

A blockage has been mentioned a few times. Which part of the system is likely to have the blockage? Could it be related to the lukewarm radiator (one of the new ones on ground floor) I mentioned in the original post? All other radiators work absolutely fine now I've added the automatic air release valves even with the pump on the medium settings so the hot water is moving about.

Thanks again.

 

[ShaunCorbs]

If you turn let’s say 5 off does that one heat up ?

 

[John.g]

Getting a bit over my head now but I think it is combined if this (attached photo) is what you mean. The tank has never moved and we never had any problem prior to the installation of new radiators and replacement of the vented cylinder.

A blockage has been mentioned a few times. Which part of the system is likely to have the blockage? Could it be related to the lukewarm radiator (one of the new ones on ground floor) I mentioned in the original post? All other radiators work absolutely fine now I've added the automatic air release valves even with the pump on the medium settings so the hot water is moving about.

Thanks again.

It certainly looks like that (circled) the cold feed is clear I would think judging by the bubbling, can you just blow down the vent and see does it bubble up in the tank.
Where is the vent teed into your system?.

Just ensure it hasn't been changed and taken off close to some motorized valve or on the wrong side of it.
There also seems to be another pipe directly across from that cold feed on the other side of the tank?? (See video)

 

[Quinla01]

If you turn let’s say 5 off does that one heat up ?

No. If I turn all the radiators off in the house and have the pump on 3 it doesn't heat up any more than having them all on. There is some heat getting to it but I'd say on a scale of 1-10 it's 3. It's in the kitchen and luckily I over specced how many radiators we have in there so we have two radiators that do work that just about keep the room warm. See (crude) drawing below. The radiator that's not heating is at the end of the run and feeds back to another new radiator that does work. That then feeds upstairs to a towel radiator which also works. The towel radiator was the first new radiator they connected so it links into the existing system somehow but I'm not sure where. One other data point, during decoration someone put a screw through one of the pipes about 1m away from the problematic radiator. We had a bathroom fitter on-site at the time who quickly bunged the tank, cut at the point of screw entry, and then somehow joined the two pipes. Not sure if maybe that has somehow caused a blockage. If so I suspect it's on the return since when I've released the bleed valve on the problematic radiator and opened the TRV there's no shortage of pressure spraying water out and also the feed pipe gets a lot warmer than the return end.

 

[ShaunCorbs]

Any chance of a pic of the problem rad and pipework ?

 

[Quinla01]

It certainly looks like that (circled) the cold feed is clear I would think judging by the bubbling, can you just blow down the vent and see does it bubble up in the tank.
Where is the vent teed into your system?.

Just ensure it hasn't been changed and taken off close to some motorized valve or on the wrong side of it.
There also seems to be another pipe directly across from that cold feed on the other side of the tank?? (See video)

I'm pretty sure it's the one I've marked below. Not sure if it's expected but where the pipe joins the system very warm and gets gradually cooler to the point of being room temperature towards the ceiling where it goes into the loft.