Gurgling boiler + Air in CH + FE tank

[SJB060685]

I don’t do plumbing, I leave that to others, I prefer oil fired appliances. However there is a formula for working out the height of vent. I tried looking back through my college books but couldn’t find it, I did find a post on this forum about it though from a number of years ago.

Height of vent above water in CWST = height (metres of static head) x 40mm + 150mm

This result is the height in mm the vent should terminate above level of water when the system is cold.

That sounds similar to what I remember.
Your vent being below water line is not installed correctly.

 

[John.g]

To get over the problem of pump over through the vent (pitching) or back up through the cold feed (in vented boiler heating systems) various systems are used, mine, (from new, 42 years ago), has a combined feed&vent and never had a problem)

 

[SJB060685]

I’ve heard of combined feed and vent but never seen one. I know they’re supposed to prevent pumping over but I know they are prone for trapping air on initial filling

 

[John.g]

I have a 1/2" gate valve on the ball cock supply, I just barely crack it open when filling my system, it might take 40 minutes or so to fill the system but I have very few problems by doing this.

 

[spatel]

I’ve heard of combined feed and vent but never seen one. I know they’re supposed to prevent pumping over but I know they are prone for trapping air on initial filling

Thanks to you and John for engaging with me and for all your help. I have attached some images of my system in the loft. What I noticed when taking pics was that bubbles popped up from the F+E cold feed. Am not too sure if this should be the case or not and whether this explains why the F+E tank has got dirty again given I gave it a thorough clean 2wks ago. In any case from the pics, it looks like a traditional system though can't rule of they combine lower down. I can't make heads or tails from the piping in airing cupboard. The exposed copper pipes I think feed into the 2 showers we have upstairs. I would imagine that another 2 should be air vents for the F+E and the CWS tank.
Would be great to see what you think. Cheers.

 

[SJB060685]

You shouldn’t have air coming back up the feed. Also the overflow outlet in F+E tank looks too high. As for the pictures it’s hard to make out the pipework, without seeing it first hand I couldn’t be sure

 

[John.g]

Thanks to you and John for engaging with me and for all your help. I have attached some images of my system in the loft. What I noticed when taking pics was that bubbles popped up from the F+E cold feed. Am not too sure if this should be the case or not and whether this explains why the F+E tank has got dirty again given I gave it a thorough clean 2wks ago. In any case from the pics, it looks like a traditional system though can't rule of they combine lower down. I can't make heads or tails from the piping in airing cupboard. The exposed copper pipes I think feed into the 2 showers we have upstairs. I would imagine that another 2 should be air vents for the F+E and the CWS tank.
Would be great to see what you think. Cheers.

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Concentrating on the Boiler & F&E system, you show the pump pumping through the M.filter and then into the boiler, you are also showing another (green) pipe Teeing into that just before the boiler, is this the cold make up do you think?, it would normally (but not necessarily so) be of smaller diameter (1/2") than the pipe (3/4") its joining. Vent Pipe: It should be relatively easy to follow it from the attic down through the attic floor and see it it is in fact Teed off the hot water cylinder coil top entry.
Also can you confirm that the lever valve is on the same bit of piping as the MV and that the MV is feeding the coil top entry.

Have you opened the lever valve fully?

Is the pump now on speed 1? and if so what effect if any has it had on boiler cycling etc.

Note: IF the cold feed is Teed in at the boiler entry then its possible that the boiler H.exchanger has become partly fouled and the pump is now forcing water up through the cold feed and into the F&E tank (hence bubbles) but someone will have to ensure that it is in fact plumbed in this manner.

 

[John.g]

When/if you do run on speed 1, have a look into the F&E tank for any "movements".

 

[spatel]

Concentrating on the Boiler & F&E system, you show the pump pumping through the M.filter and then into the boiler, you are also showing another (green) pipe Teeing into that just before the boiler, is this the cold make up do you think?, it would normally (but not necessarily so) be of smaller diameter (1/2") than the pipe (3/4") its joining. Vent Pipe: It should be relatively easy to follow it from the attic down through the attic floor and see it it is in fact Teed off the hot water cylinder coil top entry.
Also can you confirm that the lever valve is on the same bit of piping as the MV and that the MV is feeding the coil top entry.

Have you opened the lever valve fully?

Is the pump now on speed 1? and if so what effect if any has it had on boiler cycling etc.

Note: IF the cold feed is Teed in at the boiler entry then its possible that the boiler H.exchanger has become partly fouled and the pump is now forcing water up through the cold feed and into the F&E tank (hence bubbles) but someone will have to ensure that it is in fact plumbed in this manner.

Thanks for your reply,
So the green pipe which connects the pump to the M.Filter tees into the boiler and goes up somewhere. I have noticed today that after having the HW on this morning that the Green piping above the M.Filter was quite warm. Interestingly the black piping adjacent to the magna filter was cool. However, feeling the same black pipe teeing off to the boiler this is was as warm as the green pipe.
But When I put the CH on, the green pipe near the magna filter went cold and the Black pipe next to it went very hot!
When the boiler is switched off, there is a tapping noise from the M.filter (almost like when something is cooling down) and the black pipe. A few minutes later, when the pump turns off, there is water swooshing noise the from the M.filter that then goes up the black pipe. This same swooshing noise occurs when the boiler and pump are restarted.
In terms of the Vent pipe. I can't seem to follow it down (too many pipes, I get lost which it is). My feeling is that it is the same one that is connected to the M.Valve in the Airing cupboard, connected to the HWC. And yes, the lever valve is on the same bit of piping as the MV. I don't know how to tell if the MV is feeding the coil top entry??
Turning the pump to 2 has not really changed much. In fact I have noticed that the HW does not cause the boiler to fire up as frequently. so there is a period where the HW flight is lit but there is no action from the boiler. But when it does come on it short cycles like crazy. Almost every 30secs, the boiler will come off and on again and then the will be this almost cool down process from the boiler (no overheating sign ) as you can hear it making a tapping noise. I am very concerned that all of this is knackering out the boiler. Is the heat exchanger the root cause or the damage to it a consequence of whatever is happening to the CH/HW system? I had the boiler service 2 wks back and he said that it is functioning fine (with a slight kettling sound though not to worry at this stage). I will try the pump today at 1.
Thanks!

 

[John.g]

Those pipes getting hot & cold is fairly normal depending on whether HW or CH is selected, the green pipe teeing off above the boiler (cold feed) is the one to feel as high up above the boiler as you can reach, this should stay cold/cool, if its hot then it means that water is being pushed back up the cold feed which it shouldn't.

Re cylinder MV, just to the right of this you will see a very short piece of pipe going into the cylinder, this is the supply to the top of the internal coil in the cylinder, can you just follow this back a few inches and see if the MV & the lever valve are on same line?

I would suspect the boiler H.exchanger but obviously just don,t know, the pump should also be removed and checked for port blockage and the impeller might also be full of crap. If your plumber tomorrow has a similar pump with him, he might just install it even temporarily to see what effect this has. I have read that even though a pump shaft/impeller may be revolving that it may not be running at its rated speed/output hence the advice to rule out any pump problem, however improbable.

I have included a (poor) photo of my cylinder MV, if you look closely to the left of the MV you will see the vertical pipe (T piece) carrying on up, this is the vent pipe in my case.

 

[John.g]

Another question (will they ever end), when you were circulating the chemical cleaner for two weeks, I assume the heating system was i/s, any problems during this period or did they begin after drain down and refill with inhibitor?.

 

[spatel]

Another question (will they ever end), when you were circulating the chemical cleaner for two weeks, I assume the heating system was i/s, any problems during this period or did they begin after drain down and refill with inhibitor?.

Thanks Jon,
I will check tonight about the piping around the MV connected to the HWC. Whilst the chemical cleaner was in place, the heating was working though with its own problems. As soon as the CH was turned on there was the trickling noise from the rad closest to boiler (lock shield side) and knocking noises from the rad in the living room that took longest to heat ( it is very long and big rad and one that we suspected had issues as was hot at top but cool at bottom : a new TRV was installed as the old pin looked a bit stuck). Since the drain and refill, the trickling noises sounds worse from that kitchen rad closest to boiler and the knocking noise exists not only in the living room but also another rad downstairs in toiler. I have had to constantly (everyday) bleed air in one rad upstairs (suspect it is the first rad that heats up upstairs?). I thought it was getting better with the chemical feed (bleed once every 2days) but now seems back to the usual bleed everyday. This rad is hot at the TRV side (top-hot bottom-cool) but not at the lock shield side (cold top+bottom). Once air is removed, rad is blazing hot. When I try to close down the TRV (from 4 to 2), a constant trickling noise can be heard at the TRV side (disappears when back to 4 setting).
So yes the CH has issues too! Plus the furthest rad from the boiler downstairs not heating up well at all, hot at top and cool at bottom. Plumber thinks that a kink might have introduced when he was working on it and there that might be restricting flow (but hopefully not a leak! pipes are under concrete floor!).
Any thoughts on the rads?
I must say prior to any works being conducted all rads worked really well (apart from living room rad which took longer but did get hot in the end). All heated up well. Since the work, the dining room rad is the one that is suffering most, and now air trickling noises and knockings from rads. The knocking in living room continues even hrs after switching off the CH system.

 

[John.g]

Afraid I am clean out of ideas, lets see what your plumber says tomorrow?.

 

[spatel]

Afraid I am clean out of ideas, lets see what your plumber says tomorrow?.

Sure no worries John.Thanks for all you help and suggestions. Really appreciate it.

 

[John.g]

Final say before "D" day tomorrow, IMO that lever valve is a balancing valve on the hot water coil, to give a reasonable cylinder warm up time but divert as much water as possible to the CH when both systems are calling for heat. They are often fitted in the form of a gate valve on the return of the coil and were always fitted in systems with no zoning.

 

[spatel]

Final say before "D" day tomorrow, IMO that lever valve is a balancing valve on the hot water coil, to give a reasonable cylinder warm up time but divert as much water as possible to the CH when both systems are calling for heat. They are often fitted in the form of a gate valve on the return of the coil and were always fitted in systems with no zoning.

Thanks John!
In terms of plumber #2 tomorrow.
Just wondering how to strategically unload the info to him and how he should investigate in what order.
1. Boiler (whooping noise)
2. Look at piping system around boiler (determine what goes where)
3. Trickling noise from the Rads
4. Air in system
5. Blocked pump
6. Blocked cold feed
7. Condense vent block
8. f+E tank levels
9. Cold water tank feed

Sounds reasonable? Thanks!

 

[John.g]

1A. Boiler heat exchanger blocked.

 

[spatel]

1A. Boiler heat exchanger blocked.

Thanks!

 

[John.g]

Hope you are sorted, there is a very interesting thread here of a few months ago "Air problem in open vented system after boiler change"

 

[spatel]

Hope you are sorted, there is a very interesting thread here of a few months ago "Air problem in open vented system after boiler change"

Thanks John for asking but no unfortunately not. Plumber #2 was a nice chap with clear experience and knowledge but said that the fault could be at one or many places! So none the wiser unfortunately.
One thing he did say was that it would be good to rule out a leak that could be the root of the problem. Suggested that to tie of the ball cock of F+E tank, mark the level and the see where it is a few days time. Use immersion water during that time. If it isn't a leak, he suggested that there could be a block of cold feed (green piping in my diagram) just above the boiler (I think you called it the top up). He seemed to think that of there was a block it would be there. So he said to cut the pipe above the M.filter and the top, and clean/replace that bit. Alternatively, to try a magna flush piping kit to get rid of any crud. The other things he said was a noise reducer for the boiler, an air vent valve near the motorised valve close to the lever of the HWC. Finally to consider making it a sealed system. So lots of ideas but of course, its hard to know which step to take! I did ask about the heat exchanger and he said that it could be but then you might as well change it all!
Whilst he was here he did notice the trickling noise in the rad closest to the boiler and said could be pieces of debris stuck. Then he saw the new TRV on it and when he took it off and pressed on the pin, it started hammering and said that was not right.
So will need to see what can be done about that!
In any case, I shall read the thread you mentioned as it sound a similar story to mine (hopefully with a favourable outcome!!). Thanks for your help John!