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Discuss Gurgling boiler + Air in CH + FE tank in the Boilers area at Plumbers Forums
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!
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.
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.
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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.
Sure no worries John.Thanks for all you help and suggestions. Really appreciate it.
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!
Thanks!
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!
Re possible blockage of cold (green) feed at boiler, if you feel this as high up as you can it may be warm as you did see bubbling in the F&E tank.
No simple answer then. Could you run the circ pump for a extended period (would need separate supply) with boiler off and see if noise persists.
No simple answer then. Could you run the circ pump for a extended period (would need separate supply) with boiler off and see if noise persists.
How could one one run a pump without the boiler on?
Also, I have noticed that when the pump turns off whether on with CH or HW, the water levels go down quite significantly in the F+E tank. When the system is turned on again, water levels start to rise.
The wiring would have be removed in the pump terminal box and a live supply wired in there, before doing this the MVs should be manually opened with the lever(s) on the side(s).
The water level falling in the F&E tank (whatever the reason) would indicate that the cold feed isn't blocked as that is the only connection to the system apart from the vent. Can you tie up the ball cock as suggested by the plumber and see if the level changes over say 24 hrs, checked when system is cold, maybe first thing in the morning.
The water level falling in the F&E tank (whatever the reason) would indicate that the cold feed isn't blocked as that is the only connection to the system apart from the vent. Can you tie up the ball cock as suggested by the plumber and see if the level changes over say 24 hrs, checked when system is cold, maybe first thing in the morning.
I think the wiring of the pump is beyond my remit.
Yes. I will try out the ball cock trick this weekend. Would the receding of water from F+E tank when the pump is off is because the water is replacing the air and then when turned on again the water rises?
The rise and fall of water in the F&E tank could be caused by either a imbalance in the cold feed line and the vent or it could be caused by the air expanding in the system when it heats up and displaces the water, it would require ~ 5 litres of entrapped air (quite alot) when heated to 70C to displace ~ 1 litre of water. If the level in the C&F tank falls almost immediately on the pump starting then IMO its the former is the cause. If you check the level on boiler start up you can verify this or checking the level from a fully hot system when the pump stops.
At the end of the day all the theorizing in the world won't solve the problem, some will contend that the only real fix is to install a sealed system, if indeed that will fix it.
One compromise is the combined feed&expansion, it might/may work and only entails the emptying the F&E tank (ball cock tied up) and then drain off a litre or two and tee the cold feed directly into the vent as both are on the same left hand side of the tank, then blank off the "old" cold feed at the top, it can always be blanked permanently at the boiler at a later date if successful, it should only take a few hours.
At the end of the day all the theorizing in the world won't solve the problem, some will contend that the only real fix is to install a sealed system, if indeed that will fix it.
One compromise is the combined feed&expansion, it might/may work and only entails the emptying the F&E tank (ball cock tied up) and then drain off a litre or two and tee the cold feed directly into the vent as both are on the same left hand side of the tank, then blank off the "old" cold feed at the top, it can always be blanked permanently at the boiler at a later date if successful, it should only take a few hours.
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Thanks for the suggestion John of Teeing off the vent and cold feed. I will check this out. I did read the thread you had kindly suggested but am unsure if they ever solved their issue (which involved a much larger level of change to the system than I have). The boiler set point temperature is a gauge and not numbered. Initially it has been on quite high and I have turned it done significantly. Can't say I see any improvement to the system tbh. The short cycling still exists, air sound still trickling somewhere in the pipes and poor performance in some of the rads. I will try to set to minimum tonight. Its getting to a point where I can't see this being ever resolved but I shall persevere before considering a sealed system. I' m not inclined yet to go down this road until I am absolutely convinced that my piping will be able to withstand it. Thanks!
That thread was very interesting in that the system is fine at 65C but not at 70C, that was converted to a combined feed & expansion and it still did not solve the problem so maybe be a waste of time in your case, a leaking boiler HX was/is? the main suspect there I think.
If it (yours) was my system, I would, in view of old pipework etc, convert it to a semi sealed system, it would only entail installing a AAV on the removed vent, fitting a swing check NRV in the feed and installing a 12 litre E.vessel teed in just before the circ pump. You already will have a static system head of ~ 0.5 bar, on conversion to the above system, a 12 litre E.vessel with a pre pressure of 0.5 bar, will only rise to ~ 0.75 bar with hot system and that certainly won't pose any pipework problems.
Sealing the system and installing the E.vessel before the circ pump will almost guarantee no ingress of air, then just get rid of the entrained air.
Would also suggest removing the pump head and checking for any blockages in pump ports and the impeller, this can be done at anytime by just shutting the pump isolation valves and removing the pump head.
I was looking at the Main HE boiler manual today and it states that it has a pump overrun of 2 mins which implies that there is, or should have been, a ABV (automatic bypass valve) installed somewhere on the system, have you got one of these?, it will be fitted between the flow & return probably fairly close to the boiler, if this is fitted and is not set up properly or malfunctioning then it will cause all sort of problems as you could be short circuiting the CW/HW systems, have a good look around for this.
If it (yours) was my system, I would, in view of old pipework etc, convert it to a semi sealed system, it would only entail installing a AAV on the removed vent, fitting a swing check NRV in the feed and installing a 12 litre E.vessel teed in just before the circ pump. You already will have a static system head of ~ 0.5 bar, on conversion to the above system, a 12 litre E.vessel with a pre pressure of 0.5 bar, will only rise to ~ 0.75 bar with hot system and that certainly won't pose any pipework problems.
Sealing the system and installing the E.vessel before the circ pump will almost guarantee no ingress of air, then just get rid of the entrained air.
Would also suggest removing the pump head and checking for any blockages in pump ports and the impeller, this can be done at anytime by just shutting the pump isolation valves and removing the pump head.
I was looking at the Main HE boiler manual today and it states that it has a pump overrun of 2 mins which implies that there is, or should have been, a ABV (automatic bypass valve) installed somewhere on the system, have you got one of these?, it will be fitted between the flow & return probably fairly close to the boiler, if this is fitted and is not set up properly or malfunctioning then it will cause all sort of problems as you could be short circuiting the CW/HW systems, have a good look around for this.
Thanks John, I appreciate your advice and details for the conversion. I really just find it a little bit disheartening that it would need to go down this road when clearly the system has been in good operations for the last 4oyrs and that one set of minor work has created this imbalance!
In term of the ABV, I can't seem to see one. But from the reading online, this could be highly relevant given that TRV's have now been installed on all but one of the rads downstairs (only 2 out of 9 rads had TRVs previously, now 8 of them do). All the rads upstairs have got TRVs and not been touched. Based on this TRV, would you think that installing a ABV should be installed? and would you think that installation of a TRV on the wrong side of the rad is not good (as I think this might be the case of the kitchen rad closest to the boiler? -doesn't see to be a bidirectional one ---can't see arrows). Thanks!
I was also looking at the boiler manual just now and it mentions that existing alternative bypass is possible.
In my case, I noticed that when the HW is on, the bathroom rad and the towel railings do heat up. The Towel rail has 2 lockshields whilst the bathroom is fitted with a TRV on one side. Does this seem right to you in that this might be the alternative to the ABV?
In my case, I noticed that when the HW is on, the bathroom rad and the towel railings do heat up. The Towel rail has 2 lockshields whilst the bathroom is fitted with a TRV on one side. Does this seem right to you in that this might be the alternative to the ABV?
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