I've made a quick video with my phone of the issue:
formatting link
(20 secs)
The noise isn't that loud in the vid, but you can get the jist of it. If I open the valve full, the noise goes, but turns up later at another rad. The y generally only make a noise when the TRV's are closing as the room is war m, and it only affects upstairs rads.
I have an open vented system, running off a Glow-worm micron 50FF. If I tur n the pump speed down, the noise abates somewhat, but the boiler starts ket tling as the flow is too slow.
I'm guessing the problem is air, or my TRV's are crap. If it is air, what d o I need to do to get rid of it?
I open the valve full, the noise goes, but turns up later at another rad. T hey generally only make a noise when the TRV's are closing as the room is w arm, and it only affects upstairs rads.
urn the pump speed down, the noise abates somewhat, but the boiler starts k ettling as the flow is too slow.
do I need to do to get rid of it?
I should have also stated that when I vent the rads, I never get any air ou t of them.
One directional valves *normally* have an arrow on them somewhere, and you can work out which way the flow goes by feeling each end of the radiator when the system is first turned on.
I used to get a similar noise in one radiator. I used to expect to be able bleed a lot of air out - but there never was any. Different boiler now - TRV fitted and I don't hear it now. It used to sould like lumps of stuff going through the valve!
It certainly sounded like bubbles to me but the o/p said no air on bleeding.
It is an open system so low pressure and perhaps it's cavitation as flow passes through the closing TRV orifice. In that case maybe throttling the lockshield down a bit will reduce the pressure drop across the TRV and perhaps reduce the cavitation.
I see from the video that the valve is supposedly bidirectional (double ended right angled arrow) but it may have a preferred flow direction which for that one I'd suggest is correct if that is the hot end of the rad and that the pipework at the lockshield end is cooler (perhaps only marginally).
I open the valve full, the noise goes, but turns up later at another rad. They generally only make a noise when the TRV's are closing as the room is warm, and it only affects upstairs rads.
turn the pump speed down, the noise abates somewhat, but the boiler starts kettling as the flow is too slow.
do I need to do to get rid of it?
I had that problem once, the valves produced a really loud hammering sound as they closed which could be heard throughout the flat (conducted along the pipework). In fact the vibration was so severe that it shook one of the valve nuts loose so the radiator started dripping! Turned out the plumber had connected up the in and out pipes to my new boiler the wrong way round.
The noise isn't that loud in the vid, but you can get the jist of it. If I open the valve full, the noise goes, but turns up later at another rad. They generally only make a noise when the TRV's are closing as the room is warm, and it only affects upstairs rads.
I have an open vented system, running off a Glow-worm micron 50FF. If I turn the pump speed down, the noise abates somewhat, but the boiler starts kettling as the flow is too slow.
I'm guessing the problem is air, or my TRV's are crap. If it is air, what do I need to do to get rid of it?
Thanks!
Cavitation is a possibility. Steam/vapour bubbles appear and disapppear as pressure varies in different parts of the system. (Usually at restrictions eg valves and pumps) "Negative" pressure can appear so that the water boils at lower temperature. The clue is that it is worse when the sytem is hot.
The noise isn't that loud in the vid, but you can get the jist of it. If I open the valve full, the noise goes, but turns up later at another rad. They generally only make a noise when the TRV's are closing as the room is warm, and it only affects upstairs rads.
I have an open vented system, running off a Glow-worm micron 50FF. If I turn the pump speed down, the noise abates somewhat, but the boiler starts kettling as the flow is too slow.
I'm guessing the problem is air, or my TRV's are crap. If it is air, what do I need to do to get rid of it?
Thanks!
Reading your post again, cavitation seems quite likley. The phenomenum occurrs when water pressure/head is too low. You have an open vented sytem and it's worse upstair wher epressure is lowest.
So the problem may be due to low head, your loft tank is not high enough above the highest radiators or your pipework is on the small side meaning the pump has to be turned up high so causing these pressure differences leading to cavitation.
The cure is to move the tank higher or convert to pressurised system. Sometimes moving the pump to the flow side of the boiler fixes the problem but this depends to a degree on the boiler design/size of waterways. In days of yore, the pump was one the return side of the boiler which promotes cavitation but boilers had bigger waterways then and pipework was bigger.
I did put plenty of Fernox inhibitor in when I last drained the system down and filled it.
I fitted a Spirotrap last year after I spent a weekend descaled the system using Fernox DS40 cleaner. I was having a lot of trouble with kettling in the boiler.
Would an auto-venting rad bleed valve suffice, or should I fit something more like this?:
It's been one thing after another with this heating system. Among other thi ngs, I removed an air separator and amended pipework near the pump last yea r as it was very tight and I was concerned it was restricting flow, causing /contributing to kettling in the boiler. I'd like to fix this issue in one move if possible.
There's only a couple of inches of water in the header tank when cold (whic h itself it only about four feet above the hot water tank). There's not muc h space to raise the tank in the attic, would raising the it a foot or so m ake much difference? Or should I just go for it an convert to a sealed syst em (I am nervous about it exposing weak joints in the pipework)? Could conv erting to a sealed system introduce other issues?
It's been one thing after another with this heating system. Among other things, I removed an air separator and amended pipework near the pump last year as it was very tight and I was concerned it was restricting flow, causing/contributing to kettling in the boiler. I'd like to fix this issue in one move if possible.
There's only a couple of inches of water in the header tank when cold (which itself it only about four feet above the hot water tank). There's not much space to raise the tank in the attic, would raising the it a foot or so make much difference? Or should I just go for it an convert to a sealed system (I am nervous about it exposing weak joints in the pipework)? Could converting to a sealed system introduce other issues?
Thanks
Kettling is a form of cavitation but caused by localised hot water temperatures made worse by pumping pressure reductions Steam bubbles form and collapse which is what you hear. A couple more things to check to reduce restrictions. Isolating valves on the pump fully open ditto on boiler if fitted. You might try rebalancing the system starting with all lockshield valves fully open and closing them the minimum amount. You might be able to rebalance the system and reduce the pump speed so curing the problem. Zone valves/other motorised valves may not be fully opening. You are trying to eliminate all negative pressures in the system by eliminating restrictions.
Probably though the root of the matter lies in the boiler, it may be a replacement for one with much bigger waterways.
Re how much to raise the tank? Anything would help but a small amount may not be a total cure. A foot "head" of water=0.43psi Probably your best bet is to convert to sealed system and you can up the pressure 'til the problems go away.
Pity really, it's added expense and something else to go wrong. You can get a kit that includes the pressure relief/safety valve, tun dish and the expansion vessel. You'll have to site it where you can you can arrange a drain for the SV outlet.
I think I may well look more into converting to a sealed system. My underst anding is that by converting, I am removing the ability for the heating sys tem to create negative pressure, therefore remove the chance of cavitation, increasing flow and eliminating rad valve noise? Is this correct?
Tom Pickles wrote in news: snipped-for-privacy@googlegroups.com:
The "cavitation" expalnation fits with the situation I had. The noise was from a turned down lockshield (on the fastest radiator). Since having a sealed system it has not been an issue.
I think I may well look more into converting to a sealed system. My understanding is that by converting, I am removing the ability for the heating system to create negative pressure, therefore remove the chance of cavitation, increasing flow and eliminating rad valve noise? Is this correct?
I open the valve full, the noise goes, but turns up later at another rad. T hey generally only make a noise when the TRV's are closing as the room is w arm, and it only affects upstairs rads.
urn the pump speed down, the noise abates somewhat, but the boiler starts k ettling as the flow is too slow.
do I need to do to get rid of it?
I thought I'd post an update on this. After doing some research into conver ting my system into a sealed system after recommendations from replies in h ere (thanks all), it seemed like quite a lot of work with the prospect of c reating leaks in the plumbing, and it wasn't giving me a sense of confidenc e. So I did some rooting about on the net and found these:
formatting link
Managed to grab a brand new one off eBay for 80 quid delivered.
The ideal place to fit them according to the instructions is on the flow pi pe, as near to the boiler as possible. So that's what I have done, and the results are exactly what I wanted. No more air in the system, no more noise , and hopefully a little increased efficiency.
Took me about an hour to fit including draining down and refilling. For the first few days you could hear it regularly venting large amounts of air. I t has now calmed down and you can occasionally hear it let out a little air .
I thought I'd post an update on this. After doing some research into converting my system into a sealed system after recommendations from replies in here (thanks all), it seemed like quite a lot of work with the prospect of creating leaks in the plumbing, and it wasn't giving me a sense of confidence. So I did some rooting about on the net and found these:
formatting link
Managed to grab a brand new one off eBay for 80 quid delivered.
The ideal place to fit them according to the instructions is on the flow pipe, as near to the boiler as possible. So that's what I have done, and the results are exactly what I wanted. No more air in the system, no more noise, and hopefully a little increased efficiency.
Took me about an hour to fit including draining down and refilling. For the first few days you could hear it regularly venting large amounts of air. It has now calmed down and you can occasionally hear it let out a little air.
Hope this can help someone else in the future.
The problem you have is cavitation. Steam bubbles forming and collapsing due to the reduced pressure in the system caused by the pump. The system is a bad design. You might get round the problem by fitting a bypass valve which opens as TRVs close.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.