Still Got Noisy TRVs - Should I Turn Pump Down On Combi?

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Following on from my earlier post - //www.diynot.com/forums/viewtopic.php?p=1200092#1200092

System - Glow Worm 30 cxi combi in bungalow loft.
4x medium sized rads & 2 small rads.
TRVs on all rads, except hall rad.

Problem - As the TRVs on some rads that are on a lower setting than some of the other TRVs start closing, the TRVS on the rads that are still open start hissing loudly. Even If I have the heating on with all TRVS set to max, after 20 mins or so, a few of the TRVS start hissing, although not so loudly as the previous situation.

Am I right in thinking that is is quite a powerful boiler for a small number of radiators? It seems that as some TRVs close, the pressure in the system increases causing hissing noise as the water passes through TRVs that are open.

Someone suggested turning the boiler pump down, will this help? Can I do it myself?

Alternatively, is it the TRVs that are at fault? They are a budget (caleffi) brand.

Any suggestions would be appreciated.
 
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nothing wrong with caleffi trvs however mine hiss since i removed the autobypass so that is your best bet, however reducing pump speed may help but might upset the boiler in hw mode
 
I cant think of a combi where the pump should be on anything other than maximum speed. It needs to be at its fastest to allow maximum heat transfer to the hot water circuit.
Caleffi are on the naff side but I am not going to guarantee that if you pay more money for more reputable valves that it will clear the problem.
A bypass is the best way out of your problem. Whether you can achieve this by using your hall rad or by fitting an automatic bypass or a bit of both is an unknown quantity affected by factors such as the resistance of your rad circuits, the layout and pipe sizes of your system
 
Your boiler already has an integral by-pass so let`s not go there, change your cheap TRV`s. ;)
 
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just pointing out that the solution to the problem has been suggested to fit a bypass. I am merely pointing out that this particular boiler already has a bypass.

Howcome most other people who post here can make a point without being abusive. As it happens you do have a point. There is a by-pass, but think a little harder and you could decide that this by-pass may be blocked.
If you exerted your intelligence towards helping people rather than being abusive this forum would be a better place for people in need of advice to come and get it.

As for resistances of pipework etc. is all just a smokescreen from a div who probably hasn`t installed a system in his life.
Well pipework resistance was there as a subject when I got my advanced craft and again when I was at university. You really have shown yourself up for the buffoon that you are now as any fully qualified plumber should be familiar with the concept.

Don't even bother replying now as I am going to make use of the ignore button
 
Oh dear, I seem to have stirred up a bit of a hornet's nest here. I really do appreciate your answers and the fact that you have all given your time to help.

The hall rad is a bypass rad as it has no TRV.The stat is also in the hall.

When Cider says- 'nothing wrong with caleffi trvs however mine hiss since i removed the autobypass so that is your best bet, however reducing pump speed may help but might upset the boiler in hw mode' - Is it worth trying to turn the pump down to see what happens? If yes, how?

Someone has suggested the boiler's own bypass may be blocked - how do I check and unblock?

If the boiler has it's own bypass, and the hall rad acts as one too, is it worth fitting another bypass?

Would fitting wheelhead valves instead of TRVs on the worst affected rads help reduce the noise?

Any other suggestions would be appreciated.
 
The problem you have here is trying to reduce the flow through noisy rads by the cheapest and easiest method without any major contravention of 'plumbing rules'
Options open to you are

1 Follow Dhailshams advice and adjust the internal bypass. Not something I have had cause to deal with but it should be all there in the instructions.

2 Use the hall rad which has no TRV's I believe as a by-pass by opening the lockshield valve a bit more. Easy & cheap way so long as you can do it without upsetting the balancing of your system. Its also the way it would have been dealt with in the days before Auto bypasses were 'on the scene'

3. Under current practices fitting an automatic bypass would be the best official answer which all systems should now have [even some with built in bypasses specify that in certain situations an external bypass should also be fitted]. This would be a positive solution and easier and cheaper than delving into a boiler that is notorious for crap hydraulic parts and leaking o rings. But what if the AAV doesnt open before the noise starts? well you can reduce the pressure required to open the valve down from the recommended 0.3 bar as these are adjustable. Seeing as you like listening for noises this has a moving part inside and could potentially have a noise of its own.

4 Spend money and fit new TRV's. At the end of the day the valves are opening according to the demand of the TRV head and its likely that any new valve may have to let exactly the same amount of water through as the old one. The design of more upmarket valves may mean that there is some provision for noise reduction. Can the upmarket manufacturers really be so high tech about the way a jumper closes against a valve seat? Perhaps, but I doubt it.

Basically the posts earlier on the previous thread were on the ball I'm just here to make sure we outnumber the idiot. Tony has a point about the boiler being range rated. The industry standard is to set boilers to 55kbtu but your requirement may be only about 35. Correct range rating will increase the lifespan of several boiler components.

Some people are fussier than others about balancing. My view is to deal with it only when it is causing a problem.
 

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