unvented cylinder bang/crack noise

[williams85]

I installed a Gledhill 250L indirect unvented hot water cylinder which is making a bang/crack noise when the hot water is drawn from a tap. It wont happen all the time, so there is no real pattern as to when it happens? This is the second cylinder (of the same model) to behave like this at this property. The original cylinder I exchanged thinking it was faulty. I sent it back the manufacturers who tested it and claimed it was in fine, which at the time I found hard to believe. However, now the replacement is doing the same thing I have been forced to realise that there must be something else that is causing a problem. I have exhausted all the possibilities I could come up with, this one has got me stumped, any ideas?

 

[picasso]

My first thought was sticking nrv, did you change the cold water controls when you changed the cylinder and lastly what size expansion vessel are you using?

 

[CBF]

more importantly do you have the G3 cert to install unvented ? if not you are breaking the law

 

[mickyg]

i told you the problem and solution on the other thread. You haven't said what the dynamic pressure is, but I will bet its quite low, at least lower than 2bar

 

[williams85]

I didn't change the cold water controls when i swopped the cylinder, so a sticking nrv could be possible?
The expansion vessel is a 24L plus i fitted a 12L

 

[williams85]

I certainly do have the G3 cert thanks CBF

 

[williams85]

I know you posted your solution and explanation on the other thread Mickyg but I made this thread before I found the other thread who had the same problem as me.
Im not sure what the dynamic pressure is, with the problem being last year I cant honestly remember what the results were?

 

[dcawkwell]

The expansion vessel isn't matched to your incoming mains pressure causing hammering.

 

[picasso]

If it was allowed I would suggest you put a better cold water control set, but as its not I wont.

 

[mpcaine]

Hello, I have read about the "hammering" noise from your Gledhill cylinder and wondered if you had ever got to the bottom of it?? I am experiancing exactly the same with a new system installed in March this year. only happens when H/W tap or shower is used and is random (typically AM or PM once the system has been left a while). Plumber has fitted pressure control values on the feed and outputs but still does it..... been advised that it must be the quarter turn taps and the solution is to "turn them on slowly".... not quite how i am prepared to manage the situaiton... friends of mine have had many pressurised systems and never experianced this... and the noise is quite load... not good with a family and 5.30AM showers!!

Any tips, advice or suggetstions appreaciated.

M

 

[Coluk0]

I had the same problem with my Gledhill unvented cylinder each time I turned a hot tap on I got a loud bang from the cylinder/pressure vessel it was loud enough to hear through the house. The problem I believe is the size of the flexible hose coming from the pressure vessel to the combination valve. It seemed to be a very small inside diameter for pressure to be released through I changed mine to a 22mil plastic/copper pipe and it worked a treat no banging noise at all. Hope this helps.

 

[Richardthe3rd]

The expansion vessel isn't matched to your incoming mains pressure causing hammering.

This will generally cures the problem.

An eminent member 'doitall', if I recall correctly, advocates the siting method adapted by Ariston;

http://www.advancedwater.co.uk/STOMEMO/A022-088-5002/Ariston Unvented Installation Guide.pdf

 

[PcxP]

Aware this thread is old but had the exact same crack/bang not long after water was drawn (typically after 2 concurrent showers). As my Gledhill tank is in the loft above my bedroom was easy to hear and time the noises.

The original installer reviewed and could not identify the cause. However, when this installer showed disinterest in returning to service his installation and another engineer came to service instead, he stated the filling tap/flex loop was fitted the wrong way around. After switching around the filling loop, I noticed the pressure in the heating loop/supply no longer needed periodic topping up (now still at 1 bar since May). It may be that the tap with the non-return valve was on the “wrong side” (there are two taps on the filling loop, they are slightly different shapes). Other than topping up on inhibitor in the loop, no other adjustments were made.

After these changes/service items, the bang/crack stopped.