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- Thread starter Rakesh
- Start date
I would have opened the hot draw off connection on cylinder once supply water was off, before I would have opened lower taps.
Had to replace a leaking combination valve on a first floor unvented unit (valve installed wrongly at low level) and I opened the nut to top of cylinder on hot outlet.
Customer was surprised I did that, but I showed him the strong suction created by putting my hand on outlet and releasing it
Had to replace a leaking combination valve on a first floor unvented unit (valve installed wrongly at low level) and I opened the nut to top of cylinder on hot outlet.
Customer was surprised I did that, but I showed him the strong suction created by putting my hand on outlet and releasing it
W
Welder
Rakesh.
Taken to a court of law, although I cannot obvs guarantee it, I am certain the main liability would sit with those who installed and subsequently serviced this installation.
Many people think once the 12 month warranty is up they can walk away scott free. That is UTTERLY WRONG. As a professional, especially charging for a service, you have an ongoing liability for the installation.
On a seperate note, I take my hat off to you. To publically say you would take responsibility says a lot about you. You seem one of life's good guys so I, at least, will try to support you going forward.
Please keep us abreast of what happens.
Last edited by a moderator:
It's quite clear from the images it's been incorrectly fitted.
As for blame, how can you blame the person changing the taps when, the cylinder has been incorrectly fitted and two, when this is the second time it has happened.
As for blame, how can you blame the person changing the taps when, the cylinder has been incorrectly fitted and two, when this is the second time it has happened.
Hi All,
Just a follow up and attached previous rejection letter for a warranty claim on the first cylinder.
Having spoken to Technical, they need the cylinder sent back to them for inspection.
They obviously don’t check the installation but just assess the cylinder for manufacturers defects as informed by the technical department.
They straight away mentioned page 22 of the manual for drain down procedure and also page 16 for the importance of the drain down procedure.
Now I’ve always wondered how an implosion would occur on an unvented cylinder. Well, now I know.
So it sounds like the negative gravitational force from both the hot draw off and cold inlet may have caused the cylinder to implode.
With the fact that the combination valve may be incorrectly installed, the check valve may have been bypassed. I don’t know this for sure but will have to get a qualified G3 installer to give a full report.
I also don’t know if the expansion vessel being installed to the hot water draw off has had a any detrimental effect.
So even if the cylinder is incorrectly installed, I may still be liable for not knowing how to drain down the cylinder to carry out any plumbing work
When I asked Gledhill technical how much pressure both negative or positive required to damage the cylinder, they were unable to comment. I also mentioned that I’d called Heatrae Sadia and went through the same scenario, however I was told by their technical team that there is no way their cylinder would implode under those circumstances and that there would have to be 15 bar of negative pressure to explode or implode their cylinders.
Again he pointed out the two paragraphs on their manual referring drain down procedure of their cylinders and could not comment on other manufacturers.
Could anyone refer a G3 qualified experienced engineer to give me a report on the installation in the Nottingham area?
Just a follow up and attached previous rejection letter for a warranty claim on the first cylinder.
Having spoken to Technical, they need the cylinder sent back to them for inspection.
They obviously don’t check the installation but just assess the cylinder for manufacturers defects as informed by the technical department.
They straight away mentioned page 22 of the manual for drain down procedure and also page 16 for the importance of the drain down procedure.
Now I’ve always wondered how an implosion would occur on an unvented cylinder. Well, now I know.
So it sounds like the negative gravitational force from both the hot draw off and cold inlet may have caused the cylinder to implode.
With the fact that the combination valve may be incorrectly installed, the check valve may have been bypassed. I don’t know this for sure but will have to get a qualified G3 installer to give a full report.
I also don’t know if the expansion vessel being installed to the hot water draw off has had a any detrimental effect.
So even if the cylinder is incorrectly installed, I may still be liable for not knowing how to drain down the cylinder to carry out any plumbing work
When I asked Gledhill technical how much pressure both negative or positive required to damage the cylinder, they were unable to comment. I also mentioned that I’d called Heatrae Sadia and went through the same scenario, however I was told by their technical team that there is no way their cylinder would implode under those circumstances and that there would have to be 15 bar of negative pressure to explode or implode their cylinders.
Again he pointed out the two paragraphs on their manual referring drain down procedure of their cylinders and could not comment on other manufacturers.
Could anyone refer a G3 qualified experienced engineer to give me a report on the installation in the Nottingham area?
Rob Foster
Esteemed
All Gledhill stuff is absolutely rubbish, I have never come accross such badly designed equipment ever. The company now makes more money from fixing and service contracts repairing their rubbish stuff than they ever made from selling them, the main company went bust. You only have to see the cohorts of service vehicles headed up and down the motorway from Blackpool everyday where these appauling products where designed and cobbled together on Friday afternoons after they had been to the pub...centralheatking
It must be something to do with the Non Return valve in the combination valve. Maybe as the cylinder can drain backwards through the cold feed, and drain through the hot side causing Negative pressure?
That all sounds like typical manufacturer b.s, in order to get out of replacing the cylinder. To simply say that it's not our fault without offering an explanation is laughable!
Worcester specifically state that an anti vacuum valve is required if the top of the cylinder is 15m or higher. I was told that the reason for this is that they use sectional insulation instead of a bonded insulation. The bonded insulation strengthens the cylinder and makes it less likely to implode.
It sounds as though you have been competent in your work. The cylinder has not been fitted correctly and this is the most likely cause of the fault.
Good look with this one.
Worcester specifically state that an anti vacuum valve is required if the top of the cylinder is 15m or higher. I was told that the reason for this is that they use sectional insulation instead of a bonded insulation. The bonded insulation strengthens the cylinder and makes it less likely to implode.
It sounds as though you have been competent in your work. The cylinder has not been fitted correctly and this is the most likely cause of the fault.
Good look with this one.
Fitted a Viessmann cylinder a couple of months ago which I believe is made by Gledhill and it was supplied with a small 1/2” valve that will allow air into the cylinder if there’s a negative pressure, like an automatic air vent in reverse. There was no mention of it in the instructions but it was obvious what it was for. Personally I think these cylinders are rubbish, they seem too flimsy, the connections can wobble around quite a lot.
S
Sharp Point
is hazard a guess that bypassing the check valve has allowed it to siphon out.... probably through the hot draw off, that’s why Rakesh says water started coming out of the hot pipe. As we all know, you only need a litre or so to start a siphon off
Just an idea like
Just an idea like
Rakesh
For an accepted analysis of the failure will need a report prepared under Pressure Systems Safety Regulations (PSSR). The G3 qualification is to demonstrate competence to instal and commission. Whilst that would possibly help you, I think you would be better with a fault tree analysis report that covers both design and installation and thereafter, the operating situation that probably caused the failure.
As an aside, I don’t think that the information given to you by Heatrae Saudia (spelling ?) is correct. To resist a vacuum of delta 15bar against atmospheric pressure, the wall thickness of a 315 stainless 200 litre tank would need to over 10mm thick.
Andrew
For an accepted analysis of the failure will need a report prepared under Pressure Systems Safety Regulations (PSSR). The G3 qualification is to demonstrate competence to instal and commission. Whilst that would possibly help you, I think you would be better with a fault tree analysis report that covers both design and installation and thereafter, the operating situation that probably caused the failure.
As an aside, I don’t think that the information given to you by Heatrae Saudia (spelling ?) is correct. To resist a vacuum of delta 15bar against atmospheric pressure, the wall thickness of a 315 stainless 200 litre tank would need to over 10mm thick.
Andrew
The drain down procedure is irrelevant. You didn't drain the cylinder.
Unless the cylinder syphoned down the cold because the combi valve was fitted wrong.
I would not expect something like this to happen when just cutting the flow to change a few taps.
Unless the cylinder syphoned down the cold because the combi valve was fitted wrong.
I would not expect something like this to happen when just cutting the flow to change a few taps.
The Heatrae Sadia advice is either misquoted or wrong. The tank would need to be built like a submarine to withstand a pressure of 15 bar before collapsing. It would also need to be evacuated and then immersed in water to a depth of 150 m to achieve a 15 bar pressure difference.
The Gledhill warning notice states that emptying the cylinder while hot, sealing it, and then letting it cool will cause damage. Assuming that the cylinder starts at atmospheric pressure and 60°C at the time it is sealed then cools to 20°C. From this, we can deduce that a pressure difference of 0.12 bar or less may be sufficient to cause damage due to collapse.
I’m thinking the same thing. I do t know how it would siphon from the hot water draw off. I’m thinking back siphon from cold inlet as the hot can only draw off from the very top of the cylinder.
Unless my understanding of the internals of an unvented cylinder is completely wrong.
Gledhill lite is called lite for a reason... the wall thickness of the cylinder is half the industry standard and deep within the manufacturers instructions they recommend fitting an anti vac valve.
Do not use a pump when draining down, the bigger the cylinder the higher the risk
Do not use a pump when draining down, the bigger the cylinder the higher the risk
Mastermixlee
Gas Engineer
It's not fitted right no, but neither of the mistakes on Installation would cause the vacuum created that has imploded the cylinder.
There's integral non return valves on both hot and cold draw offs on the combination valves.
One could argue that the absence of an anti-vacuum valve could be a cause... But it's not compulsory - only recommended to avoid scenarios exactly like his where the specified drain down procedure isn't followed.
Best to have a Lever valve on outlet and another on balanced cold and utilise those for tap changes etc.
It's a tough one as your not g3 your technically not competent to have had knowledge of this, but on the flip side, it is in the User instructions regarding correct drain down procedure. So the responsibility would still fall down to yourself.
Boilermate thermal stores behave exactly the same way if any attempt to bung them is tried.
Installation should still be corrected regarding the pipe layout/expansion vessel location. But as it stands the 2 components would still be operating in the same way as if they are now and wouldn't have contributed to this scenario.
There's integral non return valves on both hot and cold draw offs on the combination valves.
One could argue that the absence of an anti-vacuum valve could be a cause... But it's not compulsory - only recommended to avoid scenarios exactly like his where the specified drain down procedure isn't followed.
Best to have a Lever valve on outlet and another on balanced cold and utilise those for tap changes etc.
It's a tough one as your not g3 your technically not competent to have had knowledge of this, but on the flip side, it is in the User instructions regarding correct drain down procedure. So the responsibility would still fall down to yourself.
Boilermate thermal stores behave exactly the same way if any attempt to bung them is tried.
Installation should still be corrected regarding the pipe layout/expansion vessel location. But as it stands the 2 components would still be operating in the same way as if they are now and wouldn't have contributed to this scenario.
Long & short of it is the unvented cylinder is not installed correctly (as per manufactures instructions) therefore not your problem! (especially as it has happened before & still not corrected).
Don't get involved, don't try to help (I no it is hard), if they push it simply pass it over to your Public Liability insurance company.
You do have insurance cover don't you??
Don't get involved, don't try to help (I no it is hard), if they push it simply pass it over to your Public Liability insurance company.
You do have insurance cover don't you??
Would not advise that “ostrich” attitude. The problem is a £1.5k fix. If you shun the Client and depend upon local work, word of mouth ( where you have no right of reply) may devastate your business.
A proposal to fix on a 50/50 basis may not be the bad deal it seems
Once you claim on a PLI, premiums rocket
A proposal to fix on a 50/50 basis may not be the bad deal it seems
Once you claim on a PLI, premiums rocket
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