Gledhill light unvented cylinder imploded

[Rakesh]

Those instructions are for a full cylinder drain which im guessing wasnt needed to change a tap?

Correct

 

[Best]

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

 

[Welder]

Hi Oz,
I don’t deny any wrong doing.
Fortunately, I have discussed all my findings with the help of this forum and have advised the client of the possibility that the cylinder is incorrectly installed.
I’ve also shown him the paragraph relating to drain down procedure to show that while I didn’t carry out the procedure, I have called technical support of a different manufacturer to find if what I have done by changing the taps and draining down exactly as I did would cause the cylinder to implode.
As Mentioned, it would take 15bar of negative pressure to implode a tank so I am doing everything to come to a resolution.
If I have to pay for a new tank and install it then I will do it.
The client is being understanding and thanked me for investigating the matter.
He has been let down by two installers first one of which incorrectly installed it and second installer just changed the tank for an identical one without changing or checking that it was correctly installed in the first place.
The installer has also been serving the cylinder since the install so if what’s been mentioned here is correct then the installer has no clue on what he’s doing.
I would say if the installation is incorrect then the liability lies with the installer.
If I’m proved to be in the wrong then I will correct it.

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.

 

[EvilDrPorkChop]

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.

 

[Rakesh]

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?

 

[Rob Foster]

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

 

[Scott_D]

The expansion vessel on the hot would still take up expansion.
The combination valve is wrong but I can’t see how this would cause the cylinder to implode

 

[EvilDrPorkChop]

The expansion vessel in the hit would still take up expansion.
The combination valve is wrong but I can’t see how this would cause the cylinder to implode

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?

 

[robdog6000]

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.

 

[Drewy]

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.