Would it work?

[Nelson-]

Hi all,

Firstly I'll point out I'm not an unvented installer 😀 bare with me

I was having a day dream the other day and was thinking about what would happen if you took a regular tank fed, open vented hot water cylinder setup, removed the cold water tank, plumbed the cylinder cold in conection directly into the mains and put a non return valve on it. Then disconnect the vent pipe, and instead, using a 22mm tee directly right after the hot water draw off pipe, right above the cylinder, put a pressure relife valve on one branch of the tee, and expansion cylinder on top, on the other branch of the tee.

Assuming the regular vented tank fed cylinders can take mains pressure... and not just fail (yes I know they were never meant for it) is there anything atchually fundamentally wrong with that? Hypothetically speaking if it wasnt going in someones house...

how about if you wacked a pressure reducing valve on the cylinder inlet to bring the pressure down alot, after the non return valve before the cylinder.

 

[jonnyswamp]

Are you in the trade

 

[Dotty]

Kaboom is what would happen.

 

[snowhead]

Keep dreaming.

 

[Chalked]

A pressurised cylinder working pressure is 3bar ( some are 6bar) but they are designed to take at least twice that!
A copper vented cylinder will at max take around two bar.
Here's the difference pressurised cylinders are made of coated, or stainless steel. 5mm thick, copper is about .5mm, ver soft and just soldered together.
There is more than just fitting a pressure reducing valve too. There is a prv, a tprv, a high pressure prv, a non return, cylinder thermostat a High limit cut off.
All these are to prevent it literally exploding, so
Leave it as a dream/ nightmare.

 

[Last Plumber]

You would have to be very silly.

 

[Riley]

Wind up surely

 

[Dotty]

Do you get the impression someone's driving frantically back to his pride and joy?

 

[oz-plumber]

Actually not...

I think he's driving back to an installation that has gone south, and the insurance assessor has informed him the works done are not covered.

 

[rocketmanbkk]

Who's this Nelson joker?

 

[SimonG]

Died at Trafalgar. Apparently the water heater exploded.

 

[townfanjon]

Engineer if you ask me

 

[Billy Bob Bob]

Are you in the trade

Think op forgot to take their meds

 

[Dotty]

Who's this Nelson joker?

Someone in the throes of a panic......

 

[joni os]

Stories are told that James Watt thought about his engine when watching steam lift the lid off a kettle. A wrongly installed unvented will lift the roof off your house. Google youtube for examples.

 

[mache]

Engineer if you ask me

not one who's done any training or experience with pressure vessels if he is !!!

 

[Ric2013]

Assuming you could get the pressure low enough for the cylinder and assuming you could ensure it didn't go bang... what advantage do you think this would this have over a standard vented system?

 

[tamz]

Assuming nothing. Its stupid so don't encourage him.

A back garden weekend scientist might do something like that just to see what would happen and amuse the weans but only a complete idiot would do it in a house.

 

[bert large]

A plumbing company in Cornwall installed a very similar system to that the OP is describing in my friends trawler around 20 years ago. The boat now lies in around 20 metres of water in the English channel off Dorset after the cylinder exploded blowing the bottom out of the boat.
Luckily there were no fatalities.

 

[Nelson-]

Calm down gents it's not going in a house I clearly said that... right at the start...

And I have not been rushing back anywhere 😀 I said it was hypothetical

Thanks for the answers, but noone even atempted to exsplain why...

Where as you clearly know your stuff I however do not, which is why I have to ask. I've never seen what those unvented cylinders look like outside it's casing, or know much about the workings of an unvented system.

I know very little about these things, but I'm glad I entertained some of you. I wont be trying it, you can let your keyboards cool down now 🙂

can anyone exsplain why this would not work in a non condescending way?

And the advantage was it gets rid of the cold water storage tank....

How could you do this on a boat? Boats don't have a mains water supply?

Barely any of you really red my post I did totally discount the fact it wasn't designed to take mains pressure aswel... but I need to be told this again, why extactly?

If your gonna slate someone's idea at least do it constructively not just like a condescending superior... I'll get help with my project else where it's alrite.

 

[Riley]

If your gonna slate someone's idea at least do it constructively not just like a condescending superior... I'll get help with my project else where it's alrite.

So you are contemplating it. Look just don't. In a non condescending way mate you really need to be G3 qualified in order to work on a domestic hot water system. No qualified engineer willl even entertain the idea. Unvented cylinders are a. Designed to withstand the greater pressures of mains water the metal work and seams of a normal ventedcylinder are not. and B. Have safety devices integrated such as pressure relief, a temperature/pressure relief valve, a hydroblock, immersions with much improved thermal lock out and an expansion vessel all supplied specifically by the manufacturer, in fact most if not all manufacturers insist that their replacement parts are used to ensure the safety continuity. It is not just bits hashed together with whatever you can find. These installs are notifiable giving you some idea of the need for correct installation

If you are contemplating a pressurised hot water option then YOU MUST enlist a G3 engineer DIY is completely illegal and irresponsible for your safety and you family and neighbours

 

[Dotty]

I think you were told several times over during the course of the thread the difference between vented and unvented cylinders and what the ramifications could be.

What you seem to fail to grasp is that unvented cylinders store water that is heated up. Water expands as it is heated. And, because it is a sealed container, Boyles Law comes into play. Basically meaning that the water, in a fault condition, can theoretically reach boiling point far more rapidly and explosively than it ordinarily would.

This is why unvented cylinders are designed with so many safety features and why the person installing them must be trained and qualified to work on them.

Vented cylinders are not designed to cope with the temperature or potential build up of pressure.

And that's all you need to know.

Boats have hot water systems already designed and ready to be bought off the shelf. Don't try and make your own system up. You'll put the boat on the sea bed.