Mains pressure to Cylinder

[IMM]

Best you read what was written. Any idiot can block vital blow-offs and make an explosion.

[Andy Hall]

I do. Generally it is what is in manufacturer's specifications rather than in hare brained schemes.

Although it should be noted that for a sealed cylinder, a tundish is used between the relief valves and the outside.

[IMM]

........but don't understand.

[Dave Plowman (News)]

For the OP, you'd be advised not to. IMM's nonsense could result in an explosion in a domestic installation.

He's a fool, and sometimes a dangerous one. Just ignore him.

[Dave Plowman (News)]

Correction. It's likely to be dangerous.

Could I ask why you need to get rid of the header tank? Unless space in your roof void really is a problem, this is the easy (and cheap) way to achieve the result you need.

[Dave Plowman (News)]

Excess alcohol has clearly cut in.

Avoid misinformation from a drunk like the plague.

[IMM]

[IMM]

[Christian McArdle]

Such a conversion was done on a fishing vessel. The MAIB report is here.

few quotes from the report:

SYNOPSIS An explosion in the engine room of the 16.45m UKregistered fishing vessel Fleur de Lys, DH7, sank the vessel rapidly. Fleur de Lys sank because her hull was damaged by violent rupture of the hot water storage cylinder of the unvented hot water system. These systems are equipped with safety devices designed to prevent incidents of storage cylinder overheating, overpressure and explosion such as occurred on board Fleur de Lys.

The cylinder was a conventional British Standard copper cylinder used in vented systems. Its specification was as follows: Direct type, 900mm x 450mm, 120 litre capacity, heated by an immersion heater of 3kW; Constructed of copper to BS 699:1984, classified as a Grade 4 cylinder for 6m maximum working head; Foam insulated to BS1566 Part 1: 1984;

The water cylinder body would form a missile as a result of the explosion. The missile velocities calculated were such that the missile would have been expected to breach the hull in both cases. The consultants? overall conclusion was that an explosion with either grade of cylinder would have damaged the vessel sufficiently for her to flood and sink.

Christian.

[Markus Splenius]

Shouldn't that be "Yes. But it will burst?".

Out of curiosity, just how spectacular would this be? :-)

M.

[IMM]

A full insurance job with ceilings coming down. I have seen the aftermath of an unvented explode. Spectacular.

[Andy Hall]

See Christian's post on the subject.

A missile that's enough to sink a ship

[Tony Bryer]

We had a case in Kingston where a council house tenant had got 'a mate in the pub' to bridge the meter. The immersion heater thermostat stopped working but he couldn't get anyone in to fix it because they would have gone to turn off the electricity, seen the meter and perhaps reported him. So he had to remember to turn it off each night before the water got too hot.

The regular heating of water to near boiling point scaled up the vent pipe. Unfortunately the supply had a screwdown stopcock which acted as a non-return valve. One night he forgot to turn the IH off, the vent pipe finally blocked and when the cylinder gave and the superheated water turned to steam it took the back of the house out (9" brickwork). IIRC his only punishment was to get a nice new house.

[Christian McArdle]

that this did have some modification, such as an expansion vessel and a pressure relief valve. Unfortunately, it didn't have some critical ones, such as the temperature relief, manual reset immersion thermostat and a cylinder made from something thicker than kitchen foil.

Christian.

[The Natural Philosopher]

At least.

Similar to normal but with couple of extra pipes dealing with the safety valves etc.

They are simple enough to install - let's face it plumbers are reknowned for their simian like inability to actually puzzle things out - look at dIMMwit for a classic example - so they have to be.

However because its very hard to make anything proof against a (lack of) mind like dIMM, they are supposed to be installed by a professional plumber wth a bit of paper that he has proved he can read, rather than use to wipe his hairy arse.

[IMM]

Best use a low pressure heat bank. Same performance.

[The Natural Philosopher]

It really depends on whether its above boiling point when it does.

The calassic way to pressure test a (steam) boiler is to fill it full of water and pressurises this with little or no gas inside. The tank will creak, pop and eventually rupture in complete safety. The water has no potential to expand, so as soon as its blown the tank, it just rushes out.

Contrast the case when its full of steam AND water. The steam has immense potential energy, and as has been cited, the cylinder can become a small bomb. Boiler explosions have caused many deaths over the years.

Of course, a DHW tank should neither contain air under pressure, nor be allowed to boil.

However experience shows that both situations occur under fault conditions. Therefore the sealed DHW tank is mandated to have pressure relief valves - safety valves - and a means of safely allowing high pressure steam to escape. All it takes is a stuck thremorstat and you have a bomb in the house, unless these work.

Byt teh way, even sticking a cork up the safety overflow in the street has been thought out. It has to be shown to be impossible to get your hands near the overflow pipe, by dint of a guard and there is a think called a Tundish near teh tank, that if te pipe is blocked will still allow the steam to escape - into wherever the tank is siutauted. NOT ideal, but better than an explosion.

[The Natural Philosopher]

In the limit, a sort of 30 meter away and watch it sort of spectacular.

And potentially lethal if you are sleeping next door with only a plasterboard stud wall in the way.

[Christian McArdle]

By the way, although you can't convert it to an unvented cylinder, you can safely convert it into a heat bank, which will provide mains pressure water.

The procedure is as follows:

1. Heat the cylinder any way you like. Immersion, indirect coil or even direct around the boiler, provided the boiler is open vented. You must not connect any direct outlet from the cylinder to mains pressure sealed systems.

1. Keep the existing expansion tank, or use a much smaller one mounted just above the cylinder. The water doesn't really go anywhere, so even a tiny expansion tank is sufficient. Set the ballcock to provide only about 3-5cm of water in the bottom of the tank.

2. Install two Essex flanges. One right at the very top of the cylinder, one right at the very bottom. (You can cheat on the bottom flange by putting a 'T' on the cold feed. You might even be able to cheat on the top flange by inserting a T on the vent pipe.

1. Now run a loop of 22mm pipe from the top flange to the bottom, passing on the way through a plate heat exchanger and a standard central heating pump.

2. Now take your mains cold feed and pass through a flow sensor switch. Then take the output from this through the other port of the plate heat exchanger. The outlet from this connects to your hot water pipework.

1. Connect a 3A fused electricity supply through the flow switch to the pump.

2. Refill the cylinder using copious amounts of central heating inhibitor.

Parts cost will be less than 200 quid. Mains pressure hot water will result.

Christian.

[IMM]

Best use Surry flanges.

And no silly, noisy, vibrating power shower pump and supplies "all" of the hosue, nor just the shower.