The unvented cylinder annual inspection myth?

[The Natural Philosopher]

switched fan, in the one I had to operate, once. More like a mini bessemer converter..

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "dennis@home" saying something like:

Indeed. I came in from work one day some years ago and was greeted with rumbling noise from the hall cubboard where the hot cyl was - the immersion switch had been left on that morning and the stat had failed sometime during the day. Luckily the overflow /vent was unblocked, but that had never been checked as far as I know (rented property).

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember John Rumm saying something like:

There was one a few years back where the owner /renter had been nicking power and the hot tank was on permanently. The stat had failed shut and the chalky water over the years had closed the vent pipe down. Resulting steam explosion took out the back wall of the house.

[Bill Taylor]

Or thermostatcally controlled air intake.

[YAPH]

So presumably the head of water from the tank pressurised the cylinder raising the boiling point, and then when someone opened a tap the drop in pressure caused the pressurised water to flash to steam in a classic steam explosion.

I don't suppose the legality or otherwise of the leccy supply had anything directly to do with it though.

[John Stumbles]

That bit puzzles me. Limescale typically blocks up pipes where cold fresh water gets heated, so would be more likely to block the feed pipe to a HW cylinder if it was hot enough throughout that the cold/hot water interface was actually in the pipework rather than the lower regions of the cylinder itself. The water in the vent pipe has already been heated and given up its limescale.

And if it was oop North don't they have soft water up there anyway?

[Doctor Drivel]

Depends on what part of oop north, some parts are very hard. They don't know how lucky they are having soft water. They tend to use microbore pipes as standard. I know around the Liverpool area microbore is the norm and they all know how to fit it by rule of thumb too. The are experts at uncoiling it. They are amazed when they see 15mm slapped in all over a house, thinking that is something of 40 years ago.

[Dave Liquorice]

I'd call that a boiler not a stove. A stove is a passive lump of cast iron with a door for shoving wood/coal in and a flue to take the smoke away.

Yes there are thermosatically controlled air vents but even if you shut that down (How? This has to work without electric from the temperature of the store) it takes a while for the significant amount of heat in the firebox and mass of the stove to dissipate. Oh and a lump of ash could stop the vent shutting properly, single point of failure...

[Rod]

But doesn't Liverpool actually get much of its water from Wales - i.e. not oop North? (Yes - I know - not all of it.)

[Andy Champ]

They work by having a damn great bimetallic strip with a flat plate on the end. When hot, it bends the strip so the plate covers the air inlet. Seen them on (IIRC) Rayburns.

Andy

[Doctor Drivel]

I believe it does, like Birmingham too.

[Dave Liquorice]

Fine but that only regulates the device from the temperature of the device not that of the store. It also doesn't shut the device down (as if off) and you still have the problem of lots of residual heat.

[John Stumbles]

Dunno about Liverpool. Birmingham gets its water from the Elan Valley reservoirs in mid-Wales, and that's soft.

[Rod]

Liverpool gets a load from Vyrnwy - a bit further north.

(Mind I think Shrewsbury and the other Severn towns are perhaps not always so pleased with the Welsh water they get. :-) )

[Me]

replying to tom.harrigan, Me wrote: If you own your property then you don't legally require annual certification. But if your cylinder splits or the hot water side bursts a pipe and floods the place, the insurance company will ask for your certification as it's part of your contract with insurance company to "do all within your means to look after insured property"