Big water cylinder thing?

[T i m]

Hi All,

I was round a mates yesterday and standing in his lounge was a fairly tall water cylinder thing that allowed 'mains pressure' showers etc?

It was made by Santon and a quick nose around their site makes me think it was the 'PremierPlus' model.

So, is it just the (ss?) cylinder inside is up to the mains pressure but outside that it works just like a traditional indirect copper cylinder?

He was talking of having one of those big showerheads and the need not to have pumps etc but I wondered if there could actually be a 'flow' issue? I understand the pressure could be good but some older houses can have fairly (flow) restricted mains feeds (blocked pipes etc), often masked with a tank fed systen apart from when using the hosepipe etc?

And I assume like with all 'direct' devices you get pressure drops when other folk use the loo / run a bath etc (but I guess at least hot and cold would drop at the same rate)? (and of couse with a mains fail you have no water) ;-(

All the best ..

T i m

[Doctor Drivel]

It is an unvented cylinder. Forget it. You need to have a BBA approved plumber to fit it. You also need an annual service by a BBA plumber. If no annual service and an insurance claim they don't pay out. IT can also explode. A 'heat bank' or thermal store will giove excellent mains pressure flowrates. Heat banks have plate heat exchangers and give high pressures and flows and venetd verrsion can't explode and many don't even require overflow pipes.

Look at:

(a cheap thermal stores and will make to order) (Thermal stores and will make to order) (make square storage vessels, inc thermal stores) (make heat banks and storage vessels to size) (make thermal stores and stoarge vessels) (make cylindrical heat banks and storage vessels. Will make to order) (make heat banks (thermal stores they call them) and storage vessels. Expensive but v good) make cylindrical thermal stores and storage vessels (make cylindrical thermal stores. Expensive) (make thermal stores and cylinders)

[T i m]

Ok ..

Lots of things need regular 'testing'?

I thought I read it was tested to 15 bar or summat and based on the thought that you can't compress a liquid wouldn't it just split open (not 'explode') in any case?

Ok ..

The issue is that he has this thing therefore unlikely to get rid of it now (especially as it's new)?

All the best ..

T i m

[Doctor Drivel]

It nedds one per years at about £60 a go.

If the controls fail it can explode, and when they do they take down the side of the house.

He had better get a BBA approved installer do the workk and pay £60 a year for ever. Send it back.

[T i m]

Please explain ?

T i m

[Ed Sirett]

I would like to be permitted to put forward (my best attempt) at a neutral point of view. An unvented cylinder is a HW cylinder which is a pressure vessel usually made of stainless steel. They are well insulated and usually have an outer cosmetic casing which is coloured white or slate-blue.

By law they may only be fitted by qualified people. They have a number of safety devices (just like your boiler has in various ways) which prevent the worst case behaviour.

They do not regularly blow up in fact there are few stories of them ever doing so, and the only two I heard about are

1) A deliberate test to make a cautionary video. 2) An jerry-rigged ordinary copper cylinder pressed into use as an unvented on a boat, having an ordinary immersion heater whose thermostat failed.

For one to blow up you would have to have all the following things go wrong:

The electric immersion heater thermostat fails on. The safety immersion heater thermostat fails to open. The 6 bar pressure relief valve stays shut no only by a few bar but in excess of the the limit of the vessel (which is tested to 15bar!) The temperature valve failed to open at 95C. The second pressure relief valve failed to open.

The main risk area would be an incorrectly installed discharge pipe (faults with this are very common) although every case I've seen something fairly benign would happen when it was needed.

To install one in a plausibly dangerous (rather than irregular) way you would have to really work at it. The threads on the T&P relief valve are unique to those fittings and wont fit elsewhere and can't nothing else can be made to fit in the hole in the side of the cylinder.

Thermals stores are similar in price (may be a little cheaper) and are only subject to building control or self-certification for 'guild' members.

[Doctor Drivel]

UNVENTED: Must posses an industry recognised certification to install or service as per building regulations: It is a legal requirement that the local authority Building Control Officer be notified of any proposed installation of unvented storage water heating systems over 15 litres. This notice should include:-

(a) Name, make, model and type of hot water storage system to be installed. (b) Name of the body which has approved or certified the system. (c) Details of the 'competent installer' intending to carry out the work, including details of any current Registered Operative Identity Card held, and the issuing body.

HEAT BANK: requires none (Electrical regulations apply). THERMAL STORE: requires none at all as no electrics.

You forgot the annual service charge for an unvented cylinder.

[Ed Sirett]

I did. This is a scam. The only part which the manufacturers are going to offer a long guarantee on is the pressure vessel which is effectively indestructible by any conceivable use or abuse. The parts which might fails (the expansion vessel or any of the valves) are usually not covered beyond a year or two.

So no one would pay £50 (a minimum call out job) to 'service' an unvented in order to validate a guarantee on a part which will likely outlive the owner and the installer.

[Doctor Drivel]

It is not indestructable. And copper versions less so.

The annual service is 'every' year for the 'life' of the cylinder; and that is the cylinder and all associated controls. If you do not have one serviced, and have the paper trail, if water damage due to the cylinder, insurance companies will not pay up. If it takes down the side of the house, definitely no pay up.

That is why thermal stores/heat banks are the better option. Heat banks also give higher pressures and flows than the majority of unvented. I was talking to a techie at a big cylinder company today. They make all types. He said he would not have an unvented cylinder in his house, having seen the odd one blow in a minor way in their test labs. He also worked on industrial stuff and saw a few go up too, with devastating results. He converted his own existing cylinder to a heat bank buying the parts.

He said heat banks are now more expensive than unvented, as unvented are on a production line, while stores now are not, despite less parts being in a store and plate heat exchangers dropping in price. Stores are hand assembled. 5 years ago stores were cheaper.