Unvented Direct water cylinder

[dronze]

Hi All,

I have recently moved into a flat (approx 15 years old) where the water is heated using a 'Tribune Premier Imi Waterheater'. From what I can gather this is a direct, unvented sytem (180L capacity)- as there is no central heating (storage heaters) and a tundish to the side and an expansion tank on the shelf above.

I have a few queries regarding this:

- Does my landlord legally have to service the system annually, or its this for the purposes of a warranty?

- when switched on is the tank full of water and does this all need to be heated at any time? (180L of hot water at any time seems a bit excessive for a 1 bedroom flat)

-there is no thermostat or timer on the system and it takes ages (2 hours) to heat water, so do I need to leave it on all night to have a shower in the morning (seems again, a bit excessive!)

- there are 2 power switches on the wall, do they operate the 2 heaters within the cylinder? Which is the top and which is the bottom and do they both need to be on at the same time?

Sorry for all the questions, I've never come accross anything like this before! Any help greatly appreciated.

Dronze

[Tim Downie]

If you have two immersion elements then you should probably be able to get away with using the top one for your hot water needs. If you just use the bottom one, you'll still be heating the whole cyclinder, but slowly! You'll have to trace the wiring or perhaps just feel which one is getting hot when it's switched on. The elements will have a thermostat hidden under the cover where the electrical connections are made to the heating elements but I wouldn't fiddle with these without good reason.

As to whether you leave it on all the time or not is up to your wallet! These cylinders are very well insulated these days so it shouldn't cost

*that* much more to leave it on but I'm only guessing. Try taking a few 24 hour meter readings when you've left it on all day and when you've only turned it on "on demand".

Tim

[Onetap]

The 2 switches & the storage heater may indicate that there is an Economy 7 electric system (or whatever they call it now). The meter measures electricity used during the day and that used during the night separately. The night rate is cheaper. If you get the benefit of cheaper overnight electricity, it may be worth heating the whole cylinder overnight (lower element). If not, just heat as required with the top element.

The Economy 7 thing was a lot cheaper overnight when most power stations were coal fired, they can't easily be turned down overnight. I don't know if the economics of it still make sense or whether the landlord pockets any savings.

[Andrew Gabriel]

I think it needs annual inspection by law, but I'm not 100% sure.

Well, you don't need to heat it all, unless the flat has one of those drencher showers which uses water like Niagra Falls. There will be thermostats built in to the heaters. See

- there are 2 power switches on the wall, do they operate the 2 heaters

This is the classic bath/sink operation. The top element will just heat the top of the tank, which is enough for a wash basin, and might be enough for a shower if it doesn't use too much. The bottom element heats the whole cylinder, which is enough for a bath.

If you have Economy 7 (or similar cheap night tariff), then the idea is to heat the whole tank overnight to last the whole of the following day, using the bottom element.

The switching is usually arranged so you can't switch them both on at the same time, as there's only a 3kW supply. You basically have a choice of heating a small amount quickly, or heating the whole tank slowly.

[chudford]

I believe this water heater is a sort of electric combi. The large tank is heated up and mains pressure water is passed through a series of coils in the hot water. The tank above it is just to keep the main tank topped up. You should check that its water level in the tank is OK or the system will shut down, the topping up can be either via a mains water connection or sometimes by just pouring water in the top. The top heater is for a quick heat up and the bottom one for the main tank. As has been said the bottom one should be run on a cheap rate tariff. There is also a pump in the system which sometimes stops working. They do not require any maintenance except when the fault warning lamp comes on. I have these in my flats and they very seldom give any problems.

[chudford]

Here is a link to details of a similar water heater

[John Rumm]

system, and is not covered by the unvented requirements of part 3 of approved document G:

system the OP refers to is quite different in operating principle.

[John Rumm]

Pass... It is certainly recommended that unvented cylinders be tested at regular intervals. I have also seen some people claiming it to be a legal requirement, but don't recall if definitive evidence has been offered to support this.

The direct version has two immersion heaters. One near the top to heat just the upper section of the tank, and a lower one to heat the whole tank.

So you can just use the top one if you want less hot water capacity.

The stats will be built into the immersin heaters. They include two stats - one that can be set to a preset temperature, plus a second emergency overheat stat to disable the heater if something goes wrong.

Ideally the timer capability and the control of the heaters should be handled by an external controller. However it is possible you just have manual switching. Typically you would use one at a time, since there is not much to be gained by using both - the top section of the tank would heat faster, but that will heat pretty fast with the top heater anyway. Once the top is up to temperature, the stat in the top heater will turn it off anyway.

Two use both at time would also ideally need an immersion circuit that can supply adequate power to run both heaters at once (6kW). (check the MCB rating in the CU).

If the cylinder is well insulated (they normally are) then there is not that much energy loss to worry about from having the heating on all the time.

If you have split rate electricity metering however then fitting a timer would be of benefit since the tanks probably large enough to supply you whole days requirements from one nightly "charge".

Some background reading for you:

[chudford]

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Sorry John you are correct as ever, I should have read the OP's description more carefully. Please ignore my posts.

[Doctor Drivel]

Yep. It is a potential bomb.

[Doctor Drivel]

the doc:

Building Regs:

"These are a statutory document and take priority over all other regulations and recommendations. The installation of an unvented hot water storage cylinder is classified as a "Controlled Service" and Regulation G3 applies. To meet the requirements of the Regulation, installation of an unvented system should be undertaken by a "competent installer".

All installations of unvented hot water storage systems having a capacity of more than 15 litres should be notified to the relevant Local Authority by means of building notice or by the submission of full plans. It is important to note that it is a criminal offense to install an unvented hot water storage system without notifying the Local Authority. The installation of the unvented cylinder and hot water system must comply with BS 6700 and the HSE Legionella Code of Practice."

All makers specify an annual service. This will be taken as gospel by a court or insurance company.