Electric Boiler

18 Jan 2013
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United Kingdom
I am about to refurbish a flat. It is a 2-bedroom flat in the 4th floor of block. The flat has no gas and the cost of getting gas supply is prohibitive, the Gas Board quote is for £4,000.

A neighbour has replaced a small storage water tank and an immersion heater with gas boiler. I wish to do the same, except the boiler has to be eletric. I would be grateful for advice on the most efficient eletric boiler to provide hot water, and the most cost effective electric heating system.

I tried to post this message on Saturday and for some reason it is not showing with my postings. Apologies in advance if you have seen it before.
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If you want to go down the electric boiler route first thing you need to know is what the electricity supply is to the property as this might prohibit some boilers that you can have installed, Electric boilers are extremely expensive to buy compared to gas boilers
Electric boilers have the same disadvantages of a wet heating system (leaks, etc) and the high running cost of electricity. You still have to have a hot water cylinder as electricity can't provide acceptable levels of instantaneous hot water, especially if the electricity supply to the flat is limited.

The most cost-effective form of electric heating is usually night storage heaters or a hybrid storage/peak system such as Dimplex Duoheat.
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I would be grateful for advice on the most efficient eletric boiler to provide hot water
No such item - they are all equally efficient, and all just as expensive to run.

, and the most cost effective electric heating system.
Most likely a hot water cylinder with immersion heater, and 3 or 4 storage heaters on an E7 overnight supply.

Installing an electric boiler with radiators etc. is a bad idea for several reasons.
If you are intending to sell the flat, such a system will put people off as most buyers will not have encountered such a system before.
If renting, bad idea again, since when it breaks, your tenants have no heating or hot water at all, obtaining spare parts may not be as speedy as you would like, and good luck finding someone who will even look at such a system, never mind dismantle and repair it.
Electric boilers are the most expensive system to run, so will not be liked by anyone unfortunate enough to live there.

The time, cost and mess when installing wet radiators will be far more than for storage heaters, and you will also have to find somewhere for the pipes, which in a block of flats will probably mean behind some form of boxed in skirting, as the floor is probably solid concrete.
Thank you for answers. If you do not mind I would like to rephrase my questions:
1 - Is a water tank essential to maintain the pressure flow into the boiler or the immersion heater?
2 - Since an electrical boiler cannot produce sufficient instantaneous hot water, you suggest that I should also have an immersion heater. Is it possible just to have an immersion heater in that case? If so could you suggest a good make?
A hot water tank is required if your heat source is not capable of providing the required power to heat the flow of water you require from cold (can be very cold in winter) to an acceptable temperature. This allows the heat source to heat the water over a period of time, and then you draw it off quickly as required.

Now, lets throw some figures into the mix. A 30kW gas fired combi boiler is only just acceptable (and that's debatable) for filling a bath - a 30kW electric heater would take 125A and you probably have a 100A main fuse at most (you could have as little as 60A).

Assuming you can't manage with an instantaneous heater, then you need to heat stored water. 3 choices come to mind - open vented cylinder, unvented cylinder, and thermal store - which all have different pros and cons.
Open vented is cheap, and will work regardless of your cold water supply - but you need room for a large header tank and your pressure will be low. It's likely that this won't be practical in a flat.
Unvented costs more, but you will get mains pressure hot water. Limitations include the requirements for a means of safely venting hot water in the event of a fault, and you can only get out what your cold mains will put in.
A thermal store can be open vented (so avoiding the need for a safety vent and somewhere to send the water), but still provides mains pressure hot water (so the same requirement for a decent cold water supply). It could, however, also run a wet heating system if required (I'd use a modulating pump and TRVs on all rads).
All three types of cylinder could have several large immersion heaters installed - even the densest plumber should understand those ! Also, if large enough, then a cylinder can be heated on an off-peak tariff and supply useful heat later.

Before you can make a decision, or anyone can advice which is best, you need several items of information :
1 - How much space do you have for a cylinder ?
2 - What electricity supply do you have ?
3 - What sort of cold water dynamic flow and pressure do you have ?

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