Advice needed on conversion from gas to electric water heater

I need a new system. I live in a flat which has a small kitchen and a small bathroom - very modest demands. No central heating. I have a Main Medway gas heater (about 5 years old) which supplies hot water to the kitchen and to the bath. I also have a small electric water heater that supplies the shower - a Triton T70 - which is in the bathroom. This was all working OK but a tiny water leak from the Main Medway (small drips) means I'm looking at a plumber anyway, So I'm re- thinking the whole system. At present the Main Medway is in a small spare bedroom. It's big and makes a noise when the gas goes on, so I'd prefer a smaller water heater - I'm thinking electric.
So basically, guys, what would you do with my hot water needs? Three things to think of, kitchen sink, bath and shower.
Questions: - what could I use the Triton for? e.g. it would be enough to supply the kitchen sink. - where would an electric heater go? Could it go in the bathroom? - what sort of size heater do I need for this modest job? the other factor is the washing machine in the kitchen - does this need hot water or not? And if it does, what does that mean for the capacity of the water heater? - anything else?
Thanks for all replies - I'd prefer to think this through before getting a plumber in. Please ask any questions!
andy
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Eusebius wrote:

Washing machines are either cold fill or can be converted with a Y adaptor to be cold fill. Sink, basin, shower could all be serviced by an instant type electric heater such as your triton. Even the most powerful of these devices will only fill a bath very slowly. So this requirement needs some form of stored hot water. eg Tank and immersion heater. This can then provide all your hot water. If your space heating is electric storage heaters, then the immersion and these can be run off economy 7 tariff.
hth
Bob
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Hi Bob
I don't have space for a tank, so that's not an option. Right now, the Main Medway does fill the bath OK - water is hot enough. I could leave it at that, I guess, but I'd like to know what sort of electric heater has the capacity of the Main Medway so i could consider a direct alternative. Space is an issue here.
andy
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Electric stored water systems can be quite compact. There are wall mounted 90L unvented mains pressure systems, 3kW powered, with about 80min recovery time. They are a rectangular box on a wall, look a bit like a gas boiler, self-contained and since mains pressure can be situated anywhere you like. Integral frost-stat, clean "white appliance" as it were.
Without stored water you are onto a non-starter for filling a bath, but that need not necessarily be the "600x600x1500mm" space for conventional CW tank & HW tank arrangement.
I would like one for my mother re 1-stop solution, but one wall is cinderblock & the other the chimney so I am loathe to allow anyone to screw anything to it.
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An electric shower heater is about as powerful as they get for domestic use. So you will only be able to fill the bath as fast as the shower does.. in fact you may as well use the shower to fill it.
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Right - thanks guys. So looks like I stay with gas for heating a bath if I don't want some sort of tank. I guess the alternative is to get rid of the bath and put in a shower cubicle. Does electric run do a decent shower? My Triton 7 is not up to a really good shower - it's pretty puny. Can you get a good pressure for a shower from electric?
Having established that, if I stay with the bath, then can I put the Main Medway instant gas heater somewhere else than in the spare bedroom. Possibilities are the kitchen and the bathroom. What's allowed under safety regs? In the kitchen I do have a wall with an outside flue, but it's above the gas cooker - I guess that's a no? How far above a gas hob would it have to be, or is it just a case of "not there". I guess it's not impossible to move the gas hob. doing some thinking here.
Are we making progress?
andy
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Eusebius wrote:

Pressure is not the problem so much as flow rate. Even the best electric showers will struggle to deliver 5L per min in the winter.

Both can be acceptable. The kitchen usually being a better choice than a bathroom. How about loft space? Do you have a gable wall?
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wrote:

FWIW we (wife and self) once lived comfortably for several years in an 8' by 30' trailer (caravan) that had a 20 US gallon (or smaller) electric hot water tank, for bath/shower and dish sink. We had a propane cooker and an oil heating stove. No washer. Although as mentioned one can cold-wash or warm hand wash certain items! Point of this is that with slight plumbing changes? it may be possible to live with entirely electrically heated hot water. Also if the hot water thermostat is turned higher (watch out for scalding) the hotter water can be mixed with cold for use. Later we did upgrade the electric supply to the trailer but we never had to change the electric hot water heating tank. Although gather that in UK gas costs more than electrcity, costs for the amount of heat involved for hot water use may not be significant? Terry.
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Gas costs about 35% of electricity in the uk for most people. There is an off peak electricity tariff that is about the same as gas.
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We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "dennis@home"
Cobblers. They are available, but the current demand on a marginal supply is a bit of a light-dimmer.
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saying something like:

Cobblers. The current demand for an electric shower is about as much as a domestic supply will take, which is why I said they were available about as powerful as an electric shower and why I said you may as well fill the bath using the shower. There is no point in having another instant heater that is only as powerful as the shower. If you want to fit an industrial three phase heater feel free but the average householder isn't going to.
Do try and keep up or at least read what is said, hint what does domestic mean?
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On Fri, 08 Jan 2010 12:46:14 -0800, Eusebius wrote:

=============================================== The easiest solution would be to have the Main Medway serviced and repaired. If it's good enough for the bath it will also give a decent, basic shower as well as filling the washing machine, sink and basin although not all at the same time.
You'll probably need some modification of the pipework to use the Main Medway for all outlets but that is what it's designed for.
Cic.
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The output of your Main Medway gas heater is something like 25kW. (You should be using the Medway for your shower too, rather than a separate electric shower.) You can't get anything like 25kW from an electric instant water heater on a standard domestic electricity suppply, so you'd need a stored water system. Since you mention bath, that's going to need a hot water cylinder.

You can always feed a washing machine with only cold, even if it has a hot inlet. No point feeding it hot unless there's a short pipe run and the hot water is generated more economically than instant electric. Current models no longer have a hot inlet anyway.

I think you'll struggle to beat the Main Medway for what you describe. You'll have a brilliant shower if you buy a thermostatic shower mixer designed for combi/multipoint water heaters. The Medway is very simple; there's little to go wrong and it's easily fixed. It will all still work during a power cut!
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As in previous post, if I stay with a gas water heater, can it go in the kitchen or bathroom?
andy
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One other question - what flow rate do I need a) to run a bath b) for a decent shower?
I've seen this expressed thus:
Flow rates (Litres/min)
* 3.4Ltr @ 38C * 2.7Ltr @ 45C * 2.1Ltr @ 55C
Alternatively what am I looking for in Watts?
Need some way of judging which heaters are suitable by their capacity
andy
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The most powerful instant electric showers are around 10kW (which I personally find fine, but some people find too weedy). Your Medway is well over 20kW, which is the minimum for running a bath unless you are happy to run it at a small trickle. As I said before, it will also give a brilliant shower, but you have to buy a thermostatic shower mixer specifically designed for combi and multipoint use (fast acting and unbalanced/varying pressure).
It can probably be moved if you can buy a new flue kit for it, and the new location meets requirements on outside flue clearances in the installation instructions. These heaters are hung from their flue, which will be mortared into the wall and most unlikely to be recoverable for reuse. There are different flue kits for different thickness walls (although they are all adjustable to some degree).
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this is all very useful. So can I situate a gas water heater in the kitchen? I have an outside wall with a hole in it which would no doubt take a flue. right now this is above the gas hob. could this work if the heater were sufficiently high above the gas hob? or do I need to move the gas hob?
andy
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On Fri, 08 Jan 2010 23:11:45 +0000, Andrew Gabriel wrote:

=============================================== I don't think a special *thermostatic* mixer is required judging by past experience with Main multipoints and my present Worcester (now obsolete) multipoint. An ordinary shower mixer is quite suitable although separate thermostatic valves can be fitted to prevent any danger of scalding in hot weather.
Cic.
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Which should tell you that electric on-demand water heaters will take a lot longer than gas to fill a bath... it might actually go cold first (you probably will go cold waiting :-) You basically have to store with electric water heating for bath usage.
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