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UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions. |
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#1
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Electric instantaneous water heaters - experiences please!!
I'm considering replacing am old gas water heater (Main Medway) with an electric one. As far as I can see it needs at least 18kW for a bath or shower, maybe more like 21kW or 24kW. I just need to supply a kitchen sink and a shower/bath. Adjacent rooms, small flat.
I have the usual 240v supply, and some but not all of these units are 400v. Looks like pretty heavy gauge wiring required, like 8 gauge. Is this practical?It's hard to get a lot of information on these kind of units, though they're widely used in the USA and Germany. |
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Electric instantaneous water heaters - experiences please!!
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#4
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Electric instantaneous water heaters - experiences please!!
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#5
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Electric instantaneous water heaters - experiences please!!
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#6
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Electric instantaneous water heaters - experiences please!!
In response to questions, the flat which is basically a decent size bedroom and a decent size living room + small bedroom, is heated with two open gas fires in the main rooms. This is economical, so I'm debating whether I need central heating. The Main Medway is just right for filling a bath. Negligible needs in the kitchen - just filling a sink.
I was initially going to replace the Main Medway with a combo boiler, but I'm very restricted as to where the flue can go out and it's on the 2nd floor. I have very few options, and even those aren't ideal. Right now the Main Medway is in a small utility room which I'd like to use as a bedroom. I believe that with that type of heater you can have it in a bedroom, but please tell me if regulations have changed. Combi boilers are out in bedrooms of course, and so are exit pipes from combi boilers. The layout is OK as it is and it would be a real pain to change it, hence an electric unit would make things easier. I do use a bath, so has to be 18kW minimum and 21kW or 24kW better. I'll have to find out what supply I have and if it's 100A. Keep the suggestions coming! |
#7
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Electric instantaneous water heaters - experiences please!!
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#8
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Electric instantaneous water heaters - experiences please!!
On Sunday, February 22, 2015 at 5:19:20 PM UTC, wrote:
In response to questions, the flat which is basically a decent size bedroom and a decent size living room + small bedroom, is heated with two open gas fires in the main rooms. This is economical, so I'm debating whether I need central heating. The Main Medway is just right for filling a bath. Negligible needs in the kitchen - just filling a sink. I was initially going to replace the Main Medway with a combo boiler, but I'm very restricted as to where the flue can go out and it's on the 2nd floor. I have very few options, and even those aren't ideal. Right now the Main Medway is in a small utility room which I'd like to use as a bedroom. I believe that with that type of heater you can have it in a bedroom, but please tell me if regulations have changed. Combi boilers are out in bedrooms of course, and so are exit pipes from combi boilers. The layout is OK as it is and it would be a real pain to change it, hence an electric unit would make things easier. I do use a bath, so has to be 18kW minimum and 21kW or 24kW better. I'll have to find out what supply I have and if it's 100A. Keep the suggestions coming! You could look at some kind of heatbank cylinder. Something like this: http://www.gledhill.net/pdf/spec%201...0stainless.pdf is not much bigger than a boiler, and would do better hot water than a small combi. Something like http://heatweb.co.uk/products/ds21/ would also do the central heating, but is a bit bigger. Both are heated electrically, and could be mainly heated overnight, and just topped up in the day if needed, so if you switch to a 2 rate supply, it would be a similar cost to run as gas. A |
#9
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Electric instantaneous water heaters - experiences please!!
On 22/02/2015 16:12, wrote:
I'm considering replacing am old gas water heater (Main Medway) with an electric one. As far as I can see it needs at least 18kW for a bath or shower, maybe more like 21kW or 24kW. I just need to supply a kitchen sink and a shower/bath. Adjacent rooms, small flat. An electric shower will probably only need 10kW (for a fairly feeble shower it has to be said). But bath filling with instant electric is going to be an exercise only for the very patient. I have the usual 240v supply, and some but not all of these units are 400v. Looks like pretty heavy gauge wiring required, like 8 gauge. Is this practical?It's hard to get a lot of information on these kind of units, though they're widely used in the USA and Germany. Other than for hand washing etc, its probably a non starter unless you want to go to lots of hassle. An unvented cylinder can be heated by electric (and could take advantage of cheap rate power as well). That would give a much better experience for both showers and baths. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
#10
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Electric instantaneous water heaters - experiences please!!
There are 3 phase ZIP & other instant water heaters.
However it will cost you a fair chunk to upgrade the flat supply to 3ph. It is possible to use an electric shower at 8.5-9.8-10.5-12.5kW. That is assuming the supply is at least 60A, preferably 80A (ie, not 40A). However you can forget a bath re standing losses of the bath and fill time. A 9.5kW ZIP is basically 4L/min in winter at 38-40oC ... a bath is 90L. You need a low flow head - 6L/min at best, aeration or ultra low flow. The solution is most likely a) electric shower & dedicated undersink 5L/10L stored water heater (vented/unvented) in kitchen or b) stored UNVENTED water heater of 50L capacity for a shower (Powerflow) or 90L for a bath. Note stored UNVENTED are a higher temp (60-65oC) so their effective volumetric capacity is higher than it appears re TMV (thermostatic mixer) set to say 38-41oC. It needs a G3 plumber to install big unvented (or notification and do the bulk of the work yourself IIRC), they MUST be installed with all the correct pressure & temp release pipework run correctly re sizing, bends, etc. It is not a trivial task - best to go read the instructions on one online and consider the location re pressure & temp outlet pipework. Such heaters can however be 1kW to 4kW, so work fine with a modest electrical supply. |
#11
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Electric instantaneous water heaters - experiences please!!
Looks like the Main Medway unit I have now is the easiest solution. I was informed that such balanced flue room sealed water heaters are obsolescent and may not exist in a few years - don't know how true that is.
But at least, as far as I can tell, regulations still allow room sealed balanced flue units to be used in bedrooms so I could put a bed in the room. Let me know if that's incorrect. |
#12
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Electric instantaneous water heaters - experiences please!!
*BALANCED* flue means air for combustion AND products of combustion are handled externally to the room - just like a modern combi/standard gas central heating boiler. I see no problem with that surely?
It IS however common for small flats to have a 50/90L unvented water heater on 3kW supply for shower/bath. A 50L unit will do (size) if fitted with TMV to 38-41oC, 6L/min shower head (aerator oxygenics or something), and a separate 5-10L unvented or 15L unvented water heater for the kitchen. The latter is more at the luxury end re backup if the other goes off, and 5L will still give 9L of hot water re reheat/mixed-temp time, with most likely a table-top or compact dishwasher in use. Most washers being cold fill these days too. The 5L vented units from Stiebel Eltron do not drip from the tap (people keep tightening until the costly tap is stuffed) because they effectively have an internal expansion loop. I would go for a) gas b) unvented 50L unit (& mini for kitchen re redundancy) and lastly c) instant for shower only (useless for a bath). |
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