Hello - I've been racking my brains to see whether an electric water heater could take the place of my ageing Main Medway gas heater. Thinking electric because there's very little room on outside walls for a combi boiler. My flat is a modest 2 bedroom and there's just the kitchen sink, bathroom sink, bath and shower. In Europe many domestic homes have 3 phase wiring and 400v electric heaters, but good luck if you could have this fitted in Kensington, London.

The 230v tankless options seem largely to go up to around 10Kw which should be OK for kitchen sink and a rather puny but serviceable shower e.g. Mira. Main problem is Winter when the water gets cold. But I have seen some larger more expensive Bosch and other models which may be more efficient.

Going back to basics, to fill a bath you probably need a tank with electric heating. But rather than the tank being on all the time, just switch over to the tank when you want a bath, and leave it off most of the time for tankless operation. Also, the tank would not need to be the full 80 litres of an average bath - could be just enough to get the water hot and top up with tankless operation. Maybe 50 litres or less. Also the tank has to be heated to over 50* to kill bacteria.

Is there any way I could get away with electric heating? What are my options?

The Main Medway multipoint is larger than a modern combi, so simply remove
this and put a combi where it was

Alas, not so simple. It's in a small room which will be a bedroom, so no dice. There's also no wall in the bathroom for one and it would mean compromising the kitchen. These are the reasons why I'm considering electric, which is what I want to find out about in this thread.

In article ,
Eusebius writes:
Hello - I've been racking my brains to see whether an electric water heater could take the place of my ageing Main Medway gas heater. Thinking electric because there's very little room on outside walls for a combi boiler. My flat is a modest 2 bedroom and there's just the kitchen sink, bathroom sink, bath and shower. In Europe many domestic homes have 3 phase wiring and 400v electric heaters, but good luck if you could have this fitted in Kensington, London.
The 230v tankless options seem largely to go up to around 10Kw which should be OK for kitchen sink and a rather puny but serviceable shower e.g. Mira. Main problem is Winter when the water gets cold. But I have seen some larger more expensive Bosch and other models which may be more efficient.
Going back to basics, to fill a bath you probably need a tank with electric heating. But rather than the tank being on all the time, just switch over to the tank when you want a bath, and leave it off most of the time for tankless operation. Also, the tank would not need to be the full 80 litres of an average bath - could be just enough to get the water hot and top up with tankless operation. Maybe 50 litres or less. Also the tank has to be heated to over 50* to kill bacteria.
Is there any way I could get away with electric heating? What are my options?

The Main instant water heaters are around 20-25kW output IIRC.
You can't run a single appliance of that power from a normal domestic
electricity supply.

Max UK single-phase domestic supply is 100A, but in a small house or
flat, you might have only a 60A or 80A supply. You can have a 2 or 3-
phase supply, but you'll have to pay for it to be installed (can be
very expensive if there isn't 3-phase nearby). There's no limit to
3-phase current you can have, but again, installation cost will depend
how far they have to run the supply cables to reach a point which
can supply your load. There may be 3-phase coming in to the block of
flats, which could make it an easy option. You can get [single phase]
electric showers a little above 10kW, but that's about it.

The Main appliances hang from the through-the-wall flue terminal. For
something like 40 years, Main designed each new model to hang from
all the previous models' flues, which made fitting the current models
in place of an old one quite easy. (The pipework doesn't line up, so
you will need to get that adjusted to fit.) I don't know if that's
still the case. (Only the room-sealed models without any electricity
supply, not the fanned-flue electric models.)

One issue is the room-sealed models are permenent pilot, and that
costs you around 250W gas energy continuously lost out the flue, which
is more significant in costs that it was when these systems were
designed. For a little used water heater, it's easily more than the
heater uses heating the water averaged over a period of time.

If you want to get rid of the instant gas water heating, your options
are really a combi, or stored hot water heated electrically if you
don't want gas. Yes, you can just heat the tank when you need it if
you are sufficiently organised. (I now do that even with a gas boiler
heating the tank.)

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

Eusebius wrote:
Hello - I've been racking my brains to see whether an electric water
heater could take the place of my ageing Main Medway gas heater. Thinking
electric because there's very little room on outside walls for a combi
boiler. My flat is a modest 2 bedroom and there's just the kitchen sink,
bathroom sink, bath and shower. In Europe many domestic homes have 3
phase wiring and 400v electric heaters, but good luck if you could have
this fitted in Kensington, London.

Where does your existing heater have its flue? Any reason not to replace it
with a new multipoint gas water heater?

Tim

Where does your existing heater have its flue? Any reason not to replace it
with a new multipoint gas water heater? Tim

The 2 possible locations are both on an inner wall giving into a well. And only 2 wall spaces since the rest is windows. Only two options for gas:

1. Where the existing Main is, which will be a bedroom. so that excludes a combi. Is the Main legal in a bedroom anyway? If so it could be replaced with a newer one, but these types are obsolescent and anyway they develop faults and it's £250 minimum to call a plumber to service it. Like Andrew says, the pilot light is always on as well.
2. In the kitchen next to the bedroom. This would be for a combi, but it's where the cooker is and I don't want to put the cooker on another wall, since the kitchen is small and works the way it is. I could fit a combi on the back wall and run about 14ft of pipe around the walls and out above the cooker..... not perfect.

Andrew - thanks for a REALLY informative and helpful post.

On Saturday, 10 October 2015 19:19:32 UTC+1, Eusebius wrote:
1. Where the existing Main is, which will be a bedroom. so that excludes
a combi. Is the Main legal in a bedroom anyway?

Room-sealed boilers are legal in bedrooms, AIUI.

What is your existing heating system?

Peak rate electricity costs are about 3x the price of gas. Also depending on the age and specification of your flats you may have as low as a 40 amp supply.

Owain

On 10/10/2015 17:01, Eusebius wrote:
The Main Medway multipoint is larger than a modern combi, so simply
remove this and put a combi where it was

Alas, not so simple. It's in a small room which will be a bedroom, so
no dice. There's also no wall in the bathroom for one and it would
mean compromising the kitchen. These are the reasons why I'm
considering electric, which is what I want to find out about in this
thread.

Keep in mind a boiler does not have to be on an outside wall. And if it
is, does not have to be on the inside of it!


--
Cheers,

John.

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Keep in mind a boiler does not have to be on an outside wall. And if it
is, does not have to be on the inside of it!

Maybe I'll reconsider a combi. It would help a lot if it were really thin front to back. I think this is possible with some of the Dutch ones like Intergas. Will have to have another look at those - there's also Atag.

On Saturday, 10 October 2015 23:06:31 UTC+1, John Rumm wrote:
On 10/10/2015 17:01, Eusebius wrote:

The Main Medway multipoint is larger than a modern combi, so simply
remove this and put a combi where it was

Alas, not so simple. It's in a small room which will be a bedroom, so
no dice. There's also no wall in the bathroom for one and it would
mean compromising the kitchen. These are the reasons why I'm
considering electric, which is what I want to find out about in this
thread.

Keep in mind a boiler does not have to be on an outside wall. And if it
is, does not have to be on the inside of it!

There is the outside option. You'd need antifreeze in the primary circuit.

A lot of flats are on a 40A supply.

I would question the drive for a 10kW shower. It seems to be becoming the fashion, but there's no need. I only run mine at 3-4kW. Another way to increase shower power is with a drain heat exchanger, which can harvest 50% of lost heat. Also aeration & pulsing shower heads permit some waterflow reduction. With such approaches a modest electric shower can perform generously.


NT

On 10/10/2015 19:19, Eusebius wrote:
The 2 possible locations are both on an inner wall giving into a well.

How deep is the well (or rather, how far are you from the top)

Some boilers allow quite long flues.

Andy