My friend who lives in a flat (so cannot be gas connected) is pining for having baths instead of showers (a wimin thing maybe?) Problem is that their 125 litre electric (E7) boiler cannot fill a bath and so emptying till it runs cold then and boost switching it for another load are not really viable due to the time delay.

My question is are powerful (ie 3kW) instantaneous electric water heaters suitable and viable (ignoring the eye-watering elec cost)?

Their supply has a 50A fuse which suggests ~10kW to play with, this relates to about 6 litres/min.

I've always been a bit puzzled why we don't see powerful instant elec water heaters much, it's either the powerful multipoint gas ones or, if electric, then slow immersion heater type boilers.

Perhaps the extortionate electricity cost would deter buyers?

On 28/08/2020 13:13, wrote:
My friend who lives in a flat (so cannot be gas connected) is pining
for having baths instead of showers (a wimin thing maybe?) Problem is
that their 125 litre electric (E7) boiler cannot fill a bath and so
emptying till it runs cold then and boost switching it for another
load are not really viable due to the time delay.


What capacity is the bath, and what temperature is the boiler/cylinder
supplying the hot water at?

Since a 125L cylinder of water at 60 degrees, should be able to supply a
moderate "bath full" when mixed down to temp with cold.

My question is are powerful (ie 3kW) instantaneous electric water
heaters suitable and viable (ignoring the eye-watering elec cost)?

You get some inline ones that will do the job, so long as you don't mind
the longer time to fill.

(IIRC Tim Watts posted previously about running such an arrangement at
his place while renovating and before the CH was commissioned, and it
worked well enough).

Their supply has a 50A fuse which suggests ~10kW to play with, this
relates to about 6 litres/min.

I've always been a bit puzzled why we don't see powerful instant elec
water heaters much, it's either the powerful multipoint gas ones or,
if electric, then slow immersion heater type boilers.

Probably because to get to the performance of even a low end combi would
consume all of the electrical supply capacity for most properties.

If you want performance with electric heating, the go for an unvented
mains pressure cylinder, and stick 3 immersions in it.



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Cheers,

John.

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What about bottled gas? Over in Spain they seem to use it to do this sort of
thing using things that look a lot like those old Ascot mini water heaters
on the wall with a mixer tap on the bottom.
Brian

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"Jethro_uk" wrote in message
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On Fri, 28 Aug 2020 05:13:20 -0700, wrote:

Perhaps the extortionate electricity cost would deter buyers?

I'm guessing the wiring required for *sustained* delivery of hot water
over maybe 10-15 minutes is more chunky than you think ?

There might also be some sort of issue with needing more than one phase
(since there's currently a thread on it ...) ???

Or, it's just habit. I learned long ago that "we've always done it this
way" is the biggest single drag on progress - well ahead of economics or
practicalities.

On 28/08/2020 14:17:51, John Rumm wrote:
On 28/08/2020 13:13, wrote:
My friend who lives in a flat (so cannot be gas connected) is pining
for having baths instead of showers (a wimin thing maybe?) Problem is
that their 125 litre electric (E7) boiler cannot fill a bath and so
emptying till it runs cold then and boost switching it for another
load are not really viable due to the time delay.


What capacity is the bath, and what temperature is the boiler/cylinder
supplying the hot water at?

Since a 125L cylinder of water at 60 degrees, should be able to supply a
moderate "bath full" when mixed down to temp with cold.

That was my thought. Is there any mileage in fitting a mixing valve to
the hot water output to reduce/stabilise the temperature and run the
tank at 90degsC?

If there is a cold feed then that would be the cold supply.

My question is are powerful (ie 3kW) instantaneous electric water
heaters suitable and viable (ignoring the eye-watering elec cost)?

You get some inline ones that will do the job, so long as you don't mind
the longer time to fill.

(IIRC Tim Watts posted previously about running such an arrangement at
his place while renovating and before the CH was commissioned, and it
worked well enough).

Their supply has a 50A fuse which suggests ~10kW to play with, this
relates to about 6 litres/min.

I've always been a bit puzzled why we don't see powerful instant elec
water heaters much, it's either the powerful multipoint gas ones or,
if electric, then slow immersion heater type boilers.

Probably because to get to the performance of even a low end combi would
consume all of the electrical supply capacity for most properties.

If you want performance with electric heating, the go for an unvented
mains pressure cylinder, and stick 3 immersions in it.

Or the suggestion above. Though that would make a good shower feed and
fill a bath quickly!

On 28/08/2020 13:13, wrote:
My friend who lives in a flat (so cannot be gas connected) is pining for having baths instead of showers (a wimin thing maybe?) Problem is that their 125 litre electric (E7) boiler cannot fill a bath and so emptying till it runs cold then and boost switching it for another load are not really viable due to the time delay.

My question is are powerful (ie 3kW) instantaneous electric water heaters suitable and viable (ignoring the eye-watering elec cost)?

Their supply has a 50A fuse which suggests ~10kW to play with, this relates to about 6 litres/min.

I've always been a bit puzzled why we don't see powerful instant elec water heaters much, it's either the powerful multipoint gas ones or, if electric, then slow immersion heater type boilers.

Perhaps the extortionate electricity cost would deter buyers?

Well there are plenty of simple instantaneous electric shower heaters
from 6 kW upwards. That size can run off a 30A fuse/MCB via 4 mm^2.

Do they own or rent the flat? Unless it is *tiny* I would have thought
there is no problem getting in a more normal sized domestic supply (80
or 100A) although obviously there is a cost.

On Fri, 28 Aug 2020 05:13:20 -0700, wrote:

My friend who lives in a flat (so cannot be gas connected) is pining for
having baths instead of showers (a wimin thing maybe?) Problem is that
their 125 litre electric (E7) boiler cannot fill a bath and so emptying
till it runs cold then and boost switching it for another load are not
really viable due to the time delay.

My question is are powerful (ie 3kW) instantaneous electric water
heaters suitable and viable (ignoring the eye-watering elec cost)?

Their supply has a 50A fuse which suggests ~10kW to play with, this
relates to about 6 litres/min.

I've always been a bit puzzled why we don't see powerful instant elec
water heaters much, it's either the powerful multipoint gas ones or, if
electric, then slow immersion heater type boilers.

Perhaps the extortionate electricity cost would deter buyers?

This sounds like trying to fill a bath using an electric shower.
10.5 kW showers are readily available.

I can't recall ever having a modern 10.5 kW electric shower, but the older
ones certainly wouldn't fill a standard bath with hot water in a realistic
time frame.

You don't mention the size of the bath, but a quick search suggests that a
standard 1700 * 750 bath holds about 220 litres so the hot water tank
would presumably half fill that.

I don't think anyone yet has directly suggested fitting a larger hot water
tank. I think John R more or less did.

I think the issue is that the hot water tank isn't big enough, and there
isn't enough electricity supply to directly heat cold water fast enough.

The logical solution is to fit a bigger hot water tank or a smaller bath.

You need to be prepared for a fairly long wait for the larger tank to come
back up to temperature, but again John R has made some suggestions there.

Cheers


Dave R



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wrote:

My friend who lives in a flat (so cannot be gas connected) is pining for having baths instead of showers
Someone in another group has a "heat battery" I think stores off peak
electricity into phase-change material, then heats water from it later,
he seems happy with it, but do your own research ...

https://www.sunamp.com/residential

On 28/08/2020 15:47, Fredxx wrote:
On 28/08/2020 14:17:51, John Rumm wrote:

Since a 125L cylinder of water at 60 degrees, should be able to supply
a moderate "bath full" when mixed down to temp with cold.

That was my thought. Is there any mileage in fitting a mixing valve to
the hot water output to reduce/stabilise the temperature and run the
tank at 90degsC?

A different thought has occurred to me.

It's an E7 set up. Is the bottom element working or getting a full
charge? Faulty/turned down stat etc.

I too would expect 125L of hot water to be plenty for a bath.


--
Adam

On 28 Aug 2020 at 13:13:20 BST, "
wrote:

My friend who lives in a flat (so cannot be gas connected) is pining for
having baths instead of showers (a wimin thing maybe?) Problem is that their
125 litre electric (E7) boiler cannot fill a bath and so emptying till it
runs cold then and boost switching it for another load are not really viable
due to the time delay.

My question is are powerful (ie 3kW) instantaneous electric water heaters
suitable and viable (ignoring the eye-watering elec cost)?

Their supply has a 50A fuse which suggests ~10kW to play with, this relates
to about 6 litres/min.

I've always been a bit puzzled why we don't see powerful instant elec water
heaters much, it's either the powerful multipoint gas ones or, if electric,
then slow immersion heater type boilers.

Perhaps the extortionate electricity cost would deter buyers?

Anecdotally (from the 8kW shower I've got) instantaneous hot water won't work
unless you've got a hugely powerful heater. The water will cool too quickly.
Assuming this is a shower over a bath, try having a shower with the bath plug
in . . .

As others have said, larger tank with bigger heaters.

--
Cheers, Rob

Thanks all for your ideas and advice. They are constrained by space so a larger tank is not possible (unless I put it in their lounge and call it steam punk art!). Yes both elements are pulling current. I'm going to investigate if I can fit higher power elements as, from memory, I think they're only 3kW and fitting bigger cable would be easy from their board.

On Friday, 28 August 2020 15:47:19 UTC+1, Fredxx wrote:
On 28/08/2020 14:17:51, John Rumm wrote:
On 28/08/2020 13:13, wrote:
My friend who lives in a flat (so cannot be gas connected) is pining
for having baths instead of showers (a wimin thing maybe?) Problem is
that their 125 litre electric (E7) boiler cannot fill a bath and so
emptying till it runs cold then and boost switching it for another
load are not really viable due to the time delay.


What capacity is the bath, and what temperature is the boiler/cylinder
supplying the hot water at?

Since a 125L cylinder of water at 60 degrees, should be able to supply a
moderate "bath full" when mixed down to temp with cold.

That was my thought. Is there any mileage in fitting a mixing valve to
the hot water output to reduce/stabilise the temperature and run the
tank at 90degsC?

Increasing cylinder temp is likely to be your solution. 90 is excessive though, just try adding 5-10C & see how that goes first. You may run into the problem that recent immersions often trip out at not hot enough water temp. It also increases standing losses, significant if cylinder uninsulated.

If you went as high as 90C you would need to TMV it for safety, but something is going very odd if you need to raise it that much.


If there is a cold feed then that would be the cold supply.

My question is are powerful (ie 3kW) instantaneous electric water
heaters suitable and viable (ignoring the eye-watering elec cost)?

You get some inline ones that will do the job, so long as you don't mind
the longer time to fill.

(IIRC Tim Watts posted previously about running such an arrangement at
his place while renovating and before the CH was commissioned, and it
worked well enough).

Their supply has a 50A fuse which suggests ~10kW to play with, this
relates to about 6 litres/min.

I've always been a bit puzzled why we don't see powerful instant elec
water heaters much, it's either the powerful multipoint gas ones or,
if electric, then slow immersion heater type boilers.

Probably because to get to the performance of even a low end combi would
consume all of the electrical supply capacity for most properties.

If you want performance with electric heating, the go for an unvented
mains pressure cylinder, and stick 3 immersions in it.

Or the suggestion above. Though that would make a good shower feed and
fill a bath quickly!

An instant inline water heater can certainly add to the heat delivered to the bath, though you probably won't need it once the cyl temp is increased. Worth calculating how much heat can be added in your fill time.


NT

On Saturday, 29 August 2020 11:45:29 UTC+1, wrote:

Thanks all for your ideas and advice. They are constrained by space so a larger tank is not possible (unless I put it in their lounge and call it steam punk art!). Yes both elements are pulling current. I'm going to investigate if I can fit higher power elements as, from memory, I think they're only 3kW and fitting bigger cable would be easy from their board.

If there's one thing I can safely say it's that a 3kW limit is not the issue. Even 1kW would get you a bath full of scalding water per day, it just takes longer to get hot.


NT

On Sat, 29 Aug 2020 03:45:25 -0700 (PDT), "
wrote:

Thanks all for your ideas and advice. They are constrained by space so a larger tank is not possible (unless I put it in their lounge and call it steam punk art!). Yes both elements are pulling current. I'm going to investigate if I can fit higher power elements as, from memory, I think they're only 3kW and fitting bigger cable would be easy from their board.

Where I live you have to improvise from time to time when there are
fuel shortages. I had to directly heat a bath quite recently.. I can't
recommend the method for anyone else to use unless they're really on
the ball, but here's what I did just to get me by until the fuel
tanker made a return appearance.
I got one of those immersion heater elements they make for those large
copper hot water cylinders. I manage to find a compact one that was
3kw but only 11" long; short enough to be able to dangle into the bath
from a bamboo stick placed across the width of the bath and secured
into place with zip ties. I ran some 15A cable to a nearby 3 pin
outlet, filled the bath up and switched on. It's a good idea to chuck
a thermometer into the bathwater so you can see how it's heating up
rather than periodically sticking your elbow/foot/hand/penis into it,
because it's a really bad idea to go anywhere near it while it's on.
The bath concerned was larger than normal. I don't know the exact
capacity of it, but it's bigger than average by some margin. It took
about one hour and twenty minutes to get up to a nice, warm
temperature. Provided you remember to switch off and isolate each time
you want to go near it, you should be fine. Just make sure the element
is submerged in the water at all times until you're ready to dive in.
Top tip: remember to disconnect the power first!

On Saturday, 29 August 2020 14:03:34 UTC+1, wrote:
If there's one thing I can safely say it's that a 3kW limit is not the issue.
Even 1kW would get you a bath full of scalding water per day, it just takes
longer to get hot.


I'm not sure it would. It would run so slowly it would cool down before the bath was filled.

Anyway, it would hardly be instantaneous.

Owain

On 29/08/2020 11:45, wrote:
Thanks all for your ideas and advice. They are constrained by space so a larger tank is not possible (unless I put it in their lounge and call it steam punk art!). Yes both elements are pulling current. I'm going to investigate if I can fit higher power elements as, from memory, I think they're only 3kW and fitting bigger cable would be easy from their board.

You can certainly get much more powerful elements with the standard
2 1/4 inch flange, a mate of mine uses 9kW ones that are designed for 3
phase but you can use them on a single phase with suitable cable and fusing.

On 29/08/2020 17:02, newshound wrote:
On 29/08/2020 11:45, wrote:
Thanks all for your ideas and advice. They are constrained by space so
a larger tank is not possible (unless I put it in their lounge and
call it steam punk art!). Yes both elements are pulling current. I'm
going to investigate if I can fit higher power elements as, from
memory, I think they're only 3kW and fitting bigger cable would be
easy from their board.

You can certainly get much more powerful elements with the standard 2
1/4 inch flange, a mate of mine uses 9kW ones that are designed for 3
phase but you can use them on a single phase with suitable cable and
fusing.

most houses are main fused for 15kw

2x9KW is OTT

--
"In our post-modern world, climate science is not powerful because it is
true: it is true because it is powerful."

Lucas Bergkamp

On 29/08/2020 16:48, wrote:
On Saturday, 29 August 2020 14:03:34 UTC+1, wrote:
If there's one thing I can safely say it's that a 3kW limit is not the issue.
Even 1kW would get you a bath full of scalding water per day, it just takes
longer to get hot.


I'm not sure it would. It would run so slowly it would cool down before the bath was filled.

I sense some talking at cross purposes here. ISTM the OP described a
storage system heated by immersion heaters. That not apparently being up
to the job caused the query about if a instantaneous heater could be
added to replace or augment the current setup.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 29/08/2020 11:45, wrote:

Thanks all for your ideas and advice. They are constrained by space
so a larger tank is not possible (unless I put it in their lounge and
call it steam punk art!). Yes both elements are pulling current. I'm
going to investigate if I can fit higher power elements as, from
memory, I think they're only 3kW and fitting bigger cable would be
easy from their board.


I doubt its a power issue. It sounds like the thermostat on the
immersion heaters is set to too low a temperature. Hence when you run
the bath you need to use almost exclusively hot water to get a bath at
the right temperature, and so only get the 100 ish litres of water.

If you increase the temperature of the stored hot water, then when
running a bath you will need to add much more cold water to get the bath
at a comfortable temperature. So the total volume of bath water will go
up without changing the size of the cylinder.

If you read this:

http://wiki.diyfaq.org.uk/index.php/...water_cylinder

It explains how you can work out what volume of stored hot water and at
what temperature you need to store it.



--
Cheers,

John.

/================================================== ===============\
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|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 29/08/2020 14:00:52, wrote:
On Friday, 28 August 2020 15:47:19 UTC+1, Fredxx wrote:
On 28/08/2020 14:17:51, John Rumm wrote:
On 28/08/2020 13:13, wrote:
My friend who lives in a flat (so cannot be gas connected) is
pining for having baths instead of showers (a wimin thing
maybe?) Problem is that their 125 litre electric (E7) boiler
cannot fill a bath and so emptying till it runs cold then and
boost switching it for another load are not really viable due
to the time delay.


What capacity is the bath, and what temperature is the
boiler/cylinder supplying the hot water at?

Since a 125L cylinder of water at 60 degrees, should be able to
supply a moderate "bath full" when mixed down to temp with cold.

That was my thought. Is there any mileage in fitting a mixing valve
to the hot water output to reduce/stabilise the temperature and run
the tank at 90degsC?

Increasing cylinder temp is likely to be your solution. 90 is
excessive though, just try adding 5-10C & see how that goes first.
You may run into the problem that recent immersions often trip out at
not hot enough water temp. It also increases standing losses,
significant if cylinder uninsulated.

If you went as high as 90C you would need to TMV it for safety, but
something is going very odd if you need to raise it that much.

I assumed anything over 50C ought to have a TMV. That was suggested in
my post.

snip

An instant inline water heater can certainly add to the heat
delivered to the bath, though you probably won't need it once the cyl
temp is increased. Worth calculating how much heat can be added in
your fill time.

An instant online heater will have no effect until the tank is empty and
then won't have enough power to heat any flow of water unless 10kW or more.

On Saturday, 29 August 2020 16:48:36 UTC+1, wrote:
On Saturday, 29 August 2020 14:03:34 UTC+1, tabby wrote:

If there's one thing I can safely say it's that a 3kW limit is not the issue.
Even 1kW would get you a bath full of scalding water per day, it just takes
longer to get hot.


I'm not sure it would. It would run so slowly it would cool down before the bath was filled.

Anyway, it would hardly be instantaneous.

Owain

3kW can get you a hot bath in an hour. 1kW is far above standing losses so 1kW wouldn't take a lot longer than 3hrs to get there.

It's mostly instantaneous... but if someone else has just used the lot, it becomes instantaneously very slow.


NT

On Saturday, 29 August 2020 19:14:31 UTC+1, Fredxx wrote:
On 29/08/2020 14:00:52, tabbypurr wrote:
On Friday, 28 August 2020 15:47:19 UTC+1, Fredxx wrote:
On 28/08/2020 14:17:51, John Rumm wrote:

An instant inline water heater can certainly add to the heat
delivered to the bath, though you probably won't need it once the cyl
temp is increased. Worth calculating how much heat can be added in
your fill time.

An instant online heater will have no effect until the tank is empty and
then won't have enough power to heat any flow of water unless 10kW or more.

Instant heating can run while the cylinder fills the bath. It gets you 2 hot supplies at once, one stored & one via the cold tap. Result: more hot water available. But it's moot, just turn the temp up a little.


NT

On 31/08/2020 21:38, wrote:
On Saturday, 29 August 2020 16:48:36 UTC+1, wrote:
On Saturday, 29 August 2020 14:03:34 UTC+1, tabby wrote:

If there's one thing I can safely say it's that a 3kW limit is not the issue.
Even 1kW would get you a bath full of scalding water per day, it just takes
longer to get hot.


I'm not sure it would. It would run so slowly it would cool down before the bath was filled.

Anyway, it would hardly be instantaneous.

Owain

3kW can get you a hot bath in an hour.

If you can fill a bath using only 60 - 70 L of hot water!

1kW is far above standing losses so 1kW wouldn't take a lot longer than 3hrs to get there.

See above


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Tuesday, 1 September 2020 00:54:18 UTC+1, John Rumm wrote:
On 31/08/2020 21:38, tabbypurr wrote:
On Saturday, 29 August 2020 16:48:36 UTC+1, wrote:
On Saturday, 29 August 2020 14:03:34 UTC+1, tabby wrote:

If there's one thing I can safely say it's that a 3kW limit is not the issue.
Even 1kW would get you a bath full of scalding water per day, it just takes
longer to get hot.


I'm not sure it would. It would run so slowly it would cool down before the bath was filled.

Anyway, it would hardly be instantaneous.

Owain

3kW can get you a hot bath in an hour.

If you can fill a bath using only 60 - 70 L of hot water!

1kW is far above standing losses so 1kW wouldn't take a lot longer than 3hrs to get there.

See above

I'm more used to a 4" bath, though I've not had a bath in a long time 60l can do more than that. The hotter your HW cylinder the deeper you can have. Add instant heat & you get more.

Of course there is a way you can have as much as hot as you like:
http://wiki.diyfaq.org.uk/index.php/Bathroom_electrics
But I definitely don't recommend it. Seen setups like that in the developing world. A single error = death.


NT