Hi,

I'm hoping to redo my old CH/DHW system. I like the idea of a heat bank;
the best place for me would be under a worktop near the wall-mounted boiler
in the kitchen.

I've only found one suitable heat bank for this
locationhttp://www.heatweb.com/products/cyli.../worktop.html).

As far as I know, this will be rather expensive (around £1k? - more than a
modern, complex, quality boiler, which seems a bit daft!).

Does anyone know of any other under-the-worktop models it would be worth
looking at?

Cheers,

Steve

"Steve" wrote in message
...
Hi,

I'm hoping to redo my old CH/DHW system. I like the idea of a heat bank;
the best place for me would be under a worktop near the wall-mounted
boiler
in the kitchen.

I've only found one suitable heat bank for this

locationhttp://www.heatweb.com/products/cyli.../worktop.html).

As far as I know, this will be rather expensive (around £1k? - more than a
modern, complex, quality boiler, which seems a bit daft!).

Does anyone know of any other under-the-worktop models it would be worth
looking at?

Cheers,

Steve


Mmmm, around £1000 eh!

I feel sure that a certain person will pop up with instructions on how to
build your own heat bank with an empty oil drum and the guts from an old
boiler for about 25 quid.

On Sun, 17 Jun 2007 19:39:17 +0100, Steve wrote:

Does anyone know of any other under-the-worktop models it would be worth
looking at?

http://wiki.diyfaq.org.uk/index.php?title=DIY_Heat_Bank

(This is a DIY group :-))

--
John Stumbles

On 2007-06-17 19:39:17 +0100, "Steve" said:

Hi,

I'm hoping to redo my old CH/DHW system. I like the idea of a heat bank;
the best place for me would be under a worktop near the wall-mounted boiler
in the kitchen.

I've only found one suitable heat bank for this
locationhttp://www.heatweb.com/products/cyli.../worktop.html).

As far as I know, this will be rather expensive (around £1k? - more than a
modern, complex, quality boiler, which seems a bit daft!).

Does anyone know of any other under-the-worktop models it would be worth
looking at?

Cheers,

Steve

One important thing to look at here is that by virtue of the size of an
undersink unit, the storage capacity will be quite small. Normally,
a heat bank stores water at 80 degrees as opposed to a conventional DHW
tank storing it at 60 degrees. The impact of that is that 1.3x the
volume of hot water will be produced before the stored energy runs out.
So one comparison to make is whether the proposed store is less
than 3/4 the capacity of your current cylinder. If it is much less,
then tread carefully.

The boiler will begin to reheat the store as you use water. The effect
of that will depend on the boiler output.
However, once the store is emptied, the rate at which it will be
possible to use HW at a given temperature will reduce. You can look
up the specs. of equivalent output combi boilers to get an idea of what
the final output will be.

Thanks for the suggestions chaps. In response to a couple of your comments:

- I am intending to DIY everything myself except the (gas) boiler. However
I'd not considered a DIY heat bank, but it sounds like a possibility if I
can get a suitable size and shape of tank that I can properly insulate; I'll
definitely consider this.

- The unit would fit under a worktop where there would normally be a
cupboard (rather than under the sink) and could easily be a very large tank.

Steve



"Steve" wrote in message
...
Hi,

I'm hoping to redo my old CH/DHW system. I like the idea of a heat bank;
the best place for me would be under a worktop near the wall-mounted
boiler
..
..

"Steve" wrote in message
...
Hi,

I'm hoping to redo my old CH/DHW system. I like the idea of a heat bank;
the best place for me would be under a worktop near the wall-mounted
boiler in the kitchen.

I've only found one suitable heat bank for this
locationhttp://www.heatweb.com/products/cyli.../worktop.html).

As far as I know, this will be rather expensive (around £1k? - more than a
modern, complex, quality boiler, which seems a bit daft!).

Does anyone know of any other under-the-worktop models it would be worth
looking at?

Cheers,

Steve

Consider two combi boilers. Highly cost effective. They can be split to do
separate taps and showers, so does not interfere with the others. Also one
doing upstairs heating and one downstairs. The can be combined to fill baths
quickly.

"Andy Hall" wrote in message
...
On 2007-06-17 19:39:17 +0100, "Steve" said:

Hi,

I'm hoping to redo my old CH/DHW system. I like the idea of a heat bank;
the best place for me would be under a worktop near the wall-mounted
boiler
in the kitchen.

I've only found one suitable heat bank for this
locationhttp://www.heatweb.com/products/cyli.../worktop.html).

As far as I know, this will be rather expensive (around £1k? - more than
a
modern, complex, quality boiler, which seems a bit daft!).

Does anyone know of any other under-the-worktop models it would be worth
looking at?

Cheers,

Steve

One important thing to look at here is that by virtue of the size of an
undersink unit, the storage capacity will be quite small. Normally, a
heat bank stores water at 80 degrees as opposed to a conventional DHW tank
storing it at 60 degrees. The impact of that is that 1.3x the volume of
hot water will be produced before the stored energy runs out. So one
comparison to make is whether the proposed store is less than 3/4 the
capacity of your current cylinder. If it is much less, then tread
carefully.

You don't know what you are on about. The unit the OP was looking at
"combines the output" of the boiler "and" the heat bank.

"Steve" wrote in message
...
Thanks for the suggestions chaps. In response to a couple of your
comments:

- I am intending to DIY everything myself except the (gas) boiler.
However I'd not considered a DIY heat bank, but it sounds like a
possibility if I can get a suitable size and shape of tank that I can
properly insulate; I'll definitely consider this.

- The unit would fit under a worktop where there would normally be a
cupboard (rather than under the sink) and could easily be a very large
tank.

Steve

How many baths, showers etc?

On 2007-06-17 22:14:59 +0100, "Doctor Drivel" said:


"Andy Hall" wrote in message ...
On 2007-06-17 19:39:17 +0100, "Steve" said:

Hi,

I'm hoping to redo my old CH/DHW system. I like the idea of a heat bank;
the best place for me would be under a worktop near the wall-mounted boiler
in the kitchen.

I've only found one suitable heat bank for this
locationhttp://www.heatweb.com/products/cyli.../worktop.html).

As far as I know, this will be rather expensive (around £1k? - more than a
modern, complex, quality boiler, which seems a bit daft!).

Does anyone know of any other under-the-worktop models it would be worth
looking at?

Cheers,

Steve

One important thing to look at here is that by virtue of the size of an
undersink unit, the storage capacity will be quite small. Normally,
a heat bank stores water at 80 degrees as opposed to a conventional DHW
tank storing it at 60 degrees. The impact of that is that 1.3x the
volume of hot water will be produced before the stored energy runs out.
So one comparison to make is whether the proposed store is less than
3/4 the capacity of your current cylinder. If it is much less, then
tread carefully.

You don't know what you are on about.

On the contrary. You have been reading and swallowing datasheets on
web sites again.


The unit the OP was looking at "combines the output" of the boiler
"and" the heat bank.

That's marketing nonsense. The system will still be limited. With
the store fully charged the boiler begins to add heat back once it
fires. However, the store will still be losing heat energy at the rate
of that required to heat the water minus the rate produced by the
boiler.

So for example, if 100kW of heat is required to be transfered to heat
the water and then 30kW is supplied from the boiler, the net loss is
70kW. These are typical figures for a practical system. The 30kW
will lengthen the time before the store empties, but won't prevent it
happening. Once it does, the flow rate for the same water
temperature will be only 30% of the original when the store was full.

On 2007-06-17 22:12:01 +0100, "Steve" said:

Thanks for the suggestions chaps. In response to a couple of your comments:

- I am intending to DIY everything myself except the (gas) boiler. However
I'd not considered a DIY heat bank, but it sounds like a possibility if I
can get a suitable size and shape of tank that I can properly insulate; I'll
definitely consider this.

- The unit would fit under a worktop where there would normally be a
cupboard (rather than under the sink) and could easily be a very large tank.

Steve


True, but do compare the volume of the store with that of your existing
cylinder before committing yourself.

"Andy Hall" wrote in message
...
On 2007-06-17 22:14:59 +0100, "Doctor Drivel" said:


"Andy Hall" wrote in message
...
On 2007-06-17 19:39:17 +0100, "Steve" said:

Hi,

I'm hoping to redo my old CH/DHW system. I like the idea of a heat
bank;
the best place for me would be under a worktop near the wall-mounted
boiler
in the kitchen.

I've only found one suitable heat bank for this
locationhttp://www.heatweb.com/products/cyli.../worktop.html).

As far as I know, this will be rather expensive (around £1k? - more
than a
modern, complex, quality boiler, which seems a bit daft!).

Does anyone know of any other under-the-worktop models it would be
worth
looking at?

Cheers,

Steve

One important thing to look at here is that by virtue of the size of an
undersink unit, the storage capacity will be quite small. Normally, a
heat bank stores water at 80 degrees as opposed to a conventional DHW
tank storing it at 60 degrees. The impact of that is that 1.3x the
volume of hot water will be produced before the stored energy runs out.
So one comparison to make is whether the proposed store is less than 3/4
the capacity of your current cylinder. If it is much less, then tread
carefully.

You don't know what you are on about.

On the contrary. You have been reading and swallowing datasheets on web
sites again.

You are thick.

The unit the OP was looking at "combines the output" of the boiler "and"
the heat bank.

That's marketing nonsense.

You are getting thicker.

The system will still be limited. With the store fully charged the boiler
begins to add heat back once it fires.

er...yep.

So if it takes 100kW to fill bath and the boiler can add 30kW of this then
only 70kW of heat need be stored making the storage vessel smaller, and
small enough top fit under a worktop. This is easy to understand.

"Andy Hall" wrote in message
...
On 2007-06-17 22:12:01 +0100, "Steve" said:

Thanks for the suggestions chaps. In response to a couple of your
comments:

- I am intending to DIY everything myself except the (gas) boiler.
However
I'd not considered a DIY heat bank, but it sounds like a possibility if I
can get a suitable size and shape of tank that I can properly insulate;
I'll
definitely consider this.

- The unit would fit under a worktop where there would normally be a
cupboard (rather than under the sink) and could easily be a very large
tank.

Steve


True, but do compare the volume of the store with that of your existing
cylinder before committing yourself.

He can have a square heat bank.

On 2007-06-17 23:38:02 +0100, "Doctor Drivel" said:

So if it takes 100kW to fill bath and the boiler can add 30kW of this
then only 70kW of heat need be stored making the storage vessel
smaller, and small enough top fit under a worktop. This is easy to
understand.

Not by you. The power output solely determines the rate at which
energy can be transfered to the water, and hence the temperature rise
for a given flow rate. The issue is for how long will the store be
able to supply this rate.

You can't store 70kW of heat. The kW is a measure of power, not of energy.

The contributing effect of the boiler also applies to a conventional
cylinder. That may be a little more for a direct heatbank than for
an indirect coil cylinder, but it is not correct to suggest that the
phenomenon is exclusive to the heatbank. That would be misleading.

It is true, as I said in the first place, that a heat bank can store
30% more energy than a conventional cylinder of equivalent size.
Therefore, obviously one can have a store only 3/4 of the size for an
equivalent output.


My point was that even a full appliance space under a worktop will only
accomodate a limited size of store. One should take the capacity of
the proposed store, multiply by 4/3 to be able to determine the
equivalent size of conventional cylinder that it can replace.
Whether that is adequate will depend on the pattern of use.

It's important to point out that while heatbank technology is useful,
it is not magic, can't get a two litres from a one litre pot and
certainly can't defy physics. Despite what it says in glossy
brochures and on web sites.

"Andy Hall" wrote in message
...
On 2007-06-17 23:38:02 +0100, "Doctor Drivel" said:

So if it takes 100kW to fill bath and the boiler can add 30kW of this
then only 70kW of heat need be stored making the storage vessel smaller,
and small enough top fit under a worktop. This is easy to understand.

Not by you.

Matt, I just explained it to you. Your thickness got in the way.

You can't store 70kW of heat. The kW is a measure of power, not of
energy.

The contributing effect of the boiler also applies to a conventional
cylinder.

Nope. The heat from the boiler goes directly into the DHW plate heat
exchanger in this heat bank. With cylinder the heat build up is slow as it
is indirect and heated not at the very top of the cylinder.

That may be a little more for a direct heatbank than for an indirect coil
cylinder, but it is not correct to suggest that the phenomenon is
exclusive to the heatbank. That would be misleading.

Unless a cylinder is heated directly then it will be the same

It is true, as I said in the first place, that a heat bank can store 30%
more energy than a conventional cylinder of equivalent size.

About right.

Therefore, obviously one can have a store only 3/4 of the size for an
equivalent output.

Nope. The cylinder stores 30% more energy supplemented by the boiler, say
30kW.

My point was that even a full appliance space under a worktop will only
accomodate a limited size of store.

A square vessel even more.

It's important to point out that while heatbank technology is useful, it
is not magic, can't get a two litres from a one litre pot and certainly
can't defy physics.

Matt, you need to learn some sums.

In article ews.net,
Doctor Drivel wrote:
only 70kW of heat need be stored

Isn't it about time you went to night school and learnt some basics? Far
better than wasting your time down the pub.

--
*Any connection between your reality and mine is purely coincidental

Dave Plowman London SW
To e-mail, change noise into sound.

"Dave Plowman (News)" wrote in message
...
In article ews.net,
Doctor Drivel wrote:
only 70kW of heat need be stored

Isn't

Please eff off you are a total idiot.

In article ews.net,
Doctor Drivel wrote:

"Dave Plowman (News)" wrote in message
...
In article ews.net,
Doctor Drivel wrote:
only 70kW of heat need be stored


Isn't it about time you went to night school and learnt some basics?
Far better than wasting your time down the pub.

Please eff off you are a total idiot.

Well this 'idiot' understands the difference between energy and power so
I wonder what that makes you? Apart from a pratt, obviously.

BTW, still waiting for that visit from your policemen friends. Or have
you conveniently forgotten that episode from your life of fantasy?

--
*Generally speaking, you aren't learning much if your lips are moving.*

Dave Plowman London SW
To e-mail, change noise into sound.

On 2007-06-18 01:45:29 +0100, "Doctor Drivel" said:


Nope. The heat from the boiler goes directly into the DHW plate heat
exchanger in this heat bank. With cylinder the heat build up is slow
as it is indirect and heated not at the very top of the cylinder.

Irrelevant. The issue is how long will thre be a supply of energy
from the heat bank as a result of what has been stored.




Therefore, obviously one can have a store only 3/4 of the size for an
equivalent output.

Nope. The cylinder stores 30% more energy supplemented by the boiler,
say 30kW.

The kW is not a measurement of energy. The cylinder stores 30%
more energy. It's irrelevant for comparison purposes to include
boiler contribution because that happens with a conventional cylinder
as well.



My point was that even a full appliance space under a worktop will only
accomodate a limited size of store.

A square vessel even more.

The additional pump, heat exchanger and controls all have to be accomodated.




It's important to point out that while heatbank technology is useful,
it is not magic, can't get a two litres from a one litre pot and
certainly can't defy physics.

Matt, you need to learn some sums.

You mean the kind where kW are a measure of energy?

Doctor Drivel wrote:

He can have a square heat bank.

That would be kind of pointless. Something more approximating a cube
would be more useful - it would at least be able to store some water then.

--
Cheers,

John.

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

"Andy Hall" wrote in message
...
On 2007-06-18 01:45:29 +0100, "Doctor Drivel" said:

The cylinder stores 30% more energy. It's irrelevant for comparison
purposes to include boiler contribution because that happens with a
conventional cylinder as well.

With heat bank the useful hot water from the boiler goes pretty immediately
to the taps. Does not happen with a normal cylinder and coil as most heat
rises up by convection.

My point was that even a full appliance space under a worktop will only
accomodate a limited size of store.

A square vessel even more.

The additional pump, heat exchanger and controls all have to be
accomodated.

Gosh. He is getting it. Nah he isn't.

It's important to point out that while heatbank technology is useful, it
is not magic, can't get a two litres from a one litre pot and certainly
can't defy physics.

Matt, you need to learn some sums.

You mean the kind where kW are a measure of energy?

kW/hr. Gosh

"Dave Plowman (News)" wrote in message
...
In article ews.net,
Doctor Drivel wrote:

"Dave Plowman (News)" wrote in message
...
In article ews.net,
Doctor Drivel wrote:
only 70kW of heat need be stored


Isn't it about time you went to night school and learnt some basics?
Far better than wasting your time down the pub.

Please eff off you are a total idiot.

Well this 'idiot'

Correct an idiot, so please eff off as you are a total idiot.

"John Rumm" wrote in message
...
Doctor Drivel wrote:

He can have a square heat bank.

That would be kind of pointless.

You really don't know do you?

On 2007-06-18 08:51:20 +0100, "Doctor Drivel" said:


"Andy Hall" wrote in message ...
On 2007-06-18 01:45:29 +0100, "Doctor Drivel" said:

The cylinder stores 30% more energy. It's irrelevant for comparison
purposes to include boiler contribution because that happens with a
conventional cylinder as well.

With heat bank the useful hot water from the boiler goes pretty
immediately to the taps. Does not happen with a normal cylinder and
coil as most heat rises up by convection.

This is confused nonsense. The heat exchanger does not care about the
source of its heat.



You mean the kind where kW are a measure of energy?

kW/hr. Gosh

ROTFL.

"Doctor Drivel" wrote in message
reenews.net...

"Andy Hall" wrote in message
...
On 2007-06-18 01:45:29 +0100, "Doctor Drivel" said:

The cylinder stores 30% more energy. It's irrelevant for comparison
purposes to include boiler contribution because that happens with a
conventional cylinder as well.

With heat bank the useful hot water from the boiler goes pretty
immediately to the taps. Does not happen with a normal cylinder and coil
as most heat rises up by convection.

My point was that even a full appliance space under a worktop will only
accomodate a limited size of store.

A square vessel even more.

The additional pump, heat exchanger and controls all have to be
accomodated.

Gosh. He is getting it. Nah he isn't.

It's important to point out that while heatbank technology is useful,
it is not magic, can't get a two litres from a one litre pot and
certainly can't defy physics.


I hestitae to intervene in such a 'big-end' ~ little-end' dispute between
two
obvious Laputan experts ... however let me interject some observations based
on direct experience of a heat bank;-

The heat bank has several loops which all interact within the tank itself;
one 'loop' is the 'heating loop where the working fluid is sent off to the
boiler to garner heat. This loop has a pipe at the base of the tank (input
to the boiler) and a pipe discharging the top of the tank.
After a while the tank will be filled with water ,essentially, all at the
desired teemperature for the tank.
The DHW is obtained by taking the working fluid and passing it throygh a
heat-exchanger wherein it surrenders heat to the mains water and produces
DHW. The 'cooled' working fluid re-enters the tank at the bottom.
Thus if one considers the working fluid to be a column of laminae, each
layer / lamina to be a body of fliuid each of a discrete temperature they
will self-organise with the hottest at the top and the coldest at the bottom
(stratification]..
As working fluid ciirculates through the 'boiler -loop' it re-enter the tank
at the boiler-demand temperature and, thanks to stratification', floats at
the top of the cylinder. It is this hottest layer that goes into the
heat-echanger to surrender it's heat into the DHW.
In pratical _experience_ once the boiler 'fires' it's heat is availlable to
provide DHW _almost_ instantly! [for variable valeus of _almost_ and
_instantly_]

A heat bank is not magic; there's owt for nowt; _but_ the 'useful hot water
from the boiler goes pretty immediately to the taps' _via_ the plate
heat-exchanger and for an almost imperceptable value of immediate. And;
whilst; "can't get a two litres from a one litre pot and certainly can't
defy physics."; one can _exploit_ the physics of stratification and hot
'stuff' rises while cold 'stuff' falls to ensure that the energy flow is
maximised from boller-tank-heat-echanger-DHW-taps! It's not 'physics';
it's clever engineering / plumbing.

--

Brian

"Andy Hall" wrote in message
...
On 2007-06-18 08:51:20 +0100, "Doctor Drivel" said:


"Andy Hall" wrote in message
...
On 2007-06-18 01:45:29 +0100, "Doctor Drivel" said:

The cylinder stores 30% more energy. It's irrelevant for comparison
purposes to include boiler contribution because that happens with a
conventional cylinder as well.

With heat bank the useful hot water from the boiler goes pretty
immediately to the taps. Does not happen with a normal cylinder and coil
as most heat rises up by convection.

This is confused nonsense. The heat exchanger does not care about the
source of its heat.

You need to understand how they work.

"Brian Sharrock" wrote in message
news

"Doctor Drivel" wrote in message
reenews.net...

"Andy Hall" wrote in message
...
On 2007-06-18 01:45:29 +0100, "Doctor Drivel" said:

The cylinder stores 30% more energy. It's irrelevant for comparison
purposes to include boiler contribution because that happens with a
conventional cylinder as well.

With heat bank the useful hot water from the boiler goes pretty
immediately to the taps. Does not happen with a normal cylinder and coil
as most heat rises up by convection.

My point was that even a full appliance space under a worktop will
only accomodate a limited size of store.

A square vessel even more.

The additional pump, heat exchanger and controls all have to be
accomodated.

Gosh. He is getting it. Nah he isn't.

It's important to point out that while heatbank technology is useful,
it is not magic, can't get a two litres from a one litre pot and
certainly can't defy physics.


I hestitae to intervene in such a 'big-end' ~ little-end' dispute between
two
obvious Laputan experts ... however let me interject some observations
based on direct experience of a heat bank;-

The heat bank has several loops which all interact within the tank itself;
one 'loop' is the 'heating loop where the working fluid is sent off to the
boiler to garner heat. This loop has a pipe at the base of the tank (input
to the boiler) and a pipe discharging the top of the tank.
After a while the tank will be filled with water ,essentially, all at the
desired teemperature for the tank.
The DHW is obtained by taking the working fluid and passing it throygh a
heat-exchanger wherein it surrenders heat to the mains water and produces
DHW. The 'cooled' working fluid re-enters the tank at the bottom.
Thus if one considers the working fluid to be a column of laminae, each
layer / lamina to be a body of fliuid each of a discrete temperature they
will self-organise with the hottest at the top and the coldest at the
bottom (stratification]..
As working fluid ciirculates through the 'boiler -loop' it re-enter the
tank at the boiler-demand temperature and, thanks to stratification',
floats at the top of the cylinder. It is this hottest layer that goes into
the heat-echanger to surrender it's heat into the DHW.
In pratical _experience_ once the boiler 'fires' it's heat is availlable
to provide DHW _almost_ instantly! [for variable valeus of _almost_ and
_instantly_]

Yep, that is what I said. After designing implementing countless stores and
heat banks I would know this sort of thing.

Even Stumbles noted this in his DIYed heat bank on 22.3.2007.....


With my own setup on the few occasions that we've run the bank cold (which
is inevitably when you've got into a half-full bath and the hot's run
cold) it takes just a few minutes to get a reasonable stream of hot water
out again. With the non-rapid-recovery conventional cylinder we had before
you could, if you were patient, get a trickle of hot water out after a
quarter of an hour or so.

Apart from the equivalence of a directly-coupled arrangement to an
infinitely rapid-recovery coil I think there's also the factor that even
the fastest coil is heating the top half or so of the cylinder by
convection whereas in the direct heat bank the hot flow from the boiler is
probably getting sucked directly out of the top of the cylinder by the DHW
pump.


A heat bank is not magic; there's owt for nowt; _but_ the 'useful hot
water from the boiler goes pretty immediately to the taps' _via_ the
plate heat-exchanger and for an almost imperceptable value of immediate.
And; whilst; "can't get a two litres from a one litre pot and certainly
can't defy physics."; one can _exploit_ the physics of stratification and
hot 'stuff' rises while cold 'stuff' falls to ensure that the energy flow
is maximised from boller-tank-heat-echanger-DHW-taps! It's not
'physics'; it's clever engineering / plumbing.

Yep. Combining the output of the boiler and energy in the cylinder a smaller
cylinder may be used. It also acts as a wonderful buffer for CH too. The
Germans are way into thermal storage and leave us standing on some designs.

On 2007-06-18 09:38:44 +0100, "Brian Sharrock" said:

The heat bank has several loops which all interact within the tank itself;
one 'loop' is the 'heating loop where the working fluid is sent off to the
boiler to garner heat. This loop has a pipe at the base of the tank (input
to the boiler) and a pipe discharging the top of the tank.
After a while the tank will be filled with water ,essentially, all at the
desired teemperature for the tank.
The DHW is obtained by taking the working fluid and passing it throygh a
heat-exchanger wherein it surrenders heat to the mains water and produces
DHW. The 'cooled' working fluid re-enters the tank at the bottom.
Thus if one considers the working fluid to be a column of laminae, each
layer / lamina to be a body of fliuid each of a discrete temperature they
will self-organise with the hottest at the top and the coldest at the bottom
(stratification]..
As working fluid ciirculates through the 'boiler -loop' it re-enter the tank
at the boiler-demand temperature and, thanks to stratification', floats at
the top of the cylinder. It is this hottest layer that goes into the
heat-echanger to surrender it's heat into the DHW.
In pratical _experience_ once the boiler 'fires' it's heat is availlable to
provide DHW _almost_ instantly! [for variable valeus of _almost_ and
_instantly_]

A heat bank is not magic; there's owt for nowt; _but_ the 'useful hot water
from the boiler goes pretty immediately to the taps' _via_ the plate
heat-exchanger and for an almost imperceptable value of immediate. And;
whilst; "can't get a two litres from a one litre pot and certainly can't
defy physics."; one can _exploit_ the physics of stratification and hot
'stuff' rises while cold 'stuff' falls to ensure that the energy flow is
maximised from boller-tank-heat-echanger-DHW-taps! It's not 'physics';
it's clever engineering / plumbing.

A good explanation, Brian.

My original point was not about how quickly the heatbank can produce
hot water starting from all cold condition, but rather what happens in
terms of capacity to continue to produce the initially high flow rate
of hot water at the taps.

It is obvious enough, as you say, that if the cylinder is cold and the
DHW is turned on that heat from the boiler will be transfered fairly
effectively to the heat exchanger and will produce some hot water.
Assuming that little or none goes to heating the store at this time,
the rate of production at the taps will depend totally on the boiler
and will be similar to the behaviour of a combi of equivalent heat
output.

However, there are only cases, AFAICS, where you would have this situation:

- Coming back from holiday or something, turning on the boiler and
wanting DHW quickly. This is comparatively rare.

- Heatbank has run out of stored heat and DHW Iis running in "instant " mode.

I suppose that one could operate the store by letting it cool overnight
and coming on in the morning (e.g. like an immersion heater) - it would
seem to be an odd thing to do.

The case that I was refering to was what happens when the store is hot
and one begins to draw DHW. In that scenario, the issue of whether
the heat contributed by the boiler is delivered to the heat exchanger
plus a smaller amount from the store or whether it's all from the store
and being replenished by the boiler is somewhat irrelevant. It will
still be the same time and the same amount of energy before the store
runs out.

My point was about how long is that going to be. Clearly a heatbank
is useful technology, that was not in dispute, but people who have
been used to stored hot water expect constant flow and temperature and
are frequently disappointed if they swap for an inadequate combi.

Therefore issue 1 is how long at the intended rate of use will it be
before the hot water production rate drops, and issue 2 is when it has,
will the user be happy with the result.

Issue 1 can be dealt with by having an adequately sized store and
adequately sized boiler

Issue 2 can be dealt with by having an adequately sized boiler.

Obviously one can choose appropriately.

The danger area is replacing a typically sized conventional HW cylinder
where the user has been used to a plentiful supply of HW at constant
flow and temperature with volume that always exceeds his requirements
with a small store and retaining a possibly inadequate boiler.

On 2007-06-18 09:45:06 +0100, "Doctor Drivel" said:


"Andy Hall" wrote in message ...
On 2007-06-18 08:51:20 +0100, "Doctor Drivel" said:


"Andy Hall" wrote in message ...
On 2007-06-18 01:45:29 +0100, "Doctor Drivel" said:

The cylinder stores 30% more energy. It's irrelevant for comparison
purposes to include boiler contribution because that happens with a
conventional cylinder as well.

With heat bank the useful hot water from the boiler goes pretty
immediately to the taps. Does not happen with a normal cylinder and
coil as most heat rises up by convection.

This is confused nonsense. The heat exchanger does not care about the
source of its heat.

You need to understand how they work.

The principle of stratification is not in dispute; nor is what happens
when the cylinder is cold or runs cold.

When it is hot, and energy is being witdrawn at a higher rate than the
boiler is producing it, it's completely irrelevant as to whether the
heat from the boiler is going into the store or to the heat exchanger;
the net effect is the same.

Have you looked up what the unit of energy is yet?

On Sun, 17 Jun 2007 22:12:01 +0100, Steve wrote:

- I am intending to DIY everything myself except the (gas) boiler.
However I'd not considered a DIY heat bank, but it sounds like a
possibility if I can get a suitable size and shape of tank that I can
properly insulate; I'll definitely consider this.

- The unit would fit under a worktop where there would normally be a
cupboard (rather than under the sink) and could easily be a very large
tank.

I think McDonald engineering to a smallish squattish cylinder with a rapid
recovery coil which might do the trick if the boiler has a sealed primary.

The ideal of course would be a rectangular[1] tank which would fit under
the w/t with a bit of space in front for the PHE, pump etc.


[1] what's the name for 3-dimensional rectangle? i.e. square corners,
unequal sides?

--
John Stumbles

Procrastinate now!

On Sun, 17 Jun 2007 22:12:21 +0100, Doctor Drivel wrote:

Consider two combi boilers. Highly cost effective. They can be split to
do separate taps and showers, so does not interfere with the others.
Also one doing upstairs heating and one downstairs. The can be combined
to fill baths quickly.

[Fx: CHEERING from amassed regulars of uk.d-i-y]

But you forgot to say the combis' gas feeds should be run separately back
to the meter (or better still separately all the way back to the North Sea
or Russia)

--
John Stumbles

Things don't like being anthropomorphised.

Andy Hall wrote:

You mean the kind where kW are a measure of energy?

kW/hr. Gosh

That would be kJ/h^2 dribble, try again.

ROTFL.

Interesting concept though.... perhaps he has a combi that can out
accelerate his prius.

--
Cheers,

John.

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

"John Stumbles" wrote in message
...
snip

[1] what's the name for 3-dimensional rectangle? i.e. square corners,
unequal sides?

You choose;-
Cuboid ... or ... Right Prism. .... or ... rectangular parallelepiped
..... or rectangular prism

--
John Stumbles

--

Brian

John Stumbles wrote:
On Sun, 17 Jun 2007 22:12:21 +0100, Doctor Drivel wrote:

Consider two combi boilers. Highly cost effective. They can be split to
do separate taps and showers, so does not interfere with the others.
Also one doing upstairs heating and one downstairs. The can be combined
to fill baths quickly.

[Fx: CHEERING from amassed regulars of uk.d-i-y]

Its just not the same without Humph and the lovely Samantha though....

--
Cheers,

John.

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

In article ,
John Stumbles wrote:
[1] what's the name for 3-dimensional rectangle? i.e. square corners,
unequal sides?

Box?

--
*The sooner you fall behind, the more time you'll have to catch up *

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
John Stumbles wrote:
Consider two combi boilers. Highly cost effective. They can be split
to do separate taps and showers, so does not interfere with the
others. Also one doing upstairs heating and one downstairs. The can be
combined to fill baths quickly.

[Fx: CHEERING from amassed regulars of uk.d-i-y]

But you forgot to say the combis' gas feeds should be run separately
back to the meter (or better still separately all the way back to the
North Sea or Russia)

And separate water supplies. Extra parking for the two vans at service
time. Get different makes so they don't break down together.

--
*How many roads must a man travel down before he admits he is lost?

Dave Plowman London SW
To e-mail, change noise into sound.

In article ews.net,
Doctor Drivel wrote:
Yep, that is what I said. After designing implementing countless stores
and heat banks I would know this sort of thing.

The mind boggles.

--
*Confession is good for the soul, but bad for your career.

Dave Plowman London SW
To e-mail, change noise into sound.

On Sun, 17 Jun 2007 19:39:17 +0100, Steve wrote:

I've only found one suitable heat bank for this
locationhttp://www.heatweb.com/products/cyli.../worktop.html).

Hmmm, not sure I'd have shown a Potterton Profile in the illustration if I
were trying to impress the punters.


--
John Stumbles

I forgot to take my amnesia medecine again

"Brian Sharrock" wrote in message
...

"John Stumbles" wrote in message
...
snip

[1] what's the name for 3-dimensional rectangle? i.e. square corners,
unequal sides?

You choose;-
Cuboid ... or ... Right Prism. .... or ... rectangular parallelepiped
.... or rectangular prism


no, I choose "box" )


--
Bob Mannix
(anti-spam is as easy as 1-2-3 - not)

"Andy Hall" wrote in message
...
On 2007-06-18 09:45:06 +0100, "Doctor Drivel" said:


"Andy Hall" wrote in message
...
On 2007-06-18 08:51:20 +0100, "Doctor Drivel" said:


"Andy Hall" wrote in message
...
On 2007-06-18 01:45:29 +0100, "Doctor Drivel"
said:

The cylinder stores 30% more energy. It's irrelevant for comparison
purposes to include boiler contribution because that happens with a
conventional cylinder as well.

With heat bank the useful hot water from the boiler goes pretty
immediately to the taps. Does not happen with a normal cylinder and
coil as most heat rises up by convection.

This is confused nonsense. The heat exchanger does not care about the
source of its heat.

You need to understand how they work.

The principle of stratification is not in dispute; nor is what happens
when the cylinder is cold or runs cold.

When it is hot, and energy is being witdrawn at a higher rate than the
boiler is producing it, it's completely irrelevant as to whether the heat
from the boiler is going into the store or to the heat exchanger; the net
effect is the same.

You ensure only hot water enters the top of the cylinder.

"Dave Plowman (News)" wrote in message
...
In article ews.net,
Doctor Drivel wrote:
Yep, that is what I said. After designing implementing countless stores
and heat banks I would know this sort of thing.

The mind

Please eff off.