First, thanks to Christian for introducing me to this very interesting
device a few days ago.

Here's what I'm now thinking of doing:-

Installing a heat bank capable of providing heating in the form of UFH
for an area of 40 m2 ground levels and 24 m2 upstairs

Installing woodburner with boiler and economy 7 electricity supply
(There is no mains gas and I want to avoid an oil boiler and tank on
top of wood storage space)

So, as I understand it, my hot water will be thermostatically
controlled and pumped regardless of heat source, allowing me to run a
shower unit without fear of scalding at any time of year.

During the colder months my woodburner boiler will make a day/evening
deposit in the heatbank and the heat exchanger will distribute to both
radiators and hot water supply as required.

At the end of the day if I allow the fire to go out, my pumped heating
will be making a withdrawal from the bank which will be topped up by
electricity at economy 7 rates overnight. I can use this hot water the
following morning, relighting my fire to avoid drawing on peak rate
electricity.

Therefore I must calculate what capacity my heat bank needs to be and
what heat transfer rate my heat exchanger needs to have. I need to heat
a total space volume of around 150 m3 which should be viable with about
10kw energy from what I've read elsewhere.

Jeff Mowatt wrote:

Therefore I must calculate what capacity my heat bank needs to be and
what heat transfer rate my heat exchanger needs to have. I need to heat

Even small water to water heat exchanges tend to have fairly prodigious
capacity.

a total space volume of around 150 m3 which should be viable with about
10kw energy from what I've read elsewhere.

The space heating requirements will be dictated by the surface area of
the surfaces (i.e. walls, windows, floor etc), the temperature
differential across them, and the quality of the thermal insulation of
those surfaces. The volume as such matters less. The number of air
changes in the room per hour should also be factored in. Google back on
u values and heat loss calculations for more information.

--
Cheers,

John.

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

"Jeff Mowatt" wrote in message
ps.com...
First, thanks to Christian for introducing me to this very interesting
device a few days ago.

Here's what I'm now thinking of doing:-

Installing a heat bank capable of providing
heating in the form of UFH for an area of
40 m2 ground levels and 24 m2 upstairs

Installing woodburner with boiler and economy
7 electricity supply (There is no mains gas and
I want to avoid an oil boiler and tank on
top of wood storage space)

So, as I understand it, my hot water will be
thermostatically controlled and pumped regardless
of heat source, allowing me to run a
shower unit without fear of scalding at any time of year.

During the colder months my woodburner boiler
will make a day/evening deposit in the heatbank
and the heat exchanger will distribute to both
radiators and hot water supply as required.

At the end of the day if I allow the fire to go out,
my pumped heating will be making a withdrawal
from the bank which will be topped up by
electricity at economy 7 rates overnight. I can
use this hot water the following morning, relighting
my fire to avoid drawing on peak rate electricity.

Therefore I must calculate what capacity
my heat bank needs to be and
what heat transfer rate my heat exchanger
needs to have. I need to heat a total space
volume of around 150 m3 which should be viable
with about 10kw energy from what I've read elsewhere.

Sizing the thermal store.

Assumptions:

- Average day temp of +4C. The worst case example should be calculated in
for your area.

- Ballpark of 312 Btu/h-F. "A single floor house of approx 2000 squ foot has
say a total thermal conductance of approx 312 Btu/h-F. This can be done
using normal heat loss calcs for a specific house to be more accurate."

- 16 hours of heating. Some may want 24 hours.

- Minimum temp to heat the house 60C (140F). Rads have Max 82C
(180F) and min 60C (140F). UFH min of say 40C.

Sizing for a house of 2000 squ foot heated over 16 hours:

A Btu is the amount of energy needed to raise the temperature
of a pound of water 1 degree F. When a pound of water cools 1 F,
it releases 1 Btu.

A single floor house of approx 2000 squ foot has say a total thermal
conductance of approx 312 Btu/h-F. This can be done using normal heat loss
calcs for a specific house to be more accurate.

January is the coldest month with say an average outdoor temperature of 4C
(41F). To stay warm on an average winters day with an internal temp of 71F
(21.66C) over 16 hours, the house needs 149,760 Btu (43.89 kWh).
16 hours x (71F - 41F) x 312Btu/h-F = 149,760 Btu (43.89 kWh).

Thermal store temperature = 82C (180F). Min temperature to keep the house
warm on a rad system is say 60C (140F).
149,760 / (180F - 140F) = 3744 pounds of 180 F water cooling to 140F. 3744
pounds of water = 1,698 litres. So, a store volume for CH of 1,698 litres
of water.

Boiler rating (Kw/hr) = (litres x Temp rise in deg C)/(14.3 x minutes)
(Swap minutes and kW/hr to find the fastest reheat possible from a known
boiler size)

(1,698 x 40C) / (14.3 * 60) = 79.16 kW

79.16 kW to heat the store from approx 40C to 80C in one hour.

Over six hours that will be 79.16 / 6 = 13.19 kW per hour.
So, a 1,698 litre store can be heated from 40C to 80C over 6 hours by just
over four 3 kW immersion heaters on cheap rate electricity.

Realistically a thermal store of 2,000 litres combining the CH and DHW will
need 15.55 kW ( 5 3 kW immersion heaters) to raise it temperature 40C over 6
hours.

It is a matter of doing your own calcs and reaching the thermals conductance
figure. Then replace your own figures with mine in the worked example. You
may only want Economy 7 to do a part of the daytime heating and solid fuel
the rest during the day. Adjust the calcs accordingly.

Should be easy enough to slot into a spread sheet and see what
different permutations bring up.

DD, Thanks for all those calculations!

I guess that also means that too large a thermal store would create a
significant lag between boiler input and heat output.

On Tue, 7 Feb 2006 16:05:36 -0000 Doctor Drivel wrote :
Realistically a thermal store of 2,000 litres

Two tons of water and 2m3 of space taken. For a place the size of a
decent 2-bed flat. How realistic is this?

--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk
Free SEDBUK boiler database browser http://www.sda.co.uk/qsedbuk.htm
[Latest version QSEDBUK 1.12 released 8 Dec 2005]

"Tony Bryer" wrote in message
...
On Tue, 7 Feb 2006 16:05:36 -0000 Doctor Drivel wrote :
Realistically a thermal store of 2,000 litres

Two tons of water

Water is heavy, so don't put it in the loft.

and 2m3 of space taken.

About the size of an average sized airing cupboard.

For a place the size of a
decent 2-bed flat. How realistic is this?

2000 squ metres of floor space is the size of a flat?

Realistically if the coldest day in winter is to be heated by overnight
Economy 7 then a larger store is probably required. The more the insulation
in the house the smaller the store.

On Tue, 7 Feb 2006 17:40:04 -0000 Doctor Drivel wrote :
2000 squ metres of floor space is the size of a flat?

Unless I've got the messages screwed up the OP said
"Installing a heat bank capable of providing heating in the form of
UFH for an area of 40 m2 ground levels and 24 m2 upstairs"

which makes 64m2

--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk
Free SEDBUK boiler database browser http://www.sda.co.uk/qsedbuk.htm
[Latest version QSEDBUK 1.12 released 8 Dec 2005]

"Tony Bryer" wrote in message
...
On Tue, 7 Feb 2006 17:40:04 -0000 Doctor Drivel wrote :
2000 squ metres of floor space is the size of a flat?

Unless I've got the messages screwed up the OP said
"Installing a heat bank capable of providing heating in the form of
UFH for an area of 40 m2 ground levels and 24 m2 upstairs"

which makes 64m2

I gave an e.g, of 2000 squ feet which concluded a £2,000 litre store. That
is what you were commenting on, not the OP case.

On Tue, 7 Feb 2006 18:45:22 -0000 Doctor Drivel wrote :
I gave an e.g, of 2000 squ feet which concluded a £2,000 litre store. That
is what you were commenting on, not the OP case.

So you offered the answer to a question that wasn't being asked ...

--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk
Free SEDBUK boiler database browser http://www.sda.co.uk/qsedbuk.htm
[Latest version QSEDBUK 1.12 released 8 Dec 2005]

Tony, I realised this was an illustrative volume which needed to be
scaled down significantly. All the same, even a 1000 litre bank is
going to take some time to warm up.

Really its a the convenience I need, being able to direct energy to a
common pool taking advantage of the lowest cost forms. The convenience
of being able to keep warm without worrying if the fire goes out
overnight or if I'm away for more than an hour.

I think a smaller heat bank with an apprpriate heat exchanges will be
fine.

Jeff

Just a caveat based on personal experience of wood burners. Be aware
of two things - you are going to commit yourself to locating and
processing wood for the stove for your lifetime, and secondly the
amount of heat that these stoves put into the back boiler is about the
same as is 'leaked' into the room the stove is in. If your room is
large then that is fine but 10kW into the water and 10kW into the room
makes for a very hot room. There is the third warning and that is like
Wind Generators, wood burning stoves are notoriously over-specced for
their heating capability.

Having discovered all these things I now have an oil burner which does
the regular 'keep everything warm' with the wood burner running in
parallel and taking over when it is hot - and that is a far less
stressful set up as far as I'm concerned as I don't have to work hard
keep the fire alight and I don't have to work hard to make sure I have
a large stockpile of dry wood.

Rob

Rob, Thanks for the warning. I had another warnimg last week from an
uncle who used to make a living selling logs, he told me "There be only
two people as'da get warm from a log fire, him who's a'cutting and him
who's a'carrying"

Anyway, this is what I had in mind. 4kw to room, 2.5kw to water and 6kw
to radiators.

http://www.broseleyfires.com/hercules.html

I have no idea how it apportions these figures

Jeff

"Tony Bryer" wrote in message
...
On Tue, 7 Feb 2006 18:45:22 -0000 Doctor Drivel wrote :
I gave an e.g, of 2000 squ feet which concluded a £2,000 litre store.
That
is what you were commenting on, not the OP case.

So you offered the answer to a question that wasn't being asked ...

He didn't ask a specific question on it. If you understood the calc, you
wouldn't be making such a fool of yourself.

On Fri, 10 Feb 2006 22:01:55 -0000 Doctor Drivel wrote :
He didn't ask a specific question on it. If you understood the
calc, you wouldn't be making such a fool of yourself.

If pointing out that an answer that refers to a 2000ft2 property
may well be of doubtful relevance to a property a third of that
size I plead guilty. Next you'll be telling us that you'd put one
combi in a 50m2 property and two in one twice that size!

--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk
Free SEDBUK boiler database browser
http://www.sda.co.uk/qsedbuk.htm
[Latest version QSEDBUK 1.12 released 8 Dec 2005]

"Tony Bryer" wrote in message
...
On Fri, 10 Feb 2006 22:01:55 -0000 Doctor Drivel wrote :
He didn't ask a specific question on it. If you understood the
calc, you wouldn't be making such a fool of yourself.

If pointing out that an answer that refers to a 2000ft2 property
may well be of doubtful relevance to a property a third of that
size I plead guilty.

It was clearly a worked example which you clearly didn't understand. I do
not know the heat loss of his house so gave an example of a round figure of
2000 squ foot, and assumptions with one being the heat loss. All he has to
do is calculate his heat loss and subsitute his own figures.

Next you'll be telling us that you'd put one
combi in a 50m2 property and two in one twice that size!

I will? A poor attempt at redirecting the focus of your foolishnes.

Tony Bryer wrote:
On Fri, 10 Feb 2006 22:01:55 -0000 Doctor Drivel wrote :
He didn't ask a specific question on it. If you understood the
calc, you wouldn't be making such a fool of yourself.

If pointing out that an answer that refers to a 2000ft2 property
may well be of doubtful relevance to a property a third of that
size I plead guilty. Next you'll be telling us that you'd put one
combi in a 50m2 property and two in one twice that size!

He already has to my knowledge.

'Two combis drivel' ...Like '2 Jags Pressed****'

"The Natural Philosopher" wrote in message
...

...Like '2 Jags Pressed****'

The sycophantic snotty uni man is at it again. Prescot is brill. He gets the
job done and takes no crap of snotty uni civil servants. Great man.

On Sun, 12 Feb 2006 11:21:49 -0000, "Doctor Drivel"
wrote:


"The Natural Philosopher" wrote in message
...

...Like '2 Jags Pressed****'

The sycophantic snotty uni man is at it again. Prescot is brill. He gets the
job done and takes no crap of snotty uni civil servants. Great man.

.... used to send his mother flahs n'that.


--

..andy

"Andy Hall" wrote in message
...
On Sun, 12 Feb 2006 11:21:49 -0000, "Doctor Drivel"
wrote:


"The Natural Philosopher" wrote in message
...

...Like '2 Jags Pressed****'

The sycophantic snotty uni man is at it again. Prescot is brill. He gets
the
job done and takes no crap of snotty uni civil servants. Great man.

... used to send his mother flahs n'that.

Another brainwashed sycophant has a go.

"Christian McArdle" wrote in message
.. .
Therefore I must calculate what capacity my heat bank needs to be and
what heat transfer rate my heat exchanger needs to have. I need to heat
a total space volume of around 150 m3 which should be viable with about
10kw energy from what I've read elsewhere.

To store enough energy to run for long without any heat input would
require
an enormous tank. What would help is to ensure that the timer is set to
heat
the house up before the Economy 7 runs out. A 250 litre tank should then
keep it going for a couple of hours until the solid fuel can be started.
You
will certainly need to specify multiple immersion heaters, especially if
you
want to keep the house up to temp overnight.

What is essential is to ensure that the insulation is seriously up to
spec.
If possible, double the required building regulations insulation.

With an existing house there is only;by so much you can do. Cavities,
triple glazing and insulate and sealed front doors. 400mm in the loft. But
make sure it is air-tight.

On Thu, 16 Feb 2006 23:11:06 -0000, "Doctor Drivel"
wrote:


"Christian McArdle" wrote in message
. ..
Therefore I must calculate what capacity my heat bank needs to be and
what heat transfer rate my heat exchanger needs to have. I need to heat
a total space volume of around 150 m3 which should be viable with about
10kw energy from what I've read elsewhere.

To store enough energy to run for long without any heat input would
require
an enormous tank. What would help is to ensure that the timer is set to
heat
the house up before the Economy 7 runs out. A 250 litre tank should then
keep it going for a couple of hours until the solid fuel can be started.
You
will certainly need to specify multiple immersion heaters, especially if
you
want to keep the house up to temp overnight.

What is essential is to ensure that the insulation is seriously up to
spec.
If possible, double the required building regulations insulation.

With an existing house there is only;by so much you can do. Cavities,
triple glazing and insulate and sealed front doors. 400mm in the loft. But
make sure it is air-tight.


When did it go up to 400mm? That's new, even for you........

--

..andy

"Andy Hall" wrote in message
...
On Thu, 16 Feb 2006 23:11:06 -0000, "Doctor Drivel"
wrote:


"Christian McArdle" wrote in message
...
Therefore I must calculate what capacity my heat bank needs to be and
what heat transfer rate my heat exchanger needs to have. I need to heat
a total space volume of around 150 m3 which should be viable with about
10kw energy from what I've read elsewhere.

To store enough energy to run for long without any heat input would
require
an enormous tank. What would help is to ensure that the timer is set to
heat
the house up before the Economy 7 runs out. A 250 litre tank should then
keep it going for a couple of hours until the solid fuel can be started.
You
will certainly need to specify multiple immersion heaters, especially if
you
want to keep the house up to temp overnight.

What is essential is to ensure that the insulation is seriously up to
spec.
If possible, double the required building regulations insulation.

With an existing house there is only;by so much you can do. Cavities,
triple glazing and insulate and sealed front doors. 400mm in the loft.
But
make sure it is air-tight.


When did it go up to 400mm? That's new, even for you........

The Centre of Alternative Energy have a graph and 400mm is the optimum on
cost heat saved. But that was when energy was cheaper. So, the more the
better.

On Thu, 16 Feb 2006 23:27:11 -0000, "Doctor Drivel"
wrote:




With an existing house there is only;by so much you can do. Cavities,
triple glazing and insulate and sealed front doors. 400mm in the loft.
But
make sure it is air-tight.


When did it go up to 400mm? That's new, even for you........

The Centre of Alternative Energy have a graph and 400mm is the optimum on
cost heat saved. But that was when energy was cheaper. So, the more the
better.


Ah, so nonsense then....


--

..andy

"Andy Hall" aka Matt wrote in message
...
On Thu, 16 Feb 2006 23:27:11 -0000, "Doctor Drivel"
wrote:




With an existing house there is only;by so much you can do. Cavities,
triple glazing and insulate and sealed front doors. 400mm in the loft.
But
make sure it is air-tight.

When did it go up to 400mm? That's new, even for you........

The Centre of Alternative Energy have
a graph and 400mm is the optimum on
cost heat saved. But that was when
energy was cheaper. So, the more the
better.

Ah, so nonsense then....

Matt, for those with no comprehension of such matters it would be so. For
the intelligent ones it is easy to figure out.

On Fri, 17 Feb 2006 09:53:32 -0000, "Doctor Drivel"
wrote:


"Andy Hall" aka Matt wrote in message
.. .
On Thu, 16 Feb 2006 23:27:11 -0000, "Doctor Drivel"
wrote:




With an existing house there is only;by so much you can do. Cavities,
triple glazing and insulate and sealed front doors. 400mm in the loft.
But
make sure it is air-tight.

When did it go up to 400mm? That's new, even for you........

The Centre of Alternative Energy have
a graph and 400mm is the optimum on
cost heat saved. But that was when
energy was cheaper. So, the more the
better.

Ah, so nonsense then....

Matt, for those with no comprehension of such matters it would be so. For
the intelligent ones it is easy to figure out.


.... and you're going to put this in the walls as well?


--

..andy

"Andy Hall" aka Matt wrote in message
...
On Fri, 17 Feb 2006 09:53:32 -0000, "Doctor Drivel"
wrote:


"Andy Hall" aka Matt wrote in message
. ..
On Thu, 16 Feb 2006 23:27:11 -0000, "Doctor Drivel"
wrote:

With an existing house there is only;by so much you can do. Cavities,
triple glazing and insulate and sealed front doors. 400mm in the
loft.
But
make sure it is air-tight.

When did it go up to 400mm? That's new, even for you........

The Centre of Alternative Energy have
a graph and 400mm is the optimum on
cost heat saved. But that was when
energy was cheaper. So, the more the
better.

Ah, so nonsense then....

Matt, for those with no comprehension of such matters it would be so. For
the intelligent ones it is easy to figure out.

... and you're going to put this in the walls as well?

Matt, for your limited comprehension, it said 'loft'. That is the big over
you not to the sides.

On Fri, 17 Feb 2006 11:14:12 -0000, "Doctor Drivel"
wrote:


With an existing house there is only;by so much you can do. Cavities,
triple glazing and insulate and sealed front doors. 400mm in the
loft.
But
make sure it is air-tight.

When did it go up to 400mm? That's new, even for you........

The Centre of Alternative Energy have
a graph and 400mm is the optimum on
cost heat saved. But that was when
energy was cheaper. So, the more the
better.

Ah, so nonsense then....

Matt, for those with no comprehension of such matters it would be so. For
the intelligent ones it is easy to figure out.

... and you're going to put this in the walls as well?

Matt, for your limited comprehension, it said 'loft'. That is the big over
you not to the sides.

The point is that it's pretty much worthless doing this unless one
similarly insulates walls


--

..andy

"Andy Hall" aka Matt wrote in message
...
On Fri, 17 Feb 2006 11:14:12 -0000, "Doctor Drivel"
wrote:


With an existing house there is only;by so much you can do.
Cavities,
triple glazing and insulate and sealed front doors. 400mm in the
loft.
But
make sure it is air-tight.

When did it go up to 400mm? That's new, even for you........

The Centre of Alternative Energy have
a graph and 400mm is the optimum on
cost heat saved. But that was when
energy was cheaper. So, the more the
better.

Ah, so nonsense then....

Matt, for those with no comprehension of such matters it would be so.
For
the intelligent ones it is easy to figure out.

... and you're going to put this in the walls as well?

Matt, for your limited comprehension, it said 'loft'. That is the big
over
you not to the sides.

The point is that it's pretty much worthless doing this unless one
similarly insulates walls

Matt, in your small mind it is not worth insulting at all and pay the 25%
gas price hype and even more. Boy you are dumb at times.

On Fri, 17 Feb 2006 20:41:11 -0000, "Doctor Drivel"
wrote:


"Andy Hall" aka Matt wrote in message


The point is that it's pretty much worthless doing this unless one
similarly insulates walls

Matt, in your small mind it is not worth insulting at all and pay the 25%
gas price hype and even more. Boy you are dumb at times.

I try to avoid insults.

Yes it is worth insulating in a sensible and balanced way.

However it is not worth adding insulation to reduce roof heatloss from
500W to 400W if 5kW is going out through the walls.


--

..andy

"Andy Hall" wrote in message
...
On Fri, 17 Feb 2006 20:41:11 -0000, "Doctor Drivel"
wrote:


"Andy Hall" aka Matt wrote in message


The point is that it's pretty much worthless doing this unless one
similarly insulates walls

Matt, in your small mind it is not worth insulting at all and pay the 25%
gas price hype and even more. Boy you are dumb at times.

I try to avoid insults.

So do I.

Yes it is worth insulating in a sensible and balanced way.

However it is not worth adding insulation to reduce roof heatloss from
500W to 400W if 5kW is going out through the walls.

Boy, you really do not have it do you. This is the two wrongs make a right
mentality.

Doctor Drivel wrote:

However it is not worth adding insulation to reduce roof heatloss from
500W to 400W if 5kW is going out through the walls.


Boy, you really do not have it do you. This is the two wrongs make a
right mentality.

If you can spend £x halving the 5kW loss, or you can instead spend £x
halving the 500W loss you seem to be suggesting that spending £x on the
250W saving is better.

I suggest you are either mathematically challenged or just a bit dim.
Which is it?

--
Cheers,

John.

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

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

However it is not worth adding insulation to reduce roof heatloss from
500W to 400W if 5kW is going out through the walls.


Boy, you really do not have it do you. This is the two wrongs make a
right mentality.

If you can spend £x halving the 5kW loss, or you can instead spend £x
halving the 500W loss you seem to be suggesting that spending £x on the
250W saving is better.

I suggest you are either mathematically challenged or just a bit dim.
Which is it?

It is clear you are a Chav from Essex. That says it all.

On Fri, 17 Feb 2006 22:52:57 +0000 John Rumm wrote :
If you can spend £x halving the 5kW loss, or you can instead spend
£x halving the 500W loss you seem to be suggesting that spending
£x on the 250W saving is better.

No that wasn't Andy's point (I'm sorry but I have to agree with
Drivel on this one): he said that if 5kW was leaking out the walls
then there was no point in reducing the roof heat loss from 500W top
400W. The sense of doing the latter depends on the cost v. benefit,
not the walls.

I would agree that if you have a limited sum of money you give
priority to whatever delivers the best return, but that is not the
same thing as saying that there is no point in improving the roof
insulation because so much heat disappears elsewhere.

--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk
Free SEDBUK boiler database browser http://www.sda.co.uk/qsedbuk.htm
[Latest version QSEDBUK 1.12 released 8 Dec 2005]

On Sun, 19 Feb 2006 00:05:51 GMT, Tony Bryer
wrote:

On Fri, 17 Feb 2006 22:52:57 +0000 John Rumm wrote :
If you can spend £x halving the 5kW loss, or you can instead spend
£x halving the 500W loss you seem to be suggesting that spending
£x on the 250W saving is better.

No that wasn't Andy's point (I'm sorry but I have to agree with
Drivel on this one): he said that if 5kW was leaking out the walls
then there was no point in reducing the roof heat loss from 500W top
400W. The sense of doing the latter depends on the cost v. benefit,
not the walls.

I did make the comment with a comparison of cost of loft vs. cavity
insulation in mind.....



I would agree that if you have a limited sum of money you give
priority to whatever delivers the best return, but that is not the
same thing as saying that there is no point in improving the roof
insulation because so much heat disappears elsewhere.

--

..andy