IMM wrote:

"Andy Hall" wrote in message

I'm seldom confused and certainly not here.

Imagine your post on ripped paper and written in crayon and the scene is
set.

Perhaps you should invest in a printer for your computer IMM. They are
surprisingly cheap these days. That way you will be able to file away
copies of Andy's most informative posts much more quickly, and it will
save you all that scribbling with the crayon....

Out of interest, why the crayon? Do they not allow you sharp objects?


--
Cheers,

John.

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

Andy Hall wrote:

That's a good reason. Presumably the boiler has a large thermal mass
and quite high non-modulated output and the previous cylinder was
unable to take what it could deliver.

Yup, that's what I concluded after spending a lot of time trying to
eliminate the short cycling. Put in the heatbank and presto, problem solved.


In this instance, a heatbank is ideal because it can swallow all the
output.

I do like the other advantages too. When the CH comes on, it takes no
time at all for the rads to heat up. Also we now have 'mains' pressure
HW to all the taps + showers, which means quicker bath fillups.


--
Grunff

It looks like the answer is a Worcester Greenstar running vented into a
direct heatbank with a zone valve for the rads and a second zone valve for
the towel rails and airing cupboard rad.

Ensure you get the right model. Most Greenstars require a sealed pressurised
circuit. I believe that the Greenstar HE29 "Conventional" is the model you
need.

Sounds like you want to configure as S-Plan Plus. When designing the layout,
for maximum future versatility, run an unzoned "main" round the house and
put the zone valves where the actual zone circuit starts. This way you can
add new zones easily, rather than having to route a pipe all the way to the
boiler.

Christian.

"Christian McArdle" wrote in message
. net...
It looks like the answer is a Worcester Greenstar running vented into a
direct heatbank with a zone valve for the rads and a second zone valve
for
the towel rails and airing cupboard rad.

Ensure you get the right model. Most Greenstars require a sealed
pressurised
circuit. I believe that the Greenstar HE29 "Conventional" is the model you
need.

It is called a "heating" boiler.

Sounds like you want to configure as S-Plan Plus. When designing the
layout,
for maximum future versatility, run an unzoned "main" round the house and
put the zone valves where the actual zone circuit starts. This way you can
add new zones easily, rather than having to route a pipe all the way to
the
boiler.

Sounds like he should no such thing. He needs an "integrated" heat bank and
run the rads off the heat bank. Boiler cycling is eliminated. Run the heat
bank between 72 - 75C and set a primary blending valve to 54C.

Sounds like he should no such thing. He needs an "integrated" heat bank
and
run the rads off the heat bank. Boiler cycling is eliminated. Run the
heat
bank between 72 - 75C and set a primary blending valve to 54C.

You can (and should) zone the radiator circuits even when they're run off
the heatbank, you know!

Christian.

"Andy Hall" wrote in message
...
On Thu, 2 Sep 2004 00:24:06 +0100, "IMM" wrote:


"Andy Hall" wrote in message
.. .
On Wed, 1 Sep 2004 22:49:17 +0100, "IMM" wrote:


"Dave" wrote in message
...
Thanks to all for the responses.
It looks like the answer is a Worcester Greenstar

Good choice.

running vented into a
direct heatbank

Sounds good.

with a zone
valve for the rads

One zone valve for the radiators
and a second for the heatbank would
be the most appropriate, or a diverter valve.

Located where?

On the boiler flow with one zone or diverted branch going to the
heatbank and the other to the radiators.

You don't know much about this sort of thing.

Errm no. The rads taken off the heat bank using a pump and a check
valve.

This is not the best way to connect the radiators.

Oh my God.

How can I help you?

It is the best way.

Not for a condensing boiler.

You don't know much about this sort of thing.

Apart from needing
an extra pump, it is not the most
efficient way for the boiler to
work.

What the hell are you on about?

To circulate the water from the heatbank through the radiators and
back requires a pump unless you use the one used for the DHW heat
exchanger and zone or diverter valves.

You don't know much about this sort of thing.

For the heatbank to be useful,
it needs to operate at the highest
temperature possible in order to
store the maximum amount of energy.
This is true throughout the year.
The minimum useful flow
temperature to the heatbank is 75 degrees,
with 82 being better.

You split the cylinder with a flow and return on the upper DHW section
and a
flow and return on the lower heating section. The lower section can run
at
a lower temp than the upper.

You mean two separate flows
and returns from the boiler?

Yes. Or one flow and split just before the heat bank, or one flow and a
3-way diverter valve.

That would mean more complexity

It wouldn't. Any so-called complexity is offset by greater efficiency.

and the boiler is still unable to
properly detect the heat load
of the radiators, because the heatbank
is still in the middle.

The doesn't need to know the rad temps.

If you meant on the radiator connections, there is no value in having
a reduced temperature flow and return to the radiators if the boiler
is connected to the top and bottom of the heatbank. That simply
reduces the rate of heat delivery to the radiators for a given water
flow. It won't alter what the boiler sees, other than a reduced rate
of energy use. To feed the heatbank it still has to attempt to meet
the storage temperature.

Best use an outside weather compensator and
have the temp senor on the lower cylinder section. Both sections only
need
a pump and check valve each from the boiler, with the DHW having
priority.

The outside temperature sensor is simply
another control term for the
boiler when used for space heating.

And far better giving greater efficiency and comfort conditions.

It doesn't alter the behaviour of
the heat bank load

Explain you warped thoughts? Well er don't bother.

which will
effectively damp the detection that the
boiler would have had of the return
temperature directly from the
radiators.

The compensator has a temp prob on the heat bank sylinder, raising the
lowering the cylidmer temp to exactly is required reducing inefficient
boiler cycling. This means a cheaper and simpler boiler can be bought.

The compensator will ensure the rad
circuits will run at low temperatures
most of the time promoting condensing
efficiency.

It isn't the operating temperature of
the radiators that matters,
it's what the boiler can see.
Having a large energy store in the
way, screws up the control that is intended
for a condensing boiler -

Many condensing boilers, mainly the open vented heating type will maintain a
set temperature.

i.e. to see the heating load and modulate finely..

You don't know much about this sort of thing.

This is why the heat bank should
be used as an energy store for the
hot water and not to run the radiators
when a condensing boiler is the
main or only heat source.

You don't know much about this sort of thing.

IMM wrote:

To circulate the water from the heatbank through the radiators and
back requires a pump unless you use the one used for the DHW heat
exchanger and zone or diverter valves.


You don't know much about this sort of thing.


This is exactly the kind of well reasoned, cohesive argument which has
gained you a reputation for being a leading expert on the subject of
domestic plumbing, and a superb communicator.


--
Grunff

"Christian McArdle" wrote in message
. net...
Sounds like he should no such thing. He needs an "integrated" heat bank
and
run the rads off the heat bank. Boiler cycling is eliminated. Run the
heat
bank between 72 - 75C and set a primary blending valve to 54C.

You can (and should) zone the radiator circuits even when they're run off
the heatbank, you know!

I know and they should, be run off the heat bank, directly if possible, as
the heat bank is a neutral point, "not" off the boiler. All should be off
the heat bank, with the boiler only heating the heat bank.

"Grunff" wrote in message
...
IMM wrote:

To circulate the water from the heatbank through the radiators and
back requires a pump unless you use the one used for the DHW heat
exchanger and zone or diverter valves.

You don't know much about this sort of thing.

This is exactly the kind of well reasoned, cohesive argument which has
gained you a reputation for being a leading expert on the subject of
domestic plumbing, and a superb communicator.

Exactly!! I tolerate know-it-all fools. When I write about heating and
water systems take note, lots of note, you will benefit.

I know and they should, be run off the heat bank, directly if possible, as
the heat bank is a neutral point, "not" off the boiler. All should be off
the heat bank, with the boiler only heating the heat bank.

Whoops. Did I say boiler? I was thinking off the heatbank. In any case,
having a multiple subzoned system off the boiler is easier implemented with
zone valves in an S-Plan-Plus configuration (swapping the boiler for the
heat bank as the heat source) than having, say, six takeoffs (each with
pump) from the heat bank to supply each zone.

Christian.

Whoops. Did I say boiler? I was thinking off the heatbank. In any case,
having a multiple subzoned system off the boiler is easier implemented
with
zone valves in an S-Plan-Plus configuration (swapping the boiler for the
heat bank as the heat source) than having, say, six takeoffs (each with
pump) from the heat bank to supply each zone.

P.S. It also requires less pipework in most cases, as a large bore unzoned
main can snake around the house and the zoned takeoffs taken where
convenient. Having the zoning done centrally can result in excessive
pipework requirements, although it would allow microbore for those who
prefer it.

Christian.

On Thu, 2 Sep 2004 10:21:10 +0100, "IMM" wrote:


"Andy Hall" wrote in message
.. .
On Thu, 2 Sep 2004 00:24:06 +0100, "IMM" wrote:


You mean two separate flows
and returns from the boiler?

Yes. Or one flow and split just before the heat bank, or one flow and a
3-way diverter valve.

That would mean more complexity

It wouldn't. Any so-called complexity is offset by greater efficiency.

Oh good grief.

Of what?

The boiler will operate at its most efficient for heating purposes if
it is directly connected to the heat emitters without the damping
factor of a heatbank in the way.




and the boiler is still unable to
properly detect the heat load
of the radiators, because the heatbank
is still in the middle.

The doesn't need to know the rad temps.

The boiler?

It does if its best efficiency for heating is to be achieved.





The outside temperature sensor is simply
another control term for the
boiler when used for space heating.

And far better giving greater efficiency and comfort conditions.

Yes we know that.



It doesn't alter the behaviour of
the heat bank load

Explain you warped thoughts? Well er don't bother.

There's no warp as far as I am concerned.

Do you know anything about control systems?



which will
effectively damp the detection that the
boiler would have had of the return
temperature directly from the
radiators.

The compensator has a temp prob on the heat bank sylinder, raising the
lowering the cylidmer temp to exactly is required reducing inefficient
boiler cycling. This means a cheaper and simpler boiler can be bought.

Here we go full circle.

Yes we know that boiler cycling is inefficient and to be avoided.

It is precisely what will happen if you connect a condensing boiler to
a heatbank and then use the latter to supply the radiators.
The temperature probe on the cylinder will provide information about
the temperature of the cylinder. There is no way for it to know
whether the heat use is for the DHW or for the radiators.

If you have the selection for DHW and CH before the heatbank such that
either the radiators or the heatbank are connected, in the case of the
radiators the boiler can modulate down based on the load and return
temperature from them. It will tend to drop down to match the load
and run at minimum temperature if possible - little or no cycling.
When there is a demand for hot water, the heatbank will require a lot
of heat, and for this the boiler can run at full blast, again without
cycling.





The compensator will ensure the rad
circuits will run at low temperatures
most of the time promoting condensing
efficiency.

It isn't the operating temperature of
the radiators that matters,
it's what the boiler can see.
Having a large energy store in the
way, screws up the control that is intended
for a condensing boiler -

Many condensing boilers, mainly the open vented heating type will maintain a
set temperature.

What's the point? We know that they run more efficently at lower
temperatures.

The characteristics of a heating circuit are markedly different to
those for bulk energy storage at high temperatures.




i.e. to see the heating load and modulate finely..

You don't know much about this sort of thing.

This is why the heat bank should
be used as an energy store for the
hot water and not to run the radiators
when a condensing boiler is the
main or only heat source.

You don't know much about this sort of thing.


Sigh....
..andy

To email, substitute .nospam with .gl

On Thu, 2 Sep 2004 10:36:31 +0100, "IMM" wrote:


"Christian McArdle" wrote in message
.net...
Sounds like he should no such thing. He needs an "integrated" heat bank
and
run the rads off the heat bank. Boiler cycling is eliminated. Run the
heat
bank between 72 - 75C and set a primary blending valve to 54C.

You can (and should) zone the radiator circuits even when they're run off
the heatbank, you know!

I know and they should, be run off the heat bank, directly if possible, as
the heat bank is a neutral point, "not" off the boiler. All should be off
the heat bank, with the boiler only heating the heat bank.


Only if a conventional boiler or other heating sources are used, not a
modulating condensing boiler.



..andy

To email, substitute .nospam with .gl

Only if a conventional boiler or other heating sources are used, not a
modulating condensing boiler.

I'd want to see further testing evidence for this, either way. I'm not
convinced which is more efficient.

Basically, does the higher temperature burn required to reheat the heat bank
outweigh the fact that the boiler gets to do occassional full power burns,
rather than cycling, or modulating low.

Remember, that the heat bank might still be providing a reasonably low
return temperature with a very high flow/return differential, which should
offset some of the problems with regard to condensing.

Christian.

"Christian McArdle" wrote in message
. net...
I know and they should, be run off the heat bank, directly if possible,
as
the heat bank is a neutral point, "not" off the boiler. All should be
off
the heat bank, with the boiler only heating the heat bank.

Whoops. Did I say boiler? I was thinking off the heatbank. In any case,
having a multiple subzoned system off the boiler is easier implemented
with
zone valves in an S-Plan-Plus configuration (swapping the boiler for the
heat bank as the heat source) than having, say, six takeoffs (each with
pump) from the heat bank to supply each zone.

Pumps are simple, cheap and reliable. Even a DIYer can change one. Keep it
simpe.

"Andy Hall" wrote in message
news
Explain you warped thoughts? Well er don't bother.

There's no warp as far as I am concerned.

As far as you are concerned. Professionals would assess otherwise.

The temperature probe on the
cylinder will provide information about
the temperature of the cylinder.
There is no way for it to know
whether the heat use is for the DHW
or for the radiators.

You are thick. I said you install a simple boiler and allow the controls to
get the best out of the it.

Many condensing boilers, mainly the open
vented heating type will maintain a
set temperature.

What's the point? We know that they
run more efficently at lower
temperatures.

The compensator lowers the return temperature. and you don't have an
expensive complex boiler.

You don't know much about this sort of thing. A little knowledge is
dangerous.

"Andy Hall" wrote in message
...
On Thu, 2 Sep 2004 10:36:31 +0100, "IMM" wrote:


"Christian McArdle" wrote in message
.net...
Sounds like he should no such thing. He needs an "integrated" heat
bank
and
run the rads off the heat bank. Boiler cycling is eliminated. Run
the
heat
bank between 72 - 75C and set a primary blending valve to 54C.

You can (and should) zone the radiator circuits even when they're run
off
the heatbank, you know!

I know and they should, be run off the heat bank, directly if possible,
as
the heat bank is a neutral point, "not" off the boiler. All should be
off
the heat bank, with the boiler only heating the heat bank.


Only if a conventional boiler or other heating sources are used, not a
modulating condensing boiler.

You don't know much about this sort of stuff.

"Christian McArdle" wrote in message
. net...
Only if a conventional boiler or other heating sources are used, not a
modulating condensing boiler.

I'd want to see further testing evidence
for this,

You will not see any.

either way. I'm not
convinced which is more efficient.

Basically, does the higher temperature burn required to reheat the heat
bank
outweigh the fact that the boiler gets to do occassional full power burns,
rather than cycling, or modulating low.

Remember, that the heat bank might still be providing a reasonably low
return temperature with a very high flow/return differential, which should
offset some of the problems with regard to condensing.

Christian.

"John Rumm" wrote in message
...
IMM wrote:

"Andy Hall" wrote in message

I'm seldom confused and certainly not here.

Imagine your post on ripped paper and
written in crayon and the scene is set.

Perhaps you should invest in a printer
for your computer IMM. They are
surprisingly cheap these days. That way
you will be able to file away
copies of Andy's most informative posts

I have never come accross any.

Out of interest, why the crayon? Do they not allow you sharp objects?

They probaly do not allow Andy sharp objects.

"Andy Hall" wrote in message
...
On Thu, 02 Sep 2004 00:43:45 +0100, Grunff wrote:

Andy Hall wrote:

It doesn't mean either that somebody with a good mains water supply or
who wants to redistribute space in their house won't derive benefit
from a heatbank - there are cases where they are useful as long as
they are appropriately connected.

Quite - we have pretty poor mains pressure (just under a bar - the
reservoir is about 12m above the house), and no real space problems. The
reason I put in the thermal store (or heatbank as it seems to be defined
here) was becuse the oil boiler was short cycling, despite all my
attempts to cure it. The thermal store solved this, and provided us with
a nice on demand energy store.

That's a good reason. Presumably the boiler has a large thermal mass
and quite high non-modulated output and the previous cylinder was
unable to take what it could deliver.

In this instance, a heatbank is ideal because it can swallow all the
output.

The cycling was mainly on the eating and DHW if not a quick recovery coil.

"Andy Hall" wrote in message
...
On Thu, 2 Sep 2004 00:27:01 +0100, "IMM" wrote:



Are you saying pressurised heat banks don't exist?

No - simply that some are not suitable
for pressurised operation,

You should be certified. If they are pressurised heat banks then they
are
suitable.

What are you talking about? I clearly and consistently made the
point that some heat banks are unsuitable for pressurised operation.

Logically that means that some are.

The point was that one should check before buying if pressurised
operation is being considered.

Have you always been this obtuse or is it an acquired skill?

Re-read the thread.

"Christian McArdle" wrote in message
. net...
Only if a conventional boiler or other heating sources are used, not a
modulating condensing boiler.

I'd want to see further testing evidence for this, either way. I'm not
convinced which is more efficient.

Basically, does the higher temperature burn required to reheat the heat
bank
outweigh the fact that the boiler gets to do occassional full power burns,
rather than cycling, or modulating low.

Remember, that the heat bank might still be providing a reasonably low
return temperature with a very high flow/return differential, which should
offset some of the problems with regard to condensing.

If having a heat bank that only has one flow and return to it, when large
qualities of DHW are drawn off the return will be low (only if there is no
blending valve), and even lower in winter with a cold water mains temp and
the CH on working against freezing temps.

On Thu, 2 Sep 2004 12:26:25 +0100, "IMM" wrote:


"Andy Hall" wrote in message
news
Explain you warped thoughts? Well er don't bother.

There's no warp as far as I am concerned.

As far as you are concerned. Professionals would assess otherwise.

So you wouldn't know, presumably.....


The temperature probe on the
cylinder will provide information about
the temperature of the cylinder.
There is no way for it to know
whether the heat use is for the DHW
or for the radiators.

You are thick.

I'm the one with the engineering degree. Your detailed qualification
being?

I said you install a simple boiler and allow the controls to
get the best out of the it.

As usual, you are trying to change the story as you go along.



Many condensing boilers, mainly the open
vented heating type will maintain a
set temperature.

What's the point? We know that they
run more efficently at lower
temperatures.

The compensator lowers the return temperature. and you don't have an
expensive complex boiler.

The compensator is a term to the controller in the boiler. It looks
at the outside temperature to do this - all of which is unrelated to
the heatbank.



You don't know much about this sort of thing. A little knowledge is
dangerous.

As you seem to demonstrate daily.


..andy

To email, substitute .nospam with .gl

On Thu, 2 Sep 2004 11:31:58 +0100, "Christian McArdle"
wrote:

Only if a conventional boiler or other heating sources are used, not a
modulating condensing boiler.

I'd want to see further testing evidence for this, either way. I'm not
convinced which is more efficient.

Basically, does the higher temperature burn required to reheat the heat bank
outweigh the fact that the boiler gets to do occassional full power burns,
rather than cycling, or modulating low.

A condensing boiler will operate more efficiently at lower
temperatures. Repeated cycling is going to reduce efficiency which
is a second reason why they modulate down if possible rather than
turning on and off.


Remember, that the heat bank might still be providing a reasonably low
return temperature with a very high flow/return differential, which should
offset some of the problems with regard to condensing.

Yes, but that's only into the cylinder. In effect, running the
radiators from the heatbank is the equivalent of turning the hot tap
on low. The boiler will come on and attempt to replenish the
heatbank after the thermostat on it drops a few degrees below its set
point. It will then bring the temperature of the heatbank up to a few
degrees above that. The temperature, of course, has to be adequate
for the DHW use from the heatbank. Therefore the boiler will
inevitably cycle around this temperature. There is a max limit of
20-25 degrees of temperature differential across the boiler heat
exchanger anyway.
If you connect the boiler to the radiators directly, it can sense the
return temperature from the radiators themselves rather than being
switched on and off by the heatbank thermostat.

This situation could potentially be improved if the boiler has a way
to take an analogue reading from the heatbank and modulate its output
to match the radiator heating load for the case where the radiators
are connected to the heatbank. Even then, the heatbank being in the
middle will screw up the intended control algorithm because it
introduces a massive dampening effect in the feedback path.
Not many boilers have the ability to take a remote temperature probe
for the cylinder anyway, and are reliant on a cylinder thermostat with
large hysteresis.


Christian.


..andy

To email, substitute .nospam with .gl

On Thu, 2 Sep 2004 12:34:11 +0100, "IMM" wrote:


"Andy Hall" wrote in message
.. .
On Thu, 2 Sep 2004 00:27:01 +0100, "IMM" wrote:



Are you saying pressurised heat banks don't exist?

No - simply that some are not suitable
for pressurised operation,

You should be certified. If they are pressurised heat banks then they
are
suitable.

What are you talking about? I clearly and consistently made the
point that some heat banks are unsuitable for pressurised operation.

Logically that means that some are.

The point was that one should check before buying if pressurised
operation is being considered.

Have you always been this obtuse or is it an acquired skill?

Re-read the thread.

That's what I mean....


..andy

To email, substitute .nospam with .gl

On Thu, 2 Sep 2004 12:32:35 +0100, "IMM" wrote:


"Andy Hall" wrote in message
.. .
On Thu, 02 Sep 2004 00:43:45 +0100, Grunff wrote:

Andy Hall wrote:

It doesn't mean either that somebody with a good mains water supply or
who wants to redistribute space in their house won't derive benefit
from a heatbank - there are cases where they are useful as long as
they are appropriately connected.

Quite - we have pretty poor mains pressure (just under a bar - the
reservoir is about 12m above the house), and no real space problems. The
reason I put in the thermal store (or heatbank as it seems to be defined
here) was becuse the oil boiler was short cycling, despite all my
attempts to cure it. The thermal store solved this, and provided us with
a nice on demand energy store.

That's a good reason. Presumably the boiler has a large thermal mass
and quite high non-modulated output and the previous cylinder was
unable to take what it could deliver.

In this instance, a heatbank is ideal because it can swallow all the
output.

The cycling was mainly on the eating and DHW if not a quick recovery coil.


You'll fall off if you do that....... :-)


..andy

To email, substitute .nospam with .gl

"Andy Hall" wrote in message
...
On Thu, 2 Sep 2004 12:26:25 +0100, "IMM" wrote:


"Andy Hall" wrote in message
news
Explain you warped thoughts? Well er don't bother.

There's no warp as far as I am concerned.

As far as you are concerned. Professionals would assess otherwise.

So you wouldn't know, presumably.....

Andy, rub the crayon marks off your screen.

The temperature probe on the
cylinder will provide information about
the temperature of the cylinder.
There is no way for it to know
whether the heat use is for the DHW
or for the radiators.

You are thick.

I'm the one with the engineering degree.

You are still thick.

I said you install a simple boiler and allow the controls to
get the best out of the it.

As usual, you are trying to change the story as you go along.

You can't follow the thread or the explanations

The compensator lowers the return
temperature. and you don't have an
expensive complex boiler.

The compensator is a term to
the controller in the boiler.

Oh my God! A compensator can be a stand alone unit controlling a boiler, a
valve, a step switch, etc, etc.

It looks at the outside temperature
to do this

Good. Got it.

- all of which is unrelated to
the heatbank.

failed.

You don't know much about this sort of thing. A little knowledge is
dangerous.

"Andy Hall" wrote in message
...
On Thu, 2 Sep 2004 11:31:58 +0100, "Christian McArdle"
wrote:

Only if a conventional boiler or other heating sources are used, not a
modulating condensing boiler.

I'd want to see further testing evidence for this, either way. I'm not
convinced which is more efficient.

Basically, does the higher temperature
burn required to reheat the heat bank
outweigh the fact that the boiler gets to
do occassional full power burns,
rather than cycling, or modulating low.

What tripe. A heat bank eliminates boiler cycling. One person ont his
thread bought one just to do that.

A condensing boiler will operate
more efficiently at lower
temperatures.

Go away.....

Repeated cycling is going to reduce efficiency which
is a second reason why they modulate down
if possible rather than turning on and off.

Once again....A heat bank eliminates boiler cycling. One person ont his
thread bought one just to do that.

Remember, that the heat bank might still be providing a reasonably low
return temperature with a very high flow/return differential, which
should
offset some of the problems with regard to condensing.

Yes, but that's only into the cylinder.

NO!!! From the cylinder...to the boiler...called the return.

in effect, running the
radiators from the heatbank is the equivalent of turning the hot tap
on low. The boiler will come on and attempt to replenish the
heatbank after the thermostat on it drops a few degrees below its set
point.

You have two stats to eliminate boiler cycling. You clearly know nothing
about this sort of thing.

On Thu, 2 Sep 2004 13:37:33 +0100, "IMM" wrote:


I said you install a simple boiler and allow the controls to
get the best out of the it.

As usual, you are trying to change the story as you go along.

You can't follow the thread or the explanations

I manage thanks.



The compensator lowers the return
temperature. and you don't have an
expensive complex boiler.

The compensator is a term to
the controller in the boiler.

Oh my God! A compensator can be a stand alone unit controlling a boiler, a
valve, a step switch, etc, etc.

Obviously. However, if it is an external unit to the boiler and
controlling it, then it does so by turning it on and off and cycling
it.

Reasonable to good condensing boilers have an option for an external
sensor to do the weather compensation by analogue means.



..andy

To email, substitute .nospam with .gl

On Thu, 2 Sep 2004 13:43:17 +0100, "IMM" wrote:


"Andy Hall" wrote in message
.. .
On Thu, 2 Sep 2004 11:31:58 +0100, "Christian McArdle"
wrote:

Only if a conventional boiler or other heating sources are used, not a
modulating condensing boiler.

I'd want to see further testing evidence for this, either way. I'm not
convinced which is more efficient.

Basically, does the higher temperature
burn required to reheat the heat bank
outweigh the fact that the boiler gets to
do occassional full power burns,
rather than cycling, or modulating low.

What tripe. A heat bank eliminates boiler cycling. One person ont his
thread bought one just to do that.

It depends on the type of boiler, and its thermal and control
characteristics. Grunff's application was to absorb a large amount
of heat from an oil boiler when an old coil in cylinder approach, not
surprisingly, couldn't do it.

This is not what we are discussing here, which was specifically the
impact of radiators hooked up to a heatbank. If heat is being
abstracted at a lower rate than the boiler can produce it will either
have to modulate or cycle. If you put a heatbank in the middle, the
dampening effect screws up the condensing boiler's control arrangement
such that it won't be able to modulate properly.





A condensing boiler will operate
more efficiently at lower
temperatures.

Go away.....

Repeated cycling is going to reduce efficiency which
is a second reason why they modulate down
if possible rather than turning on and off.

Once again....A heat bank eliminates boiler cycling. One person ont his
thread bought one just to do that.

Once again, it can under certain circumstances such as when a large
amount of energy is being removed to heat the water. This could be
100kW or more. The boiler, assuming it is less than this will then
come on and run at full power until it is at the set point of the
heatbank.

This is not the same situation as making a lower level continuous use
of heat from the heatbank to run the radiators. It is less than the
boiler's capacity so it has no choice than to modulate or cycle.
having the heatbank in the way, with a cylinder thermostat controlling
the boiler will inevitably lead to cycling.




Remember, that the heat bank might still be providing a reasonably low
return temperature with a very high flow/return differential, which
should
offset some of the problems with regard to condensing.

Yes, but that's only into the cylinder.

NO!!! From the cylinder...to the boiler...called the return.

Yes, but the return is not from the radiators, it is from the
heatbank; the storage effect of which means that the return
temperature that the boiler sees will be that of the heatbank,
together with its dampening effect as opposed to that directly from
the radiators. They are not the same thing, and a cylinder stat has
been added into the equation as well.



in effect, running the
radiators from the heatbank is the equivalent of turning the hot tap
on low. The boiler will come on and attempt to replenish the
heatbank after the thermostat on it drops a few degrees below its set
point.

You have two stats to eliminate boiler cycling. You clearly know nothing
about this sort of thing.

You can't eliminate boiler cycling with a simple thermostat, or even
two of them. They have hysteresis.
If you had temperature probes able to give analogue readings to the
boiler and modulate it, that would be a different matter, but this is
not that.


..andy

To email, substitute .nospam with .gl

IMM wrote:

The compensator is a term to
the controller in the boiler.


Oh my God! A compensator can be a stand alone unit controlling a boiler, a
valve, a step switch, etc, etc.

Andy, you may as well try Latin, looks like he is as good on Control
Theory as he is Physics....


--
Cheers,

John.

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

You can't eliminate boiler cycling with a simple thermostat, or even
two of them. They have hysteresis.

Indeed. The idea is to promote slow cycling, perhaps using even a third or
half the heat bank capacity before attempting recovery. The questions is
whether the thermodynamic advantage of running at full pelt outweigh that of
the lower return temperature at the less efficient low burner setting.

We are considering two systems he

1. Radiators, low hysterysis single thermostat, modulating condensing
boiler.
2. Heat bank, v.high hysterysis double thermostat, unmodulating condensing
boiler.

The high hysterysis would lead to a modulating boiler become effectively
non-modulating, as the heat bank will be able to absorb whatever heat is
thrown at it until the off thermostat fires.

Which is better, running:

1. a burner at a low modulation rate, but with a lower return temperature to
promote condensing.
2. a burner at its full rated value, with long cycling (i.e. 10-15 minutes)
but with a higher return temperature.

This is all based on the understanding that modulating boilers are actually
more efficient at full rated value, than at their minimum level.

Christian.

On Thu, 2 Sep 2004 15:05:07 +0100, "Christian McArdle"
wrote:

You can't eliminate boiler cycling with a simple thermostat, or even
two of them. They have hysteresis.

Indeed. The idea is to promote slow cycling, perhaps using even a third or
half the heat bank capacity before attempting recovery. The questions is
whether the thermodynamic advantage of running at full pelt outweigh that of
the lower return temperature at the less efficient low burner setting.


True. The other factor is how to detect the difference between the
continuous and relatively low load of the radiators vs. the large
demand for DHW.

Remember that with TRVs, the radiators also present a variable load
anyway - or to some extent with zones.


We are considering two systems he

1. Radiators, low hysterysis single thermostat, modulating condensing
boiler.

Kind of. If you have TRVs or zones then the heat load varies and the
return temperature from the radiators will change accordingly (for a
given flow temperature to them). A modulating boiler will respond
to this and adjust power level to match.


2. Heat bank, v.high hysterysis double thermostat, unmodulating condensing
boiler.

The high hysterysis would lead to a modulating boiler become effectively
non-modulating, as the heat bank will be able to absorb whatever heat is
thrown at it until the off thermostat fires.

Which is better, running:

1. a burner at a low modulation rate, but with a lower return temperature to
promote condensing.
2. a burner at its full rated value, with long cycling (i.e. 10-15 minutes)
but with a higher return temperature.

This is all based on the understanding that modulating boilers are actually
more efficient at full rated value, than at their minimum level.

This is not the case for condensing boilers. If you look at the
immediate gross and net figures for efficiency for condensing boilers
(not SEDBUK weighted, which confuses the issue here) you will find
that efficiency figures increase at lower running temperatures as well
a with matching heat output of the boiler to the load. Partial load
efficency, normally measured at 30% also increases with reducing
temperatures.

Take a look at http://www.eduvinet.de/servitec/brenne.htm
which is quite a useful German tutorial on condensing boiler
technology. Pages 35-41 are pertinent.
Keep in mind that some of the points about condensate and chimnies
have to do with local German regulations, and they talk about
"forerun" and "reverse run" temperatures - means flow and return.

For a DHW system, the objective is to get as much heat as possible in
the shortest time possible into the store. The heatbank does this
well and runs the boiler at full tilt for this short time. That is
certainly more efficient than going via an inadequate coil which
results in slower transfer of heat and cycling. The objective is
different, to CH though.

With CH, the objective is to match the load to the boiler, run the
boiler at less than full output if you can and especially to have the
flow and return temperatures as low as possible.


Christian.


..andy

To email, substitute .nospam with .gl

"Andy Hall" wrote in message
...
On Thu, 2 Sep 2004 13:37:33 +0100, "IMM" wrote:


I said you install a simple boiler and allow the controls to
get the best out of the it.

As usual, you are trying to change the story as you go along.

You can't follow the thread or the explanations

I manage thanks.

You don't.

The compensator lowers the return
temperature. and you don't have an
expensive complex boiler.

The compensator is a term to
the controller in the boiler.

Oh my God! A compensator can be a stand alone unit controlling a boiler,
a
valve, a step switch, etc, etc.

Obviously. However, if it is an external
unit to the boiler and controlling it, then it
does so by turning it on and off and cycling
it.

Go away... Cycling? On a heat bank. the compemnsator says the bottom
section of the store requires 50C, the boiler comes in and makes it 50C
without any boiler cycling. IF the day wr,ms up then it may only want 40C
and when it is below 40C the boiler comes in and reheat that section agin to
40C.

Note:
1. 50C is a low temperature.
2. It said NO boiler cycling.

Reasonable to good condensing
boilers have an option for an external
sensor to do the weather compensation
by analogue means.

That is very nice to know. But cheaper condensers can be used and when
coupled with a compensator and heat bank performance is improved all around.

"Andy Hall" wrote in message
...
On Thu, 2 Sep 2004 13:43:17 +0100, "IMM" wrote:


"Andy Hall" wrote in message
.. .
On Thu, 2 Sep 2004 11:31:58 +0100, "Christian McArdle"
wrote:

Only if a conventional boiler or other heating sources are used, not
a
modulating condensing boiler.

I'd want to see further testing evidence for this, either way. I'm not
convinced which is more efficient.

Basically, does the higher temperature
burn required to reheat the heat bank
outweigh the fact that the boiler gets to
do occassional full power burns,
rather than cycling, or modulating low.

What tripe. A heat bank eliminates boiler cycling. One person ont his
thread bought one just to do that.

It depends on the type of boiler, and its thermal and control
characteristics. Grunff's application was to absorb a large amount
of heat from an oil boiler when an old coil in cylinder approach, not
surprisingly, couldn't do it.

Can't you read. The oil boiler would be cycling mainly on CH and if a lousy
cylinder on DHW too.

This is not what we are discussing
here, which was specifically the
impact of radiators hooked up to a
heatbank. If heat is being
abstracted at a lower rate than the
boiler can produce it will either
have to modulate or cycle.
If you put a heatbank in the middle, the
dampening effect screws up the condensing
boiler's control arrangement
such that it won't be able to modulate properly.

Oh my God!! Not again!!! Can't you read!!! You put on a simple cheaper
boiler (a great advantage) and allow a compensator to control the boier
which when heatinhg, heats up a large volume of water so does not cycle.

NO!!! From the cylinder...to the boiler...
called the return.

Yes, but the return is not from the radiators,
it is from the heatbank;

Which the rad circuit pumps into from its return pipe.

the storage effect of which means that the return
temperature that the boiler sees will be that of the heatbank,
together with its dampening effect as opposed to that directly from
the radiators. They are not the same thing, and a cylinder stat has
been added into the equation as well.

You clearly do not understand. A boiler with load compensation control and
an outside weather compensator controlling it. The compensator tells the
boiler that it needs the lower cylinder section heated to say 45C, it heats
it and the rads use this temperature water because the compesator said that
is the temp you need.

You can't eliminate boiler cycling with
a simple thermostat,

At least you understand that.

or even two of them.

failed again. Two stats can eliminate boiler cycling on a direct heat bank.

"Andy Hall" wrote in message
...
On Thu, 2 Sep 2004 15:05:07 +0100, "Christian McArdle"
wrote:

You can't eliminate boiler cycling with a simple thermostat, or even
two of them. They have hysteresis.

Indeed. The idea is to promote slow cycling, perhaps using even a third
or
half the heat bank capacity before attempting recovery. The questions is
whether the thermodynamic advantage of running at full pelt outweigh that
of
the lower return temperature at the less efficient low burner setting.


True. The other factor is how to detect the difference between the
continuous and relatively low load of the radiators vs. the large
demand for DHW.

Remember that with TRVs, the radiators also present a variable load
anyway - or to some extent with zones.


We are considering two systems he

1. Radiators, low hysterysis single thermostat, modulating condensing
boiler.

Kind of. If you have TRVs or zones then the heat load varies and the
return temperature from the radiators will change accordingly (for a
given flow temperature to them). A modulating boiler will respond
to this and adjust power level to match.


2. Heat bank, v.high hysterysis double thermostat, unmodulating
condensing
boiler.

The high hysterysis would lead to a modulating boiler become effectively
non-modulating, as the heat bank will be able to absorb whatever heat is
thrown at it until the off thermostat fires.

Which is better, running:

1. a burner at a low modulation rate, but with a lower return temperature
to
promote condensing.
2. a burner at its full rated value, with long cycling (i.e. 10-15
minutes)
but with a higher return temperature.

This is all based on the understanding that modulating boilers are
actually
more efficient at full rated value, than at their minimum level.

This is not the case for condensing boilers. If you look at the
immediate gross and net figures for efficiency for condensing boilers
(not SEDBUK weighted, which confuses the issue here) you will find
that efficiency figures increase at lower running temperatures as well
a with matching heat output of the boiler to the load. Partial load
efficency, normally measured at 30% also increases with reducing
temperatures.

Take a look at http://www.eduvinet.de/servitec/brenne.htm
which is quite a useful German tutorial on condensing boiler
technology. Pages 35-41 are pertinent.
Keep in mind that some of the points about condensate and chimnies
have to do with local German regulations, and they talk about
"forerun" and "reverse run" temperatures - means flow and return.

For a DHW system, the objective is to get as much heat as possible in
the shortest time possible into the store. The heatbank does this
well and runs the boiler at full tilt for this short time. That is
certainly more efficient than going via an inadequate coil which
results in slower transfer of heat and cycling. The objective is
different, to CH though.

With CH, the objective is to match the load to the boiler,

Which a weather compensator does with a heat bank between rads and boiler.
he large volume of water being heated makes it more efficient.

On Thu, 2 Sep 2004 16:50:29 +0100, "IMM" wrote:



it.

Go away... Cycling? On a heat bank. the compemnsator says the bottom
section of the store requires 50C, the boiler comes in and makes it 50C
without any boiler cycling. IF the day wr,ms up then it may only want 40C
and when it is below 40C the boiler comes in and reheat that section agin to
40C.

Note:
1. 50C is a low temperature.
2. It said NO boiler cycling.

This is complete waffle and nonsense.

Are you now saying that you have separate flow into the heatbank
at the top for DHW and part way down for CH, or are you suggesting
having cylinder thermostats on the tank part way down?

The first of these is pointless because you might as well do the job
properly and feed the radiators directly, letting the boiler detect
the temperature and modulating accordingly into higher efficiency.

The second, with the involvement of a thermostat and a non-integrated
weather compensator box will cause the boiler to cycle as the
compensator attempts to pulse-width control it.

How is differentiation made between the DHW and CH requirements as far
as the heatbank contents are concerned? For DHW operation, the need
is to have as much of the heatbank at as high a temperature as
possible - at least 75 degrees. Yet you talk about wanting 40-50
degrees part way down. Completely pointless.




Reasonable to good condensing
boilers have an option for an external
sensor to do the weather compensation
by analogue means.

That is very nice to know. But cheaper condensers can be used and when
coupled with a compensator and heat bank performance is improved all around.

Do you mean non-modulating types? If you are going to do this, and
run them at 80 degrees out, you might as well forget having a
condensing model and just get a cheap conventional model.
Don't let Rocky hear about it though.... :-)



..andy

To email, substitute .nospam with .gl

On Thu, 2 Sep 2004 17:14:28 +0100, "IMM" wrote:


"Andy Hall" wrote in message
.. .
On Thu, 2 Sep 2004 15:05:07 +0100, "Christian McArdle"

For a DHW system, the objective is to get as much heat as possible in
the shortest time possible into the store. The heatbank does this
well and runs the boiler at full tilt for this short time. That is
certainly more efficient than going via an inadequate coil which
results in slower transfer of heat and cycling. The objective is
different, to CH though.

With CH, the objective is to match the load to the boiler,

Which a weather compensator does with a heat bank between rads and boiler.
he large volume of water being heated makes it more efficient.



Sigh.

If you have an external to the boiler weather compensator, it works by
pulse width modulating the switched live to the boiler.

If the run time of heat demand is long and this mechanism comes into
effect, the boiler is being cycled, by definition.
If the run time is short, and the thermostat stops the heat demand
first then the boiler is shut down and the compensator does nothing.

..andy

To email, substitute .nospam with .gl

On Thu, 2 Sep 2004 17:07:18 +0100, "IMM" wrote:


"Andy Hall" wrote in message
.. .
On Thu, 2 Sep 2004 13:43:17 +0100, "IMM" wrote:


It depends on the type of boiler, and its thermal and control
characteristics. Grunff's application was to absorb a large amount
of heat from an oil boiler when an old coil in cylinder approach, not
surprisingly, couldn't do it.

Can't you read. The oil boiler would be cycling mainly on CH and if a lousy
cylinder on DHW too.

Perfectly thanks, and at a reading age of greater than 6.

To quote:

"Quite - we have pretty poor mains pressure (just under a bar - the
reservoir is about 12m above the house), and no real space problems.
The reason I put in the thermal store (or heatbank as it seems to be
defined here) was becuse the oil boiler was short cycling, despite all
my attempts to cure it. The thermal store solved this, and provided us
with a nice on demand energy store."


Please explain to me where mains water is used in a CH system other
than to initially pressurise it.




This is not what we are discussing
here, which was specifically the
impact of radiators hooked up to a
heatbank. If heat is being
abstracted at a lower rate than the
boiler can produce it will either
have to modulate or cycle.
If you put a heatbank in the middle, the
dampening effect screws up the condensing
boiler's control arrangement
such that it won't be able to modulate properly.

Oh my God!! Not again!!! Can't you read!!! You put on a simple cheaper
boiler (a great advantage) and allow a compensator to control the boier
which when heatinhg, heats up a large volume of water so does not cycle.

Blustering will not alter that fact that you are attempting to alter
the content and increase the complexity of the configuration, in a
vain attempt to obfuscate the issue.

Sorry, but it won't work.



NO!!! From the cylinder...to the boiler...
called the return.

Yes, but the return is not from the radiators,
it is from the heatbank;

Which the rad circuit pumps into from its return pipe.

I'm glad it's not onto the floor!



the storage effect of which means that the return
temperature that the boiler sees will be that of the heatbank,
together with its dampening effect as opposed to that directly from
the radiators. They are not the same thing, and a cylinder stat has
been added into the equation as well.

You clearly do not understand. A boiler with load compensation control and
an outside weather compensator controlling it. The compensator tells the
boiler that it needs the lower cylinder section heated to say 45C, it heats
it and the rads use this temperature water because the compesator said that
is the temp you need.

I understand completely that this is nonsense. Of course you can
hook this up, but it is completely pointless, because the controller,
if an external device to the boiler controls it by pulse width
modulating the switched live causing cycling unless the temperature
rises so quickly that the thermostat gets there first. In the latter
case, the compensator box will have done sweet FA.

You then have the issue that by the time you've bought this, you might
just as well have bought a better boiler with integrated weather
compensation giving analogue modulation of the burner.



You can't eliminate boiler cycling with
a simple thermostat,

At least you understand that.

or even two of them.

failed again. Two stats can eliminate boiler cycling on a direct heat bank.

By definition, an on/off thermostat can't eliminate cycling.

Added to this, a bunch of extra complexity is needed to make it work.


We started with a very simple arrangement of a heatbank, fed from a
modulating, condensing boiler, in turn feeding a plate heat exchanger
on demand of hot water. The heatbank can be maintained at a high
temperature to maximise the performance. The boiler can drive this
for single short periods at or close to full power.
The same boiler, when the heatbank is not connected is connected
directly to the radiators where it can measure return temperature
directly and modulate down to low level rather than off and on.

A relatively simple and effective solution.

Now we're at several pumps and valves, multiple thermostats, weather
compensation boxes and goodness knows what else.
Who are you trying to kid?

..

..andy

To email, substitute .nospam with .gl

On Thu, 2 Sep 2004 15:05:07 +0100, "Christian McArdle"
wrote:

Hi,

Just a general point, I wonder if it would be better to run the
radiator return through the heatbank lower coil, with a pipestat and
bypass valve across it.

Then as the return temperature from the radiator rises, the valve
would open so excess heat is dumped into the heat bank, reducing the
flow temperature to the boiler to promote efficiency.

If there was a sudden demand on the radiators, the lower temperature
would close the valve so the boiler sees a lower return temperature.

Otherwise the return temperature to the boiler would slowly rise until
the boiler cuts out but the heat stored in the lower part of the heat
bank would help keep the radiators hot and delay the time until the
boiler fires again.

There's probably some more potential in this idea if I could think of
it

cheers,
Pete.