"IMM" wrote in message
...

Now this brings me back to my original point.
What does "engineered to take advantage" mean - lower return
temperatures?

Yes. Larger rads.

Can't fit larger rads hence my "silly" idea.

Hence my "silly" idea of putting the pool's heat exchanger in the return
flow.

Your idea will only work when heating is on, as the heat exchanger is on
the
return pipe, which is "silly".

No that isn't the reason its silly.
Its easy to arrange for the exchanger to be connected to the flow when the
house heating is off (really off as in summer).

As Andy and myself have highlighted, a boiler should work "inside" a
flow/return temp difference. Outside this for sustained periods can cause
big problems. When control is on the boiler you are fooling it and it may
not react the way you expect, or want.

Why do you think my arrangement would put the boiler outside its temp
difference.
If you read the previous post you'd see that it brings it into its desired
delta T.

Look at a swimming pool. What is the ideal temp? 23C? Most of the time
the
return temp from the pool will be between 15-22C, cold enough for
excellent
efficiencies in a condensing boiler. Assuming the pool is indoors. If
outdoors then the return temps may be very much lower. The boiler will be
operating all night to raise it a degree or two. Most swimming pool have
the pool heated all day and the temp setback at night. It is knowing when
time the night setback has to return to normal day temp, as it will take
hours to raise the temp.

Currently the pool gets 6 hours of heating in winter and the house 12 hours
plus.
I can't see there is a problem in extending the pool to 12 hours - or as
long as it
takes using a thermo controller.
At this point you seem to be telling me that it might work.

My main point is that in this situation there is a huge heat sink that could
be used to cool the return flow and hence increase efficiency - its a fairly
unique situation.

I would go for basic condensing boilers, and have stand-alone control for
the pool heater, DHW and CH. This is a commercial setup, so control it as
such. The likes of the ICOS and Keston Celsius are for domestic
properties.

B&Q have for sale the Ravenheat CSI for £400. This is basic. Two of these
will do with separate stand alone controls.

On the pool heat exchanger have a blending valve set to the minimum the
boiler heat exchanger can have. Say 80C flow and the boiler heat
exchanger
temp diff is 20C, then set the return to 60C. There is a danger with a
pool
of having a very large temp diff, so the blending valve puts the heat
exchanger into the correct temp diff range. You could have the blending
valve set to 40C and the boiler flow temp to 60C.


I need to think about this one.
mikej

On Sun, 26 Oct 2003 13:09:34 -0000, "IMM" wrote:



Running a 140,000 btu/h boiler to heat a pool will pay for itself in around
2.5 -3 years. Do some looking and cheaper condensers are had. It appears
he wants to pay domestic, and fit domestic, for a commercial setup. Typical
small hotel mentality. Just have a shower in those places, and that is why
foreigners laugh at our plumbing.


Conjures up thoughts of........

Quote - Sybil: 'Do you really imagine, even in your wildest dreams,
that a girl like this could possibly be interested in an ageing
brilliantined stick insect like you?'

Quote - Basil: 'Well... may I ask what you were expecting to see out
of a Torquay hotel bedroom window? Sydney Opera House, perhaps? The
Hanging Gardens of Babylon? Herds of wildebeeste sweeping
majestically...'

Quote - Basil: 'So that's two eggs mayonnaise, a prawn Goebbels, a
Hermann Goering and four Colditz salads... no, wait a moment, I got a
bit confused there, sorry...I got a bit confused because everyone
keeps mentioning the War, so could you...'
German: 'Will you stop talking about the war!'
Basil: 'Me? You started it!'
German: 'We did not start it.'
Basil: 'Yes you did, you invaded Poland...'

Quote - Basil: (on phone) 'If you're not over here in twenty minutes
with my door, I shall come over and insert a large garden gnome in
you. Good day.'





..andy

To email, substitute .nospam with .gl

"Andy Hall" wrote in message
...
On Sun, 26 Oct 2003 12:01:28 -0000, "mike.james"
wrote:

The point is that the boiler heat exchanger is rated to give 20
degrees temperature lift at full burner output - that's it. At
lower outputs it may operate with lower temperature differentials.

Right - now I've got it.
Many thanks.

I'm focusing on the return temperature thinking that the boiler can take
care of the flow temperature and bring it up to the higher level needed by
the smaller rads.
You're saying that I have to have a higher return temp to ensure that the
smaller rads are kept as hot as they need to me. So if I do drop the return
temp I'm effectively opting for the lower flow temp.

I need to think about this.
(and read the technical stuff on the Keston)

mikej

"Andy Hall" wrote in message
...
I'd let him get on with it,.......



.andy


To a certain extent that's my feeling but I just couldn't resist thinking
about how the pool could be used to make the whole thing work
better and perhaps get to the 20% extra promised by the boiler.
I still sort of think that there should be some way of making use of
a low temperature sink but I'm beginning to see that its
more difficult than I first thought.
mikej

"Andy Hall" wrote in message
...
On Sun, 26 Oct 2003 13:12:26 -0000, "IMM" wrote:

In fact Keston and others make ready to go rigs with two boilers and
all the controls and plumbing to do just that.....
There is one for the C40 and C55.

All good points that I'll pass on.
mikej

On Sun, 26 Oct 2003 13:49:38 -0000, "mike.james"
wrote:


"Andy Hall" wrote in message
.. .
On Sun, 26 Oct 2003 12:01:28 -0000, "mike.james"
wrote:

The point is that the boiler heat exchanger is rated to give 20
degrees temperature lift at full burner output - that's it. At
lower outputs it may operate with lower temperature differentials.

Right - now I've got it.
Many thanks.

I'm focusing on the return temperature thinking that the boiler can take
care of the flow temperature and bring it up to the higher level needed by
the smaller rads.
You're saying that I have to have a higher return temp to ensure that the
smaller rads are kept as hot as they need to me. So if I do drop the return
temp I'm effectively opting for the lower flow temp.

I need to think about this.
(and read the technical stuff on the Keston)

mikej


Exactly. It is a kind of circular argument, I'm afraid.

It's easy to just focus on one aspect, when in reality it's all
inter-related.

A useful, although not totally applicable analogy is an electric
circuit.

Think of it like a circuit with a 6v battery and two 6 volt bulbs.
You can't increase the voltage of the battery.

If you connect both bulbs in parallel and measure the current, if the
battery were perfect, the current from it would double when compared
with just having one bulb across the battery. This is analogous to
doubling the flow rate and you would double the power output from the
battery in effect.

However, if you connected the bulbs in series, you would get half of
the voltage across each and reduced brightness. You could
compensate this by going for 3v bulbs - analogous to upping the
radiator size.

This is a gross simplification, of course - I am not sure what the
direct electrical equivalent of a condensing boiler would be :-); biut
it illustrates the point..



..andy

To email, substitute .nospam with .gl

On Sun, 26 Oct 2003 13:52:23 -0000, "mike.james"
wrote:


"Andy Hall" wrote in message
.. .
I'd let him get on with it,.......



.andy


To a certain extent that's my feeling but I just couldn't resist thinking
about how the pool could be used to make the whole thing work
better and perhaps get to the 20% extra promised by the boiler.
I still sort of think that there should be some way of making use of
a low temperature sink but I'm beginning to see that its
more difficult than I first thought.
mikej


Even if you connect the heat exchanger in parallel to the radiators
(as they should be) there will be a downward effect on the return
temperature to the boiler.

Think about the flows of water and the heat loads. Let's say for
simplicity that you arranged equal flows through the radiators and
through the pool heat exchanger, but that the pool heat exchanger
represents twice the load of the radiators. I am assuming that the
pool heat exchanger is not limited by its dT - which actually with
good sized stainless steel plate jobs will be the case - they can be
capable of transferring 200kW in a very small size. Since everything
else is equal, you will get a twice larger temperature drop on the
return from the heat exchanger than from the radiators. When the
water is mixed to return to the boiler, it will be lower than with
either load connected alone.

I have an arrangement like this for providing heat to my garage
workshop. It runs with a separate circuit and via a heat exchanger,
for a number of reasons. When there is a heat requirement to the
garage (which is generally equivalent to a couple of large radiators),
the boiler return temperature does drop and the burner is wound up a
bit as is the flow.


The one questionmark that I raised with this is that with the pool,
the heat load is going to be vastly greater than that for the
radiators. Therefore to get a reasonable distribution of heat,
some balancing would be needed to effectively throttle back the heat
supply to the pool as IMM suggested.

They do have rather different characteristics as well, which is why
there is generally a switchover arrangement for heating cylinders.
This is why having two separate boilers may have proven to be an
effective solution, simply because the load characteristics are so
different.


..andy

To email, substitute .nospam with .gl

"Andy Hall" wrote in message
...

To a certain extent that's my feeling but I just couldn't resist thinking
about how the pool could be used to make the whole thing work
better and perhaps get to the 20% extra promised by the boiler.
I still sort of think that there should be some way of making use of
a low temperature sink but I'm beginning to see that its
more difficult than I first thought.
mikej


Even if you connect the heat exchanger in parallel to the radiators
(as they should be) there will be a downward effect on the return
temperature to the boiler.

Think about the flows of water and the heat loads. Let's say for
simplicity that you arranged equal flows through the radiators and
through the pool heat exchanger, but that the pool heat exchanger
represents twice the load of the radiators. I am assuming that the
pool heat exchanger is not limited by its dT - which actually with
good sized stainless steel plate jobs will be the case - they can be
capable of transferring 200kW in a very small size. Since everything
else is equal, you will get a twice larger temperature drop on the
return from the heat exchanger than from the radiators. When the
water is mixed to return to the boiler, it will be lower than with
either load connected alone.

I have an arrangement like this for providing heat to my garage
workshop. It runs with a separate circuit and via a heat exchanger,
for a number of reasons. When there is a heat requirement to the
garage (which is generally equivalent to a couple of large radiators),
the boiler return temperature does drop and the burner is wound up a
bit as is the flow.

The one questionmark that I raised with this is that with the pool,
the heat load is going to be vastly greater than that for the
radiators. Therefore to get a reasonable distribution of heat,
some balancing would be needed to effectively throttle back the heat
supply to the pool as IMM suggested.

They do have rather different characteristics as well, which is why
there is generally a switchover arrangement for heating cylinders.
This is why having two separate boilers may have proven to be an
effective solution, simply because the load characteristics are so
different.

1.
Assume a Keston Celsius with load compensation control. When the flow and
return temps become closer together the system assumes the house is nearing,
or up to, temp. It then modulates the burner down. When the return and flow
temps become wiser the assumption is that the house is becoming colder and
winds the flow temp up.

CH is only on the house warms up and the boiler drops the flow temp. Fine.
The pool heater is switched in. The return temp from the pool is very low
(17C) and this blends with the return of the house heating (say 30c) to say
give a combined return temp of 21C. Great for boiler efficiencies. Less
gas is being used. The control system thinks the house is cooling and
ramps up the flow temp to max. Fine, as the pool heater needs this heat.
This means the flow to the house is too high. This is fine as TRV rad
valves will compensate for any heat gain; assuming they are fitted in the
rooms.

2.
The Keston boilers quoted are small commercial jobs with no modulation.
With these boilers it is best to fit a Danfoss Randall BES 5000 outside
weather compensator (£166 from discountheating) . This will drop the return
temp of the boiler to the outside weather promoting efficiency. The room
TRVs will compensate for any highs or lows in the room trimming off locally.
The pool heater kicks in. No matter what the combined heating and pool
return temp is, there is enough heat flowing to the pool to heat it. The
burner will stay full on as the return will have a good flow and a constant
low return temp. The boiler will take a long time to make an impact on that
volume of cold water. The pool temp is only around 21-23C. That will work.
This goes for a couple of basic Ravenheat condensers too.

With either of the above have the DHW heating on a priority, cutting out the
pool heater to heat the cylinder.

Better still have one boiler do the house and DHW and one do the pool
(assuming a 25kW boiler will heat the house). With a few valves to
alternate boilers if say the house boilers drops out, always having a
backup for essential services. Or if there is a constant large demand for
DHW, it may be best to have the pool and DHW on the one boiler with a
priority system for DHW.

Now it depends on what deals you can get with boilers. The two boiler
option in a commercial concern is by far the best.



---
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"mike.james" wrote:
=

"Ed Sirett" wrote in message
...
"mike.james" wrote:

This is silly. There is no way that condensing boiler are double the
price.
=

Its an Ideal Mexico Super CF4140 - 140,000 BTU - 41kw =A3872
v
Keston C55 (55Kw) =A3 1,548.89
or the C40 (40Kw) at =A3 1,360.90
=

(Prices I've got from pumbworld which don't correspond to the prices qu=
oted
in the installation which are up by about 10-20% which makes the gap bi=
gger)
mikej

The Ideal Mexico is not a modern design of boiler it's conventionally
flued - probably the only improvement in the last 25 years is electronic
ignition - and maybe not even that. =


I'm not even sure that the Mexico would comply with part L.

-- =

Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html

"Ed Sirett" wrote in message
...
"mike.james" wrote:

"Ed Sirett" wrote in message
...
"mike.james" wrote:

This is silly. There is no way that condensing boiler are double the
price.

Its an Ideal Mexico Super CF4140 - 140,000 BTU - 41kw £872
v
Keston C55 (55Kw) £ 1,548.89
or the C40 (40Kw) at £ 1,360.90

(Prices I've got from pumbworld which don't correspond to the prices
quoted
in the installation which are up by about 10-20% which makes the gap
bigger)
mikej

The Ideal Mexico is not a modern design of boiler it's conventionally
flued - probably the only improvement in the last 25 years is electronic
ignition - and maybe not even that.

25 years? Try 33 years. It came out at the time of the 1970 Mexico world
cup, hence the name. The Morris Marina (what a dog) was not even introduced
when it came out. How they have been making this clunker for all this time
I find amazing.

I'm not even sure that the Mexico would comply with part L.

Just. 78%. This low limit is rising soon.


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On Sun, 26 Oct 2003 17:57:04 -0000, "IMM" wrote:



1.
Assume a Keston Celsius with load compensation control. When the flow and
return temps become closer together the system assumes the house is nearing,
or up to, temp. It then modulates the burner down. When the return and flow
temps become wiser the assumption is that the house is becoming colder and
winds the flow temp up.

CH is only on the house warms up and the boiler drops the flow temp. Fine.
The pool heater is switched in. The return temp from the pool is very low
(17C) and this blends with the return of the house heating (say 30c) to say
give a combined return temp of 21C. Great for boiler efficiencies. Less
gas is being used. The control system thinks the house is cooling and
ramps up the flow temp to max. Fine, as the pool heater needs this heat.
This means the flow to the house is too high. This is fine as TRV rad
valves will compensate for any heat gain; assuming they are fitted in the
rooms.

2.
The Keston boilers quoted are small commercial jobs with no modulation.

I think that you are thinking of the older models. These two
modulate from 11 to 40 kW and 14 to 55kW respectively.
The rig for them has the option of fully proportional controllers with
weather compensation and remote access and monitoring.



Better still have one boiler do the house and DHW and one do the pool
(assuming a 25kW boiler will heat the house). With a few valves to
alternate boilers if say the house boilers drops out, always having a
backup for essential services. Or if there is a constant large demand for
DHW, it may be best to have the pool and DHW on the one boiler with a
priority system for DHW.

Now it depends on what deals you can get with boilers. The two boiler
option in a commercial concern is by far the best.



---

..andy

To email, substitute .nospam with .gl

"Andy Hall" wrote in message
news
On Sun, 26 Oct 2003 17:57:04 -0000, "IMM" wrote:



1.
Assume a Keston Celsius with load compensation control. When the flow
and
return temps become closer together the system assumes the house is
nearing,
or up to, temp. It then modulates the burner down. When the return and
flow
temps become wiser the assumption is that the house is becoming colder
and
winds the flow temp up.

CH is only on the house warms up and the boiler drops the flow temp.
Fine.
The pool heater is switched in. The return temp from the pool is very
low
(17C) and this blends with the return of the house heating (say 30c) to
say
give a combined return temp of 21C. Great for boiler efficiencies. Less
gas is being used. The control system thinks the house is cooling and
ramps up the flow temp to max. Fine, as the pool heater needs this heat.
This means the flow to the house is too high. This is fine as TRV rad
valves will compensate for any heat gain; assuming they are fitted in the
rooms.

2.
The Keston boilers quoted are small commercial jobs with no modulation.

I think that you are thinking of the older models.

I am and I liked them a lot. I loved their simplicity.

These two
modulate from 11 to 40 kW and 14 to 55kW respectively.
The rig for them has the option of fully proportional controllers with
weather compensation and remote access and monitoring.

Sounds good I'll have to check them out.




---
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On Sun, 26 Oct 2003 21:52:50 -0000, "IMM" wrote:


2.
The Keston boilers quoted are small commercial jobs with no modulation.

I think that you are thinking of the older models.

I am and I liked them a lot. I loved their simplicity.

These two
modulate from 11 to 40 kW and 14 to 55kW respectively.
The rig for them has the option of fully proportional controllers with
weather compensation and remote access and monitoring.

Sounds good I'll have to check them out.


From the installation guide, they would appear to be larger versions
based on the Celsius design - according to the SEDBUK entry , on the
market since last year......




..andy

To email, substitute .nospam with .gl

In article , Andy
Hall wrote:
Its an Ideal Mexico Super CF4140 - 140,000 BTU - 41kw £872

Poor choice. The SEDBUK seasonal efficiency figure for this
one is 78.6%.

The other thing is that according to the SEDBUK database the
output is a fixed 41kW, all or nothing. In the spring and autumn
the part load efficiency (which is admittedly taken account of in
the SEDBUK calc) is likely to be a lot less:

--
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

In article , Mike.james
wrote:
Two ICOS boilers cost about the same as one Keston when
you take into account the extra installation costs not to
mention the increased space, flue etc and not being as
sophisticated..

We put twin Keston Celsius boilers in our church a couple of
years ago. The cost of the boilers is about the same as one
larger boiler but of course there is more work involved in
installation (free labour in our case so it didn't matter). In
the spring and autumn and when the building is up to temp you
can cut one boiler out and run the other more efficiently. The
other advantage is that you have usefully degree of redundancy:
if one boiler is out for any reason the other keeps going. It
does of course also mean that there are two to service, but if
the engineer is already there this shouldn't cost too much.

--
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

"Tony Bryer" wrote in message
...
In article , Andy
Hall wrote:
Its an Ideal Mexico Super CF4140 - 140,000 BTU - 41kw £872

Poor choice. The SEDBUK seasonal efficiency figure for this
one is 78.6%.

The other thing is that according to the SEDBUK database the
output is a fixed 41kW, all or nothing. In the spring and autumn
the part load efficiency (which is admittedly taken account of in
the SEDBUK calc) is likely to be a lot less:

With the return temp of the pool being very low; below condensing
temperatures. the burner box will condensate, unless back end protection is
fitted. Look inside the existing boiler and I'm sure the burner box will be
rusty (assuming the pool is being heated by this boiler).


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"mike.james" wrote in message
...

"Andy Hall" wrote in message
...
On Sun, 26 Oct 2003 13:12:26 -0000, "IMM" wrote:

In fact Keston and others make ready to go rigs with two boilers and
all the controls and plumbing to do just that.....
There is one for the C40 and C55.

All good points that I'll pass on.
mikej

From:
http://www.saveenergy.co.uk/boilers/

"Boilers are amongst the worst offenders when it comes to energy wasters in
your home. Boilers alone account for up to a third of all domestic CO2
emissions. If you don’t think your boiler should get away with it any
longer, then read on. As the current lifespan of a boiler is 10-15 years,
making the wrong decision about what boiler to have really could mean a life
sentence of wasting money and time and damaging the environment.
A heating system that uses a high efficiency condensing boiler and with the
correct heating controls can save as much as 40% on your fuel bills. It
really is time to shop your old boiler."


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"IMM" wrote in message
...

"Andy Hall" wrote in message
...

To a certain extent that's my feeling but I just couldn't resist
thinking
about how the pool could be used to make the whole thing work
better and perhaps get to the 20% extra promised by the boiler.
I still sort of think that there should be some way of making use of
a low temperature sink but I'm beginning to see that its
more difficult than I first thought.
mikej


Even if you connect the heat exchanger in parallel to the radiators
(as they should be) there will be a downward effect on the return
temperature to the boiler.

Think about the flows of water and the heat loads. Let's say for
simplicity that you arranged equal flows through the radiators and
through the pool heat exchanger, but that the pool heat exchanger
represents twice the load of the radiators. I am assuming that the
pool heat exchanger is not limited by its dT - which actually with
good sized stainless steel plate jobs will be the case - they can be
capable of transferring 200kW in a very small size. Since everything
else is equal, you will get a twice larger temperature drop on the
return from the heat exchanger than from the radiators. When the
water is mixed to return to the boiler, it will be lower than with
either load connected alone.

I have an arrangement like this for providing heat to my garage
workshop. It runs with a separate circuit and via a heat exchanger,
for a number of reasons. When there is a heat requirement to the
garage (which is generally equivalent to a couple of large radiators),
the boiler return temperature does drop and the burner is wound up a
bit as is the flow.

The one questionmark that I raised with this is that with the pool,
the heat load is going to be vastly greater than that for the
radiators. Therefore to get a reasonable distribution of heat,
some balancing would be needed to effectively throttle back the heat
supply to the pool as IMM suggested.

They do have rather different characteristics as well, which is why
there is generally a switchover arrangement for heating cylinders.
This is why having two separate boilers may have proven to be an
effective solution, simply because the load characteristics are so
different.

1.
Assume a Keston Celsius with load compensation control. When the flow and
return temps become closer together the system assumes the house is
nearing,
or up to, temp. It then modulates the burner down. When the return and
flow
temps become wiser the assumption is that the house is becoming colder and
winds the flow temp up.

CH is only on the house warms up and the boiler drops the flow temp.
Fine.
The pool heater is switched in. The return temp from the pool is very low
(17C) and this blends with the return of the house heating (say 30c) to
say
give a combined return temp of 21C. Great for boiler efficiencies. Less
gas is being used. The control system thinks the house is cooling and
ramps up the flow temp to max. Fine, as the pool heater needs this heat.
This means the flow to the house is too high. This is fine as TRV rad
valves will compensate for any heat gain; assuming they are fitted in the
rooms.

2.
The Keston boilers quoted are small commercial jobs with no modulation.
With these boilers it is best to fit a Danfoss Randall BES 5000 outside
weather compensator (£166 from discountheating) . This will drop the
return
temp of the boiler to the outside weather promoting efficiency. The room
TRVs will compensate for any highs or lows in the room trimming off
locally.
The pool heater kicks in. No matter what the combined heating and pool
return temp is, there is enough heat flowing to the pool to heat it. The
burner will stay full on as the return will have a good flow and a
constant
low return temp. The boiler will take a long time to make an impact on
that
volume of cold water. The pool temp is only around 21-23C. That will
work.
This goes for a couple of basic Ravenheat condensers too.

I see B&Q still have the Ravenheat 25 kW CSI primary at £399. This is a
basic condensing boiler with on-off control, no pump, no pressure vessel and
can be open vented or pressurised at over 90% sedbick efficency. Two of
these is the same price as the Ideal cast-iron clunker and a boiler for
backup too. Well worth considering and implememting as i suggested above
in No. 2.

With either of the above have the DHW heating on a priority, cutting out
the
pool heater to heat the cylinder.

Better still have one boiler do the house and DHW and one do the pool
(assuming a 25kW boiler will heat the house). With a few valves to
alternate boilers if say the house boilers drops out, always having a
backup for essential services. Or if there is a constant large demand
for
DHW, it may be best to have the pool and DHW on the one boiler with a
priority system for DHW.

Now it depends on what deals you can get with boilers. The two boiler
option in a commercial concern is by far the best.



---
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