John Stumbles wrote:
On Tue, 16 May 2006 20:49:08 +0100, John Rumm wrote:


What did your system cost to have installed? And what does it consist of?


Hint: google for fisher and solartwin :-)

Yup, found it ta...

(it does help when you have read the original post so that you know the
name of the system to google for!)


--
Cheers,

John.

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Mary Fisher wrote:

I have also given the url.

Must have missed that...

The solartwin one?

OK I have downloaded and read through the installers manual....

Interesting system... the "direct" plumbing approach solves a number of
the normal complications of similar systems (although introduces some as
well).

What form of water softening do you use with it, or do you have soft
water in your neck of the woods anyway?

Most people seem to think that the payback time is the most important aspect
of such installations. We don't (we don't consider the payback time on
anything else we buy either) but for those people we've worked out that on
present gas prices we'll recover the cost in ten years (if we live that
long). I doubt that present gas prices won't stay what they are so nobody
can determine what the payback time will be.

Payback time is only one measure as you say (although in many cases the
economic cost of an activity also has a good correlation with its
environmental cost as well)

Have you made any estimate of its heating power on a sunny day?

That includes you and Parry and all the other sceptics.

Why do you call me a sceptic? The only scepticism that I expressed with
regard to solar water heating, was when used with a combi boiler that
does not also have some form of storage. For example the system you have
would be of no practical benefit in this circumstance since the flow
rate through the panel is far to low to do much in the way of either
pre-heating the inlet water or directly blending with the output of a
combi.


--
Cheers,

John.

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John Stumbles wrote:

I'd have thought a (much cheaper) phosphor-dosing scale inhibitor would
serve this purpose, as it does for other water-heating appliances such as
combi boilers. Do you have some evidence to show that this is not the
case?

I was wondering this as well, since the install manual made no reference
to combimate type devices. (although to give them credit they also
neglected dribble style pet elctro/magnetic rocks as well).

--
Cheers,

John.

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Steve Firth wrote:

On Tue, 16 May 2006 17:18:10 +0100, Peter Parry wrote:


you also need to install an ion exchange water softener
otherwise the panel will quickly be ruined because of scale from the
hard water.


Say what? The water in the panel should be recirculated and contain rust
and scale inhibitors (as in a primary boiler circuit). The heat should be
transferred to a separate hot water cylinder of exactly the same type as is
used on non-solar systems.

Not on the system Mary was talking about - it takes cool water from the
cold DHW *feed* at the base the cylinder, runs it through the solar
panel (using a small PV powered solar pump connected via microbore
pipe), and returns it to the top of the cylinder via the DHW/vent outlet.

Hence the panel and pump are going to be being a reasonably frequent
supply of fresh water.

This seems to be one of the more useful documents:

http://www.solartwin.com/PDF/Method_Statement.pdf

(The only thing I can't see is how they prevent the solar pump running
when the cylinder temperature already exceeds the panel output temp...)

--
Cheers,

John.

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John Stumbles wrote:

Mains pressure
hot/warm water ---------
from thermal store | combi |
------------------+---| DHW |------
| --------- |
| -----
| | H |
| | TMV |-------
| | C |
| -----
| |
---------------------

To save potential complications from feeding the combi with prewarmed
water (which could in some cases be *hot*), you could do:


---------
mains cold | combi |
-----------------------| DHW |-------
--------- |
-----
| H |
| TMV |-------
| C |
-----
preheated water from store |
------------------------------------------

(with optional additional blending valve at the output as you suggest)

Or if you want to take advantage of the prewarmed water for the combis
DHW input you might need:

---------
mains cold | combi |
-------------- ---| DHW |--------
| | --------- |
----- | -----
| C | | | H |
| TMV |- | TMV |-------
| H | | C |
----- -----
| |
| |
preheated | |
water | |
| |
-------------------------------------------

Set the output temp of the first TMV so that it does not exceed the
maximum inlet temp on the combi.

Obviously you will use energy from the store faster this way and will
reach the point where the combi is supplying the bulk of the heat sooner
(and hence you may need to reduce flowrate to maintain temperature)

--
Cheers,

John.

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On Tue, 16 May 2006 17:18:10 +0100 someone who may be Peter Parry
wrote this:-

In many boilers the pumps and
control valves are integrated within the boiler.

Some boilers have pumps, some of these also have controllers which
will activate the pump for short periods to prevent it sticking.

Valves tend to be outside the boiler. If they are sticking often
then water treatment may need looking at.

Corrosion where?

The boiler casing. It is a fairly common cause of terminal failure
of room sealed boilers.

That corrosion is largely caused when the boiler is warming up and
acid is being deposited on the surfaces. Warm it up less often and
there is less of it, prolonging boiler life.

but didn't see anything about how solar heating can save more gas
than people think.

I pointed out the specific circumstances in which it would save more
gas than people think in my original posting. Obviously if the
boiler has electric ignition then the saving will not even be that
of turning off a pilot light for some months.

What is wrong is to claim it makes _economic_ sense when quite
plainly in the vast majority of cases it doesn't

The claim people make in this group is that at current prices solar
water heating is a long term financial investment. Discussing your
distortions of the claims people make does not help your argument
one bit.

For example the oft quoted solution of the solar powered motor pumped
panels on the direct side of the water system makes great claims
about the economic sense of doing this (saving the few watts an
electric pump takes)

You have already been pointed to the government report which states
that 17-23% of the carbon dioxide benefits can be lost in pumping
and running the control system 24 hours a day from mains
electricity. BTW, unless variable speed pumping is in use it takes
more than a few watts to run the pump.

Against this one has to put the environmental cost of producing the
solar panel. However, one also has to allow for the fact that solar
powered pumping has stimulated people to think of low water volume
systems, with relatively slow speed pumping.

but makes little or no mention of the fact that
for most people living east of a line drawn roughly from Lincoln to
Bristol you also need to install an ion exchange water softener
otherwise the panel will quickly be ruined because of scale from the
hard water.

A quick reality check on your assertion is to note what the
manufacturer of the system most mentioned has to say on this
http://www.solartwin.com/is_solartwin_suitable.htm

"Need I control water hardness?

"Control for “direct” Solartwin's is uncomplicated. First phone the
water company for “parts per million calcium carbonate” (also called
“ppm CaCO3”). If they quote “typical” or “average” (not maximum)
figures, allow 20% tolerance i.e. add 20% to their figure i.e. treat
a single figure of 200 as 240.

"* If hardness ever exceeds 200 ppm CaCO3 (very hard water) use
either an ion-exchange (salt-regenerated) water softener or an
“indirect” Solartwin. We supply and fit softeners. Please call.

"* At 100 - 200 (maximum) ppm CaCO3, you can use Fernox
Superconcentrate Limescale Preventer. Your first little bag of
crystals on a string is free. Simply hang it in the cold tank.
Replace it twice a year. A free 6-monthly postcard reminds you.
Fernox SLP is food grade. It costs about £10 from DIY shops. Or you
can use an ion-exchange water softener or an “indirect” system.

"* Under 100 ppm, and with “indirect” Solartwins, use no hardness
control.

"All other water hardness treatments or conditioners, including
electromagnetic, magnetic, electronic, physical or ultrasonic
methods must not be used. The above 239/240 ppm maximum thresholds
are reduced to 199/200ppm respectively for all “fortic” type hot
water cylinders as well as irregularly used hot water systems, such
as in holiday homes."





--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

The message
from Steve Firth contains these words:

FWIW, prices have been dropping fast recently. I've picked up a 300 litre
20 vacuum tube unit for the tractor shed/store at the farm. We're
installing a bathroom/office at the back of the store and the only source
of hot water will be solar. The total cost of the unit + installation is
£700, cheaper than an LPG system.

Cor - got any more?

--
Skipweasel
Pay no attention to that man behind the curtain.

On Tue, 16 May 2006 22:42:46 GMT, raden wrote:


And he's still waiting for someone in uk.d-i-y to return a fan ...

I know, my apologies - it's still in the car travelling miles except
to where it should be going. Might need to have some sustaining
fluid attached to it when it gets to you. (It didn't bother with the
postcards as Frimley, Luton and Stevenage seem to lack interesting
ones!).

--
Peter Parry.
http://www.wpp.ltd.uk/

On Tue, 16 May 2006 21:32:17 GMT, John Stumbles
wrote:


I'd have thought a (much cheaper) phosphor-dosing scale inhibitor would
serve this purpose, as it does for other water-heating appliances such as
combi boilers. Do you have some evidence to show that this is not the
case?

"Best practice in water hardness control is more important for direct
than for indirect solar water heating systems. Direct solar water
heating systems may need robust hardness control: and water softeners
may be difficult to install in a few properties. Unless they are
plumbed “indirectly”, water harness control for direct solar is
usually achieved by polyphosphates where the water hardness is
100-200 ppm CaCO3 and by the use of an ion exchange softener above
this figure. Ion exchange water softeners are thus regarded as
essential best practice...

Barry Johnston, MSc
Managing Director, Solartwin.com"

Above 200 mg/l as calcium carbonate equivalent includes most of
Eastern England in an area bounded on the west by Southampton,
Bristol, Birmingham and Lincoln.

http://www.britishwater.co.uk/html/s...water.html#Map



--
Peter Parry.
http://www.wpp.ltd.uk/

On Wed, 17 May 2006 03:25:21 +0100, John Rumm wrote:

John Stumbles wrote:

Mains pressure
hot/warm water ---------
from thermal store | combi |
------------------+---| DHW |------
| --------- |
| -----
| | H |
| | TMV |-------
| | C |
| -----
| |
---------------------

To save potential complications from feeding the combi with prewarmed
water (which could in some cases be *hot*), ...
---8---

Although the temperature at the inlet to the combi may be hot, there
should be no flow, therefore no demand, until the temperature falls
below the TMV set point. Therefore the combi should only be heating warm,
never hot, water.

Of course if the combi has problems with this then your plan B will be
called for.

---------
mains cold | combi |
-----------------------| DHW |-------
--------- |
-----
| H |
| TMV |-------
| C |
-----
preheated water from store |
------------------------------------------

Solar heating of water and combi-boilers do not mix.The combi is
designed to operate on at least 1.2 bar mains water pressure, and water
heated by solar means would not be able to
deliver this as it would have to be stored before delivery to the
boiler.
What's the point? A combi boiler is specifically designed for
efficiency anyway.
Les.

On Wed, 17 May 2006 07:57:52 +0100, David Hansen wrote:

I pointed out the specific circumstances in which it would save more
gas than people think in my original posting. Obviously if the
boiler has electric ignition then the saving will not even be that
of turning off a pilot light for some months.

If a boiler does _not_ have electric ignition but has a constant pilot
light then it is a dinosaur with seasonal efficiency in the region of 65%.
The controls are likely to be primitive, too. It will make far more sense
to replace it with a high-efficiency boiler with updated controls than put
in solar water heating.

(I'm not talking about the OP's installation which, we've already
ascertained, is a condensing boiler with proper controls.)

On Wed, 17 May 2006 07:57:52 +0100, David Hansen
wrote:

On Tue, 16 May 2006 17:18:10 +0100 someone who may be Peter Parry
wrote this:-

The boiler casing. It is a fairly common cause of terminal failure
of room sealed boilers.

That corrosion is largely caused when the boiler is warming up and
acid is being deposited on the surfaces. Warm it up less often and
there is less of it, prolonging boiler life.

The boiler casing (the outside box) doesn't have acid deposited on it
as it is only exposed to incoming air. It does get condensation and
damp from the outside atmosphere (to which it is open in a room
sealed boiler) when unused. As it is a spare part which is almost
impossible to get for older boilers corrosion on it often ends their
life.

For example the oft quoted solution of the solar powered motor pumped
panels on the direct side of the water system makes great claims
about the economic sense of doing this (saving the few watts an
electric pump takes)

You have already been pointed to the government report which states
that 17-23% of the carbon dioxide benefits can be lost in pumping
and running the control system 24 hours a day from mains
electricity.

The "government report" also signally failed to mention that on a
cold sunny day with little solar gain the device also happily pumps
your gas heated hot water into a nice big radiator on the outside of
the roof to cool it down. What is the energy cost of this?

BTW, unless variable speed pumping is in use it takes
more than a few watts to run the pump.

The tiny little Solartwin pump I have at the moment appears to be
about a 5W max unit, I'm not sure if this is their common pump (I
think this panel came from the trial you refer to).

Against this one has to put the environmental cost of producing the
solar panel. However, one also has to allow for the fact that solar
powered pumping has stimulated people to think of low water volume
systems, with relatively slow speed pumping.

but makes little or no mention of the fact that
for most people living east of a line drawn roughly from Lincoln to
Bristol you also need to install an ion exchange water softener
otherwise the panel will quickly be ruined because of scale from the
hard water.

A quick reality check on your assertion is to note what the
manufacturer of the system most mentioned has to say on this
http://www.solartwin.com/is_solartwin_suitable.htm

That you for confirming that what I said was correct. Most people
east of that line have water with more than 200ppm hardness.


--
Peter Parry.
http://www.wpp.ltd.uk/

On Wed, 17 May 2006 02:57:56 +0100, John Rumm wrote:

John Stumbles wrote:

I'd have thought a (much cheaper) phosphor-dosing scale inhibitor would
serve this purpose, as it does for other water-heating appliances such as
combi boilers. Do you have some evidence to show that this is not the
case?

I was wondering this as well, since the install manual made no reference
to combimate type devices. (although to give them credit they also
neglected dribble style pet elctro/magnetic rocks as well).

I see David Hansen has quoted solartwin's recommendation of
phosphor-dosing for all but the hardest water.

On Wed, 17 May 2006 08:04:16 +0100, Guy King wrote:

The message
from Steve Firth contains these words:

FWIW, prices have been dropping fast recently. I've picked up a 300 litre
20 vacuum tube unit for the tractor shed/store at the farm. We're
installing a bathroom/office at the back of the store and the only source
of hot water will be solar. The total cost of the unit + installation is
£700, cheaper than an LPG system.

Cor - got any more?

http://cgi.ebay.co.uk/SUMMER-TX-SOLA...cm dZViewItem
http://cgi.ebay.co.uk/SOLAR-HEATER-1... cmdZViewItem


Although I've now found a place that will supply me factory direct and I'm
thinking of importing them myself. There are several different models
available either with a 300 litre storage tank, or with a 300 litre thermal
store. The thermal store seems like the better option to me, since the unit
is sealed, doesn't use a pump and is simpler to install.

On Wed, 17 May 2006 03:09:31 +0100, John Rumm wrote:

Steve Firth wrote:

On Tue, 16 May 2006 17:18:10 +0100, Peter Parry wrote:


you also need to install an ion exchange water softener
otherwise the panel will quickly be ruined because of scale from the
hard water.


Say what? The water in the panel should be recirculated and contain rust
and scale inhibitors (as in a primary boiler circuit). The heat should be
transferred to a separate hot water cylinder of exactly the same type as is
used on non-solar systems.

Not on the system Mary was talking about - it takes cool water from the
cold DHW *feed* at the base the cylinder, runs it through the solar
panel (using a small PV powered solar pump connected via microbore
pipe), and returns it to the top of the cylinder via the DHW/vent outlet.

That's err a bloody stupid system.

The message .com
from "Les" contains these words:

What's the point? A combi boiler is specifically designed for
efficiency anyway.

The point is that however efficient the boiler is, the cost of heating
water can be reduced further by warming the feed.

--
Skipweasel
Pay no attention to that man behind the curtain.

On Wed, 17 May 2006 10:14:10 +0100 someone who may be Steve Firth
wrote this:-

Not on the system Mary was talking about - it takes cool water from the
cold DHW *feed* at the base the cylinder, runs it through the solar
panel (using a small PV powered solar pump connected via microbore
pipe), and returns it to the top of the cylinder via the DHW/vent outlet.

That's err a bloody stupid system.

No, it's a system that has advantages and disadvantages just like
anything else. Proponents believe the former outweigh the latter.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

On Wed, 17 May 2006 08:59:20 GMT someone who may be John Stumbles
wrote this:-

If a boiler does _not_ have electric ignition but has a constant pilot
light then it is a dinosaur with seasonal efficiency in the region of 65%.
The controls are likely to be primitive, too. It will make far more sense
to replace it with a high-efficiency boiler with updated controls than put
in solar water heating.

Who said anything about this being an either/or question?


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

On Wed, 17 May 2006 10:01:07 +0100 someone who may be Peter Parry
wrote this:-

The boiler casing (the outside box) doesn't have acid deposited on it
as it is only exposed to incoming air. It does get condensation and
damp from the outside atmosphere (to which it is open in a room
sealed boiler) when unused. As it is a spare part which is almost
impossible to get for older boilers corrosion on it often ends their
life.

Perhaps you have experience of boilers in corrosive atmospheres, the
seaside perhaps, but I have yet to see a boiler in a house suffering
from this alleged problem.

The "government report" also signally failed to mention that on a
cold sunny day with little solar gain the device also happily pumps
your gas heated hot water into a nice big radiator on the outside of
the roof to cool it down. What is the energy cost of this?

Already covered by http://www.solartwin.com/technical_faq.htm

"Q: During the winter months when most of the hot water will be
generated by the boiler, what happens if there is enough sun to set
the pump in action. At which time there is not enough thermal energy
to heat up the water sufficiently so that when it is returned to the
hot water tank it reduces the temperature there?

"A: The pump runs only on solar energy in the form of electricity.
It has no temperature sensor, only a high pressure bypass in case
the panel or its pipes are frozen. In response to your question:
First - best not to have the hot water system on all day since this
is wasteful anyway and does not allow for optimum solar performance.
Most boilers have separate timers for this, but not all. Ideally
time the boiler to add heat to the domestic hot water after 4pm.
Second, even in winter some hot water is made by Solartwin, not all
by the boiler as you say. Third - the panel is well insulated and so
will still raise the temperature of water going into it since it
collects heat from the sun and not the air. Fourth - at 100% sun and
a water input temperature of 50C and air temperature of freezing our
mathematical model (based on extensive tests at Napier University)
suggests that the water will still leave the panel at least 10C
hotter than when it went in. Fifth - if they really want to put cold
water in under these circumstances they can connect a second
cylinder behind the first and draw water off it! This will also
allow for more summer hot storage and is a neat solution for people
with AGAs and Rayburns. "

BTW, unless variable speed pumping is in use it takes
more than a few watts to run the pump.

The tiny little Solartwin pump I have at the moment appears to be
about a 5W max unit,

The panel is limited to 4W output and the pump under-run. However,
the fact that this system uses low power pumping does not mean that
they all do. Even with variable speed pumping I suspect that 50-100W
is a fairly typical electricity consumption for a mains powered
system.

but makes little or no mention of the fact that
for most people living east of a line drawn roughly from Lincoln to
Bristol you also need to install an ion exchange water softener
otherwise the panel will quickly be ruined because of scale from the
hard water.

A quick reality check on your assertion is to note what the
manufacturer of the system most mentioned has to say on this
http://www.solartwin.com/is_solartwin_suitable.htm

That you for confirming that what I said was correct.

I have left in what you said, "little or no mention of the fact that
for most people living east of a line drawn roughly from Lincoln to
Bristol you also need to install an ion exchange water softener".

In response I pointed to the most well known supplier of solar
pumped panels, where they explicitly talk about water hardness.
Therefore your statement that they make, "little or no mention", is
incorrect.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

On 17 May 2006 01:45:30 -0700 someone who may be "Les"
wrote this:-

Solar heating of water and combi-boilers do not mix.The combi is
designed to operate on at least 1.2 bar mains water pressure, and water
heated by solar means would not be able to
deliver this

Water heated by solar would not be able to be at this pressure? Why?

as it would have to be stored before delivery to the boiler.

It could be stored in a thermal store, with the supply to the boiler
being separate from the stored water.

What's the point? A combi boiler is specifically designed for
efficiency anyway.

1) A combination boiler burns gas, the price of which is going up
and is likely to continue going up.

2) The price of sunshine is not going up and is unlikely to go up.

3) Therefore it seems sensible to use sunshine as the fuel as much
as possible.




--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

On Wed, 17 May 2006 13:04:51 +0100, David Hansen
wrote:

On Wed, 17 May 2006 10:01:07 +0100 someone who may be Peter Parry
wrote this:-


The "government report" also signally failed to mention that on a
cold sunny day with little solar gain the device also happily pumps
your gas heated hot water into a nice big radiator on the outside of
the roof to cool it down. What is the energy cost of this?

Already covered by http://www.solartwin.com/technical_faq.htm

However not covered,measured or even mentioned by the report you
quoted.

"A: The pump runs only on solar energy in the form of electricity.
It has no temperature sensor, only a high pressure bypass in case
the panel or its pipes are frozen. In response to your question:
First - best not to have the hot water system on all day since this
is wasteful anyway and does not allow for optimum solar performance.

Most households want hot water in the morning which means the tank
will start hot (unless someone has a remarkably effective water
consumption predictor or the last person likes a cold wash).

Third - the panel is well insulated and so
will still raise the temperature of water going into it since it
collects heat from the sun and not the air. Fourth - at 100% sun and
a water input temperature of 50C and air temperature of freezing our
mathematical model (based on extensive tests at Napier University)
suggests that the water will still leave the panel at least 10C
hotter than when it went in.

What about the more realistic situation of less than 100% sun where
the pump is running slowly but the heat gain is minimal? Today with
an air temperature of about 15deg and solid overcast the solartwin
pump is managing to fitfully pump a trickle of water but the inlet
temperature and outlet temperature are the same (26 deg +- 0.1deg).
If it was cold that would mean hot water would be circulated through
the panel and heat loss (the "well insulated" front is simply
twinwall polycarbonate).

Whenever an advantage can be gained from a figure it appears -
whenever it's a disadvantage we get subjective descriptions.
Suppliers of gas boilers have to give comprehensive performance data
to buyers and their efficiency is independently checked. Why are
"alternative" suppliers not obliged to do the same and give
measurements of performance? More to the point why are they so
unwilling to supply this data if their products are as good as they
say?

Fifth - if they really want to put cold
water in under these circumstances they can connect a second
cylinder behind the first and draw water off it!

Which rather defeats the advertising about a "simple to install"
system.

BTW, unless variable speed pumping is in use it takes
more than a few watts to run the pump.

The tiny little Solartwin pump I have at the moment appears to be
about a 5W max unit,

The panel is limited to 4W output and the pump under-run. However,
the fact that this system uses low power pumping does not mean that
they all do.

If 4W is adequate to transmit all the power collected by the solar
panel on a bright day in midsummer why do others need (or chose) to
use much larger pumps?(My 30 year old system used a mains powered 15W
pump made specifically for solar hot water pumping).

Even with variable speed pumping I suspect that 50-100W
is a fairly typical electricity consumption for a mains powered
system.

That seems rather high - a controller should be no more than 3W and
the pumps I've seen recently are generally about 30W.

I have left in what you said, "little or no mention of the fact that
for most people living east of a line drawn roughly from Lincoln to
Bristol you also need to install an ion exchange water softener".

In response I pointed to the most well known supplier of solar
pumped panels, where they explicitly talk about water hardness.
Therefore your statement that they make, "little or no mention", is
incorrect.

Ah, I had misunderstoop your meaning, I had assumed you were talking
about the relative numbers who could use phosphate dosing rather than
an ion exchange softener.

--
Peter Parry.
http://www.wpp.ltd.uk/

On Wed, 17 May 2006 12:30:32 +0100, David Hansen wrote:

No, it's a system that has advantages and disadvantages just like
anything else. Proponents believe the former outweigh the latter.

Yes but that proponent also believes in imaginary friends so I think I'll
give it the credibility it so obviously deserves.

John Stumbles wrote:

Although the temperature at the inlet to the combi may be hot, there
should be no flow, therefore no demand, until the temperature falls
below the TMV set point. Therefore the combi should only be heating warm,
never hot, water.

Many combis have a maximum input temp in the low 20's, hence with the
solar water at say 30 to 40 degrees, and the selected blended output at
60, the combi will still be required to do half the lifting.


--
Cheers,

John.

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

Les wrote:

Solar heating of water and combi-boilers do not mix.The combi is
designed to operate on at least 1.2 bar mains water pressure, and water
heated by solar means would not be able to

Yes it would, if you collect the heat in a thermal store, you can have a
mains pressure feed to the combi heated by the (unpressurised) store.
Also we were talking about blending the the store heated mains flow with
the output of the combi - not necessarily its input.

What's the point? A combi boiler is specifically designed for
efficiency anyway.

Some are, some aren't. Not really the point though is it.


--
Cheers,

John.

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| John Rumm - john(at)internode(dot)co(dot)uk |
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On Wed, 17 May 2006 15:47:44 +0100 someone who may be Steve Firth
wrote this:-

Yes but that proponent also believes in imaginary friends

Which proponent is that?


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

On Wed, 17 May 2006 12:31:05 +0100, David Hansen wrote:

On Wed, 17 May 2006 08:59:20 GMT someone who may be John Stumbles
wrote this:-

If a boiler does _not_ have electric ignition but has a constant pilot
light then it is a dinosaur with seasonal efficiency in the region of 65%.
The controls are likely to be primitive, too. It will make far more sense
to replace it with a high-efficiency boiler with updated controls than put
in solar water heating.

Who said anything about this being an either/or question?

I did, above. I said that it would make more sense to replace an
inefficient boiler with a high-efficiency one than install solar water
heating and keep the dinosaur. Do you agree?

Of course if resources permit one can go for both. I don't think I was
implying that one couldn't.

"Peter Parry" wrote in message
...

Why argue about it?

You're not going to prove anything

On Wed, 17 May 2006 15:55:20 +0100, John Rumm wrote:

Many combis have a maximum input temp in the low 20's, hence with the
solar water at say 30 to 40 degrees, and the selected blended output at
60, the combi will still be required to do half the lifting.

I haven't looked at the specs of combis with this in mind but I'm curious
to know what they'd do when given water warmer than this. Except maybe
invalidate your warranty :-)

Still, whether the combi gets its input from the cold mains or the store
is of secondary importance compared to being able to combine the two in
this way (assuming it works).

On Wed, 17 May 2006 20:05:09 GMT someone who may be John Stumbles
wrote this:-

Who said anything about this being an either/or question?

I did, above. I said that it would make more sense to replace an
inefficient boiler with a high-efficiency one than install solar water
heating and keep the dinosaur. Do you agree?

That depends on the situation. For example, if someone was able to
run an old boiler for a few more years and then install a micro CHP
unit I suspect that would be better for the environment.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

On Fri, 19 May 2006 13:11:06 +0100, David Hansen wrote:

... I said that it would make more sense to replace an
inefficient boiler with a high-efficiency one than install solar water
heating and keep the dinosaur. Do you agree?

That depends on the situation. For example, if someone was able to
run an old boiler for a few more years and then install a micro CHP
unit I suspect that would be better for the environment.

OK, but that would be an extremely unusual situation and, dare I
say?, a rather contrived example.

I was (and am) trying to establish a rule of thumb that you don't put in
solar water heating before you've addressed draughtproofing, insulation
and heating efficiency. This isn't an academic exercise: I know someone
who's just signed up for a (very expensive) solar system. His rambling old
5-bedroom house has draughty external doors, many draughty single-glazed
windows, at best 50mm loft insulation, probably no insulation in the
cavity walls, and a standard efficiency boiler with a programmer + room
thermostat as controls (single zone). He coukld have spent 1/10th the
money and resources and saved vastly more energy than the solar system is
going to produce.

Now this guy isn't your average SUV driver who thinks he's green
because his wife buys Ecover but an economist working for a radical
economic/ecological think-tank FFS! If he doesn't know better what hope is
there of getting Joe/Jo public to make ecologically-sensible decisions?

Don't get me wrong I'm all for renewables, and have no objection to people
with the money putting in solar systems (after they've got the other
factors right) even though it may not pay back economically. Likewise the
(proposed?) local regs in London requiring renewables in new developments.
As with condensing boilers as the technology becomes more widespread the
costs should come down furthering deployment of the technology, which is
IMHO A Good Thing.

BTW picking up on your mention of microCHP I looked into the MicroGen and
WhisperGen but they didn't seem to be available at the moment. There are
also issues of what to do with surplus electricity produced (I think this
came up here or on uk.environment recently?). Do you know of any
domestic-scale installations in the UK?

On Fri, 19 May 2006 20:47:42 GMT someone who may be John Stumbles
wrote this:-

That depends on the situation. For example, if someone was able to
run an old boiler for a few more years and then install a micro CHP
unit I suspect that would be better for the environment.

OK, but that would be an extremely unusual situation

I don't think so.

and, dare I say?, a rather contrived example.

It is an example of a situation I am familiar with in a few places.

I was (and am) trying to establish a rule of thumb that you don't put in
solar water heating before you've addressed draughtproofing, insulation
and heating efficiency.

All these things need to be done, but within limits. These limits
are not precise, but depend on individual priorities.

Certainly insulation of pipes and cylinders is a priority. However,
the best way of insulating a cylinder may be to replace it with a
solar cylinder. If doing so it may make sense to use it properly. I
don'y think there are any hard and fast rules, it is a matter for
the art of engineering.

BTW picking up on your mention of microCHP I looked into the MicroGen and
WhisperGen but they didn't seem to be available at the moment.

They have been installed in a few trial areas IIRC.

There are also issues of what to do with surplus electricity produced

In the UK the electricity output will largely tie up with maximum
demand, for example lighting demand is highest on winter nights when
central heating is also turned on.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

On Fri, 19 May 2006 22:29:00 +0100, David Hansen
wrote:


All these things need to be done, but within limits. These limits
are not precise, but depend on individual priorities.

In the UK the electricity output will largely tie up with maximum
demand, for example lighting demand is highest on winter nights when
central heating is also turned on.

Does this qualify for the finest non-answer to a question of the year
so far?


--
Peter Parry.
http://www.wpp.ltd.uk/

On Sat, 20 May 2006 00:08:06 +0100 someone who may be Peter Parry
wrote this:-

Does this qualify for the finest non-answer to a question of the year
so far?

It is an answer to the question that was posed. It may not be the
answer that you wanted to hear, it is not a complete answer, but
that does not make it a non-answer.



--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

"Peter Parry" wrote in message
...
On Fri, 19 May 2006 22:29:00 +0100, David Hansen
wrote:


All these things need to be done, but within limits. These limits
are not precise, but depend on individual priorities.

In the UK the electricity output will largely tie up with maximum
demand, for example lighting demand is highest on winter nights when
central heating is also turned on.

Does this qualify for the finest non-answer to a question of the year
so far?

No, you have that crown :-)


--
Peter Parry.
http://www.wpp.ltd.uk/

On Fri, 19 May 2006 22:29:00 +0100, David Hansen wrote:

On Fri, 19 May 2006 20:47:42 GMT someone who may be John Stumbles
wrote this:-

There are also issues of what to do with surplus electricity produced

In the UK the electricity output will largely tie up with maximum
demand, for example lighting demand is highest on winter nights when
central heating is also turned on.

IIRC the electrical output of a microCHP rig is in the order of kilowatts.
That's a lot of lighting, even without using low-energy lamps.

In article ,
David Hansen writes:

In the UK the electricity output will largely tie up with maximum
demand, for example lighting demand is highest on winter nights when
central heating is also turned on.

In many areas of the country, summer aircon demand has
outstripped winter heating/lighting demand for a few years
now.

--
Andrew Gabriel

"Andrew Gabriel" wrote in message
...
In article ,
David Hansen writes:

In the UK the electricity output will largely tie up with maximum
demand, for example lighting demand is highest on winter nights when
central heating is also turned on.

In many areas of the country, summer aircon demand has
outstripped winter heating/lighting demand for a few years
now.

Which areas are those?

Assuming you're talking about UK that is ...

Mary

--
Andrew Gabriel

On Sun, 21 May 2006 08:51:20 GMT someone who may be John Stumbles
wrote this:-

In the UK the electricity output will largely tie up with maximum
demand, for example lighting demand is highest on winter nights when
central heating is also turned on.

IIRC the electrical output of a microCHP rig is in the order of kilowatts.
That's a lot of lighting, even without using low-energy lamps.

Indeed, which is why it was an example. However, unless every
building is to have such a plant I doubt if all the plants will
produce more than the total lighting load. Every street light will
not have such a unit.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

On Mon, 22 May 2006 08:15:23 +0100, David Hansen wrote:

On Sun, 21 May 2006 08:51:20 GMT someone who may be John Stumbles
wrote this:-

IIRC the electrical output of a microCHP rig is in the order of
kilowatts. That's a lot of lighting, even without using low-energy
lamps.

Indeed, which is why it was an example. However, unless every building
is to have such a plant I doubt if all the plants will produce more than
the total lighting load. Every street light will not have such a unit.

My original question was what to do with the surplus electricity. Indeed
I'm not sure what the regs are, currently, wrt to connecting microCHP into
a mains installation. I understand suppliers are concerned about the risk
of their engineers getting fried by power fed back from a CHP generator
into what would otherwise be a dead part of the system under fault
conditions.

Apart from that are there ways of selling surplus power (I recall someone
talking about trading RECs)? Or does one just give it away?