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