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/