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Re: Solar water heating system value - Page 8

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Posted by Mary Fisher on March 11, 2006, 4:22 pm


b) it might at present

a) Is that your sole criterion for the value of solar water heating?

 > Certainly our house would be very suitable for solar water

Then do it. save money and emissions in some other imaginative way.

Posted by meow2222 on March 10, 2006, 5:48 pm
David Hansen wrote:

When you choose sealed you're choosing not drainback, so the above
doesnt seem to make sense, unless you know of a sealed drainback

I cant see how this is a problem. The loft is normally fine, sitting on
the usual dividing wall. The tank is below the panels for drainbacks,
it only needs to be above them for thermosyphons, which are not the
usual choice.

again I dont see any downside with vented system maintenance. Sealed
system maintenance does introduce extra issues, and for CH seems to
result in more maintenance need in practice, as well as being less easy
to work on.

That is one of the plusses for vented systems, that they will never go
into that dangerous region of pressurised steam. Any sealed system that
does requires extra certification, which isnt free, and must be
designed to withstand much higher pressures. If it is not pressure safe
then its just dangerous. Vented eliminates any such risk. Worst case
for vented is steam coming out the overflow pipe, a non issue, or in
the highly unlikely event of both a system boiling and a blocked
overflow pipe, the steam simply comes out from around the tank lid.

Imho this is more the hype than the reality. The one advantage of a
solar panel pump supply is simplicity, but thats all. The electricity
created by the solar panel is the opposite of a worthwhile investment
for 99% of end users. The control system is a bit crude, and will
result in the system actively cooling your HW some of the time instead
of heating it. In short it isnt worth it, unless you're just not
skilled to do anything better.


Posted by Doctor Drivel on March 10, 2006, 7:40 pm

Sealed and pressurised are two differnt things.  You can have a sealed
system with an air gap in the top of a cyldiner, yet it is not pressurised -
only when heated.  When cold it will be atmospheric.

It isn't a problem an open vented drainback system does not requires a
header tank at all, just space in a tank or cylinder at a lower level for
the panels to drain into.

It is true a solar powered pumps may reverse the panel/cylinder and
dissipate heat.  But it is its overall performance that matters over a year.

Posted by David Hansen on March 13, 2006, 8:08 am
 On 10 Mar 2006 09:48:43 -0800 someone who may be meow2222@care2.com
wrote this:-

All people are not alike. Some want something simple. There are many
reasons for this approach. Lack of skill is just one reason, another
reason is less to go wrong. If people want that sort of thing then I
see no reason to denigrate them. The Solartwin system has not got
any lights or things like that, though they do supply a digital
thermometer, it just works away in the background and lets people
get on with more important things. The Imagination system has a few

At the other end of the spectrum is something controlled by say
http://www.resol.de/en/Produkte/Solarregler/Solarregler.html  the
Resol BS Pro. This may wring every last bit of heat out of the
panel. Whether it is worth having or is just a boy's toy is
debatable. I say each to their own.

  David Hansen, Edinburgh
 I will *always* explain revoked encryption keys, unless RIP prevents me

Posted by nicksanspam on March 10, 2006, 10:25 am
 David Hansen  <> wrote:

shows the unit promoted by one supplier...

Sounds like a drainDOWN system. DrainBACK systems have no valves.


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