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Check valves for passive solar hot water system - Page 6

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Posted by daestrom on November 2, 2007, 1:06 am

Indeed.  If the bottom of the tank is at least as high as the top of the
collector, you can't get reverse syphon unless the fluid has a negative
coefficient of expansion.  The only liquid I know of that has that is water
when between 32F and 39F.  If his system is that cold, then who cares about
reverse flow.


Posted by daestrom on November 2, 2007, 1:06 am

See, I didn't argue with you that time :-)


Posted by Mike Scaife on November 2, 2007, 2:05 am

From experierence if mounted directly above and because the pipe size is 20
to 25mm the rate at which hot water inside the bottom of the cylinder cools
is dependent on the length of the pipe, if the pipe is a bit longer then
cooling is minimized. At least until someone turns on a hot water tap and
floods the bottom of the cylinder with cold water.
Generally to get sufficient slope on the outlet panel to cylinder
connection, this will dictate the minimum required height in any case. so in
practice the height is never 0.0.

Nick I'm thinking of building a glass conservatory at the end of our
kitchen, faces due north and west. Which would be equivalent to South - East
in your part of the world. Size 5 by 3.5 meters double glazed. From your
experience is this a worthwhile endeavour to capture some extra heat. Its
going to cost a bit, nice to sit in having breakfast in the mornings.


Posted by nicksanspam on November 2, 2007, 12:36 pm

Sure, if there's a conservatory or kitchen door you can close at night.


Posted by mark.fox on November 1, 2007, 1:19 pm
 No doubt. And it's not exactly freeze tolerant either. Discovered that
a few minutes after posting.

Actually, if it was placed on the return line from heat exchanger to
collector, it wouldn't experience such wild swings in
temperatures. ... Nope. It would still be turned to goo. That just
won't do.

The 0.6 meter separation between top of collector and bottom of tank
(what Nick labeled S) is something I'll try. Once I get my first
collector finished (finally have a design I'm happy with), I'll have
plenty of freedom to play with different configurations. I'll play
with it and share my observations.



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