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Commercial vs. homemade hot water panels.? - Page 4

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Posted by sylvan butler on December 7, 2006, 10:26 pm

I wouldn't...  But the epoxy under the tubes (between tube and absorber)
will have minimal UV exposure.

And metal (or graphite) filled epoxy is affected much less by UV than


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Posted by Steve O'Hara-Smith on December 8, 2006, 7:03 am
On Thu, 7 Dec 2006 15:26:40 -0700

    OK now I'm curious - why not put the tubes behind the absorber ?

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Posted by Jeff on December 8, 2006, 10:20 pm
 Steve O'Hara-Smith wrote:

  Mike in NZ says that the smoothest absorber surface should be facing
the glazing. This is to minimize convective losses.

Hence, tube under is better design loss wise. Solar Flares design is a
little iffy, but inexpensive. I suspect he'll smooth out the rough edges.


Posted by Solar Flare on December 11, 2006, 1:09 am
 We got some sunshine this weekend and brutal winds. I ran a 1000W
heater all Saturday night off my batteries and the the damn things
were still topped up in the morning!

Except when I got there the eaves were dripping water....pipe burst?
Drain down system was not sloped enough and froze inside the copper
manifold pipe?....shut off one side of the roof panels and it stopped.
Saturday got up in the attic and guess what? A  1/2" compression
fitting pulled apart!! Easy fix...back in business. 1600 litres of
water rose about 4 degrees C today before sunset!. Still only at 16C
though. No showers with that one yet...LOL
Small 12,000 BTU propnae water heater coming for next weekend. Damn
that concrete slab was cold though.

Posted by Solar Nut on December 9, 2006, 4:53 am

I have tried metal filled epoxy to adhere copper pipe to aluminium fins,
works for a while then due to the unequal rates of expansion between the two
metals, the joint interface always cracks.

Some sort of thermally conductive silicone rubber would be better as it will
allow joint movement. Dont know where you can purchase it, no one in NZ
sells it, the standard black silicone rubber is readilly available but is
not very conductive and would be next to useless over large voids.

Mike (NZ)

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