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Old 12-12-14, 01:55 AM   #41
AC_Hacker
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Originally Posted by Mikesolar View Post
5 panels in parallel will have inconsistent flow charactistics no mater how well it is piped and it must be piped in a reverse return fashion.
Would your argument against parallel piping in solar collectors apply equally to parallel piping in hydronic heating?

-AC

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Old 12-12-14, 07:30 AM   #42
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Consider the flow rate needed to be between 0.5 and 1L/min/m2 of collector (aperture area, not gross area) being on the higher side for series installs. With 22mm piping and not too long a run, the head loss should not be too much. The issue is guaranteed flow through all tubes or the header and enough positive pressure. Also, make sure you have at least 0.5 bar at the top of the panel (when cold) or winter time flow may be an issue.
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Old 12-12-14, 07:39 AM   #43
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Would your argument against parallel piping in solar collectors apply equally to parallel piping in hydronic heating?

-AC
Nope. Funny things happen with solar that are way more controllable in hydronic heating. Balancing is much easier when every loop is on one floor or there is a balancing valve on each loop. This isn't the case with solar where you often have 2 phase (liquid and steam) operation and the minor differences in piping can force fluid through one panel and not another. Placement of balancing valves on the roof is important as well. They should be on the output side of the bank of collectors so that there is always a positive pressure on the header. That creates an issue of the effect of steam or very hot temps on valves and their longevity.

All this, and more, is why I have gone back to flat panels. Tubes are efficient, but much more finicky.
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Old 02-22-15, 04:41 PM   #44
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Trying to maintain some momentum, motivation, and progress on this so I got a start on the fiberglass liner.

I'm using a 1/2 oz veil and two layers of 1 1/2 oz mat in vinyl ester resin. First step, cut the material



Then I put two sheets of melamine on the shop floor and taped the joint with aluminum tape. Unrolled a layer of veil and one layer of mat on the temporary casting table.



Wet it out with resin. Air roll. Add the second layer of mat and air roll again.



Let cure, trim to size, and scuff the edges for the corner tape.



The finished layup is just under 2 1/2 mm thick on average.



And a translucent green.



The sheets in the tank waiting for the corners to get taped. This might not happen for a while. I'll need good weather so I can open the doors and vent the foul odour of the resin until cured.


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Old 02-22-15, 04:43 PM   #45
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Very nice work. Keep it coming.
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Old 02-22-15, 09:00 PM   #46
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Very nice work.
Thanks Mike.
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Old 02-22-15, 11:03 PM   #47
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Default Pond liners anyone?

Nice glass work guy!
I notice that lots of folks take the easy route & use pond liners in a big sheet in their storage tanks and let the water pressure force it into the corners.
But I wonder if it can stand the temps you're looking at??
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Old 02-23-15, 09:29 AM   #48
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Nice glass work guy!
I notice that lots of folks take the easy route & use pond liners in a big sheet in their storage tanks and let the water pressure force it into the corners.
But I wonder if it can stand the temps you're looking at??
Thanks Ron. The thought of wrestling half an acre of pond liner into a deep box held no appeal for me (easy route? I think not!). And how to tidy up the top edge? Visions of empty caulking tubes and staples would have kept me up nights. But as you say lots of folks do it. The track record is there and I think it's a good option for those so inclined. As for temperature I know nothing of pond liner but I chose the V.E. resin for it's elevated service temperature tolerance so I'm hoping it's ok.
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Old 02-23-15, 10:17 AM   #49
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Looks great! I too would be interested to know exactly how high of temps that fiberglass can take.
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Old 02-23-15, 10:42 AM   #50
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Looks great! I too would be interested to know exactly how high of temps that fiberglass can take.
According to the resin manufacturer the heat distortion temperature is 239F.

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