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dbc

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Posts: 219
Reply with quote  #51 
Greg, It's funny; I had a similar idea.  I have some sections of 'sheep fence' sitting in the yard  that I briefly thought about using for the upper screen frame.  I abandoned the idea because the fence panels I have are 6-inch grid, and the 'wire' is way too big and heavy (I had to cut it with bolt cutters), and I thought it would add too much mass to heat up.  A smaller gauge fence panel may work though.  The other part I never figured out was how to attach the screen - maybe some flat bars like Bert used on his ZP, or 'sew' it on with thin wire?  The stuff I have is so stout, I was even thinking of using it as a mount for a collector.  Here's 2 pieces I wired together for a garden project a few years ago.  With the bottom poked into the ground it's pretty stable:

Wire frame, 102917.JPG 

A welded-wire grid frame may also reduce the need to pull the screen as tight.

Thanks, too, for posting Krautman's latest pictures.  i think he's some kind of mechanical genius.


Rick H Parker

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Reply with quote  #52 
A grid would not prevent the screen from sagging. However a grid would break a sag into smaller units and reduce the depth of sagging.
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Rick H Parker
Kansas, USA
Electronics Engineering Technologist
gbwillson

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Reply with quote  #53 
I took the wooden screen frames out of my ZP last week and even after three years they were still tight as a drum. Well, 3 of them were. The 4th had one board twisting a bit which loosened the screen a tiny bit. As soon as the board is flattened inside the collector the screen should tighten up again. 

I was trying to think if I could use this to increased the current 1" screen gap after my tests last spring found that a 1 3/8" screen gap performed best. Problem is, the opening between the two halves of my ZP is only 1", and I can't make the opening bigger as it would greatly weaken the framing.

I think some sort of stiff grid, on top and bottom of a screen layer would keep the screen flat and relatively sag free. Keep in mind, the idea of a frameless screen is to save space, so if it is too thick it won't be much thinner than an extruded screen frame from the hardware store(Normally 5/16" thick).

Could be cheaper too.

Greg in MN
gbwillson

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Reply with quote  #54 
Craig finally mounted his new ZP collector up on the roof this week. Just in time too, as tomorrow is forecast to be more like early January with a high of 22˚F and a low of 13˚F. The ducts are routed into the attic for now, and have yet to be routed into the living space below. He mentioned that he wants to draw the intake air from the existing intake ducting, and the output air will likely be routed inside wall cavities down to the basement.

The collector should hold up for a long time, especially since the exterior skin is aluminum, including the oversized 10" aluminum ducts he is using to protect the duct insulation. He hopes to have a final output volume of over 500CFM. I'll update again as he finishes ducting and has some output numbers to share.

Greg, for Craig in MN

IMG_1164.jpg 



KevinH

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Posts: 554
Reply with quote  #55 
Looks good.  I was going to recommend painting the sun side of the exterior ducting black next year.  Since these stay up during the summer, however, it may be best to leave them silver, otherwise the ducting would have to be covered as well as the collector in the summer.

Kevin H
MN
gbwillson

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Reply with quote  #56 
Kevin-

Last Winter I suggested Craig cover his insulation with black plastic. Not only to keep the UV rays off of the insulation cover, but to help melt any snow off the ducts quickly. After he covered his ducts he noticed the incoming air was a bit warmer than without the black plastic. He had very long, elevated and exposed duct runs, so I could see how the black plastic might warm the insulation a bit, compared to a shiny mylar cover. 

Greg in MN
KevinH

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Posts: 554
Reply with quote  #57 
I checked mine today (19F and windy).  Just under the black covering it was 64F.  Under a shiny silver duct sleeve it was 33F, so even it gets warmed a little.  On the back away from the sun it was 21F, so the insulation is doing its job.  This is on the cold air input side.  The hot air side would be a bit warmer.  It is about 6 feet of duct total, so not a big run, but wrapping the ducts in black material is cheap and helps reduce the losses (only if the ducts are exposed to the sun).

Kevin H
MN
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