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gbwillson

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Reply with quote  #21 
It's 12:30pm. So here is a pic of the collectors after 3+ hours of sunshine. 3 hours of that has been stagnated. I'm leaving the fans off until they are completely clear. One thing to note is that the ZeroPass collector on the right shows much less melting of the remaining ice and snow. I'm wondering if it is because even stagnated, the air tries to stay between layers, or that the screen simply gets hotter when stagnated? Hmmmmmmm


Greg In MN[wave]

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solardan1959

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Reply with quote  #22 
Greg,
   I feel your pain...  I left the almost foot of snow on my sunspace last night for insulation and when it was 25 in there this morning I thought it was warmish in there.  But with the prospect of sun I cleared most of the snow off before I went to work.  There was a "crusty" layer up to 1/2 thick in places but I thought that would burn off kind of quick.  There was some bright spots but mostly very hazy sun during the day but I was disappointed to find it around 35 when I got home at 4:30 and still had the layer of crust on it.  Well I guess it was about 10 degrees last night and might have gotten to 20 but probably not.
   We ended up with 2 feet here and I had to clear my fireplace vent on the roof because the two feet up there covered it up and blocked the air input vent.  To early for this stuff with no sun in the near future.
Dan
Scott Davis

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Reply with quote  #23 
Great shots Greg,

Quote:
One thing to note is that the ZeroPass collector on the right shows much less melting of the remaining ice and snow. I'm wondering if it is because even stagnated, the air tries to stay between layers, or that the screen simply gets hotter when stagnated? Hmmmmmmm


Very interesting and curious indeed!  Looking forward to hearing how they perform with identical airflow!

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gbwillson

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Reply with quote  #24 
Since tomorrow and Saturday are forecast to be colder than today I may have to try something different. Once the units begin to heat up, put my fans on the exhaust ducting on very low speed. This, I hope, will force the warmed air near the top of the collectors to be forced downward. Can anybody suggest ways to quickly clear the glazing? I finally get a clear day after waiting three weeks and I'm tired of watching ice crystals melt SLOOOOOOOOOWLY! Actually, when temps are this cold, ice doesn't really melt, it evaporates. About an hour after I shut down for the day the sun was still hitting the face of the collectors. A nice heavy frost had already covered the glazing on both collectors. [frown]

Greg in MN[wave]
solardan1959

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Reply with quote  #25 
hair dryer? I have a heat gun that works great I got at Harbor Freight.
Dan
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Reply with quote  #26 
Greg, did you complete your testing and come to a conclusion which is better?  i looked around the forum and couldn't find and answer, i am at the critical construction stage and could go with either design concept, so I am curious to know what you concluded.  
Thanks
Paul
gbwillson

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Reply with quote  #27 
Paul-

I've been waiting for over three weeks for a sunny, cloudless day to test. While I've had some mostly sunny days, both collectors gave me lots of heat. Finally today with a clear sky, I simply couldn't melt the snow and frost off the glazing of either collector, as it was too cold and the wind was blowing at 30 MPH. 
But let me say that in very limited and less than perfect testing conditions, my ZeroPass has more than held its own.  A performance snapshot is not enough. We already know what to expect from the 2-screen heat. So now I have to find the optimal settings for the my ZeroPass, establish a baseline, and THEN compare it to the 2-screen. Then I can play around with spacing, airflow speeds, pushing versus pulling air etc. But I am encouraged with the very limited results…so far.
Greg in MN [wave]
netttech

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Reply with quote  #28 
Greg,

You mentioned the frost, clearing the glazing. I reread the posts & see you are using Twin-wall glazing (as I am).

I think the TW is a double-edge sword. It is better for extreme cold, but also the 2nd layer 'screws' us with frost, ice, snow. The 2nd layer prevents excessive less heat loss exiting the glazing, thus more frost.

(taken from an earlier post) <<<In addition, in theory, it should keep most of the heat away from the glazing, enhancing performance.>>

Here's a suggestion for the frost, glazing issue. Can you remove the top section of the trim the holds the glazing??

If so, take stiff wire (coat hanger?), paint it black & feed it down thru the corrugation between the inner-outer layers of the twinwall. Perhaps 2-3 sections across the width of the panel would be enough. The wire should be thin enough to have minimal affect on blocking the sun.

My logic is, being black, the wire should heat up & radiate the heat to outer layer of the twinwall. I have no idea how many sections on each side of the wire may be heated, but it may melt away enough frost to allow more sun in.

I considered doing the same thing to my twinwall glazing when I spotted the frost-twinwall affect on my hot water panel. I decided against it since the lower glazing is single layer plexiglass. It obviously heats up faster, assisting the upper glazing to melt the frost away. I don't get the extreme cold as often as you do.....but may reconsider adding these wires to my twinwall on one section for experimentation.

Jeff
Central IL
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Seatec

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Reply with quote  #29 
I have never had a problem like that, mine will clear in minutes when the sun hits the panels, but mine is 1/8 lexan. My new panel is double wall, so it may do the same. I don't think I would use the double wall again, it's just junk compared to the the single glazing, breake easy, cost as much, but it is lighter.
Scott Davis

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Reply with quote  #30 
I suspect the wind was your biggest enemy.  At 30 MPH and 5F, it simply pulled the heat away from the exterior before it got up to 32F and could melt.  I think that if you winds are lower, even if it is still cold, you will be fine.
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