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gbwillson

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Reply with quote  #41 
Late yesterday, I pulled off the glazing and brought it into the workshop to address the condensation issue. As it warmed, the ice melted from the outside and a great deal of fogging occurred. I noticed that both the top AND bottom were tightly sealed with foil tape. The top was not such an issue, as that is what is recommended. But the bottom was too. I remember now that I had just begun to poke little pin holes in the bottom tape to keep critters out and allow condensation to evaporate and I got a phone call and never went back to finish the holes. Well…if I sealed both ends with humid indoor air, with no way to get out, it only makes sense that the glazing was fogging all the time. I ended up opening up both ends completely. In the spring when the unit is put into storage, I'll cover the holes, if needed. I checked outside this morning and the glazing looked pretty clear, but there is no sun to warm things up. Hopefully this has solved the issue of the fogging and icing.

Even with the glazing issues, the collector was putting out really good numbers. I'm especially encouraged, that it is doing so well in spite of the gazing handicap. When the sun is hitting the ZeroPass well, It's numbers are nearly as good as the 2-screen. I say nearly as any numbers I spout with half the glazing fogged, frosted or iced, will be badly disadvantaged. These observations are but a quick snapshot of the performance; More opinion than firm numbers. This week I hope for clear skies to verify the data instead of subjective opinion. Until then, I really need to be patient and verify my starting point. Otherwise, I won't know if any changes I make made a difference in performance.  I'd like to start tweaking the ZP as soon as possible to squeeze the most I can out of her. The first adjustment I will be trying is to close the gap between the screens. I started testing the gap is ¾". With a 43" width x .75" this gives me 32.25 Sq In. gap at each end. The 6" ducts are 28.26 Sq In. So almost even. If I adjust the gap to ½", the ZP will only allow 21.5 Sq In of air flow. It's a little pinched, but I have read that the laminar flow is virally eliminated if the gap is small. I still have plenty of CFM's left for the fan available if I need more flow to overcome the resistance, and a much stronger fan just waiting to be put to use, if needed. Another thing I want to try that I mentioned back in October, was to have the screens taper, or get smaller near the exhaust. If the screen intake was ¾" and tapered to ½" or even ⅜" of an inch at the exhaust, it might produce an unexpected result. Hmmmm

So if anyone has a thought or idea you would like to see tried on my ZP, I would be more than happy to add it to my testing agenda. As it is so quick and easy to gain access to the insides of my collector, including removal of both manifolds, my biggest limitation is the weather. 

Greg in not so sunny and warm MN[wave]

gbwillson

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Reply with quote  #42 
Fogging/frosting in between the layers of my twin wall glazing continues to plague my ZP collector. Two days ago I pulled off the tape that was sealing both ends Thinking this would solve the problem. Nope! The problem is still there. The screen collector has not had this problem. Somehow, moist air is getting inside the twin-wall and mucking things up. If it gets in, it should be able to dry out too, but it's not. The few times the glazing has been clear the ZP has performed as well as or better than the 2-screen. Unfortunately, this had been a rare occurrence. I'm really not sure what to do at this point. It's so cold out that I can't see anything but emergency repairs right now. And I sure won't be bringing the collector back to the workshop. As it is, the performance is taking a big hit as the glazing is roughly ⅓ to ½ covered in frost or condensation most of the day. Part of me thinks the channel might be doing such a great job of keeping the airflow away from the glazing that it can burn off the fogging in this very cold weather. I'm frustrated to say the least.

Greg is pounding his head on the desk in MN[bawl]
Rick Stone

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Reply with quote  #43 
I wonder if this anti fogging spray or something like it would help if you sprayed it down inside from the top.

http://www.amazon.com/Jaws-Quick-Antifog-Spray-1-Ounce/dp/B0012Q2S4W/ref=sr_1_1?ie=UTF8&qid=1386746770&sr=8-1&keywords=anti+fog+spray+glasses

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gbwillson

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Reply with quote  #44 
Quote:
Originally Posted by Rick Stone
I wonder if this anti fogging spray or something like it would help if you sprayed it down inside from the top.

http://www.amazon.com/Jaws-Quick-Antifog-Spray-1-Ounce/dp/B0012Q2S4W/ref=sr_1_1?ie=UTF8&qid=1386746770&sr=8-1&keywords=anti+fog+spray+glasses


Rick-

I'd try almost anything at this point. I hadn't thought about applying anything to prevent fogging. But the problem would be applying it between the layers. While you could spray down between each rib, you would not be able to apply it evenly. And I can only imagine how much fun it would be to "buff out" the 192 channels. The outside air is at least twice as humid as the indoor air, so somewhere outside air is leaking between the layers and being it's so cold outside and the glazing staying cool, freezes instead of evaporating. 

Greg
 
Scott Davis

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Reply with quote  #45 
Hi Greg,

If you just force the fan on for a few minutes, will the condensation clear?

__________________
Take care, Scott MD
gbwillson

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Reply with quote  #46 
Scott-

I thought the same thing would happen, but as the air in the house is much warmer, and drier, airflow seems to make the problem worse until the collector really starts to heat up. Then it gets a little better up to a point, but still way too much moisture between layers. The glazing on the 2-screen is not sealed at the bottom end. I added aluminum tape and a drip cap to the top. Moisture is somehow being pulled, or more likely pushed, into the channels.

Greg
gbwillson

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Reply with quote  #47 
GH-

I have to admit I thought of covering the unit at night. The collector must have a leak internally that is allowing the warmed inside air to get into the channels. Enclosing the entire unit and drawing out the moisture will be short term. As soon as I turn on the fan, the house air is reintroduced to the unit. I just have to find out where the leak is and how to fix/patch it. My guess is where the exhaust manifold connects to the body of the unit. Which makes it very hard to access as the exhaust manifold is over 10 feet off the ground. I'd have to bare handed to do much work, and climbing an aluminum ladder in this weather to work is tough. 

Greg in MN
Rick Stone

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Reply with quote  #48 

Rick-

I'd try almost anything at this point. I hadn't thought about applying anything to prevent fogging. But the problem would be applying it between the layers. While you could spray down between each rib, you would not be able to apply it evenly. And I can only imagine how much fun it would be to "buff out" the 192 channels. The outside air is at least twice as humid as the indoor air, so somewhere outside air is leaking between the layers and being it's so cold outside and the glazing staying cool, freezes instead of evaporating. 

Greg
 
Greg,
   Another idea, seal the top of the twinwall with silver foil tape leave the bottom open. Drill small holes on the inside of the heater thru one layer of the twinwall into each of the cavities. This would allow heated air from the inside to travel down inside of the twinwall like a defroster. Yes, you would loose a little cfm but I think that a small hole 1/16 or 1/18 would not lose a lot of air and maybe it would help with the fog.
  If it did not help you could plug the holes with a small dab of silicon. How is that for thinking outside (or rather inside) the box?

Rick
Talmo GA
cutnchop

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Reply with quote  #49 
Talk of the outside air being twice as humid doesn't make sense to me in the context of freezing inside the glazing.  The outside air may hold more moisture in terms of Relative Humidity but less in terms of actual moisture when compared to the warmer inside air.

By the way I used the foil on the twin wall lexan panels of my greenhouse and it lasted about 3 years before it started coming off.  I used relatively thin strips of tape so wider ones would probably last better.
gbwillson

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Reply with quote  #50 
Yesterday was a literal heat wave of 15 degrees outside. With almost no wind it felt downright balmy. I taped over the holes only on top end of the glazing. This is the way I sealed the 2-screen and it has had a condensation problem. I cranked up the fan to max speed so I would have quite a bit of overpressure. As I stepped back outside I had to laugh as an embarrassing loud, non-odorous sound, was emanating from the bowels of my ZeroPass. One of the cleats that holds the glazing frame(and glazing) had come loose or more likely, the wood dried out as it now sat almost ⅛" away from any contact. I shoved a shim in the gap to tighten things up. Once I did that it was pretty quiet all the way around unless you held your ear close. I want to check these further, but as I live in a city, on a bus line, overlooking a huge train yard at rush hour, I figured I'd have to try again when things quiet down. Looking back at the way the manifolds were attached, I noticed a spot where there may be some air/moisture leakage. The ends of the glazing fall right over the butt joint between the manifolds and the collector body. I used ⅜" green treated plywood for the back of the collector. During construction the panel started to warp badly at one end. I figured once I attached the side and end boards everything would flatten out. While it never flatten out completely, it looked like it would be fine once I caulked and used weatherstripping for any potential leaks. My thinking is now that the collector was allowing air and moisture to gain access between the inner and outer glazing surfaces. When both ends were sealed tight, I may have sealed in moist air.

There was no sun today, but the collector showed a definite improvement. The glazing had very little condensation and my guess is this will dry out over a few days. Interestingly, the inner surface of the glazing had a pretty formation of ice crystals that it never had before.  No sun is expected until Sunday. 

Greg in MN[wave]
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