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Scott Davis

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Reply with quote  #11 
Hi Greg,

You backed out the artificial boost by using an input temp of 72.5, so your total increase as a result of the collector was 36.7 degrees without the influence of the artificial boost.  That the screen was able to turn in a higher performance while being disadvantaged by a 9.7 degree higher starting temp is pretty conclusive evidence that the screen is superior.

Looks like it is time to adjust your zero pass screen widths for optimum efficiency.  Having the double layer screen standard will be helpful there too, as you can see what overall effect your changes have, even though conditions will change for various tests.

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gbwillson

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Reply with quote  #12 

Quote:
Originally Posted by Scott Davis
Hi Greg,

You backed out the artificial boost by using an input temp of 72.5, so your total increase as a result of the collector was 36.7 degrees without the influence of the artificial boost.  That the screen was able to turn in a higher performance while being disadvantaged by a 9.7 degree higher starting temp is pretty conclusive evidence that the screen is superior.

Looks like it is time to adjust your zero pass screen widths for optimum efficiency.  Having the double layer screen standard will be helpful there too, as you can see what overall effect your changes have, even though conditions will change for various tests.


Hi Scott-

I ran outside and pulled off the screen intake duct to check on the temp probe. It is down the throat of the intake right where the crimping starts. I had it stuck to the side, so I attached it to the bracket and moved it into the middle of the air stream. It didn't seem to make a difference. So I still don't know the cause. I could try swapping out temp probes. But from what you stated, that wouldn't be needed.


I'm not sure what you mean when you said "backed out" the artificial boost. Are you saying the artificial increase was negated somehow? If the intake on one is 10 degrees higher, I would expect the results to be roughly 10 degrees higher output temps. So in this test, the screen output WAS 10 degrees(9.7) higher, for an advantage of 1.8 degrees over the ZP. So we don't need to find out why the screen has the unknown intake increase, as long as we know and account for this increase by comparing the difference between input and output temps only? If so, 1.8 degrees is really a small advantage and within any margin of error. 

 I check the temps again after check the probe. The latest numbers look like this:

ZeroPass

Input    64.4
Output  78.8
Diff       14.4 degrees



2 screen

Input      72.5
Output    83.5
Diff         11 degrees

Advantage ZeroPass of 3.3 degrees. Again, not enough data for anything conclusive, but you are right in that I could try adjusting the screen spacing to see if a trend happens one way or another.




KevinH

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Reply with quote  #13 
Are the ducts in the sun? Are the screen collector ducts getting more sun on them?  Unless there is heating happening in the ducts, you should be getting input temps on both collectors a little lower than the basement air temp.  That would make the screen collector performance even better.  If you could get the probes inside the ducts a foot or two from where they enter collectors, that would probably help. They need to be away from hot surfaces or sun hitting them. The probes also need to be at the same location in the ducts, such as the center.  Where is the output temp being measured?

Kevin H
MN
Scott Davis

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Reply with quote  #14 
Hi Greg,

If I'm understanding correctly, your temp input at the screen collector was 72.5 and output was 109.2, for a total temp rise of 36.7 degrees.  Since your input temp is after the temp rise from any ducting, all 36.7 of the rise is due to your collector.

Now, keep in mind that the hotter start temperature does matter and hurt your screen a bit, as your screen collector ran hotter, losing more to ambient.  If your screen also started at 62.4, it might have had a 38 or 39 degree temperature rise instead of 36.7.

Also keep in mind that a in terms of measuring performance, a couple degrees matter.  For a 40 degree temp rise result, 4 degrees is 10%.

What your first measurements showed is that the screen definitely outperformed the zero pass.  Had your input temps been identical, it would have outperformed it by a little bit more.

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gbwillson

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Reply with quote  #15 
Hi Kevin,

None of the ducts are really getting much sun as they are on the back(north)f side of the collectors. That being said, I have now blocked the screen intake duct so it gets less sun than the others. All of the probes are attached to the intake duct collar to an L bracket as far down the duct as it can go without interfering with the duct connections. Output temps pretty much the same location. 

Greg in MN [wave]
Ky-Jeeper

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Reply with quote  #16 
Agreed
Quote:
Originally Posted by KevinH
Are the ducts in the sun? Are the screen collector ducts getting more sun on them?  Unless there is heating happening in the ducts, you should be getting input temps on both collectors a little lower than the basement air temp.  That would make the screen collector performance even better.  If you could get the probes inside the ducts a foot or two from where they enter collectors, that would probably help. They need to be away from hot surfaces or sun hitting them. The probes also need to be at the same location in the ducts, such as the center.  Where is the output temp being measured?

Kevin H
MN
Ky-Jeeper

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Reply with quote  #17 
Gbwillson.

If your ducts are showing from the front side of the collector let it do its thing. Mine are the same way and painted black for even more solar absorbtion. Its a good thing. Just means it a better preforming heater. Move your intake probes back away from your collectors. 

Looking forward to your results.
gbwillson

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Reply with quote  #18 
Quote:
Originally Posted by Ky-Jeeper
Gbwillson.

If your ducts are showing from the front side of the collector let it do its thing. Mine are the same way and painted black for even more solar absorbtion. Its a good thing. Just means it a better preforming heater. Move your intake probes back away from your collectors. 

Looking forward to your results.


Ky-

Unfortunately, the probes are mounted as far back from the collector box as possible without mounting them inside the flex duct. I'm thinking it's a bad temp probe. I know it is not the thermometer as I traded that was the first thing I tried. Only thing left is to swap out the probes. 

Greg in MN [wave]


gbwillson

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Reply with quote  #19 
Hi gang-

Yesterday was really an interesting day. On the one hand, It was exciting to finally be able to fire up both heaters as it was a mostly sunny day. On the other hand, it was frustrating as the intake probe for the 2 screen was reading about 10 degrees warmer than the air it was taking in from the basement and I didn't know why. I swapped out the thermometer as it has a plug-in for the probe cord. It didn't change anything. The sun was not warming the ducting as the silver cover was getting no more sun than the other ducts. Only thing left to try is to swap  out the temp probe. That's gonna to wait..

I got a little ahead of myself yesterday. I started out by trying to compare the results of the two heaters. And then I ran into an issue with the intake readings for the 2-screen. What I needed to be doing was to fire up the 2-screen and let it fill the house with cheap heat. While at the same time play around with the ZeroPass to maximize performance. In essence, I took known performer, the 2-screen, and compared it to a prototype that hasn't yet been optimized. While the ZP currently has a screen gap of ¾", we don't know if that is the optimal spacing. Nor if having a larger intake, an extra layer of screen, or optimal fan speed, or pushing versus pulling the air is better or worse. There is still much to be tested before going head to head against the proven performance of the 2-screen collector. What the two direct tests did show was that each heater won one of the tests. The margin in one test was 1.8 degrees, the other 3.3 degrees. So essentially the two units are comparible, performance-wise. Having a baseline, before any ZP modifications is good. But now I have to maximize performance numbers and compare the ZP to itself. Then I will compare the maximized results of my ZP to the 2-screen. 

Greg is testing in MN [wave]
gbwillson

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Reply with quote  #20 
FINALLY have some sun today…

And bitter cold. The air temp right now is 5 degrees and the wind is blowing at 30 MPH, so the air feels like -22 degrees on bare skin. We had 6" of snow yesterday and today bitter cold. Extreme cold usually means sunshine. So around 8:30 this morning I brushed off the snow as best I could.  
Just before 11am I fired up the heaters and the output was disappointing. With an input temp of 55 my output was in the low 90's. I felt it should be much higher. I looked for air leaks inside before trudging out to check things out. Right away I knew why my performance was in the crapper. It is so cold and windy that the collector can't get warm enough to clear the glazing. I turned off the fans again so they can continue to stagnate.

The pic below shows the heaters 2 ½ hours after the sun started hitting them. The glazing is barely starting to melt the snow. I'll take the dog for a walk and see if they are ready to fire up when I get back.

Greg in frosty MN[wave]

Note: I didn't see it the first time, but take a look at the screen collector on the left. Notice the frost and snow line right up the middle of the collector. The little bit of air flowing is helping to keep the center cold, while the sides are warmer.

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