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dbc

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Posts: 257
Reply with quote  #51 
Getting close on the collector internals.  Painted the gasket on the center divider black, and glued on the gaskets around the stud-track frame.  After a couple days set-up, I put the screens in.  Here's the back screens held in with my custom Simpson 'C-clips':

2) Back screens clamped, 060718.jpg 

I made some curved pieces out of aluminum flashing to go in the turnaround end.  The pieces are 1 3/8 inch wide to match the screen gap.  The edges are folded over to hopefully prevent sawing against the screen.

3) Curved ends, 060718.jpg 

Here are the pieces fastened into the collector.  The slotted ends are held by the same screws that hold the C-clips:

4) Curved ends installed 01, 060718.jpg

Next, I added the front screens.  These screw into the clips from the front.  I drilled some shallow 'pockets' in the screen frames, so the screw heads don't stick out:

6) Front screens installed 01, 060718.jpg 

So now the inside is all together.  The resulting screen gap is 1 3/8 inch, and the front surface of the screen assembly is mostly flush with the track frame.  It seemed like it fit a little better a couple weeks ago before I stapled on the screen and painted everything.  I think the wood warped or shrank a little bit, or both, but it will have to do now.  At least all the mounting holes lined up.  Here's a close up of the screen gap; kind of hard to see 'cause the frame was in the way:

9) Screen gap 02, 060718.jpg 

Next up is to attach the glazing.  That should be a 'bolt-on' operation, assuming all the holes line up.  Then I need to figure out something to keep the glazing flat - thinking of some cross-bars made of 3/4 EMT fastened to the frame with corner brackets.  I didn't really design in any attachments (like T-nuts in the plywood), so now I'll just need to wing it.  Going to think on it a bit.  After that I need to remove the old 4x8 slanted 2-screen collector from the wall mount and modify the mount for the new collector.  Have a rough plan for that.

Bruce

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Posts: 132
Reply with quote  #52 
Looking good Don!  I bet 1/2 inch conduit would be enough, but you really go for the max on everything ;-) I like the C clip idea...almost no restriction to airflow, something that I need to consider when I do my 6x12.  I am assembling materials and building some components now and have looked back to see how you did your low voltage relay for the snap switch...which is a good idea electrical code-wise. I have built a fan housing inside an old printer frame that has a built in circuit breaker and on-off switch and am working on the window panes to run the ductwork and snapswith wiring through now.  I can't find the parts you used for the relay...do you have it handy to post or guide me to the post, if there is one?  

Thanks,
Bruce
gbwillson

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Reply with quote  #53 
Don-

Being that your collector airflow path is only 2' wide you might want to try pulling air through your collector instead of pushing. Each path is narrow enough that the air might not stay solely in the middle once it leaves the intake. A small deflector could be used if needed. In any case, pulling the air would simplify the issue of sealing the glazing, and eliminate any glazing bulge. It's worth a try in any case. Just a thought...

Greg in MN
dbc

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Posts: 257
Reply with quote  #54 
Got glazing too:

11) Glazing, 060818.jpg   

Bruce,  I don't remember where I bought the relay, but I think I ordered the relay, plug-in 24V transformer, and snap disc from SupplyHouse.com.  I know they have all these items.

The relay is a White Rodgers model 90-290Q, SPST/NO,24VAC.  I think it is also available from Home Depot, although they may have to order it. 

The 24V transformer is a plug-in 'wall wart' style, mainly for ease of construction.  I have a Orbit model WT1-57-027R, 24V/750 ma.  There are many varieties, like doorbell transformers and such, if you have a convenient place to install them.  It only has to power the relay coil.  You could just as easily use a DC relay and plug-in adapter.

Snap-disc is a White Rodgers 3F01-110, 110 F close / 90 F open.

I don't remember if I ever posted a schematic, but I found this in my notes.  I think this is from my first collector, which had 2 snap switches (110/90 and 120/110).  I had 2 ranges because I didn't really know what I was doing (imagine that!) or what would feel best.  I abandoned the 120/110 pretty quick, but I left the selector switch and wiring, and ended up using the 120/110 side for the 110/90 snap disc in my (second) 2x16 ZP collector.  Anyway, here's the schematic:

12) Schematic, 060918.jpg 

My fan has a power cord, so the relay actually sends 120VAC to a dedicated receptacle for the fan.  The 120V receptacles are grounded, although I didn't show that on the sketch.  The fan has a 3-prong grounded plug, although the transformer doesn't.  The fan is a Suncourt TF106-CRD, 6-inch centrifugal, 120VAC, 420CFM (free air).  I got the fan at Home Depot.

The room thermostat in the 24V control loop is probably not a great idea; it got me in trouble last year when it started to shut off the fan during sunny spring afternoons.  The collector overheated and started to stink.  Now I just set it so it's always on or always off, depending on the season.  When the stat is switched off (like now), the collector is covered.  The thermostat is an old, passive bi-metallic, designed to control an electric baseboard heater.

I also still plan to add a 'force ON' switch, basically an on/off switch wired around the normal control elements, to use for air-flow tests, etc.  Just haven't got around to it yet.

I think I agree with you on the 1/2 inch EMT for cross braces.  I checked a 5 ft scrap I have, and it seems stiff enough.  I was mainly concerned about the corner braces to fasten it to the collector fitting inside the EMT and still being long enough get a good bite on the collector.  With 1/2 inch, the corner bracket will probably screw through the glazing angle pieces, but I guess that's OK - it will go into the same piece of plywood either way.

Greg - your suggestion has a lot of merit, especially in terms of aesthetics.  The collector looks pretty sleek now, but not so much with some EMT cross-bars.  Thing is, I had hoped to test the U-turn around idea against the straight-through layout of the 2x16, to see if the turn was compatible with ZP flow.  I guess I have already run roughshod over the 'scientific principle' by changing the screen gap to 1 3/8 inch (it's about 1 1/8 on the 2x16).  I also switched from aluminum screen frames to wood; I decided to minimize expenditure after I had the trouble with too-thick paint.  After repainting I let it bake in the sun for a long time, but I still won't know until I can test.

Moving the fan to the output side is also kind of awkward with my setup, but I still may try it.  I'd like to get some experience with pushing air first (in the interest of science, of course).

I'm also still considering DC fans with direct PV operation.  I have some sketches for an outside fan-box with 4 or 6 DC fans, either 12 or 24V.  The box will have tapered end with duct ports, so the whole thing can install in line with the air duct.  That would be easier to move or reverse.  I'll start another thread when I get a little farther along.  Also need to design a voltage regulator rated to handle the total fan load.  I think the best place for a row of DC fans is probably inside the collector, although all of mine are too shallow for that.  Maybe next time..

gbwillson

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Reply with quote  #55 
Perhaps during the airing out stage you could try pushing versus pulling the air through the collector. Pipes or bars could be clamped in place to seal the collector during testing. It might not be conclusive of the output numbers were close, but if you had a 10-20˚F difference between the two it might lead you to a logical conclusion.

Also, if you do need to brace the exterior to prevent glazing bulge, you might consider T-bars or angle brackets painted black. While it might cost a tad more than the pipe, I think it would look a heck of a lot better and worth the extra cost. 

Greg in MN
Bruce

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Posts: 132
Reply with quote  #56 
Thanks for the details...I have to digest this a little bit, but I think I have a good rough design for the fan control now.

Greg, I am curious as to why you are pushing the trial of pulling air instead of pushing it.  From everything I recall from my reading here, pushing has been preferred over pulling, except for the glaze bulging.  You certainly are more experienced than I on this matter, and I am curious as to why you seem to think it might be worth pursuing?  No offense intended, really....I am intrigued with this, too ;-)  I am designing my project to be able to switch the pushing fan to pulling, or add a pulling fan to the small 8 inch pushing one. It is only time and money for research, I guess. ;-)
dbc

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Posts: 257
Reply with quote  #57 
Greg, I already bought and cut the EMT, so I'll probably just go with it.  I couldn't bring myself to start sinking wood screws into the sides of the collector, especially since they would only be threading into 3/8 plywood (+ the track), and could introduce leaks.   I came up with another way - a 'sandwich' around to the back with flat plates, made from 1/8 x 1 1/2 aluminum flat bar.  The EMT will go through holes in the plates and be held with compression-type conduit connectors.  I should have a picture in the next day or two.  It's functionally similar to what I did on the 2x16, but with different (stiffer and cheaper) parts.  If it doesn't work or if I don't need it (pulling air), I will be able to remove the whole thing and--as they say in the back country--leave no trace.

I need to find a better local source for aluminum angle, etc. than Home Depot or Lowes.  It's really expensive there, so I only use it sparingly.  I agree, angle would probably look and work better.  Not sure what you're referring to with T-bar.  Is that the material used in place of let-in diagonal bracing in building construction?  I've seen it but I don't know where to get it.

I was considering painting the cross-bars white to match the frame, but black may blend in better.  Maybe I'll go way artistic and paint them black where they front the glazing and white where they go against the frame.

I don't really want to spend much more money on this box, since I already think it has too many compromises.  My bottom line test is becoming, 'would I do this again?'  I think probably not on the U-turn scheme, at least not for a zero-pass.  It adds too much extra work and cost for what you get, and it seems to run counter to the low internal resistance advantage of the zero pass.  I won't judge too soon, since that's what I wanted to check in the first place.  A U-turn may be more compatible with a tube design, like Kevin's, where the internal air stream is more contained.

Still need to modify the wall mount, then I can at least test air flow.  Not sure if now's a good time to check heat rise; it's been really hot here lately.
dbc

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Posts: 257
Reply with quote  #58 

Bruce - Krautman Craig used fans at each end on his 4x16 zero-pass.  He built two, and I think they both have that set-up.  His units move a lot of air and are really high-performance.  Check out the info in this section for his collectors, lots of great information there.  He worked a lot with Greg W (they're neighbors, I believe Greg got him into it originally), and his units have a lot in common with Greg's 4x16 ZP.  They also did some air flow vs. screen gap testing here, which was really interesting.

gbwillson

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Reply with quote  #59 
Bruce-

The reason I suggested Don try pulling the air is that the path of the air is only 2' wide, so the touchiness in adjusting an even airflow should be greatly reduced compared to a 4' wide airflow path. And with the return at the far end, there is likely going to be air bunching up near the inside of the return. I wish Don had place a few thermometers at the turn to measure what is happening with the air at the return. I recall that SolarDan did that on one of his collectors and it showed large hotspots from poor airflow at the return.

Airflow being pushed or pulled reacts differently inside a collector, depending on the design. Air being pulled through a collector will always take the shortest path to the exit, which sometimes leaves poor airflow or "dead" spots in the corners. Air being pushed differs in that the air crashes into everything, including the corners, before being pushed to the exit. Pushed air tends to have more resistance inside a collector when compared to air that is pulled. A straight ZP performs best when the air is pushed through the collector. Don's ZP has a return, so the air will act differently. Yes, my friend Craig had to add a second fan at the exhaust, which basically acts as a booster fan. But this also has the advantage in that he can have a two-tiered airflow, depending on the output temps. And the ZP needs a LOT of air to keep the output temps efficient. I suggest that anyone with a new collector at least try out pushing versus pulling before final instal. There will likely be a difference in airflow and performance that might not be expected. 

With my first ZP I tried various ways to PULL the air through the collector so that the airflow was even across the 4' width of the airflow. I placed various fins and vanes in the airflow to try and even out the air from side to side, but it wasn't effective as the vanes would need to be changed if the airflow changed only a little bit. It was incredibly touchy. I also played around with an adjustable slot opening for each manifold. It allowed me to control how much air moved through the manifold slot form side to side. It worked, but to make any adjustments, you would have to pull the cover off. You also had to adjust the slots at both the intake AND the exhaust. Not good! 

Soon after, I went back to the drawing board, so to speak, and removed all adjustments, fins, or vanes of any sort. I measured the speed of the air at the exhaust manifold slot, and much to my surprise, it was even from side to side! I tried the same thing when I pulled the air through the collector, but when pulled, air will take the shortest path, which is straight down the middle of the collector. So the simple solution was to overpressure the intake manifold, which in turn evenly distributes air from side to side through the screen slot. Easy Peasy? Not at all as I spent plenty of hours trying various methods to even the flow. But the solution WAS simple, even if the path to get there wasn't.

Greg in MN




pianoman8020

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Posts: 42
Reply with quote  #60 
Bruce -
You have a very nice panel build. A couple of items have caught my eye. The color of the collector outside frame is white where it should be black. This is so that light/heat is adsorbed instead of reflected and increase your efficiency by a few percents.

The 90 deg. hold-down angles around the perimeter do not seem strong enough and will allow excessive leakage. Edge temperatures (leakage) could be checked with a small infrared gun when the collector is hot and under pressure.

The hold-down cross bars on the lens should be bright in color. They not only hold the lens down but the block a small amount of sunlight. I used 1/2" EMT then smashed the ends and bent them to a 90 degree angle for mounting onto the sides of the collector. Works good. I should of used 1/4 x 1" aluminum bar mounted on edge with end brackets. This would block less light and reflect off angle light into the collector. 
Keep up the good work!!

Jim for IL 
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