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dbc

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Reply with quote  #1 
I started building another zero-pass collector - this one is 4x8 with both duct ports at the same end, like this:

Drawing, 4x8 ZP, 101517.JPG 

I considered both this layout and a zero-pass dual pass with the return channel behind the front ZP section.  I decided on the first, because the ZPDP would require a deeper frame than could be built with stud track.  The single-level turnaround zero pass seemed easier to build, and it would have roughly the same 2x16 internal air flow path as my 2x16 ZP.  The U-turn at the end is the new element here.  I recently read a quote in a motorcycle magazine stating that air can go fast or go around corners, but it won't do both.  I guess I will be testing how that plays out in a zero pass collector.  The external air ducts will be a lot shorter than on the 2x16 model.  The new 4x8 will replace my old 4x8 slanted 2-screen eventually.

I started the frame by making some corners out of metal stud, similar to what Bert did last year on his ZP.  I bend the lip flat on the stud, so it wouldn't interfere with the internals to be added later.  Here are the corners and a picture of one of them glued into a frame section:

Corners, 101517.JPG 

Corner glued in, 101517.JPG 

After the corners were glued to the long top and bottom frame pieces, I glued 3/8 inch plywood strips into the top and bottom frame channels:

Top and bottom frames with wood, 101517.JPG 

Next, I ran up against a slight riddle concerning the assembly sequence.  To glue the frame ends to the stud corners, I would have to wait to put in the end plywood strips.  I also had to get the back panel inside the frame before it was all joined together.  I ended up gluing the frame ends to the top corners only, then fitting the back panel into place, and finally gluing the sides to the bottom corners, which were already attached to the bottom piece.  It was kind of wobbly to handle, and I had to re-glue in a couple places, but it all fit together OK.

I glued the back panel to the back of the frame with silicone.  Once that dried, I riveted all the corners.  By the way, I decided to put everything together with glue only until I had the frame together, because I have found that it's hard to get the plywood strips flat against the frame when the rivets are in the way.  Here's the frame with the back panel glued in:

Frame with back 02, 101517.JPG 

The little polyiso spacers are there to hold the back panel tight against the frame until the silicone dries.

Today I glued the plywood strips into the ends of the frame.  I had to compromise one detail on my original plan - The end plywood pieces don't go all the way to the back of the frame; they fill the area between the front of the frame and the polyiso.  (The polyiso goes all the way to the metal frame on the ends, but goes only to the face of the plywood on top and bottom.  I had to shave a little off one long side to make it fit.)  Here's the frame as it is today.  There are trimmed 2x4 pieces in front of the plywood to help the clamps:

Frame with end wood, 102917.JPG 

I forgot to take a picture of the back, but it is just the polyiso with aluminum flashing glued to the back side, overlapped in shingle fashion.

Next I need to work on the duct ports.  The holes are already cut in the flashing.  I need to cut the polyiso, then fit in some 12" x 24" aluminum sheet metal pieces on the front to attach the duct take-offs, snap disc, etc.

I started this project way too late in the year (working mostly outside), so I'll be at the mercy of the weather for a while.  I'm still considering options for the screen absorber - more next week.

Bert

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Reply with quote  #2 
Don,
Looks good.
Too bad you can't get the metal stud with more depth. I have a feeling that the extra air space with the air traveling through the back would have less resistance than the split version. Might retain the heat more as well with a faster airflow.
In any case it should work out okay.
Looking forward to seeing it progress.

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Bert K.
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gbwillson

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Reply with quote  #3 
At the mercy of the weather...Understatement of the year!

I'm stuck right now doing a little repair work on my old ZP in my tiny, unheated garage. I moved it there last week as the silicone wants 12 hours before it gets wet and rain was in the forecast. So...now it's been 20 degrees below normal and we aren't supposed to see 50˚F for at least the next 10 days. And all the adhesives and paints I'm using for a few minor repairs want at least 50˚F. Ugh[mad][mad][mad]

I know the sketch of the new build is not to scale, but the divider makes the turn look too tight. There are 12" on either side, and what looks like another 12" from the divider to the return end. You may want to consider shortening the divider another 6" so the return has more space. I think Dan played around with returns like this and noticed how much better the air flowed with a little more breathing room.

Greg in MN


dbc

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Reply with quote  #4 
Bert,

I have seen 6 inch wide track available from commercial drywall wholesalers, but you have to buy a lot of it.  I agree, wider track would give you a lot more flexibility.

I haven't crossed the point of no return yet on which type of collector to build.  All I have completed so far is just the frame and back.  I cut 6 inch holes in the back flashing, but not through the polyiso yet, so I can still change the port locations (I saved the round cut-out pieces - just glue 'em back on where they came from or cover that area with a second sheet).

I can stack on another frame, probably out of 1 5/8 in. or 2 1/2 in. track (Home Depot has both of those), which would give enough depth for a ZPDP.  It would be a lot easier than the first frame, since there's no back.  I did stack 2 frames on my old 2-screen; it was slow work, but not that hard.  Now you've got me wanting to try it!  I think there is more to explore with the ZPDP design, since there aren't may examples built yet.  I've got a hunch you're right, that it will flow better than what I am doing now.

Greg,

Sorry to hear about your uncooperative weather.  I guess you don't want to drag everything back to the basement.  I burned most of a beautiful 70 degree day (yesterday) waiting for glue to dry (it's 30 today with freezing drizzle).

I should have looked at that drawing (it's old) before posting, because it doesn't accurately show what I am planning.  I agree completely the turn section looks too tight.  My concept is that the turnaround is part of the continuous zero-pass flow path (as much as it can be).  I was planning to make it have the same cross section as the straight parts (about 22 1/2 inches).  Thing is, Bert has me half convinced I should build a ZPDP instead.  I'm chewing on that now, trying to figure out some of the details.
gbwillson

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Reply with quote  #5 
Don-

Ya know, if you are unsure as to how to route a 4x8 ZP, why not make two test collectors, making the collector box out of nothing more than polyiso? I build one using glue, screws, and a few wooden reinforcement points for mounting items. It's light, and plenty strong enough for testing over a winter season or two. And once you have the best performer, you might be able to add a protective skin at some point for added longevity.

Greg in MN
dbc

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Reply with quote  #6 
Greg,

I think I speculated about a polyiso-only collector box in one of my blue-sky ramblings in the Hot Air section.  I have been thinking about trying it sometime.  Some other people have done it already, but not with a zero-pass.  The back on my 2x16 is just polyiso with aluminum flashing skin - it worked pretty well.  The real key is how you add the attachment points.  I had some small plywood 'inlays' inside the 2x16, although they were captured between the edges of the stud track.  Attaching the glazing is another big one.  I thought of making wood sides slightly taller than the polyiso, so the glazing would sit on the edge of the polyiso edge with the wood coming out flush with the front of the glazing.  You could attach glazing clamps or angles to the wood from either the front or side.

What kind of glue did you use?  Seems it would need to work on both the covered face and the 'raw' edge.  Gary Reysa glued thing to polyiso with Great Stuff foam, but I have found that tricky to work with (haven't tried it on a collector) - it really expands and sticks like crazy to everything, including you.

I remember Julian Jameson did something like that on his low-profile collectors (interesting thread, with a good video - the collector internals were real simple).  His was surrounded with a poplar frame for strength and durability added after the polyiso box was together.  I remember he used screws to temporarily join the polyiso together, but don't remember if he glued it also.
stmbtwle

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Reply with quote  #7 
Pretty sure he glued it, polyiso will barely hold a screw. I use Gorilla glue, even then I peel off the foil or paper on the surfaces to be glued.
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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
gbwillson

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Reply with quote  #8 
I built a test box for my ZPDP out of polyiso. And like Willie I used polyurethane glue on the joints after I cut away the foil. I figured if I didn't remove the foil, the joint wouldn't be any stronger than the foil adhesive. It's been banged around quite a bit, but it still seems pretty strong. But exposed to the elements, I'm betting any exposed foam edges would be turning to dust. I used screws too. Big long deck screws if I recall.

I've tried using Great Stuff as an adhesive, but there IS a trick. Once you have it applied and stuck items together, I pull joints apart for a minute or so. This seems to stop most of the swelling. First time I used GS to stick some insulation to a board, I didn't do this and came back an hour later and the GS had pushed the board and insulation panel a good inch apart! 

Greg in MN
stmbtwle

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Reply with quote  #9 
There are different grades of the stuff, the blue expands less than the red. Also I suspect that if the parts were clamped (or screwed) they might not come apart.

Haven't tried it though.

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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
dbc

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Reply with quote  #10 
Willie, Greg,

Thanks for the info on the glue.  I will experiment with some scraps and get some practice.
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