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gbwillson

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Reply with quote  #31 
Don-

Last winter my ZP had a structural "blowout" when the trim bracing that held down the glazing failed. The screws holding down the exterior trim hold downs stripped out when I changed to a more powerful fan. So I had to use temporary external cross pieces to keep the glazing flat and prevent the air from bypassing the ZP sir slot. It bulged out almost 6"! So I fashioned attached a pair of roof truss ties to each end of a scrap of wood(link below). These were used as temporary clamps to hold the external cross braces in place. They looked like crap, but they were very cheap and easy to build, and got me through winter. One side of the tie has a slot for adjustment. But I actually ended up only needing to slightly bend the ties. This allowed me to bend or flex them into place without scratching. Tension could be adjusted by slightly increasing the bend. Could you use one of these to hold the back of your collector clamps? The front and side PVC/wood trim could be used for looks, but the back wouldn't be seen. This way you wouldn't have to have such a perfect fit trying to slide the "clamp" into position.

When Krautman needed some external hold-downs for his workshop ZP, he used ⅛"x1" aluminum bar stock. He heated the aluminum where the bend would be and bent the bar into an L-shape. Problem was, the corner wasn't a sharp 90˚ bend, but very rounded. A notch, either ground or cut at the bend point, may have allowed the bar to form a proper 90˚corner. He screwed them to the side of his collector box. But I like the clamps above. It allows for quick and easy access to the inside of your collector. No screws or fasteners needed!!!

In the drawing above you have a full length metal angle on top of the glazing. I assume that surrounds the glazing. What is this being use for? And where will the weatherstripping be placed?

 
Greg in MN

http://www.menards.com/main/tools-hardware/fasteners-fastener-accessories/structural-connectors-reinforcements/plated-truss-connectors/roof-truss-ties/usp-structural-connectors-1-1-4-x-2-x-2-3-4-roof-truss-tie/p-1444445535658-c-8886.htm?tid=-753964110711199512

dbc

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Reply with quote  #32 
Greg,

I will try to answer your questions first:

The weatherstripping will be glued to the front face of the track frame.  The glazing sits in front of the weatherstripping, then the angle hold-down piece fits over the glazing and against the side of the track frame.  The angle pieces are there to hold the glazing against the front of the frame.  No screws through the glazing, or into the front of the frame, just into the side.  This much of the assembly is pretty conventional - similar to what you have on your 4x16, also Bert's and Mranum's and probably others too.

On most designs I've seen, the angle hold-downs are screwed into the side of the frame, or into whatever wood reinforcements are inside the frame, using rivnuts, plusnuts, t nuts, or just good self-tapping screws.  Mranum posted a closeup of his attachment, which I think is in earlier part of this thread.  This was what I originally planned to do also.

The new wrinkle is the idea of using clamps to hold it together instead of screws.  With this assembly, neither the glazing or the hold-downs would be attached to anything, just held tight against the frame in a 'sandwich', under the clamps.  My collector won't be directly against the wall, so I can clamp around the front and back.  It may be possible to delete the hold-down pieces altogether if the clamps are spaced closely enough, although I think the hold-downs will help distribute the clamping pressure more evenly and prevent crushing the glazing.  It's worth a test (if I ever get that far).  Here's a couple more crummy sketches, side view and front view, that may help.  The dimensions are exaggerated to show detail:

side view.jpg 

front view.jpg 
 
You could use something similar to prevent the glazing from bowing out - just make the front piece continuous across the glazing instead of only a short tab to catch the edge.  You would need to unscrew something to get it back off, unless the back tabs could pivot and let you pull the clamp off from the front.

I am struggling to visualize exactly how you used the roof truss ties on your cross-braces.  Were the ties screwed into the collector frame?  They look like a useful item - I like the slot.  Maybe you could screw 2 of them together into a 'C' shape for clamps with a piece of thin wood, plastic, or something, on the inside of the C, with holes cut out around the screw head to keep it from gouging into the frame.

dbc

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Reply with quote  #33 
A little more progress this weekend - some details that needed to be domne before I put the back panels in.  I attached some angle brackets at the ends that meet in the middle, so I can pull the two panels together.  Here is a picture one of them.  The brackets are bolted through the frame, plywood, and some small plates:

Bracket.JPG 

Plate.JPG 

I finally decided to install some 8-32 T nuts as attachment points for the glazing hold-downs.  This took a lot of time, measuring, marking drilling 40 holes, then drilling bigger holes in the plywood and hammering in the T nuts.  I still don't have to use them; I still want to take a stab at some clamps.  if I don't screw the hold-down angle pieces to the frame, I can fill the holes with silicone and cover with some foil tape.  It will all be under the angle piece anyway.

Next I pulled the tops off the frames and slid the back pieces in to check for fit.  Here is a picture of the left frame, 'topless'.  You can see some of the T nuts hear the front of the frame:

Back dry fit.JPG 

Finally, I removed the backs, ran a bead of silicone all the way around and slid the back pieces in for good.  Here is a pic of the back glued in.  The small blocks of polyiso are temporary; they are there to keep the back panel pressed against the back of the frame until the silicone sets up.

Back glued in.JPG 

Plan for next week is re-attach the frame tops.  That will be fun - trying to get it all together without getting silicone all over everything.  I'll probably clamp it for a while, then rivet the top, and glue in the permanent polyiso strips into the frame.

Then I can start thinking about the inside, screens, etc.

dbc

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Reply with quote  #34 
This weekend, I joined the top pieces onto the rest of the frames - silicone and rivets.  It all went together pretty well - tight against the edge of the back polyiso all the way around.  I glued 1 inch polyiso into the track on the ends, and then glued some 1/2 inch polyiso strips into the long sides (top and bottom).  Here is a photo - kind of hard to see because it's all shiny now:

Insulation.JPG 

The reason I used 1/2 inch on the long sides is that I am planning to glue in some small 1/2 inch OSB blocks, fit tight into the track, as attachment points.  here is a picture of one of them.  I covered the inner face with foil tape to protect it and make it easier to paint:

Block with foil tape.JPG 

After I put these into the frame, I will fill in the spaces between with more 1/2 inch polyiso to end up with a continuous surface.  This surface will be abut 1/8 inch inside the edge of the stud-track lip.

Starting to think more about the screens.  I dont' know if it's enough to just lay them in there with only the glazing to hold them against the  back.  With the blocks, I can screw some small pieces of aluminum angle to press against the top of the screen frame.

I estimate I will have 5/8 to 3/4 inch from the top of the screen assembly to the front of the frame (glazing).  Planning to put in either 3/4 aluminum square tubing, or maybe 1/2 inch EMT over the ends of the screen frames near the air ducts.  This will further stabilize the screen and also serve as an air baffle to keep the air stream inside the ZP channel.

First I need to make the screens and see how they fit.

gbwillson

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Reply with quote  #35 
Don-

Your build is looking really good! I don't think using ½" polyiso will make a noticeable difference since the bulk of the heat loss would be through the glazing. Although heat loss will be limited by using higher a higher velocity airflow. And having usable internal attachment points will be a major bonus. Not that you need it now, but some big box stores sell OSB with a foil face, but if your needs are only small chunks for attachment points, foil tape should work great.

With my ZP the screen frames were made out of 1x2's so each frame added ¾" thickness to the overall build. This made for a tight fit. The only place I had to add a spacer was between the two screen frames. There was no more room! This configuration made for a ¾" distance between the glazing and the front-most screen. Same thing with the back screen being ¾" away from the back polyiso back. I added 1" spacers between the two frames. So everything was pretty much held in place since there wasn't any room left. With such limited space, I might have used a thinner frame for the back screen. This would have allowed either a wider screen gap, or more distance from the front screen and the glazing. 

What will you be using to hold your screens in place? Krautman used actual extruded screen frames, and Bert used a stretcher bar system, at least for his upper screen. Both would give you more room inside with which to change spacing. 

Greg in MN
gbwillson

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Reply with quote  #36 
Don-

Somehow my reply to your post #32 didn't post last week. I think I forgot to hit the reply button. In that post you can't visualize how I used the roof ties to secure the cross braces. 

IMG_0961.jpg 

My "clamps" were used to hold down my temporary cross 1x1 braces. The two ties were attached at both ends of a chunk of wood as shown above. As you can see, one side of the ties has a slot for large adjustments or simply bend one end you accommodate a wide variety of materials. My ZP collector glazing first blew out when changed to a more powerful fan last winter. I used both C-clamps and one handed clamps to hold the cross braces. But as we got closer to spring, the metal clamps would get wet and I didn't want to rust out good clamps. So I built "clamps" for less than a buck in about two minutes. Low tech to be sure, but they did the job. I shouldn't need them once I make the needed repairs this fall. But I will likely use some variant of these clamps for my next collector since it would allow almost instant access to the innards of the collector, if needed. I don't like the look or hassle of so many screw either to the front or side of any trim to hold things together. In any case, your collector will likely have less air flowing through it since it's only half as tall, so the span of any flexing should be greatly reduced too.

Greg in MN




dbc

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Reply with quote  #37 
Greg - Thanks for posting the photo of one of your clamps made from truss ties.  It's not too far from what I was thinking of - actually better because the span is adjustable.  Still looking for something a bit more elegant, but that should work for the intended purpose of holding the glazing against the front.  I too am resisting the idea of screwing the glazing hold-down pieces into the collector frame.

I am planning to use standard 5/16 inch screen frame material.  The front and back frames will be tied together with 1 1/4 inch gap in between, using 2-inch long 10-32 screws with nuts holding the screen frames in place.  Here is another crummy sketch, showing a cut-away view looking from the end of the collector:

Screen attachment drawing.JPG 

The drawing is not quite to scale.  It also shows the angle brackets I plan to use to hold the screens down.  These brackets will be short pieces of 3/4 inch aluminum angle.  I may have to grind down one side if I end up with less than 3/4 inch.  The brackets will be screwed into the wood blocks I am fitting into the stud track frame.  At this point I am not planning to screw the brackets to the screen frame, although it looks that way in the sketch.  The 2 inch screws will be in the corners and at various points along the screen assy.  Not sure how many will be required, but the screws will not likely line up with the brackets and blocks, and I don't think they need to.  The brackets just need to hold the screen frame tight against the back of the collector.  The sketch shows the assembly above the back, but the screw heads will probably crush into the polyiso, so the back frame will be right against the back.

At the end of the screens adjacent to the air ducts, I will probably fit some kind of square tubing (or maybe a piece of J-channel) across the frame and screw that into the wood blocks (one set of blocks will line up with the end of the screens).  Idea here is to also close off the space between the screen frame and the glazing to keep the air stream inside the ZP channel.

I haven't really tested any of these ideas, but... I am sort of making this up as I go, with helpful guidance of course from the more experienced builders on simply Solar!

Almost forgot - I will actually have 1 inch insulation inside the track on the long sides as well as the ends.  The polyiso on the long sides is just built up in two 1/2 inch layers.  The outer layer is continuous, while the inner layer is broken up by the little wood attachment blocks.


gbwillson

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Reply with quote  #38 
I think a hold down with a specific opening might actually be better. In my case I needed something fast and cheap since it was the middle of winter. But a set clamp opening would allow for a consistent compression of the weather stripping that seals the glazing. And that might make for a more attractive clamp setup as well. Krautman's one piece trim and glazing assembly could easily be held down with only a few clamps. I know my next collector will have quick access to the insides. Not that I really expect a need like last winter, but It makes things so much easier, especially in your case where the collector is permanently mounted. 

In the drawing above, I don't see a dimension for the space between the polyiso and the back screen. But as you say, the bolt heads will likely push into the polyiso. Could you glue small pieces of flashing where the bolt head will contact the polyiso? Looking at the bolts i assume this is adjustable. Not that you plan on changing things, But the bolts do give you the ability to adjust the gap between the screens, if needed. I also see the benefit of the bolts essentially making the two screen frames into a single piece. it would make the two frames stronger and less likely to bow or twist too. Only issue is it would be a little more troublesome to clean the screens should they need to be taken apart at some point for maintenance.

Making it up as you go...I fly by the seat of my pants too often. If you are like me, you have already thought of a few different ways to make your "next" collector better, before this one is even finished. So goes the creative mind, I guess! 

Greg in MN
dbc

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Reply with quote  #39 
Yeah, I get a lot of crazy ideas for 'next time', especially while I am standing there working on 'this time!'

The drawing looks like there is some space between the back screen and the polyiso, but I was actually planning (so far) to press the back screen frame all the way against the back because of limited space.

I am using standard aluminum screen frames, 5/16 inch deep, which puts the back screen material above the polyiso by just the thickness of the frame.  Two screen frames = 5/8 inch + 1 1/4 inch air gap = 1 7/8 inch total for the 2 screens and air gap.  I have 2 9/16 inches from the polyiso to the front of the collector, which leaves 11/16 inch between the front screen frame and the glazing.  Since the front screen frame is 'upside down', with the screen on the bottom, the front screen itself is a full 1 inch below the glazing.

I can still modify this plan by changing the gap, or by raising the whole assembly up on the 2-inch screws (might need 2 1/4 inch instead if I do that).  I can glue some little pieces of flashing or alum sheet as you suggest for the screw heads to rest on - probably will do that if I raise the screens up.

The slots where the two collector sections meet are about flush with the polyiso back, so I may need a strip of something under the screen frame too if they are up off the polyiso.

The other factor in the spacing decisions is that I wanted to leave enough room between the front screen frame and the glazing to (1) screw some brackets into the wood blocks to hold the screen assy down, and (2) put a piece of tubing or channel above the end of the screen frame keep the air from flowing in front of the screen, next to the glazing.  That's not to say I need the full 11/16 inch; 7/16 inch will still keep the front screen 3/4 inch below the glazing.  I would just need to find the right material to fill the space, maybe some 1/2 in. J-channel (used on exposed drywall edges).  Home Depot has a bunch of that.

To summarize - I now have 5/16 inch behind the back screen and 1 inch above the front  screen.  Would it be better to even that out a bit by raising the screens up?

About the glazing clamps, I am intrigued by the spring-loaded hinges Krautman used (or will use) for his stretcher bar.  I wonder if some smaller versions could be used at the corners of the glazing clamps to keep them pressed tight?

Before I forget - I did glue the little wood blocks into the frame and filled in the spaces between with a second layer of 1/2 inch polyiso.  Here are a couple photos.  The light is strange, but you can see the blocks along the sides.  The scrap OSB I had turned out to be 7/16 inch, so the blocks are very slightly recessed from the polyiso.  Think they will still work OK.  I taped the joints where the blocks meet the infill polyiso - I love that foil tape.  This step took a long time, and was probably more trouble than it was worth, but it's done now.

Insulation + blocks 03, 072616.JPG 

Insulation + blocks 02, 072616.JPG 

Block installed, 072616.JPG 






Bert

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Reply with quote  #40 
Looks really good. It's coming along nicely.
I think that 1" gap from the glazing is good. That's about what mine came out to.


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Bert K.
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