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Posts: 2,461
Reply with quote  #71 
As you don't yet know the performance of this unit and how well air flows through it, I would suggest not deciding on any permanent braces for now. I'd try clamping a temporary horizontal brace to start and see if additional bracing at the manifolds is needed. It will be interesting to see how the flow and performance compares with your 2x16 ZP. 

Greg in MN


Posts: 303
Reply with quote  #72 
Agree.  I just went and bought another 10 ft. piece of EMT for a single horizontal brace.  I even have a tentative plan for how to attach it, using two of the aluminum plates from my first idea (cut off one hole and screw the plates to the sides of the collector).  Before I do any of that, I will test with temporary clamps.  I am configuring the mount so it will be easy to take the collector on and off, which I will likely have to do to permanently attach the brace, or braces.  If the single horizontal plan looks like it needs more help, my current idea is to loop one or more pieces of thin steel cable (1/8 inch?) around crosswise, and join the ends with a turnbuckle.  I'm curious to see if the glazing will still want to push up within each 2 ft. span.

Looking forward to testing; hope to get there soon.

Posts: 303
Reply with quote  #73 
I modified the 4x8 wall mount to accept the new collector.  This is the right-side mount before any changes.  The left side is an exact mirror image (don't know what that dark blotch is on the wall; I didn't do it):

Right frame, bare, 062018.jpg 

I added a piece of framing channel to the bottom stand-off for the collector to rest on.  I left it slightly long to leave room for yet-unknown future changes, like a deeper collector and/or a hinged cover.  Also, I needed 2 1/4 inches for the angle brackets that will clamp against the front of the collector frame (like on the 2x16):

Right frame with lower piece, 062018.jpg 

Right lower, close up, 062018.jpg 

Then I added another piece of channel to the front uprights to provide a fastening point for the collector top brackets.  It wouldn't need this piece if the existing front angle iron was taller.  The collector will sit a couple inches lower than the old one, and I didn't want to go any lower than that.  The top of the front channel will be the same height as the top of the mounting brackets on the collector.  To attach the collector, I just need to set it on the lower rails, bolt the lower angle brackets to the channel against the front of the collector frame, temporarily clamp the top brackets, and drill through and bolt them one at a time.  The top will be bolts and nuts (not spring nuts); I installed the front framing channel 'backwards' so I could fasten it to the angle iron with spring nuts, using the existing holes:

Right frame, final, 062018.jpg 
So now the collector is ready to install, but first I wanted to add a Test switch to the Controller that will energize the fan relay independent of the snap disc and thermostat.  Basically the fan will come on and stay on when the Test switch is closed.  Here is the (ahem) Controller (I need to update the labels.  The selector switch is now for the 2x16 vs 4x8; the original 4x8 had two snap discs).  The small switch on top is the new test switch.  The low-voltage cables on the right go to the snap-discs and the thermostat.  The 120V cord is for the fan; the 120V receptacle is energized via the relay in the controller.  The cable coming out the bottom goes to the live 120V source lower on the wall:

Controller, 062118.jpg 

  I wanted to add the switch for air-flow testing, and so I could let the collector run and air out any fumes.  For airing out, I plan to disconnect the ducts to the front room, although I will leave the air filter box in the path.  To test air flow, I will leave all the ducts in place except the last flex piece on the output side, which I will replace with the test stub with cross-vane insert, so I can measure with the Kestrel meter.  This is exactly what I did with the 2x16, so hopefully I can gather some realistic data for comparison.

I got a 6x8 tarp I can put over the glazing during installation (and for the summer months afterwards).  Next up is to haul the collector outside and install it on the mount.  May wait for a cloudy day for that.


Posts: 303
Reply with quote  #74 
In preparation for moving the collector outside and running some air flow tests, I made an off-season shade cover.  It's a simple 1x2 frame with a tarp lashed around it:

2) Cover frame, painted, 062318.jpg 

3) Tarp tied on, 062418.jpg 

5) Tag lines, 062418.jpg 

The first view is the back side, which will sit against the glazing.  The tag lines on the ends are to tie it to the handles on the collector, or to the mount, whatever works best.  One thing I'm not sure about is whether water will collect in the bottom of the tarp.  I may just fold and staple it to the front of the 1x2 frame and cut off the excess, or use the same technique with some other material.

Here's the collector sitting on the mount.  Everything lined up real well.  The bottom rests on the framing channel and is held with angle clamps bolted to the lower channel.  This allows easy side-to-side adjustment.  The top mounting brackets are exactly centered on the frame uprights.  Kind of hard to see those details here; forgot to take close-ups:

7) Collector on mount, 062518.jpg 

The top brackets are just clamped for now, because I will probably have to take the collector back off to permanently install the glazing cross braces.  I will drill and bolt the tabs to the frame uprights for the final installation.

Next I connected the air ducts to the existing stubs on the outside wall.  These are left over from my original 4x8, so they are a little weathered, but not torn or leaking.  They're a lot shorter than the ducts to the 2x16:

9) Outside ducts, 062518.jpg

Moving inside, I disconnected the existing output air duct where it comes through the wall.  This is the last piece, the other end of which connects to the upper grille on the wall of the front room.  In its place, I installed a temporary flex section + 3 foot rigid duct with a cross-vane in the end.  These are all the exact same pieces I used to test the 2x16 ZP, installed in the same way.  Nothing is changed on the intake side:

6) Test duct, 062518.jpg 

The light was bad, so it's hard to see the vane in the end, but it's there.

It was now time to fire up the fan and test air flow.  First I tested with no bracing in front of the glazing.  The glazing bowed out quite a bit, about 1 1/8 inch at the center, 1/2 inch over the plenum (directly in front of the center divider), and about 3/4 inch at the turnaround, right over the end of the center divider.  Here's how it looked (kind of hard to see the bowing clearly):

10) Bowing, no braces 01, 062518.jpg 

11) Bowing, no braces 02, 062518.jpg 

You can see the lower clamps better in these shots.  I measured airflow with the Kestrel 1000 meter, using MPH in Averaging mode.  I followed Greg's procedure of holding the meter in front of the open duct, and powering it off and back on without moving it.  I moved it slowly around in front of the open duct to average the flow in different areas for a couple minutes until the reading stabilized at 11.7 MPH.

Next I clamped a long piece of 1/2 inch EMT lengthwise, directly over the center divider.  This cut the bowing about in half (1/2 inch at center, 1/4 inch over the center divider at the plenum, and 3/8 inch at the end of the divider.  Better, but still way too much.  Airflow measured out at 11.8 MPH, basically the same as before.  I tried tying a rope crosswise over the EMT, looping around to the back, with the ends cinched with a motorcycle tie-down strap.  This didn't reduce the bowing much at all.  Here's a picture (without the rope):

12) Bowing, long horiz brace, 062518.jpg 

The final test configuration was with three cross-braces running top to bottom (across the air flow path).  These are made to bolt on, but I just clamped them to test.  This setup was by far the best at controlling bowing.  Deflection was maybe 1/8 inch at the center (I was pushing on the glazing pretty hard and was probably flexing the whole interior a little and maybe the twin-wall too), and definitely less than 1/8 inch at the plenum and at the turnaround.  Doing this again, I may upgrade to 3/4 EMT or bite the bullet and buy 1 inch x 1/8 aluminum angle.  Here's a picture with the three 1/2 EMT braces:

14) Bowing, 3 vertical braces, 062518.jpg 

I don't know yet it it will be better or worse with the braces bolted instead of clamped.  I think I am going to go with these.  Airflow for this setup was 11.5 MPH.  This reading was 15% higher than I got with the 2x16 (10.0 MPH), which improvement I assume is due mostly to the shorter duct runs.  The U-turn collector geometry doesn't seem to be choking things much.  I figure there may be some bunching at the turn, although I did make the cross-section the same all the way around (22 1/4 inches wide as I recall).

I used the Comair-Rotron Airflow Calculator to convert to CFM:  11.5 MPH through 3 inch radius round duct =  198.7 CFM.  I guess this is reasonable; I tested the same fan last year (Suncourt TF 106, spec 409 CFM free air), and saw only 15.3 MPH / 264.4 CFM for just the fan with 3 ft of rigid duct and a short flex piece to connect the two.

I haven't done any heat rise tests yet.  It's only 5 days after the summer solstice; mid-day sun here is now at 74 degrees elevation angle, and my collector has zero tilt.  I don't think much radiation is getting into the collector now.  May wait until October or so to test further.


Posts: 149
Reply with quote  #75 
It looks great! Thanks for the update...now just wait for the cold?   I think I will use the through bolts to hold the EMT to the dividers. I have not yet bought the twin wall or things that go with it, but I have gotten to the point that the materials are in the way, so I have started the 2x6 frame.  I decided to R&R the gutter and fascia before I started.  When I looked up through the access panel in the eave, I saw daylight and had to replace the roof.  I guess I am ready to start my project in earnest now.  Sorry for all my kabutzing here, but I do appreciate your work and the sharing of ideas you have done.

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Reply with quote  #76 

It sure looks like using vertical bracing is the way to go. But before you commit, I suggest temporarily bracing the center of the horizontal brace so it doesn't bulge. You can see how much the ½" conduit bends, and ¾" might not be much better. A stiff iron pipe, or angled brace should eliminate most, if not all of the bulging. And if that still leaves the manifolds needing a bit more bracing to seal them, I have an idea for how you can complete the seal.

Keep in mind that you don't yet know the temp rise at your current CFM. You might find that you need to reduce the airflow to have a comfortable output temp, which in turn will lessen the bulging. Probably not, but as you are far ahead of the game, it might not hurt to wait for proper cool weather testing.

Greg in MN


Posts: 303
Reply with quote  #77 
I looked at several ideas to stiffen the long horizontal EMT brace:

1) First try was the rope + tie-down strap.  That didn't help much.  I thought about using steel cable with a turnbuckle behind the collector, but I thought that might crush the corners of the box before it held the tube down tight.  If I used steel cable, I would add some angle 'bearings' where it passed over the corner.

2) Next thought was to fit a piece of angle aluminum, taller than the EMT OD, cross-wise at the center (vertically) with a hole through one leg for the EMT.  Problem there is that the tube would be held off the glazing by the wall thickness of the angle stock.

3) Finally, I considered putting a piece of EMT (or angle) cross-wise over the top of the horizontal tube.  You could put spacers at the top and bottom so the cross brace could apply tension without having to bend all the way down to the collector surface, or you could use something like the aluminum plates I made last week to hold the cross tube out the right amount.  Here's a rough mock-up of what I am trying to describe:

15) Cross brace mockup, 062718.jpg 

It would be fairly critical to screw the plates at just the right depth.  You might need more than one cross brace, at least one over the plenum entry and one somewhere in the middle.  I don't think it would look that good either.  Not sure if it would be much of an improvement over the 3 vertical braces.  I guess I'm still open to other ideas.

By the way, I gave the vertical braces the 'penguin' paint job - black center with white ends.  I'll take a picture and send in another post.

I may squirt a bead of silicone to seal the front corners better, although I don't think water can get into the enclosure anyway with the gaskets that are there.  Mainly to prevent water from seeping behind the angle pieces.

I thought the output temp from the 2x16 was pretty good last winter, warm but not too warm.  The fan started quickly and stayed on until around 3pm without cycling as long as the sun was shining (collector faces slightly east).  I should have re-measured output temp when the sun angle was lower but I never got around to it.  Overall, I felt the airflow was about right for the 2x16.  Curious to see how the new unit works later in the year.  One thing I don't exactly know yet is whether air will leak over the top screen frame at the intake or over the center divider, short-circuiting the intended flow path.  I don't think it will be much with the 3 vertical braces, but if heat gain seems too low (considering the slightly higher airflow) that may be a contributing factor.

I suspect the U-turn geometry is not especially well suited to a Zero Pass, which tends to put outward pressure on the glazing (fan in input).  Having a non-structural center divider didn't help either.  I was trying to mimic the 2x16 internal airflow path as closely as I could, given that the air has to turn 180 degrees.  Time will tell, but I don't think I would repeat this design.  Which brings up another question:

Has anyone 'scientifically' determined what the minimum absorber length is for useful heat gain?  At what air flow?  I'm speculating about a one-piece, one-way 4x10 collector, probably ZP, but maybe 3 inch corrugated aluminum duct.  If I went ZP, I would try aluminum screen frames with taped spline (was going to do that this time, but I went cheap).  In a 4x10, the screen absorber would be about 8 ft. long.  Is that long enough?  10 feet is about as long as will fit inside my work area.  Still want to test the current model though.

Late Edit:  Here is a photo of one of the painted braces fitting loose on the collector.  The interior looks blacker when the collector is out on the wall, so the center part should blend in better:

16) Painted brace, 062718.jpg 


Posts: 303
Reply with quote  #78 
Feeling the need to wrap this project up, so I permanently fastened the three vertical glazing braces with gasketed screws and silicone, and installed the collector on the mount.  Here's how it looks; the closeups are of the upper and lower attachments:

Collector, complete, 063018.jpg 

Top bracket, 063018.jpg 

Bottom bracket, 063018.jpg 

I reviewed my notes from testing the 2x16 last year, and decided to re-test airflow holding the Kestrel a bit farther back from the end of the test duct.  I also made an effort to keep the body of the meter out of the aperture as much as possible.  Air flow tested out today at 11.1 MPH.  This translates to 191.8 CFM using the Comair-Rotron air flow calculator, 3.6% lower than I saw earlier in the week.  The new reading is probably more accurate, or at least more directly comparable to test results for the 2x16.  The air filter element is somewhat dirty (plan to change it before winter), but it's good enough for now.  The back room is pretty dusty.  I briefly tested air flow without the filter element; flow increased only slightly to average 11.2 MPH.

After I finished testing, I disconnected the duct from the wall grille to the air filter box, and clamped a piece of screen over the filter box intake.  I let the output exhaust into the back room for a while, then decided I don't really need any more heat in there right now, so I'm letting the output dump outside behind the collector:

Output outside, 070118.jpg 

The new 'test' switch I added to the controller worked as expected, but mostly I'm letting the fan run under control of the snap-disc.  That's working too; the collector has been running all day, even with the 70+ degree sun angle.

I've been checking for any unsavory smells.  I don't smell paint (good - I was a little worried about that).  The most noticeable, though faint, smell around the outside of the collector is Liquid Nails, which I used to glue the plywood strips inside the stud track.  That was from last fall, early in the build.  I hope it dissipates sitting out in the sun.  I've noticed at other times that Liquid Nails has an especially persistent smell; don't think I will be using it again on any solar projects.  Silicone would have worked fine in that application, a bit more expensive, but worth it for health and safety.

Guess I will continue to let the box out air out until fall.  Then I can test temperature.  I drilled some small holes in the in/out duct stubs so I can fit the thermocouple probe inside.  The holes are taped over with foil tape.  Also - I checked for bulging behind the glazing cross-bars.  It's about the same as it was.  I experimented with fitting some small pieces of 1/8 inch felt behind the EMT right over the center divider.  It's a tight fit, but it might prove helpful.  I will experiment when the time comes.


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Reply with quote  #79 
Looks great Don!

You might want to cover the exhaust with a scrap of screen until you make the final connection in the fall as critters might like a new home with a 4x8 skylight. Bees and wasps in my area are looking and building new homes at an alarming rate. 

You mentioned small pieces of felt behind some of the EMT. Why not behind all places where the EMT contacts the twinwall? It might make for a slightly tighter fit, but it would also reduce any abrading between the two surfaces.

Greg in MN

Posts: 303
Reply with quote  #80 
Greg - It's hard to see in the photo, but there is a screen over the temporary output duct.  Also a screen on the now-open input port of the air filter box.  I put plugs in the end of the disconnected ducts (a flex splice with one end capped).  Here's one:

Capped duct, 070218.jpg 

So now there should be no way for wildlife to get inside the system without deliberately attacking it.  We have a lot of bees and wasps, who seem to always want to build a nest where you don't want them (You guys can have the whole field, just stay out of the collector!)

I have quite a bit of the 1/8 felt left, so I will see how much I can fit in between the glazing and the EMT; should minimize scuffing and keep the inside transitions sealed better too - good idea, thanks.

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