Close to putting up panels and thinking about hanging an extra set of panels...

Photowhit · November 2012

So I'm close to mounting panels and had to buy 20' long boards for a 16.5' length needed, the long board leaning against the mount is 16' So the original plan was to hang @18" off the top and bottom. The array of 20 - 200 watt 28.2VMP 7.1IMP in a 4 across 5 tall configuration.

I have an additional 4 panels 185watt 36.4 VMP 5.1 IMP panels I could easily place at the top of this array and add into the 2 mMidnite Classic lite CC, I might have a bit of clipping on perfect days. The panels are slightly smaller, so there is a goofy factor, but the mount holes are inside of an inch of each other, no one to please but myself. I would waste a bit of wattage and I won't mount the other panels until next spring at this point.

So options are;

1. Do the original plan, and trim the boards.
2. Mount the extra panels...
3. Leave the extra lumber sticking out above the array, thinking you paid for it and you might add panels later...

Attachment not found.

westbranch · November 2012

Re: Close to putting up panels and thinking about hanging an extra set of panels...

I vote for leaving....your options open till next spring

H2SO4_guy · November 2012

Re: Close to putting up panels and thinking about hanging an extra set of panels...

Add Panels!!! Add Panels!!! You know what a power junkie you are! You can always find a use for extra power, and with solar, it's use it or lose it. Even if you just heat water, it's that much less that you have to heat with propane or some other way. And besides, I hope you can share with the class on uses for surplus power so I do have an ulterior motive. I thought about ground support, but I was worried about damage and theft, so I built a deck with a roof over it to mount them on and wish I had purchased more panels. Is there ever enough?

Skip

CATraveler · November 2012

Re: Close to putting up panels and thinking about hanging an extra set of panels...

Easy to cut later, harder to extend later. It also appears easy to extend width wise.

Photowhit · November 2012

Re: Close to putting up panels and thinking about hanging an extra set of panels...

Well very cold today, I got my mounts drilled and bottom bracket up and some friends brought over some scaffolding which I put up, I thought it would make the end easier, but realise it will help working underneath the top row as well.

So a couple people for leaving them extended and one for going ahead and installing them odd panels... I think I'll at least leave them extended. Likely I won't add panels at this point, I realised I had rewired a combiner box to run 2 sets of 5 strings and while I have space for a couple more fuses, I may not have the time to get the fuse holders and get this up and contributing this year. Goal #1 is to get this up and contributing so I can take tax credit this (and extended for next year).

FWIW, it would be a real pain to extend them width wise, the panels will extend past the end of the 20' width, and the double 2x8's will have 2x4's between them to support the mounting boards. So it would have to be a complete redesign, I think.. The other 2.6Kw array will be over the mobile home shading the front porch and perhaps the Family room area. It will be angled about 25 degrees more westernly.

Photowhit · December 2012

Re: Close to putting up panels and thinking about hanging an extra set of panels...

Well I went with goofy, It won't be too easy to mount 2 more panels, I could do it with the double height scaffold, but I'm at about 14 feet at the tall corner now. 2 more panels to mount now and there are some that match available, but I'm currently layed off and don't want to stretch. If I trim them down, I'll likely do it before I return the scaffolding...

Attachment not found.

zoneblue · December 2012

Re: Close to putting up panels and thinking about hanging an extra set of panels...

what are you using to mount the panels to the timber, a piece of metal right angle bracket ?

Photowhit · December 2012

Re: Close to putting up panels and thinking about hanging an extra set of panels...

I used aluminum angle. After changing some panels that had been up 5 years, without the buffer between the aluminum and the 'new' pressure treating, I saw little or no reaction between the wood and the aluminum. I guess I was the accidental experiment as I had intended to move the panels, adding some larger panels before the year was out, but only changed them out after almost 5 years. I guess the oxidation layer on the aluminum is pretty hard to get through. I did give my self a break, and after the first set done with 1 1/2 x 1 1/2 inch, I switched to larger pieces. I like 1 /1/2 x 2 1/2, I do raise the panel off the pressure treating, usually using the thickness of the angle bracket, since it's handy and uniform.

Attachment not found.

waynefromnscanada · December 2012

Re: Close to putting up panels and thinking about hanging an extra set of panels...

Photowhit wrote: »

. After changing some panels that had been up 5 years, without the buffer between the aluminum and the 'new' pressure treating, I saw little or no reaction between the wood and the aluminum.

Wonder what was different between your construction and mine - - - perhaps I live in a wetter climate?
I added (the new chemistry) treated 2X4s to my aluminum angle rack to stiffen it up, and found substantial corrosion after just one year. Removed the treated wood, installed a plastic tape barrier, reassembled and no more corrosion after 4 years.

CATraveler · December 2012

Re: Close to putting up panels and thinking about hanging an extra set of panels...

From the photo it appears that you could extend to the side given that you add 2 more vertical posts for support.

Photowhit · December 2012

Re: Close to putting up panels and thinking about hanging an extra set of panels...

Thanks Wayne, I'll keep an eye on the mounts, perhaps there was a different pressure treating formulation? I did use somewhat heavy brackets, 3/16ths on most of it some have 1/8th inch which I thought I would be uncomfortable with, but they are roughly 3 times thicker than the panels aluminum.

On extending the array, I designed it for just what's there, I asked an engineer(not a building type...) if they thought I could add an extra panel at the top, since I have the extra lumber and they thought it wouldn't present a problem. The 20 foot long 2x8's stop about 12 inches before the panels do, so tieing into this array would be somewhat problematic. I also would find it a true pain to get the posts just right. I actually did much better on this than I had originally thought, with the 4. I kept the distances, front to back and side to side, the same so the bottom and top mounting would be in the same plane. When I first measured corner to corner I came up with @4" off. Later I remeasured a few times when I came up with about an inch. I must have measured to the inside or had my tape catch on something at the corner.

Still when setting my first diaginal panel mounting board I wasn't quite square and to keep the panels starting in the same place, I ended up having almost 2" more over hang over the 20' length, my guess is that's still less than 1 degree, not too bad, I won't beat my self up over it. I really could have tacked in the bottom mounts and mounted all the panels with the same over hang, and then squared up, but I only had about 6" to play with. (if I had much of a parralellagram I might have fallen off/outside at the top)

Another issue with extending the array, is a power line easement that is about 12-14 feet (or at least the cleared area is) from the back corner of the array.

I will have more panels over the front porch, that will partially shade the family room area, and perhaps helping with the heat gain. If it wasn't a tin can, i would have gone with a roof mount of some type, as the angle isn't too bad (the array faces near due south.)

zoneblue · December 2012

Re: Close to putting up panels and thinking about hanging an extra set of panels...

Thanks for the photo!

Sorry, heres another question on the mounting!

Given that the rails will not be perfectly straight, nor fixed immaculately (hey no offence meant

, how did you get the holes in the angle to line up exactly with the holes in the panels?

Secondly, did you consider expansion differences? I dont know how the panel itself manages expansion, they must have either chosen glass and aluminium and composite that have similar coefficients, or there is some mechanism for flex. But im wondering if the difference between the expansion of the aluminium panel frames and the wood might put some pressure on the panels. Just a thought, especially as the aluminium probably swings quite a bit in temperature.

As i ponder using 4x2 rails or some U channel aluminium...

Photowhit · December 2012

Re: Close to putting up panels and thinking about hanging an extra set of panels...

I made a jig to drill the holes that attach to the panel, so they are a constant spacing, and distance from the corner, then I put on the mounts, then mount to the wood. Indeed the near right mount is the only one attached top and bottom until the panels are mounted. The wood the panels are mounted to is somewhat loose, only attached to the mounting 2x4 (that will be attached) and it is between the 2 - 2x8x20 bottom boards. I actually mounted 2 or 3 panels before screwing this down, letting the panels establish the square, and as they are attached the screws pull the board slightly up, since the weight has been pushing these slightly down. Holes n the aluminum at 9/32nds so there is a little wiggle room.

For expansion, the panels are mounted on the top of a 5 1/2" boards that are attached at the bottom, all panels and rows of panels have roughly 3/8ths in gap between. I don't think I'll have to worry about expansion. I'll keep an eye on warping and after a few years I guess I might have an issue with shrinking, I drilled out the mount holes for the mounts at 9/32nds as well, but over 16 feet a 1/4 inch of shrinking, might split the wood, but so long as the panels have some mounting they should rest above/on the wood. The pressure treated wood is protected somewhat from the elements by the panels, Lets call this a 40 year experiment.

The thing I worry about, is having put the 4x4's directly in the ground, more than anything else. I really should have put concrete peers in the ground and attached the 4x4's above the ground. I don't trust the 'new' pressure treating under ground. I did use the ground contact 4x4's and they are heavily salted, but this is what I worry most about

mtdoc · December 2012

Re: Close to putting up panels and thinking about hanging an extra set of panels...

Photowhit wrote: »

The thing I worry about, is having put the 4x4's directly in the ground, more than anything else. I really should have put concrete peers in the ground and attached the 4x4's above the ground. I don't trust the 'new' pressure treating under ground. I did use the ground contact 4x4's and they are heavily salted, but this is what I worry most about

What I would be most concerned about is wind. It looks like the trees behind offer protection and I don't know what your weather patterns are like but a large gust of wind coming behind that huge solar panel sail would put tremendous force on those 4x4s at the point where they enter the ground.

I think it was the user Organic Farmer who recently had some large (?6x6} posts snapped off that way..

Photowhit · December 2012

Re: Close to putting up panels and thinking about hanging an extra set of panels...

I don't have a lot of exposure from behind, I do have a cleared easement a few feet away, but there is pretty good protection. My cabin system is just 2x4's and has withstood 60+ mph straight line winds, into the face, but is even better protected from behind.

I vaugly recall a thread about a 6x6 snapping off but I believe it was a pole mount or just 2 posts with an array, creating a fulcrum at the base. Mine is braced between the 4x4's so it should act as a unit each protecting the others (or at least the other 2 it's connected to). It shouldn't create leverage to break/snap the 4x4, rather the force will be traveling up or down the 4x4.

Phase 2, mounting panels over the mobile home will include some leverage points as I would like to cantilever the array over the roof, without mounting it to the roof. It's a mobile home with no leaks or rust, I don't want to tempt fate. I may bail out and just make the array over the front porch, but it will be nearly 20' long and would also shade an area I'd like to have some plants. That's next spring, plenty of time to go through a dozen ideas!

BB. · December 2012

Re: Close to putting up panels and thinking about hanging an extra set of panels...

I would highly suggest some exterior grade plywood and a lot of deck screws (I really love deck screws--they hold like the dickens... But the code requires nails instead)... At the very least add gussets at the corners... Add some full sheets over the box frame.

Not a builder--But is there not some sort of rule of thumb for housing that 1/4 of a wall should be shear wall (plywood over studs, with lots of nails)?

For example, here is a California specific shear wall suggestion (PDF Download) for earthquake strengthening.

Here are some more Google results.

Also, having bolted joints between Wood/Concrete Footings/etc. to prevent lifting and side thrust from moving structure relative to the ground is critical.

"soft stories" (such as a two story home with the garage at ground level) was a major failure point for many homes here after earthquakes. As where homes just "sitting" on foundations (no bolts) or the short "cripple walls" that make up crawl spaces.

-Bill

Photowhit · December 2012

Re: Close to putting up panels and thinking about hanging an extra set of panels...

I'm not sure where you are, I guess california, but you sure can put up a building, by code and never use a nail, at least here. I would not increase the ability to torque the mounting posts by adding a side wall or back wall, That is what and why the bracing is there for. It would be like adding siding to a bridge, it would increase the non lateral and horizontal loading. Heck, I'm even somewhat uncomfortable mounting the power center (@4x5 feet)on the more protected side near the mobile home.

The only thing I would fear at this point is a 20" wet snow, I will put in a load bracing across the middle, for just such an event, but likely next year after I get wired up and running some loads. I do fear a failure to insects/rot of the standing posts, and will watch them

FWIW - my 12' high array suffered a 17" wet snow 2 years ago and it had no problem, the frame has much less support than this and is 2x4 framing, basically free standing with a single brace like and 'N' across the back. Much farther than a 2x4 should stand un supported or braced.

All hardware Stainless, screws, nuts, washers and bolts other than the mounts. All screw holes, with minor exceptions, predrilled.

I'll sadly post if I have any problems with the array mount, brackets, or structure. Heck, my brother would love to tell me how it should be done, and he's had more dang schooling, (EE at Georgia tech, Masters Artificial Inteligence at Michigan and a Masters in Materials Engineering at Stanford) and he didn't say a word...

Photowhit · December 2012

Re: Close to putting up panels and thinking about hanging an extra set of panels...

Bill, I realized you can't see the bracing in the second photo, did you see the bracing in the first photo? That hasn't been removed, and the addition of load bracing will solidify the level brace and the 2/3rds corner brace front to back, not allowing them to bow much, There is already a wood block between the corner to corner braces across the back, they are wide boards and shouldn't need gussets.

BB. · December 2012

Re: Close to putting up panels and thinking about hanging an extra set of panels...

I am no builder--But if you could install shear panels (and paint to protect against weather) on the two sides and first and last bay of the rear--Make a lean to/shed for storage?

I just don't trust unbraced 4x4 structures for side loading and worry about lifting forces (4x4 direct in soil?). It all depends on how much wind you get in your area.

Perhaps somebody with more experience than I can comment on your current bracing scheme.

-Bill

CATraveler · December 2012

Re: Close to putting up panels and thinking about hanging an extra set of panels...

I think that you're exposed to wind as you have a very large cross section that the wind can get behind and apply forward and upwards pressure.

Your house is different in that the wind will go around or over but not under. Plus houses evolved and are tested over time unlike your panel setup.

I also don't understand the bridge analogy. Relative speaking bridges have very little cross section to wind - mostly just steel structure. But even the Golden Gate bridge will be closed under the right wind conditions. Your panels on the other hand have a large cross section and relative little structure.

You may not and I certainly hope you never have a problem with the structure.

Photowhit · December 2012

Re: Close to putting up panels and thinking about hanging an extra set of panels...

BB. wrote: »

... unbraced 4x4 structures for side loading and worry about lifting forces (4x4 direct in soil?)....

Well I asked, I guess you don't see the bracing. The posts are in concrete at the base, I even put some SS screws in the 4x4 so once it shrinks it will still have some attachment to the concrete, though I've removed posts after 12 years and they didn't put free of the concrete.

BB. · December 2012

Re: Close to putting up panels and thinking about hanging an extra set of panels...

Glad to hear the posts are in concrete with screws to help prevent pullout (I guessed I confused that with another person's post about direct in dirt posts).

The bracing in the first picture would still worry me. That type of bracing works well in tension but less well in compression (you can pull on a straw and not tear it apart, but if you push on a straw--it is pretty strong until it gets pushed a bit off center, then collapses).

I am not saying too much about the bracing and shear walls and what is "enough" bracing, because I know I am well out of my depth here. I would be worried if 4 vertical posts are enough.

You might see if you can find a structural (or civil) engineer in your area that could do the calculations and make some suggestions. It may be a few hundred dollars well spent.

-Bill

mtdoc · December 2012

Re: Close to putting up panels and thinking about hanging an extra set of panels...

Photowhit wrote: »

The thing I worry about, is having put the 4x4's directly in the ground, more than anything else. I really should have put concrete peers in the ground and attached the 4x4's above the ground. I don't trust the 'new' pressure treating under ground. I did use the ground contact 4x4's and they are heavily salted, but this is what I worry most about

Bill, I think this quote was what you may have read - as did I - and thought there was no concrete in the ground.

Photowit - sounds like maybe you have the posts set in concrete footers that don't extend above grade??

As I stated previously and others have also stated - the wind getting behind and under the array could be a concern depending on how strong of winds you get at your location. I'm no engineer either but it seems to me that wind coming from behind and under the array will not be shed easily -as would wind coming frontside onto the array. The forces in this case would be very large. I considered building a similar ground mount but ended up building a shed instead because of the same concerns. My solution to such things is to just overbuild it (instead of paying an engineer to tell me the minimum structure needed).

Bill's idea of adding a plywood shell around the back and sides would allow wind to be shed without getting caught up under your large PV sail! It could also be done in a way to give you a nice out of the weather storage area. It would also gusset the frame and provide more strength to the structure.

Maybe it's unnecessary - especially if you never get high winds there - but if you do, the consequences could be catastrophic ....

Photowhit · December 2012

Re: Close to putting up panels and thinking about hanging an extra set of panels...

I'll take another photo from the front, I have pretty good forest behind the array.

Using for storage will be done regaurdless, but there is @3/8ths inch around all the panels, to help keep thermal gain down, so anything under will get wet.

I still have no idea where you want gussets, these are large boards with lots of purchase, only place even practical would be at the top of the tall 4x4's. I could easily make the 2/3rds brace from the short to tall 4x4's into an 'I' beam. If I get much/any movement out of the array it will break the binding board between the back 2 braces between the 2 tall 4x4's.

FWIW - we had a 20 mph wind with gusts to @30 while I was working on it, but only 3 panels high. We'll get 60 mph straight line winds, once in a while, and if I was setting this up with no trees around I would think more bracing was in order. I've had a small array setup where I was working on an 'A' frame that was flipped over, and I've owned a sea worthy sail boat, so wind, wind loads and wind shadows are all familiar concepts for me.

mtdoc · December 2012

Re: Close to putting up panels and thinking about hanging an extra set of panels...

Good to know you've thought about the wind issues. I live on a small lake in a valley below a mountain ridge named "Hurricaine Ridge" - for a reason. We get at least a couple of storms a year with large swirling, gusting winds around our lake. Despite 200+ foot tall trees all around I've seen neighbor's lose shed roofs, etc.

As far as gussets what I was referring to is probably more accurately called a gusset plate. Though in wood frame construction it is typically plywood "gusset plates" that are used to brace corners - especially of trusses.

If you put triangular plywood sheathing on the 2 sides of your frame and plywood across the back of the frame, in addition to blocking wind from getting under some of the panels, the plywood would also act as large gusset plates to strengthen and stiffen up the framing.

Anywhoo - just ideas. Maybe unnecessary?

Photowhit · December 2012

Re: Close to putting up panels and thinking about hanging an extra set of panels...

Photo fron directly in front of array. A little too close didn't want to get my burn pipe in the photo...

Attachment not found.

westbranch · December 2012

Re: Close to putting up panels and thinking about hanging an extra set of panels...

Photowit, re gusseting or cross bracing: the principle is to create a triangle to add maximum strength to any corner in your structure.

for example, the last picture, in the lower right corner a 2x4 brace, with 3 screws in each end (placed in a triangle like shape) will strengthen that face of that corner. One more brace is needed on the front to back side as well to strengthen that side as well. you could even place a horizontal brace from the front facing 2x6(?) to the side one and make it 'like a rock', sorry Chevy

edit, you should have at least 2 bolts in each 2x6 to post connection for strength/rigidity too...

niel · December 2012

Re: Close to putting up panels and thinking about hanging an extra set of panels...

you guys even have me confused as to what you are referring to that needs reinforcement. he has a lower brace from front to back and he has cross bracing between the back posts. the plywood would be quite an undertaking to just block some winds and the blocking would stress the structure as a whole rather than on the pvs themselves and would need to be totally enclosed on the sides too in order to block off winds from hitting the pvs from behind. matters not as winds can push from the front of them too making rear wind protections moot.

anyway, the only points i can see reinforcing would be from the rear of the back posts to the ground behind the whole structure making the framework look more like an A rather than a right triangle. i don't think it necessary to go to the top of the posts either as you can go up most of the way, 3/4s, 2/3rds, or even half way and would help stop forward or rearward strains. having reinforcement off of the sides of the rear posts is an option too, but one that i don't think will be necessary as winds could then pass through the structure unimpeded unless the plywood is implemented on the side giving it wind resistance.

westbranch · December 2012

Re: Close to putting up panels and thinking about hanging an extra set of panels...

Niel, what I was getting at is that even a minor amount of movement is bad

and indicates a weak point.
A few little things (ie 3 screws rather than 2) can make a big difference 8) that will keep the array standing vs on the ground. Mostly, making/including a few key, or many, triangular braces in the structure is all that is needed, depends on the size and shape.

Photowhit · December 2012

Re: Close to putting up panels and thinking about hanging an extra set of panels...

westbranch wrote: »

Photowit, re gusseting or cross bracing: the principle is to create a triangle to add maximum strength to any corner in your structure.

I'm not sure you've not seen the triangles? The back is basicly a box with an 'X' corner to corner, yes I did tie the cross boards together, heck it's one of those puzzles for kids, how may triangles are there?

On the sides there is a board that establishes level, which will remain, true 5/4 x 5 1/2", and a second that travels @2/3rds the way to the upper mount, and the lower and upper mount themselves, which are very firm, screws to 2x4s broads side to broad side, with the 2x4 spanning the 2 2x8's with 3 screws in each, which also gives the 2 2x8's 80% of the strength of a paired 2x8s which can cantilever over 6' with a dynamic load (imagine a cantilevered porch)

westbranch wrote: »

for example, the last picture, in the lower right corner a 2x4 brace, with 3 screws in each end (placed in a triangle like shape) will strengthen that face of that corner. One more brace is needed on the front to back side as well to strengthen that side as well. you could even place a horizontal brace from the front facing 2x6(?) to the side one and make it 'like a rock', sorry Chevy

There may be a false impression do to the size of the structure, just above the panels mounted to the 4x4's are 2 2x8x20' boards with the back one 2" higher than the front one, they have 6 drilled and screwed #10 3 1/2 SS wood screws, not 6" below that is the established level board (which will remain) which has another 4 drilled and screwed, below ground is 30+ inches of 4x4, of the 30" of 4x4 above ground, and of the near 6' of 4x4 only 18"- 2 feet don't have something establishing it's place in the world, The other front may have less than a foot.

I could box the 5/4 x 5 1/2 board running to 2/3rds the height, but that might be over kill(it would be stronger than the 4x4), I said else where I could make it an 'I' beam, but that would create drainage problems. I will be 'hanging' my power center from the 4x4 near the house along the slanted side, about 4x5', so you get a partial wall...lol

westbranch wrote: »

edit, you should have at least 2 bolts in each 2x6 to post connection for strength/rigidity too...

I'm content with the 4 screws, the 2x8's will get a single SS 1/2" bolt once I get all the pieces, 1/2" x 10" drill bit being the trick, I hear Harbor Frieght has a cheap set, we'll check it out. (them bolts ain't cheap!)

westbranch · December 2012

Re: Close to putting up panels and thinking about hanging an extra set of panels...

sounds like you have it well together. Too bad you can't use galvanized steel (bolts) with those treated materials, its a lot cheaper.

Close to putting up panels and thinking about hanging an extra set of panels...

Comments

Categories