Mounting panels with unistrut

[Brett V]

Unistrut channel nuts.

Unistrut P1006 Series Spring Nut, Channel Nut with Spring

Unistrut Channel Nuts are designed to conform to the flanges on the inside of the channel.

unistrutstore.com

mid clamps
Solar Panel Mid Clamps 1.06" - Pack of 20 https://a.co/d/8BqNvhG

end clamps
Adjustable End Clamps -Planet 4 Solar (UISolar) Pack of 20 https://a.co/d/a5B5un2

of course size quantity and thread size as needed. I used 5/16 stainless hex bolts sourced from eBay. There are a lot of suppliers with varied pricing…do a little searching to get what you need at the best price.

 

[42OhmsPA]

Here's what I used for my ground mount array. Worked great, my only complaint is the width of the mid clamps. I'd find narrower ones next time.

I picked up stainless 1/4-20 bolts from the local Amish supply store.

1/4"-20 Cone Nuts, Strut Channel Nuts with Zinc Electroplate Finish, Twirl Nuts for Use with Strut Channel (10 Pack) (1/4"-20) https://a.co/d/eHkgdPf

The included clamp nuts don't work with standard strut, that's why I bought the cone nuts above.
Solar Panel Mid Clamps 1.06 Inch Solar Panel Bracket Aluminum Solar Mid Clam with Solar Mounting Brackets 32-50 mm Panel Clamps Adjustable End Clamps Panel Clamps (56 Pieces) https://a.co/d/eK48elg

 

[Brett V]

Worked great, my only complaint is the width of the mid clamps. I'd find narrower ones next time.

I wasn't thrilled with the space either but it probably helps reduce the potential for wind lifting the mount. I wish I had your woodworking skills!

 

[42OhmsPA]

I wasn't thrilled with the space either but it probably helps reduce the potential for wind lifting the mount. I wish I had your woodworking skills!

Thanks. That's a good point about the wind.
You can get there, it's really not that difficult. Just have patience, use the square and measure 3 times cut twice.. . There are some imperfections that annoy me but I can't complain to much for working alone.
I wish my conduit bending skills were a whole lot better, they will get there over time m

 

[Hedges]

Here's what I used for my ground mount array. Worked great, my only complaint is the width of the mid clamps. I'd find narrower ones next time.

I see it has adjustable tilt.

Horizontal braces provide good compression against the wall, but little tensile strength. The anchor screws to some extent, but especially the toe nails through brackets. I've used brackets for a shelf and noticed they barely bite.

 

[42OhmsPA]

I see it has adjustable tilt.

Yea, honestly I'll probably tilt it a little steeper and leave it be, it seemed like a great idea at the time.

Horizontal braces provide good compression against the wall, but little tensile strength. The anchor screws to some extent, but especially the toe nails through brackets. I've used brackets for a shelf and noticed they barely bite.

I'm not completely following?
Are you saying it's good, bad or could be better?
I still have to add bracing between the posts. The diagonals I added to the frame are at least 1.5" into the wood. For the joist hangers I ran screws to hold the wood instead of nails to make sure they bit well. I used 3.5" tapcons into the concrete wall. (I remember ripping an old deck apart and thinking how little the joist hangers did for strength, more for support)

 

[Hedges]

Well, the posts in concrete look sturdy.
I saw that joist hanger attached to brick wall, thought it could restrain against array tilting toward wall, but not pulling away.

You may only have wind. I'm in California so think about earthquakes, 1 g in any direction, oscillatory motion. So my 2" rigid pipe uprights have diagonals in X and Y.

 

[DrewLoker]

I used 5/16 stainless hex bolts sourced from eBay.

Thanks for the replies and suggestions.

Part of my challenge was that I "committed" to 3/8" at HomeDepot when I bought 3/8" cone nuts, bolts and lock washers. But, I assumed I would be able to find 3/8" square washers and/brackets. But, most are 5/16" or 1/4".

Should I just drop down to 5/16? (I got the wrong length of bolt anyway...need 2-1/2".)

 

[Brett V]

Thanks for the replies and suggestions.

Part of my challenge was that I "committed" to 3/8" at HomeDepot when I bought 3/8" cone nuts, bolts and lock washers. But, I assumed I would be able to find 3/8" square washers and/brackets. But, most are 5/16" or 1/4".

Should I just drop down to 5/16? (I got the wrong length of bolt anyway...need 2-1/2".)

Home Depot has a pretty liberal return policy.

 

[DrewLoker]

Home Depot has a pretty liberal return policy.

Right…but I live in the country, so, can’t just pop into HD…thus the shopping on Amazon to source things. But that is one area Amazon has not been competitive. I do have an Ace Hardware in the nearby town.

But the question is of support of 3/8” vs 5/16”. I had decided to go 3/8 for the small price increase, but better specs. But of the 2pm or so items in my AZ cart, most would have to be modified one way or another…drill out holes for 3/8”, replace flange nut, etc. If I drop to 5/16”, it does simplify the seelction.

EDIT: I stuck with 3/8…and found the square washers locally.

 

[justgary]

I used some scrounged heavy gauge hat channel. Very similar to unistrut, but it let me drill and through bolt the panels directly to the strut on the brim of the hat.

 

[ricardocello]

I designed and built my own Unistrut ground mounts, it was definitely a learning experience.
Cutting strut and 2" poles, cleaning, painting, etc. is a lot of manual work compared to buying a kit.
But they are built and installed, and working well.

I did do the mechanical engineering beam loading simulations, as I really want it to survive the 109 mph winds.
I'm not a PE however, so this design is not suitable for permitting.

My requirements:
All metal must be locally available, and fit in my pickup truck.
Thus, Home Depot, Lowes, and local metal shops only.
For Unistrut accessories, I ordered directly from Unistrut Buffalo, cheapest prices I could find.
I've got bifacial panels, so these are 5' off the ground.
And I want to be able to set the tilt angle easily by just swiveling the array 4 times a year.
The 2" gold galv pipe clamps holding the panels to the cross beam are rated 800 lbs each, and there are 8 of them.

I've attached my plans below, perhaps it can give others some ideas.

 

[Hedges]

Just two vertical pipes?
Wind could bend them. I'd add a second pipe to make inverted "V". My location has earthquakes, so 3rd pipe in a different direction.

Do you also have a strut to hold array at some fixed or adjustable tilt?

 

[ricardocello]

Just two vertical pipes?
Wind could bend them. I'd add a second pipe to make inverted "V". My location has earthquakes, so 3rd pipe in a different direction.

Do you also have a strut to hold array at some fixed or adjustable tilt?

The anchors/poles are rated 3000 lbs lateral in this soil, and pullout at 2500lbs.

I am installing a third anchor connected to the bottom of the array in the center to form a triangle for stability as you suggest,
with an adjustable channel to get any angle between 45 and 10 degrees. Not installed yet, maybe this weekend.

 

[Hedges]

The anchors/poles are rated 3000 lbs lateral in this soil, and pullout at 2500lbs.

"Lateral", but that says nothing about bending moment.
I don't think height of pole figures into your equation, but it must to determine if the upright will buckle at the base and fall over. How much bending strength must Archimedes' lever have?



Form a triangle with another pole. Assume all ends are pivots with no torsional resistance. Geometry will then let you calculate lateral force and pull-out force for a given wind force (which you can probably get from a table.)

 

[Hedges]

I am installing a third anchor connected to the bottom of the array in the center to form a triangle for stability as you suggest,

Third leg to a point off the line of the other two should eliminate the bending problem.
Transfers it to the horizontal, which always has that (but distributed force, supported multiple places.)

I've poured concrete in thin metal fenceposts to make them stronger. Now can't buckle, has to stretch the metal.

Kinks are often done deliberately to facilitate bending. Prevent that and it is a stiffer, stronger structure.

 

[Sanwizard]

How are the panels attached to the unistrut ? I had planned to make up a fitting using a short piece of 90 angle but there may be other methods.

There are large square washers at home depot near where they store the Unistrut. The spring nuts work great with the washers. Use bolts from the hardware isle that fit the washers(3/8 or 1/2).
Unistrut works great for ground mount or roof mount.

 

[Hedges]

If you use 1/2" threads anywhere, I find the spring nuts' thread deformed by crimp process to retain spring. You might get the bolt in, but it seizes and can't be removed.

I chased some with a tap. When possible I buy without the spring. Plastic cone or no retainer.

 

[ricardocello]

"Lateral", but that says nothing about bending moment.
I don't think height of pole figures into your equation, but it must to determine if the upright will buckle at the base and fall over. How much bending strength must Archimedes' lever have?

View attachment 171181

Form a triangle with another pole. Assume all ends are pivots with no torsional resistance. Geometry will then let you calculate lateral force and pull-out force for a given wind force (which you can probably get from a table.)

I ran a cantilever beam calculator quickly to see what the deflection on the vertical supports would be at 3000 lbs dynamic load from 108 mph wind (30 psf) with the panels tilted 90 degrees (worst case, mine actually won't go below 45). Deflection was 6.3" per 5' pole, which means they would snap. Max deflection should be L/180 or 0.3 inches.

So the third leg is really mandatory. I'll have to do a real simulation to see what it actually buys me.
Or I can add 45 degree supports.

 

[ricardocello]

There are large square washers at home depot near where they store the Unistrut. The spring nuts work great with the washers. Use bolts from the hardware isle that fit the washers(3/8 or 1/2).
Unistrut works great for ground mount or roof mount.

stainless 5/16 and 1/4 hardware holding 5’ unistrut on sides in portrait orientation bolted directly to panel mounting holes
tape and nylon washers and painted unistrut to avoid corrosion
unistrut crossbeams with 5 hole U bracket, spring nuts(hate them), 3/8 stainless 1” hardware with washers, use anti-seize on bolts