diy solar

diy solar

Unistrut panel mounts

NMNeil

Solar Enthusiast
Joined
Mar 14, 2020
Messages
441
I'm hoping this will help others who are contemplating using UniStrut for their panels.

Not saying this is the best way, it's just how I do it.

Mine is an off grid system, or will be when it's complete, and I'm fortunate to have a roof that faces due south and at almost the perfect summer/winter compromise angle, has no shading at all and as I live in SE New Mexico the panels receive about 6 - 8 hours of usable sun every day. So the photos will be showing my half complete system, but you should get the idea.

Measuring the width of the panels; I'm using used SanTan 250W, and allowing for 1/2" between them for the hold down bolts, I came to about 39' 7"; so four 10' long struts will be perfect for my 12 panel row, plus an extra one; the reason for the extra will become clear shortly.

I use the 1.5" struts. A touch expensive at about $30 each, but they give a good airflow gap under the panels.

Starting with the extra strut and a 10" metal cutoff blade in my well worn Craftsman chop saw, I use precision guesswork and cut between the holes of the strut to get, in my case, 60 pieces. For want of a better word I'm calling them clips.
After a touch of grinding and filing of all the potential bloodletting sharp edges and a squirt of an exterior spray paint, you have these:
10.JPG20.JPG
There are many ways to find the rafters and I just tapped around until the sound changed. Lots of YouTube videos on locating the rafters so pick your own method.

Having found and marked the position of the rafters you now need to determine the distance from the top of the panel to the roof ridge.

Now decide on the location of the first and last clip for the row.

Drill the appropriate size hole for the 3/8" by 3 1/2" long lag bolts.
30.JPG
Now squeeze out a good amount of roofers mastic.
40.JPG
Clip with washer and lag bolt.
50.JPG
Screw it down to be left with this:
60.JPG
The nails are from when I replaced some shingles about 6 years ago ;)

Now before we start with the cries of "Where's the flashing?", remember I'm in New Mexico and we are lucky to get 10" of rain for the year, and it's getting less. I used my method over 5 years ago and not a single drop of rain has made its way past my roof into the attic. I did use flashing beneath the shingles on two or three places where my drill missed the rafter, but if you are in a rainy area this may not work for you, this is a "How I do it", so may not work for your climate. Be inventive.

Install the last clip for the row and run a string between the 2 to keep all the other clips aligned.
70.JPG
Add all the other clips, in my case on alternate rafters.
80.JPG
 

Attachments

  • 110.JPG
    110.JPG
    87.7 KB · Views: 25
  • 90.JPG
    90.JPG
    39 KB · Views: 21
Install the Unistrut captured nuts
90.JPG110.JPG
And bolt down the rails

120.JPG
Where the struts meet I use UniStrut plates to secure everything together. (Being magnetic is very, very handy as they don't tend to slide down the roof)
130.JPG
140.JPG
Now for the main tip for making installing the panels a lot easier and safer.

Find a predrilled hole in the panel frame and put a couple of 1 1/2" long stainless screws washers and nuts in the hole, like this.
150.JPG
These are what actually hold the panel in place, not pressure from the hold down bolts, which just stop the panels lifting. This means you don't have to pretend you're Arnie when you tighten the bolts down to such an extent that you distort the frames and possibly crack one of the cells.

You can now put the panel in place and let the screws stop against the strut. No more trying to put the hold down bolts into panels that are trying to slide down the rails and into your front yard. Drop the small bolts over the struts and the panel stays there, plus all the panels will automatically align with each other.
160.JPG
Get the second panel in place and put a hold down bolt with large square and spring washer in place. For the end panels just lay one of the clips on its side like so:
180.JPG
Rinse and repeat, and you have a very strong and fairly inexpensive panel mount.
170.JPG
 
That is about the same cost as Ironridge racking at $3.20 per foot. I love Unistrut for many purposes. It is more rigid than Ironridge so for a ground mount i would use it. I used Ironridge for a patio cover since I needed the engineering drawings that Ironridge provided.
 
Last edited:
Not sure about your pricing comparison.
Unistrut for a 40' string = 8 * 10' struts, plus the extra for the clips; 9 * $30 = $270.
Add $100 for lag screws, mastic and other odds and ends gives a total of $370 or $9.25 a foot :confused:
 
Unistrut is very user friendly. In some places, it is also known as "Globe Strut" Super-Strut" and so-on.
Hot-Dip Galvanized, Cold-Dip, Stainless, Aluminum and Fiberglass strut can also be found.
A very wide range of fittings is available including trolleys and hinges.
Basically, an erector set for big boys.
(y)
 
Back
Top