unistrut frame for ground mount solar array

[alterego]

Has anyone used unistrut for a solar array frame system. Rather Than a solar frame system.

[peakbagger]

Yes I have built two arrays using unistrut. The biggest issue is that standard unistrut is generally galvanized, therefore if you are in corrosive environment you have to isolate the contact point on the panel from the strut. I made washers that I could slide in to isolate one array while the other array has shown no deterioration but I am in low corrosive area. Most strut hardware is galvanized, I strongly encourage you to use all stainless steel fasterners.

[alterego]

strut nuts

Yes I have built two arrays using unistrut. The biggest issue is that standard unistrut is generally galvanized, therefore if you are in corrosive environment you have to isolate the contact point on the panel from the strut. I made washers that I could slide in to isolate one array while the other array has shown no deterioration but I am in low corrosive area. Most strut hardware is galvanized, I strongly encourage you to use all stainless steel fasterners.

Did you use spring loaded strut nuts and large flat washers? I was also wondering about rubber washers under the flats.

The brackets that are sold on the Internet or from most manufacturer are 9 or 10 each. It seams crazy expensive. Let alone the cost of the solar rails. And they are built like strut. It seams that you could build the same for less than half.

[peakbagger]

I use strut nuts without springs and then short stainless steel bolts with lock washers slid through the solar panel frame. Its a PITA to screw in the nuts as it tight in there and you have to use an open end wrench and only get about 120 degrees of rotation. The reason I dont use springs is I line up all four bolts and strut nuts on the panel frame and then set the panel in place on the rail. As the long as the bolts aren't tight, the strut nut can be rotated to engage the unistrut. I bought a sheet of thin HPDE and cut squares with a pair of scissors and then cut a slot from the edge to the center. I then can slide them between the panel and strut and then tighten the bolts.

I don't have a lot of options to buy unistrut locally as the electrical supply house charge full retail for walk ins. I buy mine at Home depot and buy spring nuts and just cut off the spring

An important thing with standard strut is that you can only have certain span. The strut companies issue design guides that are very helpful. In some cases you can special order double and triple strut which has a much larger span and load rating.

[alterego]

dbl strut

I use strut nuts without springs and then short stainless steel bolts with lock washers slid through the solar panel frame. Its a PITA to screw in the nuts as it tight in there and you have to use an open end wrench and only get about 120 degrees of rotation. The reason I dont use springs is I line up all four bolts and strut nuts on the panel frame and then set the panel in place on the rail. As the long as the bolts aren't tight, the strut nut can be rotated to engage the unistrut. I bought a sheet of thin HPDE and cut squares with a pair of scissors and then cut a slot from the edge to the center. I then can slide them between the panel and strut and then tighten the bolts.

I don't have a lot of options to buy unistrut locally as the electrical supply house charge full retail for walk ins. I buy mine at Home depot and buy spring nuts and just cut off the spring

An important thing with standard strut is that you can only have certain span. The strut companies issue design guides that are very helpful. In some cases you can special order double and triple strut which has a much larger span and load rating.

Through work I can get double strut in 20 foot lengths. This will get me a span wide enough for 6 panels in portrait. I would like to have a minimum of 18 60 cell panels. So 6 wide and 3 high.

[peakbagger]

Without looking it up, I would expect double strut will probably cover you. One reminder is that you need to put in some diagonal braces so the array frame doesn't rack. If you need stainless fasteners, Hamiltons Marine in Maine is a good source. Its heck of lot cheaper to buy a box then to buy them at hardware store or home depot. I also recommend getting some neverseeze as stainless does like to gall.

[FishGun]

I have also built 2 arrays with strut. Single-pole pic attached:

2033.jpg

I was also worried about corrosion and isolated 2 of the mounts with rubber tape/washers. Then having talked with a couple installers in my area found that they don't isolate at all...alum frame right to galv. Just over a year in so we'll see.

Ditto on the PITA with strut nuts and slow assy. But it's not too bad. Pro's wouldn't want to assemble this way every day...

[peakbagger]

I have a 10 year old system that has little or no evidence of corrosion between the frame and the panel. There is corrosion on the unistrut where it butts up against red cedar clapboard.. I am away from coast and its a low corrosion area. I do have a strut that runs horizontally that acts like a lip at the base of the rack and is in contact with the base of the panels, the strut appears to have lost some surface coating which is an indication that there is some sacrificial activity. I bought some surplus panels from a traffic warning sign application and there was obvious corrosion where the panels were mounted to the frame. This would be salt spray and highly corrosive. I also think different panels have different levels of corrosion protection on the frame and some are sold to confirm to specific specification for corrosion. My poly washers on my pole mount array might have cost $15 for the material so I used it. My plan is for the array to be up for a long time and if a few extra minutes makes them last longer I will do it. For a short term application I may not. Same theory as Stainless, I reconfigured an array after 5 years of the use, all the stainless came off easy but in some spots I had uses zinc plated and they came off hard.

[alterego]

I have also built 2 arrays with strut. Single-pole pic attached:

[ATTACH=CONFIG]5955[/ATTACH]

I was also worried about corrosion and isolated 2 of the mounts with rubber tape/washers. Then having talked with a couple installers in my area found that they don't isolate at all...alum frame right to galv. Just over a year in so we'll see.

Ditto on the PITA with strut nuts and slow assy. But it's not too bad. Pro's wouldn't want to assemble this way every day...

I am sorry I did not come and see the pics of the strut frames you posted earlier.
I can not tell from the pic. Do they have the ability to rotate and change angle. What did you do for the angle adjustable nature if any?

[solarfrank]

We use it in the past but now Irondige has a ground mount system for 2" and 3" pipes and for rails you can have span of 12 ft and between, and 3-5 modules on landscape. They have a nice tool only to design your array and you will receive all the details .

[solarix]

I buy standard structural aluminum shapes from a regular aluminum supplier (free shipping) and construct mounting systems of our own design. No corrosion, no painting, easy to work with. Our crazy, strict building department makes us get an engineering analysis on it (those guys with their new wind loading software go way overboard too) as it is not a "manufactured" system. But we still save a ton over buying a "solar" mounting system. Two thumbs up for the Ironridge grounding clamps though - and also for something called a Gator clamp.

[FishGun]

I am sorry I did not come and see the pics of the strut frames you posted earlier.
I can not tell from the pic. Do they have the ability to rotate and change angle. What did you do for the angle adjustable nature if any?

Yes they rotate (azimuth E to W) but elevation is at a fixed angle of 30deg. Couldn't come-up with a cheap/strong enough elev design that I liked.