diy solar

diy solar

Mounting panels with unistrut

I typically use like hardware. Stainless steel/stainless steel. Zinc/zinc. But I'm not a purist. If it has to be done I'll use whatever hardware is on hand and slap a light coat of anti-seize (whatever flavor I have on hand or find first in the cabinet).
I don't think Stainless is a very good idea for most things.
Where I work all the young electricians like to use it but I prefer galvanized grade 5 bolt and galvanized hardware and strut.

Then it all rusts at the same speed without surprises.

I have seen 1/2 SS bolts mixed with common nuts and in a matter of just a few years the nuts are gone
Also stainless seems to have more issues with snapping in shear loads.
Grade 5 bolts more often bend than snap.

All bolts need to be the same grade as well to reduce th3e possibility of things loosening up

There are fibre glass unistruts made for special application where corrosion materials effect even stainless

This was how we made racks for panels in the old days.
I still like this product and its great to build a frame from with plenty of bracing, then you can bolt strut or anything else on you like.
but its time consuming and the young electricians do not like it

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There is a story where I work about the chairman of the board that was infatuated with the alloy Monel.
Its a mix of copper and nickel ( same ratio the ore comes out of the ground at Creighton ) and resembles gold, it never rusts...
It was named after him so the story goes..
He has a very expensive yacht built and had all the nice decorative touches and hardware made out of Monel to make his boat pop!
Legend has it when the boat was put in the salt water in Jersey it began to corrode so fast you could see it happen and the yacht was scraped because the corrosion issues could not be corrected.
 
Stainless is definitely not as strong as other materials. Whenever I use a stainless bolt, the washer(s) and nut are too. That often necessitates a run to the hardware store. I may have the right parts in my 1/4" bin, but going to the hardware store and sourcing it from there ensures that everything is stainless rather than a mix. It would be nice to partition my 1/4" bin into stainless and not-stainless, but I don't have that much storage space nor the motivation to do so.
 
Looking at that galvanic chart it looks like I should isolate the aluminum from those stainless fasteners. I'll try some of the same galvanic spray I've been using to cover sawlines in the struts.
 
Done 'far too many' marine installs on panels on ocean going boats, and I can say with certainty that panel mounts are an issue wherever they are exposed to sea spray...
My personal favourite installation method is to use rubber strips to separate the panel from the 'usually' stainless frame (often it is a rear mounted rail frame 'arch' over the stern here)- standard rubber strips are perfect, and use stainless mounting hardware ie bolts, fitted with nylon 'tophat' washers fitted to the panels frames with stainless washers on top of the 'tophat' washers...
If you haven't heard of these washers, they are commonly available in a variety of sizes (those used to dealing with the older electronics will recognise them immediately, as they were often used to mounting the larger TO series transistors where they had to be electrically isolated from the hardware)- these are also available in much larger sizes up to a M12 bolt!!!
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This way, only similar metals are in contact and the galvanic reactions are minimised...
In the case of the panels mounted on the boats arches, the arch has stainless bars welded in with appropriately drilled holes to fit the panels concerned, with the top of those bars fitted with a 'rubber' strap/weatherseal with adhesive backing, the panels are fitted on top of that, and each bolt uses the panels mounting hole with a stainless hex head bolt, with a suitably size S/S flat washer under it (load spread), then the tophat washer sized to fit the bolt and panel mount hole that separates the panel frame from the mounting hardware- under the bar can be the usual S/S washer/lock washer/nut as usual...

Haven't found any other method that doesn't have longterm corrosion issues (and in a marine environment, it really doesn't take that long for evidence of it to start appearing...) I have seen the wire clamps used for making the 'S/S wire handrails' wires used standard 'gal' wireclamps at the ends instead of stainless crimp ones and within a year they were almost completely eaten away...
IE instead of using the proper stainless tube 'crimp' fittings like this (readily available, but require you buying a set of 'crimpers' for them)
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They used the standard 'hardware store' ubolts with wire clamp' fitted with two nuts often used for guywires and the like for TV masts etc
Bad mistake...
 
For fasteners of all types and virtually anything else for real hands-on projects check McMaster-Carr online. They have massive inventory, great service, and instant shipping from at least 3 regional US locations. They can be beat on price sometimes, but nobody beats their service or inventory. I have been using them for 50 years. www.mcmaster.com
RE: Stainless steel fasteners. I have found that for all but the most critical applications that 18-8 is totally adequate and cheaper than 304 & 316. That said, all stainless threads are prone to galling, the 100% fix is to use silicon bronze nuts. No gall, no corrosion, no problems, no nothing except initial discoloring.
 
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That is a bit confusing. Most cells purchased come with stainless steel hardware. Mine did. No issues, but I haven't tried to disassemble it either.
Yea you won't generally
even steel and aluminum will corrode if you have a strong enough electrolyte present.
Aircraft will use stainless steel and aluminum as well, just matters the type of place you're parking it. Can't park that system on a beach constantly, for example.

Put a nut between the stainless steel and aluminum should be fine in most cases for as long as any of the metal would last.

I have big stainless bolts since they're great, aluminum brackets, zinc/steel spring nuts going into zinc/steel unistrut


(if you get the ones I linked you have to drill a slightly bigger hole in the aluminum brackets for the bigger bolt)
If anyone can find my bracket style in stainless steel or even galvanized steel let me know I can't find them I'd prefer not to use stinky aluminum at all


If I was by a beach I'd probably get all stainless..
 
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Looking at that galvanic chart it looks like I should isolate the aluminum from those stainless fasteners. I'll try some of the same galvanic spray I've been using to cover sawlines in the struts.
Well its not ideal...

If I recall some boat manufactures used to put stainless 304 bolts directly o the skin of aluminum hulls if they were fresh water but boats made for salt water had nylon insulators.

Canadian military had a specification that allowed Aluminum, lead stailness steel, Cadmium, zink, and a few others I can no longer remember but these were deemed OK....
NAVY was way more picky Copper on steel or stainless on steel, what zink and Magnesium alloys to use as could be used for anodes in fresh and salt water...
Maybe we have a navy man here who is more current than me???
I think 304 bolts are OK on stainless
 
I'm in a nice dry desert with 10% humidity. Not too many beaches nearby, unless you like the smell of brine shrimp and flies. Maybe some nylon or teflon washers would be OK on those bracket bolts.
 
I'm in a nice dry desert with 10% humidity. Not too many beaches nearby, unless you like the smell of brine shrimp and flies. Maybe some nylon or teflon washers would be OK on those bracket bolts.

I would be concerned if your near salt water spray.
But I think your fine, if it bothers you get some insulation nylon washers
 
Has anyone used unistrut to vertically mount panels? I'm going to mount panels on the wall of our barn, I'm thinking of running horizontal unistrut and have the bottom of the panel rest on the unistrut like a shelf rather than just relying on clamps to hold the weight. I'd make a few contact points out of insulating material to prevent the aluminum frame from touching the unistrut.
 
Use the correct hardware as recommended by the manufacture

But yes it’s probably fine to mount on horizontal strut if done to manufacturer specifications
 
Has anyone used unistrut to vertically mount panels? I'm going to mount panels on the wall of our barn, I'm thinking of running horizontal unistrut and have the bottom of the panel rest on the unistrut like a shelf rather than just relying on clamps to hold the weight. I'd make a few contact points out of insulating material to prevent the aluminum frame from touching the unistrut.

If you read enough installation instructions involving unistrut, you'll find that the connection to the unistrut (of panel laying on the strut) may not be enough for grounding and some of the brackets used to hold the panel to the unistrut have prongs on them to pierce the anodize layer on the panel.
 
If you read enough installation instructions involving unistrut, you'll find that the connection to the unistrut (of panel laying on the strut) may not be enough for grounding and some of the brackets used to hold the panel to the unistrut have prongs on them to pierce the anodize layer on the panel.
I would use a WEEB to clamp the panel in place, but I was thinking it would be easier/better to let the weight of the panel sit on the unistrut rather than bearing the weight on the clamp itself. Maybe I'm over thinking this. The instructions say that the clamping diagrams apply to both horizontal and vertical installations, so maybe I should just clamp it like it was tilted on a ground mount system. I'm going to mount it on the wall behind the existing array:
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I'm thinking of running horizontal unistrut and have the bottom of the panel rest on the unistrut like a shelf rather than just relying on clamps to hold the weight.
Like this you mean?
 
Like this you mean?

That's a good solution.
 
Like this you mean?
Thanks, I like the hanger he made to carry the weight. Lots of good ideas there.
 
Won't shading from the existing array be an issue? :unsure:
No, surprisingly in the winter the shadow from the top of the array just touches the ground in front of the barn wall. I'd like to say I planned it that way but at the time I had no idea I would add more panels. I picked that distance to easily allow the machine I mow with to fit behind the array. Every once in awhile a blind squirrel finds a nut.
 
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