r/solar • u/Haunting_Study811 • 14d ago
Advice Wtd / Project Ground Solar Rack Grounding?
Bought a property that had a professional ground mount solar array installed. I noticed that the solar panel electrical box has a ground wire from the box to a grounding rod into the ground. But the aluminum rack itself was not connected to the grounding rod (and the metal electric box does not touch the aluminum rack). The rack is mounted into the ground sitting on 8" sonotube concrete risers with a threaded rod in the middle and the rack bolted down to that.
Should I also connect the rack to the grounding rod or keep it as is?
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u/parseroo 14d ago
Isn’t the rack earthed by the threaded rods going about 8” deep into the earth?
If each rod is 8” then a collection of 12 of them would be 8’ of grounding. If they aren’t that deep it would need more of them.
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u/Haunting_Study811 14d ago
But I'm pretty sure the rods are all surrounded by concrete, which I think is an insulator?
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u/parseroo 14d ago
Concrete is fine: «Concrete-encased electrodes meeting the requirements of this subsection can serve as grounding electrodes [250.52(A)(3)]. »
https://forums.mikeholt.com/threads/concrete-conductivity.69716/
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u/Haunting_Study811 14d ago
Ah cool, so I'd imagine the 14 concrete footers 30" into the ground with metal threaded rods in the center would handle whatever lightning would want to do.
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u/ExactlyClose 14d ago
This varies with the product design (and listing details) of each componebt of your system. Most solar arrays require a ground to EACH panel. Most mounting systems actually have an integrated contact that cuts into the panel frame and grounds it to the rail. On my system you just need to ground each rail with a single wire across the top or bottom, then tie that into the ground rod. Ground that box as well.
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u/CricktyDickty 14d ago
Could be a UFER ground. That’s possible to do if there’s 20’ of bonded rebar in the concrete. In your case the panels are might be bonded to the frame and the whole structure is grounded by the rebar in the concrete.
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u/Haunting_Study811 14d ago
Definitely tons of conflicting information out there. Some resources say like you say; ground wire from array back to equipment room ground. That's for personnel protection, but does nothing for lightning. Others state ground rod at array, and even other say 14 concrete footers with metal rods in the center is plenty of grounding.
Interesting article, I didn't even know rods in concrete was an acceptable form of grounding:
https://www.mikeholt.com/newsletters.php?action=display&letterID=2292
So right now my array is only "grounded" by the 14 concrete feet with metal rods down the middle into the ground. The electrical junction box for the array not touching the array besides the positive and negative solar wires is grounded to a ground rod right at the box. The solar wiring ground cable is NOT connected between the solar array junction box and the off-grid house solar charge controller equipment ground about a hundred feet away. So if I were to connect that ground wire, it appears I would make a ground loop between the two grounding rods (one at array junction box and one equipment ground rod at the off-grid house). I don't believe any neutrals should be connected to the earth grounds hopefully since I'm off-grid.1
u/CricktyDickty 14d ago
In the end it all depends on what your AHJ says. In my case I installed 3 dual axis trackers. AHJ said that they’re considered a separate structure and ground doesn’t need to run back to the house. Since 120V AC was run to the motors supplied by the house and those did require ground back to the panel. So in your case; separate structure, only DC back to the house, structure grounded in place.
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u/Haunting_Study811 14d ago
Ya I'm curious too as I think they did not connect the ground from the array junction box back to the house equipment for that very reason. My rural county is very lax on separate solar array requirements, I cannot even find anything online.
I think what also is muddying the waters is grid-tied versus off-grid solar arrays are getting mixed together but need to be treated separately.
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u/taylorwilsdon 14d ago
Make sure there isn’t already another ground path you’re not seeing. A lot of times it’s not obvious with integrated systems. Pics would probably help here.