jzampieron
Solar Enthusiast
I did use 10ga THHN for grounding my iron ridge ground mount. My AHJ just wanted to make sure I had a full grounding rod and it was well affixed. YMMV.
Can I use thhn wire for ground/earth and bury it?
- Thread starter doox00
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#6 bare copper is code when attaching any conductor to a ground rod.
I always wrote a correction notice for anything else attached to the ground rod, due to conductors being subject to physical damage.
I am not connecting to a ground rod though.
zanydroid
Solar Wizard
It Is still in a grey area people are not familiar with.
What are the motivations for going this less standard but still NEC listed wiring route? Direct bury depth would likely be the same for USE, PV, conduit
Did you get feedback from your engineer/designer?
timselectric
If I can do it, you can do it.
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Yup
You have to remove the insulation, to get a good connection. lol
I have 3 ground mounts, all are using direct bury wire (2' deep). I already have all the trenches dug (I have a mini excavator, so was easy) and the wiring for the arrays done. I was using direct bury 10 gauge for the ground wire (in the same trench as the PV wires) but ran out on the last array, so wanted to know if I could use the THHN, but I do have more of the red pv direct bury wire, so I will use that and just mark the ends green.
zanydroid
Solar Wizard
I wouldn’t cover that before it gets finaled out, if AHJ objects (since it’s not NEC compliant to relabel that). And there will always be a potential for future problems if the exposed points get inspected for future changes
It is not NEC compliant to use a different color wire as long as the ends are marked/color coded properly?
zanydroid
Solar Wizard
That was already discussed up thread by tim in #20
There is a minimum size for remarking and #10 is way too small.
Not sure if EGC is required to be remarked all the way down the wire. Probably at least all the exposed pull points and endpoints
wpns
Solar Joules are catch and release
I would never suggest this, but what about splicing the THHN into the middle of the ground wire, so you have the 'proper' ground wire showing on both ends?
I mean, I'd use conduit so as not to have to ever dig it up again, and I'm _so_ glad my ground mount array wires come in through conduit, but it's _A_ solution...
I don't plan to ever dig it up again, the ground is mostly all sand in my area and all the ground mounts are at an elevated part of the properly so the water table is much deeper than the 2'. Plus the longest run I have is like 50-60', and two of them are under 15' in length.
timselectric
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No
Not until it's #4 AWG or larger.
timselectric
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The requirement is end to end. But of course the inspector can only inspect what they can see.
timselectric
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If you have any burrowing animals in your area. They love to chew on insulation.
jzampieron
Solar Enthusiast
Table 250.66 is for "alternating current" grounding. My ground mount system is a DC coupled system with DC optimizers. There is no AC out at the ground mount.
Thus, best I can tell 250.122 applies, which means my 10 gauge THHN is code compliant b/c I have 15A fuses at my combiner box.
Either way, I'm not a code expert, just doing the reading and my ground mount did pass inspection and the AHJ specifically looked at the ground rod during the open-trench inspection. Again, YMMV.
wpns
Solar Joules are catch and release
I thought the ground mount array ground wiring was for lightning protection, but I guess it should be sized for ground fault as well.
timselectric
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Lighting protection is a completely different system.
Built above and around what you want to protect. Never connected to or through what you want to protect.
wpns
Solar Joules are catch and release
Weird, my ground-mount array has a separate ground rod for the non-current-carrying metallic bits (panel frames, rails, mounting frame, etc. Now that I think about it, there's a separate ground rod for the roof-mount non-current-carrying metallic bits too. Are both of these wrong?
On top of that they will love making new holes and tunnels in that freshly dug up tench dirt so it is even more likely they find that wiring if you have them in your area and why I put all mine in conduit.. since that is exactly what they tried to do to mine.
timselectric
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Yes, but it's acceptable (although not recommended) to have auxiliary ground rods, as long as you still connect (bond) everything back to the existing grounding system.
wpns
Solar Joules are catch and release
And if you don't, what's the (electrical) problem that occurs? My ground mount array would be hard to fix, long sad story...
timselectric
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It's not kept safe for anyone to touch. It's an electrical hazzard, waiting to happen.
We ground/bond everything, to make sure that it can never become a shock hazzard.
Zwy
Emperor Of Solar
For some reason I had moles suddenly attracted to the ground mount. PV underground wires are in conduit so I wasn't concerned. My only guess is the MT Solar mount slightly wiggles creating a squeak and this drew in the moles.
Zwy
Emperor Of Solar
Yes.
The purpose of the EGC back to N-G bond is to prevent electrical shock if a person was to touch a mount or PV frame that has become accidentally energized by alternating current.
Anything that connects to your house/building electrical system that is metallic needs to be grounded by an EGC.
This has nothing to do with lightning.
Zwy
Emperor Of Solar
50 to 60 feet would cost $35 to $45 for 3/4" PVC SCH 40 for underground and an additional $12 for the SCH 80 needed above grade. The 15 feet is a no brainer.
Penny wise and pound foolish is no way to go thru life. If that amount for conduit will break you...........
I just trenched in 240 feet of 2" SCH 40 PVC plus needed 15 feet for the SCH 80 ends. I also trenched in 130 feet of 1.5" SCH 40 and an additional 20 feet of SCH 80 for the shop system. 2 years ago I trenched in 420 feet of 1.5" from array to house.
The 2" will only contain four 10AWG AC current carrying conductors at this stage. Down the road, I might run 4/0 and the conduit will be large enough.
Plan ahead, spend the money once and wisely, you forget about what it cost yesterday when you need to pull wire again or change the system.
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