Can I use thhn wire for ground/earth and bury it?
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TM48
Solar Wizard
It is not rated for direct burial.
I know that but it would only be used as earth/ground, they use bare copper and direct bury it when used as ground. Does anyone know for sure if it would fail an inspection?
wpns
Solar Joules are catch and release
It works just fine, doesn’t really matter what the insulation on a buried ground wire is. Only your AHJ would know for sure if it’ll pass inspection.
timselectric
If I can do it, you can do it.
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No, it would not pass an inspection.
Assuming that your inspector isn't completely useless. (Some are)
Assuming that your inspector isn't completely useless. (Some are)
wpns
Solar Joules are catch and release
Weird, what’s the (electrical) reason for that?
zanydroid
Solar Wizard
Yes (appropriately sized), which depends on if it's EGC or GEC.
This doesn't really come up much in DIY though. Since we don't really recommend supplemental ground rods, and people only bury new ground rods every time they make a new structure.
zanydroid
Solar Wizard
Probably a physical damage reason.
I believe you need an explicit NEC exception to run bare EGC outside of a wiring method. There are such exemptions for under solar array and retrofit EGC for old circuits without ground.
Was thinking of when a ground is run to the main structure ground rods. Not supplemental. I know there are depth considerations for different conduits but was curious.
timselectric
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It can be directly buried for the ground rod. (GEC)
Not for circuit grounding. (EGC)
timselectric
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Not rated for direct burial.
But does it matter since it is just a ground/earth though? I am running PV wires from a solar array, using direct burial wire for the array, I wanted to use the thhn that is grounded to the array back to the solar shed where all the grounds run to and gets hooked to a grounding bar that the rest of the system grounds too.
timselectric
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It depends on its purpose.
If it's an EGC, it's purpose is electrical safety, and must be protected from physical damage.
A GEC is usually very short, and less likely to be damaged. But even then, it should be protected if it is located in a place where it's likely to be damaged.
timselectric
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You are mixing terms.
The EGC for the solar array, has nothing to do with earth. Other than the fact that the earth is also connected to the grounding system.
The grounding system should only connect with earth at one location. This is usually at the same place as the N/G bond, but not always.
Q-Dog
¯\_(ツ)_/¯
Stranded wire exposed to moisture will corrode much faster than a solid wire of the same size. If you are going to bury it, the jacket has to be rated for direct burial.
wpns
Solar Joules are catch and release
Is 10AWG big enough? Go with the THHN and put it in flexible conduit.
my plans call for 10 gauge ground to each array.
timselectric
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That would depend on its size. If smaller than #4 AWG, it can not be re identified as ground. If #4 or larger, it can.
My stamped engineered plans show 10 gauge grounds to each array.
timselectric
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Depending on what your inspector will be okay with, you might be able to get away with spray painting the ends completely green, where they can be seen.
My local inspectors would be fine with this. But yours may not.
zanydroid
Solar Wizard
Not sure why you would have that much direct burial individual circuit (current carrying) conductors sitting around. I'd take a pause before buying stuff. I'm not sure direct bury individual PV conductors are recommended/allowed, over using 10/2 USE cable or something. By default I assume things need to be in a multi-conductor wiring method, unless someone gives me a code citation excusing running conductors separately. There probably is a PV direct burial exemption, since they sell it. But just because I see it in a catalog, doesn't mean I understand the conditions of use.
Also your wiring callouts (3) are mislabeled as low voltage 48V, it's probably carrying 300 VDC
Yeah i noticed that too, the 48v is for the batteries, each array is about 350v.
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