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I'm working to finish up my DIY ground-mount solar project, and I need some advice for one of the final connections. For reference, the project is all done with micro-inverters at the panel so we're only talking about an AC connection, and I live in Wisconsin (2017 NEC).

The array is about 40 inches from the wall where I will be mounting a weatherproof junction box to make ingress to the house. Another weatherproof box will be on one of the array posts to make the junction between the microinverter equipment and whatever conduit setup I end up using here. The only possibly complicating factor is that the gas meter is in the general area, and occasionally the gas man is likely to need to walk back there and check on it (during construction I was careful to keep a path there accessible, and make sure that the array structure is more than 36 inches from the meter in any direction).

While I know that it would be compliant to just do schedule 80 PVC conduit buried 18 inches deep to make this connection, the ground in this area is awful to dig and the concrete I poured to anchor the 4x4 posts for the array further complicate the routing of underground conduit.

Would it be acceptable to just run schedule 80 conduit across the gap above ground, as long as it was plainly visible and supported on either side? If that's the case would it be better to mount it right along the ground itself, or 6 inches up etc?

Initially I was going to use LNFC (waterproof flexible PVC), in much the same way the HVAC guys always do for AC condensers. This would be by far the simplest solution, but after more research I think it would fail inspection because LNFC doesn't provide protection against physical damage (not sure how the HVAC guys get away with it though).

This picture captures the situation. I highlighted the most direct route (that potentially interferes with the path to the gas meter) in red, but also an alternate path using more conduit in orange that would ever be in anyone's way as there is no walking access to the far side.

solar wiring area

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    I think the HVAC guys benefit from reasonable interpretation of protection from physical damage. It's completely subjective. If you have a compressor 24 inches from a wall, and all the plumbing and electrics running to it above ground, the inspector COULD decide that people, lawn mowers, and larger animals will walk around and not behind the compressor. The inspector could also demand that homeowners all bury everything ... but I haven't seen that. I have never seen a flexible conduit run 40 inches perpendicular to a building. I think you're stretching the HVAC analogy.
    – jay613
    Oct 4, 2023 at 19:35
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    I am not an expert and not familiar with the NEC. I find it hard to imagine it would prohibit running conduit above ground for two feet, in an area that doesn't get foot traffic (and isn't meant to.) I also cannot believe a gas man couldn't manage to step over a conduit safely. Commercial/industrial work areas (like commercial building roofs) have way more hazards to work around, and somehow those regularly get serviced safely. Oct 4, 2023 at 19:39
  • You can get around the NEC's burial depth if you embed the conduit in a slab.
    – popham
    Oct 4, 2023 at 23:05
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    Liquidtight Flexible Metal Conduit - That's how AC guys get away with PVC; there's metal inside LFMC. - Whatever you do, don't have to be screwing stuff to stucco.
    – Mazura
    Oct 5, 2023 at 0:15
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    It needs to be safe not only for the intended use, but also for emergency access and for people who do not follow or understand your intentions, including children. Unless you completely block off that path on the end, it will be used as a path -- and you don't want to block off that path if there is any scenario where you might want to use it as an emergency exit, or the fire department would like to use it to get water to the other side of the house. Oct 5, 2023 at 5:14

3 Answers 3

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If it's less than or equal to 600V - With very little digging, (not quite none, unless you build the soil up around it, I guess) you can take advantage of conditions specified in Table 300.5 permitting conduit (RMC or PVC) protected by 4 inch thick concrete cover that extends 6" beyond the installation (side to side) to be buried 4" deep (i.e. top level with the bottom of the 4" thick slab.)

That should be a very manageable pour using bagged mix for 40" x 4" x (12"+ the outside diameter of the conduit.) About 1.5 cubic feet for 16" wide, which is probably overkill. 1.3 cubic feet for 14" wide. 5 bags (40 lb) or less (depends on the size of the bag, too - the 80 pound ones make twice as much per bag, of course, and they have 50 and 60 and 90 lb sizes as well.)

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Check with your local code authority but raising it above head height would be acceptable. I believe that would be in the 10' or 3 meter range. Be sure to recheck your wire size etc.

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I think the above-ground idea would be a tripping and suing hazard, and not up to NEC, though I can't quote the code.

If you built a wall along one of those marked paths, essentially cul-de-sac-ing the area behind the panel array, you could run conduit along the wall.

I understand that metal conduit can be 6" underground instead of 18 or 24. Less digging, and a built-in ground if desired.

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  • Above ground would probably need covering anyway. Maybe 3 or 4 inches of cement/permanent covering if digging not possible.
    – crip659
    Oct 4, 2023 at 19:20
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    Perhaps the "wall" could be two or three strut channels crossing the path, one of which serves as both support and physical protection for the conduit. Put them on the far side of the gas meter. I think the interpretation of protection from physical damage is very much up to your inspector ... can you ask them?
    – jay613
    Oct 4, 2023 at 19:31
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    With a little hindsight ... the concrete pad suggested in another answer seems like a better result for less effort and a lot less money than a strut-channel crossing.
    – jay613
    Oct 5, 2023 at 15:02

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