400V dc wiring 10' over head what kind ofconduit should be used to meet code?

[khanh dam]

ground mount overhead wire wiring .jpg The picture basically shows what I am trying to do. I'd rather not dig 18" deep to satisfy code in hard clay soil and
under a 4' wide 4" deep cement slab, so I'm thinking of using metal conduit overhead.

is PVC electrical conduit fine? or does it need to be galvanized metal conduit? I know if the dc wires go inside the home it has to be metal.

I'm not a code expert and the code for solar has changes so much since my last project I was hoping people can verify this will work. thanks for the time.

[Mike90250]

Why not use "Service Entry" wires ? Maybe sleeve it with PVC labeled DC ? Ask your local code inspector what would make him happy that you can afford to do !

[khanh dam]

My local building permit inspector won't give me any advice until after they show up for an inspection typically so best to try and get it right by the book. Plus I need to submit a permit application and it would be to my benefit to have the drawings be correct before. Typically if I can give my references competently they let me have my way. If inspector asks me question and my response is I don't know then they might say it needs to be buried and I'd be stuck with that decision due to my ignorance.

https://www.ecmweb.com/code-basics/nec-rules-outside-branch-circuits-and-feeders

above says 10' or 12'


but this article says 8.5' is fine.

https://iaeimagazine.org/magazine/2015/04/14/support-of-exposed-cable-for-pv-systems-requirements-and-recommendations/

The NEC considers conductors and equipment above 8.5′ to be sufficient to be guarded against accidental contact [110.27(A)]. The 8.5′ measurement is new in the 2014 NEC for circuits above 300 volts up to 600 volts. By placing cables or equipment above 8.5′ (8′ for 300 volts and below), it may be possible to prevent damage due to accidental contact in a public area. These requirements in 110.27 are for shock protection, not for physical protection, so appropriate measures must still be taken to prevent physical damage where necessary.

[khanh dam]

I need to submit a permit with drawings first. Would be to my benefit to get it correct.

https://iaeimagazine.org/magazine/2015/04/14/support-of-exposed-cable-for-pv-systems-requirements-and-recommendations/

says 8.5 ft so I will go wtih that.

[SunEagle]

I need to submit a permit with drawings first. Would be to my benefit to get it correct.

https://iaeimagazine.org/magazine/2015/04/14/support-of-exposed-cable-for-pv-systems-requirements-and-recommendations/

says 8.5 ft so I will go wtih that.

The problem you may run into is the "length" of that over head conduit. Typically you will need to support it every 8 to 10 feet. That may be difficult unless you build some type of bridge support.

With an aerial wire you can run it a lot farther at a lower cost since you do not use a conduit but have some type of cable support or "messenger" to keep the wires from sagging.

The height of the cables will be regulated by what is passing underneath them. They need to go higher for vehicles then for humans just walking under them.

[khanh dam]

I definitely want conduit because it has a physical protection element to it. If some kit fly's their drone into it, or a ladder wacks it, etc it will be protected. It's a residential back yard only people will occassionally walk under it. Now I just have to figgure out how to attach metal conduit elbows together. I was in lowes last night and they had the long sweep elbows, but I couldn't figgure out how they are connected?

[Ampster]

I agree with SunEagle, that conduit needs to be supported along its length. The fittings are not designed to be in tension like an overhead wire would be.
I understand the inspector's reluctance to design a project. The work around may be to ask them which version of the NEC that they follow and specific interpretations regarding DC conductors. You need to read the specific code applicable to your jurisdiction first to frame the question to them.

[foo1bar]

If some kit fly's their drone into it, or a ladder wacks it, etc it will be protected. It's a residential back yard only people will occassionally walk under it. Now I just have to figgure out how to attach metal conduit elbows together.

If it were me, I'd go with either buried or the normal overhead line type setup (ie.same as what's feeding a lot of houses from the power poles)

I'd be less worried about something hitting an overhead service entrance cable setup than hitting overhead conduit. A cable will flex a bit. A conduit is IMO more likely to separate at a joint, losing structure and then you have copper wires inside of it trying to support weight (bad) - possibly leading to insulation wearing through where the conduit rubs on it. And then sparks and a fire as the conduit provides a connection to ground for the wires inside.

FWIW, I'd probably go with buried.
You can rent a ditch-witch usually.
And I don't see the slab you're concerned about - but sounds like a regular sidewalk - I'd probably do the poor-man's horizontal-bore with water to get under. Or cut out and re-do the concrete.

[Markyrocks69]

I definitely want conduit because it has a physical protection element to it. If some kit fly's their drone into it, or a ladder wacks it, etc it will be protected. It's a residential back yard only people will occassionally walk under it. Now I just have to figgure out how to attach metal conduit elbows together. I was in lowes last night and they had the long sweep elbows, but I couldn't figgure out how they are connected?

Theres 2 different kinds. 1 being a set screw type that uses a coupler with 2 screws to connect two pieces. The other type has threaded ends that then get screwed together. If you do go with conduit I'd definitely recommend the threaded type for this. I agree with what has been said by others that the conduit is a bad plan. Just string a steel cable (rated for outdoor use) I'd imagine at least 1/4" thick with tensioners on both ends and then wrap the use-2 cable around the steel cable. Also I wouldn't make it any lower than the cables servicing your house. That way if the inspector says anything you can point at those wires and say " it's ok for those wires how are these any different?". Probably not much he could say. This all does sound like a pita but either that or bury them. Metal conduit needs support (1") at least every 8 feet so youd either need to install posts or make a bridge which would probably be ridiculous. And whatever you do i would assume that the wire or conduit or any other metal in this contraption needs to be grounded. Bc I could see an inspector hitting you up for that.

[khanh dam]

the drawing is not to scale distance from home to solar panels is probably 8 to 10 feet so conduit can be secured to both structures using standard U clamps. Will probabaly buy some 1.5" conduit from Lowes so it will be much stiffer than 3/4" conduit. Will be running four 10awg thhn wires inside. The home has underground power connection.

[Markyrocks69]

the drawing is not to scale distance from home to solar panels is probably 8 to 10 feet so conduit can be secured to both structures using standard U clamps. Will probabaly buy some 1.5" conduit from Lowes so it will be much stiffer than 3/4" conduit. Will be running four 10awg thhn wires inside. The home has underground power connection.

1.5 is probably way overkill. The emt that has the treaded ends is like twice the thickness of the standard set screw type. With that in mind you probably aren't bending the type with the threads in a manual bender without a ocy acetylene torch. You had said you planned to buy elbows so that shouldsho be a problem. And I did take a quick look at the code for conduit support and it looks like 10 ft is the maximum span so I'd suggest trying to plan it out so that is exactly the distance. I suppose you probably could add like a small horizontal piece of support on one side or the other.

[Ampster]

......... Also I wouldn't make it any lower than the cables servicing your house. That way if the inspector says anything you can point at those wires and say " it's ok for those wires how are these any different?". ........

Besides the fact that the house service is underground that argument won't work because the POCOs don't have to follow the building codes. They have their own rules.

[Markyrocks69]

Besides the fact that the house service is underground that argument won't work because the POCOs don't have to follow the building codes. They have their own rules.

That may be true but I think that youd be hard pressed to refute the logic. That and the poco (I'm sure) bases their rules off of something. Its obviously a moot point bc the wire is buried. But I'm a firm believer of going above and beyond so as there is no doubt. If I thought the code was 10 ft I'd go 12, if I thought it was 12 I'd go 14. In the day and age of inspector being judge jury and executioner I'd rather be safe than sorry especially from a DIY perspective. An inspector I'd assume would give a licensed electrician more wiggle room just by the assumption that he knows what hes doing. A homeowner doing the work they may be up your behind with a microscope. Which my inspector was definitely all over me. He was even complaining about stuff that after I took a few minutes to think about what I did and why realized that he just wasn't understanding what was actually happening in the particular scenario. And I had forgotten bc it had been a minute since I actually did the work in that area.

[foo1bar]

1.5 is probably way overkill. The emt that has the treaded ends is like twice the thickness of the standard set screw type.

EMT can not be threaded.
Rigid metal conduit can be threaded.
IMC can be threaded.

And as I said before - I wouldn't put conduit in an overhead situation like described.
I'd go underground.
Both because of ease-of-satisfying code/inspector.
And because of aesthetics.
You'll have to do a bunch of digging for the array foundation anyhow since it's a ground-mount. So IMO adding an ~8' long, ~2' deep trench isn't going to be that much more.