2017 NEC Subpanel (not in building)

[wwhitney]

it is in an open field and attached to a 4x4

That is a definite gray area, it requires deciding what a structure is and whether you have one. The 2017 definitions:

"Structure. That which is built or constructed, other than equipment."

"Equipment. A general term, including fittings, devices, appliances, luminaires, apparatus, machinery, and the like used as a part of, or in connection with, an electrical installation."

So is the 4x4 equipment or not? Maybe it's an "apparatus used in connection with an electrical installation." Or maybe not.

If the 4x4 is not equipment, it's a structure, and you need a GES. If it is equipment, it's not a structure (as the panel is certainly equipment), and you don't need a GES.

Further comments:

1) Maybe many GESs are actually a good idea in this context? Although if there is any earth voltage gradient, you'll end up with current flow on all the EGCs.

2) Does the article on RV parks not address this question? I haven't checked.

Cheers, Wayne

 

[Dennis Alwon]

The way I have seen it interpreted in NC is that anything other than equipment is considered a structure.

 

[wwhitney]

The way I have seen it interpreted in NC is that anything other than equipment is considered a structure.

Yes, but what is equipment? Is a wood 4x4 equipment? Are two pieces of unistrut projecting out of the ground equipment?

I meant to add that if the panel were part of a power pedestal that is intended to be installed directly into the earth as its support, and likewise the RV power outlets, then those definitely are equipment, and so there is no structure, and no GES is required.

Cheers, Wayne

 

[roger]

Yes, but what is equipment? Is a wood 4x4 equipment? Are two pieces of unistrut projecting out of the ground equipment?

I meant to add that if the panel were part of a power pedestal that is intended to be installed directly into the earth as its support, and likewise the RV power outlets, then those definitely are equipment, and so there is no structure, and no GES is required.

Cheers, Wayne

Well, the OP is all over the place so we don't know what he has, for example see posts #6, 7, & by 19 we have 150 panels

 

[Dennis Alwon]

Yes, but what is equipment? Is a wood 4x4 equipment? Are two pieces of unistrut projecting out of the ground equipment?

I meant to add that if the panel were part of a power pedestal that is intended to be installed directly into the earth as its support, and likewise the RV power outlets, then those definitely are equipment, and so there is no structure, and no GES is required.

Cheers, Wayne

Wayne you love to over think it.....LOL

Equipment. A general term, including fittings, devices, appliances,
luminaires, apparatus, machinery, and the like used as a
part of, or in connection with, an electrical installation.
(CMP-1)

 

[wwhitney]

Well, the OP is all over the place so we don't know what he has, for example see posts #6, 7, & by 19 we have 150 panels

FWIW, the 150 count includes the RV spaces. Anyway, we are good at speculating endlessly about what an OP means and can certainly keep this thread going.

Seriously though, for the RV spaces only (as opposed to the upstream panels that the OP was about), does Article 250 distinguish between (a) the first product pictured below, where the bottom is buried in the ground, and (b) the second picture below, mounted on a wood 4x4 post with some conduit running up to the enclosure?

Cheers, Wayne

 

[infinity]

IMO a post is not a structure but there shouldn't even be an element of the NEC that includes the word structure for these panels. The panel regardless of how it's mounted should have a GES. Why should a panel mounted to an outbuilding require a GES and one mounted to a piece of wood in the ground not?

 

[roger]

FWIW, the 150 count includes the RV spaces. Anyway, we are good at speculating endlessly about what an OP means and can certainly keep this thread going.

One reason a lot of threads get closed is a member changing the scenario after others have made a serious attempt at answering the question.

 

[wwhitney]

One reason a lot of threads get closed is a member changing the scenario after others have made a serious attempt at answering the question.

Well, in this case my comments/questions do bear directly on my understanding of what the OP is asking, but perhaps we'll need to await their further comment to confirm.

Cheers, Wayne

 

[Tulsa Electrician]

551.75 sums it up for me. The word building or structure for me has nothing to do with the reason for the required Grounding electrode per 250.32.
If it (rod(s) type grounding electrode) was not there is could pose a hazard to some one standing on the ground who could come in contact with the electrical equipment. The required electrode would minimize the the possible difference in touch potential between the equipment and earth. I would also not only drive two rods I would space them the further apart. Yes, NEC says no less than six foot apart however the added distance increases the paralleling efficiency. How many RV sites have the water hydrant right next to the pedestal and the ground is soaking wet from the dripping hose and a water puddle that your standing in or near plugging and unplugging the RV. Something else to think about is that water hydrant, what if it was supplied by a well pump. Many good reasons for that electrode to be there. If you go back to 551.75, I feel there was a reason they put that informational note there.
The wording of 551.75 (2014 NEC) pretty well sums it up: " All electrical equipment and installations in recreational vehicle parks shall be grounded as required by Article 250".

* Source: Soares Grounding and Bonding: "The paralleling efficiency of rods is increased by spacing them twice the length of the longest rod."

In interest of safety please install the grounding electrode.

 

[wwhitney]

551.75 sums it up for me.

Yet (2017) 551.75(B) says:

Grounding Electrode. Power outlets or recreational vehicle site supply equipment, other than those used as service equipment, shall not be required to have a grounding electrode. An auxiliary grounding electrode(s) in accordance with 250.54 shall be permitted to be installed.

Sounds like ground rods at each RV space are not required.

Cheers, Wayne

 

[Tulsa Electrician]

Thank you for pointing that out.
I went and read 2017 NEC. Looks like a Grounding electrode is not required per 2017 NEC. I do like the fact they allow auxiliary grounding electrode(s).
I also like the way they cleaned up the wording.

I do not have a copy of the 2020 NEC. Any change there?