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Exposed Underground SEC


caryseidner
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If the grading would have been a little higher I never would have noticed this. I'm certain this is wrong and safety concern. Are the exposed conductors only supposed to be covered by grade, or should the conduit have been extended to a particular depth?

The conduit is supposed to be extended to the required burial depth for those conductors in that location. (300.5). From what I can see in your picture, that would be 24" deep in this case.

- Jim Katen, Oregon

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Jim,

The conductors are copper 3/0. Is the (300.5) is the NEC?

Yes. That's the article that deals with Underground wiring. It includes a nifty table that shows how deeply different sorts of electrical things are supposed to be buried. For instance, with your direct burial conductors, you're supposed to have 24" of soil cover over them in most locations. If you have a 2"-thick concrete slab over them, you only need 18" of cover. If you put them under a building, they don't need any cover, but they have to be in a raceway. It's a handy table.

So, 300.5(D)(1) actually says: Direct-buried conductors and cables emerging from grade and specified in columns 1 and 4 of Table 300.5 shall be protected by enclosures or raceways extending from the minimum cover distance below grade required by 300.5(A) to a point at least 8 feet above finished grade. In no case shall the protection be required to exceed 18" below finished grade.

So my memory was faulty. The required burial depth is 24" but the conduit only needs to extend down 18".

Getting sloppy . . .

- Jim Katen, Oregon

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Also common sense prevails with something like this.

Imagine one of those weed whackers going to work on that. Or more specifically a weed whacker which has blades rather than string. The insulation could be easily removed.

Then the family dog comes along and gets zapped via the nose or other end by marking his territory. Or a small boy with a metal stick going along walls or fences banging/poking on things.

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Slip risers.

I've always called it movable sleeve because no one knew what to call it.Is slip riser referenced in the NEC?

I think it's called a "slip joint" on the meter riser. I also think there's a requirement in the NEC as of '02. The local POCos here require it as well, but don't always notice if it's omitted.

I don't know of any specific requirement for a slip joint. But 300.5(J) dates back to the '96 edition and it requires that "where subject to movement by settlement or frost, conductors, raceways, & cables have to be "arranged to prevent damage to the enclosed conductors or to equipment connected to the raceways." With conduit, I think that pretty much equals an expansion joint, slip joint/riser, sleeve, or whatever you want to call it.

Pre-'96, I'm not aware of any such requirement and I've never see one used then.

- Jim Katen, Oregon

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But what about the conductors? They can't stretch.

The installer is *supposed* to provide an "s" loop in the conductors in the trench just before they enter the conduit (if they're direct buried). If they're completely in conduit, there should be a provision for some flexibility at each connection point.

- Jim Katen, Oregon

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As Jim stated, 300.5(J) covers this issue. This is from one of our our local POCOs:

http://inspectpa.com/download/slipriser.pdf

Jeff,

Do any of your POCOs require a steel ell in that location? We've had issues here where the string cuts through the PVC as it goes around the corner while pulling those fat service cables.

- Jim Katen, Oregon

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As Jim stated, 300.5(J) covers this issue. This is from one of our our local POCOs:

http://inspectpa.com/download/slipriser.pdf

Jeff,

Do any of your POCOs require a steel ell in that location? We've had issues here where the string cuts through the PVC as it goes around the corner while pulling those fat service cables.

- Jim Katen, Oregon

No, not for residential but I do see them for commercial at the base of the poles that the conductors run down. The problem is that everyone transitions to PVC and they always separate there so at the base of every pole (XFMR on pole, not pad mounted) there is always a gap with the conductors on the secondary exposed.

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