Is there anything in the NEC the requires spacing between underground PVC conduits containing 480V conductors? We have an application that has a considerable number of varied size conduits containing 480V conductors. The conduits are installed in a very disorganized manner without spacers and they run in every direction possible. The conduits are tied to each other to presumably keep them in place during backfill.
Underground PVC Conduits
- Thread starter slo7682
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wirenut1980
Senior Member
- Location
- Plainfield, IN
Re: Underground PVC Conduits
I can't think of anything in the NEC requiring spacing of the conduits, at 480 V there can't be much of an issue with excessive heating. I would prefer a neater install however...
I can't think of anything in the NEC requiring spacing of the conduits, at 480 V there can't be much of an issue with excessive heating. I would prefer a neater install however...
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: Underground PVC Conduits
310.15(B)(2)(b). I think you have a significant problem on your hands.
310.15(B)(2)(b). I think you have a significant problem on your hands.
wirenut1980
Senior Member
- Location
- Plainfield, IN
Re: Underground PVC Conduits
Charlie, my 2002 NEC is packed away right now (moving) and all I have is an electronic copy of the 1999 NEC. Does the '02 or '05 specify how much spacing will be maintained? It seems awfully ambiguous as it is written.
Charlie, my 2002 NEC is packed away right now (moving) and all I have is an electronic copy of the 1999 NEC. Does the '02 or '05 specify how much spacing will be maintained? It seems awfully ambiguous as it is written.
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: Underground PVC Conduits
The 1999 version has the same statement, in the same location. Neither NEC version gives a minimum or maximum distance for the spacing. This has led to some ?interesting? (or shall we say ?colorful??) discussions of what the code means by ?spacing shall be maintained.?
I think the issue here is allowing some portion of the length of a conductor to have a significantly higher (or lower) impedance than a different portion (but of the same length), located further along the same conductor. If two parallel conduits (they need not be part of the same circuit) are sometime close to each other, and sometimes far apart, then the mutual inductance and the capacitance will vary along the length. That can create hot spots, and result in premature failure.
The 1999 version has the same statement, in the same location. Neither NEC version gives a minimum or maximum distance for the spacing. This has led to some ?interesting? (or shall we say ?colorful??) discussions of what the code means by ?spacing shall be maintained.?
I think the issue here is allowing some portion of the length of a conductor to have a significantly higher (or lower) impedance than a different portion (but of the same length), located further along the same conductor. If two parallel conduits (they need not be part of the same circuit) are sometime close to each other, and sometimes far apart, then the mutual inductance and the capacitance will vary along the length. That can create hot spots, and result in premature failure.
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