314.28 "Same Conductor"

[wwhitney]

Hopefully this is not an FAQ, but 314.28(A)(2) says in part "The distance between raceway entries enclosing the same conductor shall not be less than six times the metric designator (trade size) of the larger raceway."

Does this apply only to unspliced conductors, or does the "sameness" of a conductor extend across a splice?

If the former, seems like there are cases where the only applicable minimum dimension would be from Table 312.6(A), per 314.28(A)(2)'s exception. E.g. all conduit entries are into the back of the box opposite a removable cover. Or a box where the cover and one side are removable, with all entries opposite that cover and that side (is such a thing commercially available?).

That would make for some very small allowable splice boxes, like a 6x6x4 box with two 2" conduits entering the back and 4/0 conductors spliced within.

Cheers, Wayne

 

[LarryFine]

Does this apply only to unspliced conductors, or does the "sameness" of a conductor extend across a splice?

I would say the former.

 

[augie47]

I would say the former also.
The requirement primarily addresses damage to conductors on a pull which would not be applicable on spliced conductors.
I always think of the boxes I have seen mounted in I beams between the flanges,.

 

[don_resqcapt19]

Hopefully this is not an FAQ, but 314.28(A)(2) says in part "The distance between raceway entries enclosing the same conductor shall not be less than six times the metric designator (trade size) of the larger raceway."

Does this apply only to unspliced conductors, or does the "sameness" of a conductor extend across a splice?

If the former, seems like there are cases where the only applicable minimum dimension would be from Table 312.6(A), per 314.28(A)(2)'s exception. E.g. all conduit entries are into the back of the box opposite a removable cover. Or a box where the cover and one side are removable, with all entries opposite that cover and that side (is such a thing commercially available?).

That would make for some very small allowable splice boxes, like a 6x6x4 box with two 2" conduits entering the back and 4/0 conductors spliced within.

Cheers, Wayne

Based on the title of first level subdivision (2) and the first sentence, it is my opinion that it applies to both spliced and unspliced conductors. If the 6x does not apply to spliced conductors, then there is no reason for that word to appear in (2).

It appears the quoted language is intended to clarify what the measurement is where there are two different size raceways.

All of the text books and other training materials I have seen, apply the 6x to spliced conductors.

 

[wwhitney]

Based on the title of first level subdivision (2) and the first sentence, it is my opinion that it applies to both spliced and unspliced conductors. If the 6x does not apply to spliced conductors, then there is no reason for that word to appear in (2).

Not following your logic. The title of (2) is "Angle or U Pulls, or Splices." And clearly the first paragraph applies to all of those.

But the section could still include requirements that apply only to splices, or requirements that apply only to angle or U pulls. So it is plausible that the second paragraph applies only to pulls, not splices.

It appears the quoted language is intended to clarify what the measurement is where there are two different size raceways.

What what measurement is? The first paragraph only applies to an individual entry and concerns the distance between it and the opposite wall. There are never two different size raceways at once in applying the first paragraph, no clarification is required. The second paragraph is a separate requirement that stands alone, and it involves two different raceways.

For example, suppose we have a box (front cover is removable) where there are just two 2" conduit entries, both on the top side, for a u-pull. The first paragraph says the box has to be 12" tall. The second paragraph says we need 12" between the two raceways entries on the top (is that 12" clear or 12" c-t-c?). So if the entries are at opposite ends of the top, the box width has to be at least 14.5" (if 12" is c-t-c) or 17" (if 12" clear is required).

From a practical perspective, if we are splicing in the box, why is there any need for the box to be 14.5" or 17" wide? Just use a wire connector that works for both wires coming in parallel to each other, like an insulated mechanical multi-tap connector. Seems like an 8" wide box would work fine. [Maybe 6", although apparently the OD of a 2" locknut is 2-7/8", so that would be close. Plus you'd have to check the size of the wire connector.]

Cheers, Wayne

 

[infinity]

But the section could still include requirements that apply only to splices, or requirements that apply only to angle or U pulls. So it is plausible that the second paragraph applies only to pulls, not splices.

You've tapped into the frustration that just about everyone has with the box calculations not being clear. The entire code section needs to be re-written with a separate section for splices only. When two raceways enter on the same side of a box no spacing between the two raceways is needed to make a splice.

For example a 6x6x18 box could have two 2" conduits in one end and there would be no issue with pulling in the conductors or splicing them.

 

[don_resqcapt19]

Well, it appears that Wayne is correct, but I have never seen it that way in a text book.

Public Input No. 793-NFPA 70-2014 [ Section No. 314.28(A)(2) ]
Statement of Problem and Substantiation for Public Input
The problem with the "enclosing the same conductor" portion of the text implies that splices are excluded from this regulatory paragraph. I have spoken to inspectors, who in turn have spoken to other inspectors, and all of them come up with the same conclusion - that since the charging statement of this code has splices in the title, it is included in all paragraphs of this code. I also suggest replacing the word "or" with "and" in the charging statement to alleviate further confusion. My experience and problem with the current wording in this code arose when I installed a 12x12x6 jbox with two 2" conduits, one in the back and one in the side. I thought I had the correct minimum size box when I read the phrase, "enclosing the same conductor." Since I was splicing, I believed that the paragraph for spacing between conduit entries did not apply. The inspector sent an email to a UL employee and an IAEI member after our debate and came to the conclusion that it does include splices and that the jbox was in fact the wrong size for the conduits used. Even with our inspector's extensive experience in the trade, he still entertained my inquiry to the point of his own investigation to seek out clarification; this leads me to believe this problem could arise again and that making these simple phrase changes will help minimize similar errors in the future, potentially saving companies and clients varying amounts of money.
Committee Statement
The installation cited in the substantiation was correct. The title of this paragraph was carefully punctuated to make this clear. A splice involves two different conductors. Refer to the panel statement on Comment 9-36 in the 2008 cycle on this topic, which states “The title is grammatically correct. The rule covers both angle and U pulls (principal application). These are related and should be grouped. The rule also, coincidentally, covers the spacing requirement for spliced conductors, which is an additional application.” So, there is a minimum size rule for enclosures containing splices, but since conductors on opposite ends of a splice are necessarily not the same conductor the second paragraph grants some relief with respect to spacing between the relevant wiring entry points. This is only logical. A rule designed to protect insulation from pulling stress is plainly irrelevant to applications where there would be no pulling stress.