When pull boxes are used for angle or straight pulls do the de-rating factors 310.15(B)(2) apply, where the pull box exceeds 24" in length? It refers to 376.22(B) for sheet metal auxiliary gutters, but could not find anything as it related to de-rating for pull box applications?
Pull Box / Conductor De-Rating
- Thread starter Mike01
- Start date
- Status
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
de-rating factors for 310.15(B)(2) or (B)(3)(a) in the 2011 are for raceway not box fill.
- Location
- Illinois
- Occupation
- retired electrician
While the code panel does not agree, the derating applies anywhere that you have more than 3 current carrying conductors bundled for more than 24".
That being said, the exception to 310.15(A)(2) will likely permit you to omit the derating even if the conductors are installed without maintaining spacing for more than 24" in the pull box.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Since bundling is not defined every large panel would have to comply with de rating
- Location
- Illinois
- Occupation
- retired electrician
The code section does not use the word bundling, but yes, anytime conductors are installed "without maintaining spacing" (what ever that means) for more than 24", derating is required.
- Location
- Illinois
- Occupation
- retired electrician
The following is the proposal I sent in on this issue. (red = text to be deleted) I really don't understand how the panel comment and the words "or multiconductor cables are installed without maintaining spacing for a continuous length longer than 600 mm (24 in.) and are not installed in raceways" can both be correct. They need to either accept my proposal or delete the wording that is in conflict with the panel's statement.
________________________________________________________________
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Typical response from the cmp when the statement clearly calls for single conductors or cables not in a raceway. I have found other comments on different issues to be similarly strange.
Don
IMO although the rule is poorly written, it applies only to raceway or multiconductor cables. The OP need not read 310.15(B)(3)(a) when he's considering adjustment factors for pull boxes because the rule clearly says "in a raceway or cable" in it's heading. There's no need to read any further than that if we're concerned only with pull boxes. The content of the rule itself is confusing and contradictory, but your proposal changes the intention.
- Location
- Illinois
- Occupation
- retired electrician
John,
I am only reading the words as written in the current rule. Who says the heading and not the actual rule states the intent of the rule? My point is that the "heading" is in conflict with the actual rule and that the heading needs to be changed.
If the rule only applies to conductors in raceways or cables, then what do the following words mean?
It seems very clear to me that derating is required outside of raceways or cables.
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I believe that the heading states the intent of the rule. The rule is called " More Than Three Current-Carrying Conductors in a Raceway or Cable", therefor it is intended to be applied to more than three current-carrying conductors in a raceway or cable.
I agree that the heading is in conflict with the rule, or more accurately, the rule is in conflict with the heading.
I also agree that the words you quoted make it clear that derating is required outside of raceways and cables, as you stated. However, if I am concerned with a pull box I will never read those words because I will stop reading that section when I come to the part in the very beginning that says " in a Raceway or Cable".
- Location
- Illinois
- Occupation
- retired electrician
That is exactly why my proposal is to delete the those words from the heading.
Confusion
Confusion
That is wehre I got confused because the cables are being installed in a pull box they will not necessarly be "bundled" togerther, also sections refers to another sectoin for wireways but a pull box would be outsize the scope of these two sections as I saw it. When sizing the pull box for the angle pull it makes it difficult, because have to maintain the reqquired clearances from conduit to conduit and for a straight pull if I put section barriers between the conductors of each pipe making them seperate sections in the same pull box no-derating required but if I remove the barriers but maintain the distance de-rating would be required....confusing...
Confusion
That is wehre I got confused because the cables are being installed in a pull box they will not necessarly be "bundled" togerther, also sections refers to another sectoin for wireways but a pull box would be outsize the scope of these two sections as I saw it. When sizing the pull box for the angle pull it makes it difficult, because have to maintain the reqquired clearances from conduit to conduit and for a straight pull if I put section barriers between the conductors of each pipe making them seperate sections in the same pull box no-derating required but if I remove the barriers but maintain the distance de-rating would be required....confusing...
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