Spare Conductors - NEC 2011

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erickench

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Location
Brooklyn, NY
Hi guys, I live in New York city and we are still on the 2008 NEC, with a few amendments. Eventually, we will adopt the 2011 NEC and apply our amendments to it. I was reading in this month's EC&M magazine, and I came across Mike Holt's article on code basics. The article mentions a clarificaton as it pertains to spare conductors in a raceway and the ampacity adjustment procedures that was made in the 2011 NEC. I believe that the 2011 NEC stated that spare conductors are not included whenever you have to make ampacity adjustments. I know that there was some confusion, and that was cleared up in the 2014 NEC, but I can not ignore the inevitable when it comes time for the city to adopt the 2011 NEC. Can anyone point out this note or article that pertains to spare conductors not be counted for ampacity adjustment calculations? I'm looking at the 2011 NEC and not 2014. Thanks.:D
 

charlie b

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Location
Lockport, IL
Occupation
Retired Electrical Engineer
Don was right. That note does have your answer. It says to include all conductors. That means ALL. It does not say you can exclude the spare conductors. Indeed in the 2014 it explicitly directs us to include the spares.

In both the 2011 and 2014, it goes on to say that the total number of conductors can be reduced, if you follow the rules in two of the paragraphs that follow. Basically, you don't always have to count the neutral, and you never have to count the EGC. But in the 2011, you begin by counting all the conductors, and then you subtract the EGC and perhaps the neutral. But nothing tells you not to count the spares.
 

erickench

Senior Member
Location
Brooklyn, NY
Don was right. That note does have your answer. It says to include all conductors. That means ALL. It does not say you can exclude the spare conductors. Indeed in the 2014 it explicitly directs us to include the spares.

In both the 2011 and 2014, it goes on to say that the total number of conductors can be reduced, if you follow the rules in two of the paragraphs that follow. Basically, you don't always have to count the neutral, and you never have to count the EGC. But in the 2011, you begin by counting all the conductors, and then you subtract the EGC and perhaps the neutral. But nothing tells you not to count the spares.

You mean to tell me that before 2011 they were not counting the spare unused conductors?
 

don_resqcapt19

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Location
Illinois
Occupation
retired electrician
You mean to tell me that before 2011 they were not counting the spare unused conductors?
For the 1993 through 2008 codes, the code did not actually require that you count the spare conductors for the purposes of derating as they are not "current carrying conductors".
6-57 Log #635 NEC-P06 Final Action: Accept
(Table 310.15(B)(2)(a))
_______________________________________________________________
Submitter: James M. Daly, Rep. NEC/CEC Ampacity Harmonization Task Group

Recommendation: Revise first column heading in Table 310.15(B)(2)(a) from ?Number of Current-Carrying Conductors? to ?Number of Conductors (See Note 1.)?.

Add a Note below the Table before FPN No. 1 to read:
1 Number of Conductors is the total number of conductors in the raceway or cable adjusted in accordance with 310.15(B)(4) and (5).

Substantiation: A companion proposal is being submitted for Table B.310.11.
This Table was originally added to the Code in 1940 and the column heading remained as ?Number of Conductors? until 1993. During the 1993 NEC revision cycle, the column headings in Table 310.15(B)(2)(a) and Table B.310.11 were editorially changed to ?Number of Current-Carrying Conductors?. There was no Proposal, Comment, or Panel Action to make the change. A chronological history of the changes in the Tables is attached for reference.
This reinstatement of the original column heading permits the user to take the total number of conductors in the cable or raceway and subtract the neutral conductors not required to be counted under 310.15(B)(4) and the grounding or
bonding conductors not required to be counted under 310.15(B)(5). The result is the number of conductors that may be simultaneously energized and this number would be used to select the adjustment factor from the Table. The Note is proposed for clarity since there has been some confusion that the column referred to the total number of conductors in the raceway or cable. The correction to the column heading also correlates with the column headings in Table 400.5 in the NEC and Table 5C in the 2006 Canadian Electrical Code, Part I.

This Proposal was generated by the NFPA/CSA NEC/CEC Ampacity Harmonization Task Group which consisted of the following members: ...

Note: Supporting material is available for review at NFPA Headquarters.
Panel Meeting Action: Accept
Number Eligible to Vote: 11
Ballot Results: Affirmative: 11
 
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