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Thread: "Clean" Romex installs...

  1. #1
    Test, Don't Guess! cacher_chick's Avatar
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    Default "Clean" Romex installs...

    Maybe a silly question, but for the sake of good practice and appearance, when running wire is there a preference when it comes to pulling 2-3 cables through a single hole in a stud or joint OR drilling a separate evenly spaced hole for each cable? For clarification, I mean common residential receptacle and lighting circuits.

  2. #2
    Extreme DIY Homeowner Scuba_Dave's Avatar
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    I run up to 3 cables thru a hole (#12 or #14)
    Less holes in joist etc the better
    DIY Handyman (not 4 hire)
    I have enough to do to my own house

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    Licensed Electrical Contractor Speedy Petey's Avatar
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    Typically, up to four NM cables in a hole will NOT cause or bring up any issues.

    2x4's I usually drill 7/8" holes dead center. Bigger framing gets 1" or 1-1/8" holes.
    Answers based on the 2008 & 2011 NEC. If you're on the '14 already I feel sorry for you.

  4. #4

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    We always put multiple cables in a single hole. As many as will comfortably fit.

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    Code Enforcement codeone's Avatar
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    For 2008 NEC, Article 334.80 for Ampacity of NM cable states.

    Where more than two NM cables containing two or more current-carrying conductors installed, without maintaining spacing between the cables, through the same opening in wood framing that is to be fire- or draft- stopped using thermal insulation, caulk, or sealing foam, the allowable ampacity of each conductor shall be adjusted in accordance with Table 310.15(B)(2)(a) and the provisions of 310.15(A)(2) shall not apply.
    Where more than two NM cables containing two or more current-carrying conductorsare installed in contact with thermal insulation without spacingbetween cables, the allowable ampacity of each conductor shall be adjusted in accordance with Table 310.15(B)(2)(a).

    Table 310.15(B)(2)(a) Adjustment Factors for More Than
    Three Current-Carrying Conductors in a Raceway or Cable

    Number of ---------------- Percent of Values in Tables
    Current-Carrying ------------- 310.16 through 310.19
    Conductors ---------------- Adjusted for Ambient
    --------------------------- Temperature if Necessary
    _________________________________________________
    4 - 6 ______________________80
    7 - 9 ______________________70
    10 -20______________________50
    21 -30______________________45
    31 -40 _____________________40
    41 and above__________________35
    _________________________________________________

    Being that you can use the 90 degree column for derating purpoes its not usually a problem with #14,#12,and #10 conductors untill you pass 9 current carrying conductors.
    That would make 4 cables = to 8 current carrying conductors since the exception doesnt apply.
    or you could have one of the cables be a three wire then 4 would equal 9 current carrying conductors and would be ok.

    Sorry havent figured out how to get the Tables to look right.
    Last edited by codeone; 12-30-2009 at 07:16 PM.

  6. #6
    Licensed Electrical Contractor Speedy Petey's Avatar
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    Quote Originally Posted by codeone View Post


    Being that you can use the 90 degree column for derating purpoes its not usually a problem with #14,#12,and #10 conductors untill you pass 9 current carrying conductors.
    That would make 4 cables = to 8 current carrying conductors since the exception doesnt apply.
    or you could have one of the cables be a three wire then 4 would equal 9 current carrying conductors and would be ok.
    Just a quick note.

    Don't for get that the neutral of a MWBC (multi-wire branch circuit) does not count towards derating, so for home runs or branch circuit wires you can even have four 3-wire cables. In fact, only two of the conductors in a 3-way switching setup will ever carry current so IMO they apply as well, although it is not written that way.
    Answers based on the 2008 & 2011 NEC. If you're on the '14 already I feel sorry for you.

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    Code Enforcement codeone's Avatar
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    Quote Originally Posted by Speedy Petey View Post
    Just a quick note.

    Don't for get that the neutral of a MWBC (multi-wire branch circuit) does not count towards derating, so for home runs or branch circuit wires you can even have four 3-wire cables. In fact, only two of the conductors in a 3-way switching setup will ever carry current so IMO they apply as well, although it is not written that way.
    Thanks for pointing that out Speedy Petey.
    Mel

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