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Thread: Conduit Fill

  1. #1
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    Conduit Fill

    Where am I making my mistake ?
    Given 3" Sch 80 PVC and 600kcmil Cu.
    I was asked how large a conductor I could add given 3 conductors in the conduit.
    Table C9 shows 3 600 kcmils allowed in a 3" Sch 80 but when you go back and do the math using Chapter 9, (3) 600 kmil THWNs have a combined area of 2.6028 which exceeds the Table 4, over 2 wire, available area of 2.577.
    At my age, I'm accustomed to restaurants asking me to pay in advance, but now my bank has started sending me their calendar one month at a time.

  2. #2
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    Note 7 to the Chapter 9 Tables allows rounding up the allowable number of identical conductors when the first digit after the decimal place is 8 or 9. 2.577/0.8676 = 2.97, so it gets rounded up to 3.

    Cheers, Wayne

  3. #3
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    Good catch Wayne. My math matched Gus and I was "huh?".
    "Electricity is really just organized lightning." George Carlin


    Derek

  4. #4
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    edit
    Cheers and Stay Safe,

    Marky the Sparky

  5. #5
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    That part gets everyone. When I was doing the tables for Annex C I had to come here and ask how to make my formula round up from .8 instead of .5
    They say I shot a man named Gray and took his wife to Italy
    She inherited a million bucks and when she died it came to me
    I can't help it if I'm lucky



  6. #6
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    Thanks
    At my age, I'm accustomed to restaurants asking me to pay in advance, but now my bank has started sending me their calendar one month at a time.

  7. #7
    Join Date
    Dec 2010
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    Quote Originally Posted by augie47 View Post
    Where am I making my mistake ?
    Given 3" Sch 80 PVC and 600kcmil Cu.
    I was asked how large a conductor I could add given 3 conductors in the conduit.
    Table C9 shows 3 600 kcmils allowed in a 3" Sch 80 but when you go back and do the math using Chapter 9, (3) 600 kmil THWNs have a combined area of 2.6028 which exceeds the Table 4, over 2 wire, available area of 2.577.
    By letting someone ask an old person to do math!
    If you aim at nothing, you will hit it every time!

  8. #8
    Join Date
    Jul 2005
    Location
    Tennessee
    Posts
    15,416
    At my age, I'm accustomed to restaurants asking me to pay in advance, but now my bank has started sending me their calendar one month at a time.

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