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Thread: .8 rule

  1. #1
    Join Date
    Feb 2012
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    Default .8 rule

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    EMT FILL QUESTION

    I am studying for exam and ran across this. Does the .8 rule pertain to this application? Thank you for your time!

    4. Find the size EMT nipple required to enclose 3 each 500 kcmil THHN conductors between two panels

    a) 1 1/2 inch

    b) 2 inch

    c) 3 inch

    d) 3 1/2 inch


    ## CORRECT --> The area for 3 -500 kcmil THHN conductors is 3 x .7073 = 2.1219 For 60 percent fill using the .8 round off method requires a 2 inch EMT.


    Bob
    Last edited by dkerr; 10-02-2018 at 07:50 AM.
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  2. #2
    Join Date
    Feb 2012
    Location
    Kent, WA
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    Default

    Sort of. You take the 60% conduit fill area of 2" EMT which is 2.103 inches and divide that by .7073 (the area of one conductor). That comes to 2.97 conductors allowed. If the result was 2.8 or greater, you'd be allowed to round up to 3 conductors in that conduit using the .8 round up rule. The question should have also stated that the nipple was 24" or less in length so you know you can use 60% fill instead of 40%.

    So what you're supposed to be rounding up is conductor count, not area required.
    Mark
    Kent, WA

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