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Thread: Can three #8 and one #10 wires be in ½” metal conduit?

  1. #16
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by Wet_Boots View Post
    By the way, did the tables change when large appliances went from 3-blade plugs to 4-blade plugs? Way back when, there wouldn't have been anything in a range outlet, for instance, for a fourth wire to connect to, so it wasn't going to be in the cable with the two hots, right?
    The use of old rubber insulation on conductors would only allow two #8 conductors in a ½ inch flexible conduit, reference the 1940 edition of the NEC

    I didn’t know that three conductor was ever allowed for ranges and dryers since the requirement for an EGC. In 4237 of the 1940 edition ranges were required to be grounded.

  2. #17
    DIY Member electrotuko's Avatar
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    Wet_Boots, thanks for pointing to online Conduit Fill calculator.
    I used this place to find ODiameters for THHN 90C wires:
    http://www.bestelectricsales.com/dat...eWire-THHN.pdf
    For 8 AWG shows 0.212", for 10 AWG is 0.160".
    Running online calculations for three 8 AWG and one 10 AWG results in:
    The conduit fill is: 39.79%

    Still not clear can I run more than three 8 AWG wires inside ½” conduit?
    Or even your idea to run bare 8 gauge wire, can this be OK?
    I just do not have room in my box to install ¾” metal flex cable, no open knockout available for this size.

  3. #18
    Moderator & Master Plumber hj's Avatar
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    quote; no open knockout available for this size.

    Then you make one that size.
    Licensed residential and commercial plumber

  4. #19
    DIY Member electrotuko's Avatar
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    Still confusing regarding NEC specs for conduit fill.
    I seen in the store already made metal flex cable with three 10 gauge wires inside, this looks even smaller diameter than regular 3/8" metal flex.
    Running online calculator for three 10 gauge wires shows:
    The conduit fill is: 52.08%
    And ofcourse a warning:
    Warning: Conduit Fill of 40.0% has been exceeded

    How you would comment this case?

  5. #20
    DIY Member electrotuko's Avatar
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    OK OK, just got 3/4" metalf flex, this time will comply with NEC Code, even it does not make sense to me in this case.

  6. #21
    Sprinkler Guy Wet_Boots's Avatar
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    It's usually easier to just oversize things and skip the calculations. I have some interest in shoehorning (within the confines of the rules) conductors and grounds into 1/2 and even 3/8 steel flex, in order to make some new wiring look like older wiring that's been there for awhile. That has me running the fill calculator, with both solid and stranded THHN, and scratching my head over what is or isn't considered a full-load conductor.

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