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-   -   Sub Panel Wire (https://www.askmehelpdesk.com/showthread.php?t=335953)

  • Mar 30, 2009, 05:15 PM
    Gus_19
    Sub Panel Wire
    I recently did a walkthrough with the electrician who is helping me get my basement wired up. During that time I believe he had told me to pick up approximately 10ft of 4/4/2 electrical wire to run a 100A Breaker from my 200A panel to a 100A sub panel. Another guy told me I should get 4/3 wire because there shouldn't be a need for a ground on the sub panel as it would just create a loop. Both guys are great with electrical and from my understanding, know their stuff.

    What wire size will I need to run from my 200A main breaker to the 100A sub panel?
  • Mar 30, 2009, 05:46 PM
    stanfortyman
    Create a loop??

    The guy who told you to get a wire without a ground does NOT know his stuff.

    I assume because of the short 10' distance this is within the same structure as the main panel.

    Previously any sub panel within the same structure as the main panel required a "4-wire" feeder. Two hots, neural and a ground. Detached structure sub-panels had exceptions to this rule.
    In the 2008 NEC ALL sub-panels require a 4-wire feeder.
  • Mar 30, 2009, 06:27 PM
    KISS

    Ground is usually assumed in electrical work.
    Just as 14/2 is 2 conductors is #14 with ground an this usually NM-B cable which implies the ground.

    Thus in your notation, the cable type is not specified. We can assume that it's NM-B.

    Thus 4-4-2 allows a higher neutral current than 4/3. 4/3 is really 4-4-4 in the original notation. There is never any 2 conductor cable with two different wire sizes.

    4-4-2 is better than 4-4-4 and both likely contain a ground.

    I get 1-1-1 with a minimum of #6 ground

    Subpanels need the ground. Ground an neutral must not be connected in the sub-panel. Additional hardware may be required as well as removing a ground bond screw and purchasing an additional ground bar commonly called a "ground bar kit".

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