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Thread: MLO Sub-panel with inverter and loads wire sizing

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  1. #1
    Join Date
    Feb 2017
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    usa
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    MLO Sub-panel with inverter and loads wire sizing

    Hey Guys,

    I have a situation and wondering if my thinking is correct and looking for the applicable codes.

    I have a 60A subpanel which has a 20A breaker for an inverter and a 20A breaker for a light.

    This would be legal according to the sum rule in 705.12(d)(2)(3)(c). But how do we size the wires coming out of the subpanel? Because the currents are going in opposite directions the max current on that wire be 20A and should be sized for that shouldn't it?


    Thanks

  2. #2
    Join Date
    Oct 2009
    Location
    Austin, TX, USA
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    10,159
    Quote Originally Posted by ryangittens View Post
    Hey Guys,

    I have a situation and wondering if my thinking is correct and looking for the applicable codes.

    I have a 60A subpanel which has a 20A breaker for an inverter and a 20A breaker for a light.

    This would be legal according to the sum rule in 705.12(d)(2)(3)(c). But how do we size the wires coming out of the subpanel? Because the currents are going in opposite directions the max current on that wire be 20A and should be sized for that shouldn't it?


    Thanks
    Yes. The most current those conductors will carry is 20A.

  3. #3
    Join Date
    Feb 2017
    Location
    usa
    Posts
    35
    Quote Originally Posted by ryangittens View Post
    Hey Guys,

    I have a situation and wondering if my thinking is correct and looking for the applicable codes.

    I have a 60A subpanel which has a 20A breaker for an inverter and a 20A breaker for a light.

    This would be legal according to the sum rule in 705.12(d)(2)(3)(c). But how do we size the wires coming out of the subpanel? Because the currents are going in opposite directions the max current on that wire be 20A and should be sized for that shouldn't it?


    Thanks
    Just realized that this is a stupid question. The conductors are sized based on and protected by the OCPD on the other end.

  4. #4
    Join Date
    Oct 2009
    Location
    Austin, TX, USA
    Posts
    10,159
    Quote Originally Posted by ryangittens View Post
    Just realized that this is a stupid question. The conductors are sized based on and protected by the OCPD on the other end.
    That, too.

  5. #5
    Join Date
    Feb 2017
    Location
    usa
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    Quote Originally Posted by ggunn View Post
    That, too.
    Haha thanks

    Sent from my SM-G950U using Tapatalk

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