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Thread: 100A Main Panel…..100A Branch Circuit?

  1. #1
    DIY Member lahabra's Avatar
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    Smile 100A Main Panel…..100A Branch Circuit?

    Can I feed a sub panel with a 100A breaker in a 100A main panel?

    I have read all of the stickers in the main panel and it dos not indicate any limitation the size of branch circuits.

    I am working with a very common 100A main #JA110AS made by “Crouse Hinds”. It is still made today by “Murray”.

    Picture of main panel:
    http://electrical.hardwarestore.com/...er-621280.aspx

  2. #2

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    As long as the main panel has a 100a main breaker, there's nothing to prevent you from installing another 100a breaker for another panel.

    My question would be: Is the main panel already supplying another panel somewhere else? If so, you may run into problems overloading the main by putting over 100 amps of load on it.
    Just my 2¢ worth.

  3. #3
    Electrical Contractor/Instructor jwelectric's Avatar
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    You can feed three or four 100 amp subpanels with that set up as long as the calculated load on the main does not exceed 100 amps

  4. #4
    Licensed Electrical Contractor Speedy Petey's Avatar
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    Typically a buss will have a maximum branch circuit breaker rating. Most are 100 or 125 amps.

  5. #5
    DIY Member lahabra's Avatar
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    Quote Originally Posted by 480sparky View Post
    Is the main panel already supplying another panel somewhere else?
    No.

    When I’m done the main will only feed the new sub panel. Then I will connect 21 new circuits to the sub panel.

  6. #6
    Computer Programmer Bill Arden's Avatar
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    Nice main panel.

    I'm currently powering my 100A garage panel using a breaker coming out of my 100A house panel.

    The inspector was ok with it, but I know that I could trip the main if I turn everything on at the same time.

    Your case is better since the main panel only feeds the second panel and thus it is unlikely to overload the main panel.

    Edit: There is one thing you will have to deal with. The ground and neutral can only be tied together at the main and you then have to remove the ground screw in the second panel and run 4 wires to the main.
    Important note – I don’t know man made laws, just laws of physics
    Disclaimer: I'm a big fan of Darwin awards.

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