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(2) 100 amp breakers on 200 amp service?

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  • (2) 100 amp breakers on 200 amp service?

    ok so I have a question that even several electrical contractors here are unable to answer.

    so I have built a shop.

    200 amp main box, I would like (2) 100 amp breakers in the main box. 100 amp going to sub-panel for house and another 100 amp sub-panel going to shop. No other breakers on main panel.
    sounds pretty strait forward right? on all the main boxes that I have seen they say 100 amp breaker on bottom of panel and 70 amp breaker any were else.

    ok so I know that your not suppose to exceed the 80% rule. but since every house I have seen whether 200 or 100 amp service have filled there quota in there main boxes. why can't I with (2) 100 amp breakers?

    any clarity on this?

    the only dumb question is the one that is not asked!

  • #2
    If you add up all your individual circuut breakers in a typical box, you'll always exceed the main breaker rating. But the 80% rule is applied for a particular circuit on a continuous basis. So a 20 amp circuit should not exceed 16 amps continuous load. And your 100 amp breaker feeds a sub panel. The continuous load on all the circuits in the sub panel should not be 100 amps total but more like 80.

    Lets see what sparky says Are there any sparkies left


    phoebe it is


    • #3
      Agree with Rick but I am not an electrician either.

      Are you wanting to install a box immediately downstream of your meter and
      upstream of your existing home main panel that would have two 100A breakers
      in it, one for the house and the second for the shop.

      "It's a table saw, do you know where your fingers are?" Bob D. 2006
      "?ǝɹɐ sɹǝƃuıɟ ɹnoʎ ǝɹǝɥʍ ʍouʞ noʎ op `ʍɐs ǝlqɐʇ ɐ s,ʇı"



      • #4
        So I got a hold of another sparky and was told he does it all the time. So I'm good.
        the only dumb question is the one that is not asked!


        • #5
          It's ok to do so provided breakers are sized correctly for the load and wire type. You also can't exceed the 200amp service rating. Btw, Just because your main panel is a 200 does not necessarily mean you have a 200amp service.
          The main breaker is selected by an electrician after doing a load calculation for all loads. It has nothing to do with adding up the sum of the breakers or using a 200amp breaker because you have a 200amp panel.


          • #6
            2 ground rods 8 feet deep.
            8 feet apart #4 wire.
            How deep should the top be to the ground? Just below the surface? Or deeper. See pic.
            the only dumb question is the one that is not asked!