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  1. #1
    Join Date
    Mar 2007
    Location
    Missoula, MT
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    Default 100 Amp breaker feeding a 200 Amp panel

    A house has a 200 Amp main shut off, with a 100 Amp breaker feeding the garage panel. Is it ok for the panel in the garage to have a 200 Amp main shut off?

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    John Thompson
    Shelter Works Home Inspections, LLC
    Missoula, MT

  2. #2
    Join Date
    Jul 2008
    Location
    Snowbird (this means I'm retired and migrate between locations), FL/MI
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    4,086

    Default Re: 100 Amp breaker feeding a 200 Amp panel

    Service entrance 200 amp main protects at that limit from that point "downstream" including the panel assuming all is installed, bonded, grounded and "wired" correctly.

    Feeder originates at 100 amp breaker protection. The protection at the origin of the feeder (100 amp breaker) provides protection to its limits everything (feeder conductors themselves, and what follows, i.e. the sub-feeder panel, its main, etc. circuits, etc.) "downstream" ASSUMING there is no other potential source of energy/electricity to flow (i.e. no generators, pv, etc. inter-connection. Is that 100 amp breaker a combination device?

    Big question, garage attached or detached, and proper circuit, bonding, grounding, wiring method, distance, presence of other equipment requiring additional considerations (arc welders, etc.) and if detached, no secondary metallic paths, if attached proper protection and separations maintained.

    Last edited by H.G. Watson, Sr.; 08-07-2010 at 10:14 AM.

  3. #3
    Roger Frazee's Avatar
    Roger Frazee Guest

    Default Re: 100 Amp breaker feeding a 200 Amp panel

    Quote Originally Posted by John Thompson View Post
    A house has a 200 Amp main shut off, with a 100 Amp breaker feeding the garage panel. Is it ok for the panel in the garage to have a 200 Amp main shut off?
    John
    There is nothing wrong with protecting a feeder to a 200 amp main breaker panel in the garage detached or attached with a 100 amp breaker at the service equipment. You simply have a 200 amp breaker in the garage panel that acts as a disconnect. If the garage should for some crazy reason pull more than 100 amps on either hot leg the 100 amp breaker protecting the feeder will trip. So the 200 amp breaker in the garage panel serves no protective purpose other than a means to deenergize the panel.


  4. #4
    Join Date
    Mar 2007
    Location
    Missoula, MT
    Posts
    33

    Default Re: 100 Amp breaker feeding a 200 Amp panel

    Thanks guys!

    John Thompson
    Shelter Works Home Inspections, LLC
    Missoula, MT

  5. #5
    Join Date
    Feb 2009
    Location
    Southern Vancouver Island
    Posts
    4,549

    Default Re: 100 Amp breaker feeding a 200 Amp panel

    Ideally, that garage panel would have "100 amps Max" written on it with a felt pen. At least that is what I usually see here, but hey, I'm in another country.

    John Kogel, RHI, BC HI Lic #47455
    www.allsafehome.ca

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