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  1. #1
    Join Date
    Mar 2009
    Posts
    238

    Default Limit To Add Breakers To Existing Panel

    I have a newer(About 10-15 years old max) 100amp panel that was installed by a licensed electrician but with only 6 or so breakers. The older home has limited lighting and outlets so my plan is adding circuits circuits in particular splitting the existing circuits and adding a few items here and there.

    Currently all lighting for the second floor, stairways, basement, and a handful of outlets are on 2 - 15amp breakers distributed through the house through a 12/3 then spliced into knob and tube. Resulting in 2 - 15 amp eventually becoming 2-15amp and 3-20amp.

    Its a pain dividing everything up but since I am adding more breakers than were originally there is there a limit as to how many breakers you can have in a 100amp service panel even though each new circuit is nowhere near its 80% advised load of which its capable.

  2. #2
    Join Date
    May 2008
    Location
    Pacific Northwet
    Posts
    1,674

    Default Re: Limit To Add Breakers To Existing Panel

    The limit will be listed on the label inside the breaker panel door.

    It should show how many slots there are; there can usually be one breaker per slot. Double-pole breakers, used for 240V appliances such as ranges, dryers, and water heaters, take two slots.

    There is an exception: if your panel allows it, you may be able to install "twin" or "duplex" breakers in a single slot.

    In most cases a larger panel will be limited to 40 (or is it 42?) breakers total. For example, a 30-space panel will allow ten duplex breakers and 20 standard, for a total of 40 (or 30 standard).
    The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.

  3. #3
    Join Date
    Jun 2007
    Location
    Fayette County, Ohio
    Posts
    5,842

    Default Re: Limit To Add Breakers To Existing Panel

    The only limit is the number of spaces the panel has. The individual breaker protects the wiring connected to it and nothing else. The main breaker prevents a total overload.

    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  4. #4
    Join Date
    Mar 2009
    Location
    wisconsin
    Posts
    159

    Default Re: Limit To Add Breakers To Existing Panel

    dont know what your electricain was thinking.. but if it was me id call the utility have them unook ya and put a 42 space in.. Cake work if ya know what your doing.. for a DIYer not sure what the best route would be. perhaps a sub panel; you can buy a 100 sub panel 42 space and feed it out of your existing panel. Kinda cobbled up. This would be a good job to call a electrician buddy or perhaps hire it done.

  5. #5
    Join Date
    Mar 2009
    Posts
    238

    Default Re: Limit To Add Breakers To Existing Panel

    I think I may have mis-stated my question. I'm not in a situation of not enough spaces. I can clearly count how many spaces are available and I don't intend to fill it completely. My question which seems to be answered now was that if I only have 100amp service, is there a limit to how many breakers I can install regardless of available open spaces.

    e.g. do I have to count the amperage of all installed breakers and stay within a certain limit but it sounds like I dont have to worry about it.
    My advice and opinions come from hands on knowledge...and This Old House Hidden Content

  6. #6
    Join Date
    May 2008
    Location
    Pacific Northwet
    Posts
    1,674

    Default Re: Limit To Add Breakers To Existing Panel

    Put in as many breakers as you want, up to the limitations of the panel. The 100A main breaker will limit the total amperage on the incoming lines and the internal buses of the panel.

    If you couldn't have more than 100A worth of branch circuit breakers, then there wouldn't be much point to the main breaker, would there?
    The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.

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