How to add more circuits?
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  1. #1
    Join Date
    Jul 2008
    Location
    Athens,Louisiana
    Posts
    1,449

    How to add more circuits?

    I've got a minor problem and I'll bet the readership here can help me solve it.

    32x100' building with new 200 amp service panel mounted about 25' from the front. There is a 70 amp box added about 25' from the main on a circuit from the main 200A box(with #4 AWG wire). I want to continue that wire back another 30' and install another breaker box in a garage area after I change the 70A breaker in the 200A main panel to a 100A breaker. This auxillary box will control a central air/heat unit,an electric H/W heater,a dryer,two bathrooms,two bedrooms,and of course the 24x32 garage. I want to have 220V hookups for a 50A welder,a 30A plasma cutter,a 30A air compressor and the various wall plugs everywhere.

    Can I jump from the 200A main panel to a 100A auxillary panel in this manner and have a fully functional electrical system? Will the #4 AWG handle such a setup or do I need to go to #2 AWG?

    I've been told that the maximum auxillary box is the existing 70A circuit (70A breaker in the main panel) I know they make the 100A breakers that can be used to replace the 70A that's already there(any problem with that?)

    I should explain... This is an old Firehouse(brick walls..tin ceiling) that the front 1/3 was totally renovated..all firerock and all new wiring in flexible conduit...believe me it's right($30 grand worth by the PO). We are adding 3 BR & 2 Baths and the all important work area. I really don't want to run 50-75' homeruns from the main panel to the back 2/3's if I can install a 100A panel off the 200A main back in the shop...from there the longest run would be 15-25'.

    I know just enough about wiring to get by,but I know some of you deal with this as a profession...your input would be appreciated.

    Thanks for any insight into this--Dave

  2. #2
    Join Date
    Jun 2008
    Posts
    146

    Re: How to add more circuits?

    That # 4 AWG is not suitable for 100A there is only 1 place that it is allowed and for what your asking it does not apply you need to run a new feed.What brand of panel?

  3. #3
    Join Date
    Nov 2006
    Posts
    5,767

    Re: How to add more circuits?

    Quote Originally Posted by mudbugone View Post
    ...This auxillary box will control a central air/heat unit,an electric H/W heater,a dryer,two bathrooms,two bedrooms,and of course the 24x32 garage. I want to have 220V hookups for a 50A welder,a 30A plasma cutter,a 30A air compressor and the various wall plugs...
    That's a lot.

    You may want to calculate some specific expected loads, to see if even 100 amps is enough.

    Bigger wire will be more expensive now, but nowhere near as much as changing to it later.

    Good Luck
    Last edited by denrep; 07-29-2008 at 02:05 AM.

  4. #4
    Join Date
    Jul 2008
    Location
    Athens,Louisiana
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    Re: How to add more circuits?

    Quote Originally Posted by Norcal01 View Post
    That # 4 AWG is not suitable for 100A there is only 1 place that it is allowed and for what your asking it does not apply you need to run a new feed.What brand of panel?

    The 200A is a true Square D and the 100A will be a Square D or a Cuttler Hammer. I've got some #2 wire.

    If I have to I could run some circuits from the 200A main box to ease the load on the 100A auxillary box.
    ************************************************** ************************************************** **
    My main question is ..Can this be done with the 100A breaker in the 200A main box feeding the auxillary box thru the 100A breaker?
    ************************************************** ************************************************** **
    I can feed off the 200A main for the lesser wiring demands closer to that box...I would just prefer to feed off the auxillary box if possible.

    The house where I now live runs on a 100A main box with an extra smaller box added.

    I may have to rethink the electric H/W heater & dryer to keep things under the max draw into the garage/shop area..

    Thanks for the feedback guys...Dave

  5. #5
    Join Date
    Jul 2008
    Location
    Athens,Louisiana
    Posts
    1,449

    Re: How to add more circuits?

    Quote Originally Posted by denrep View Post
    That's a lot.

    You may want to calculate some specific expected loads, to see if even 100 amps is enough.

    Bigger wire will be more expensive now, but nowhere near as much as changing to it later.

    Good Luck
    The bigger wire is the issue here.... I've got a bunch of #2 wire to extend to the rear of the building for the auxillary box,which sounded like a better idea than running "boo-koo" numbers of single runs back there at the price of wire now. We all know that all that stuff won't be running at the same time,but I understand it could be at the maximum load.

    Kinda makes me wonder about the 200A box...shouldn't it handle everything mentioned without a problem? and if so,all I'm doing is extending a leg from that main to the rear so all this actually feeds off the 200A main.

    I'm just thinking out loud here guys & hoping to learn something about the overall system hookup since as I said I just know enough to get into trouble. I really don't like electricity,but It's something I've got to deal with at this point.

    I knew there were some here with more knowledge about this than myself.

    Thanks,Dave

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