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Thread: 6 AWG to 100 amp subpanel?

  1. #1
    DIY Junior Member seattle_steve's Avatar
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    Default 6 AWG to 100 amp subpanel?

    I'm installing a sub-panel for a new addition. My load calc suggests a 50amp load for the sub-panel. So, I'm planning a 50amp feeder breaker in the main panel with #6 feeder wire to the sub-panel. But, the local retail stores don't carry (Siemens) panels smaller than 100amp. I checked with the local inspector (Seattle) and he said that it's common practice to feed a larger sub-panel (e.g., 100amp) from a smaller main feeder breaker/wire (e.g. 50amp, #6 wire).

    The problem is that the 100amp main breaker in the sub-panel I bought lists a wire gauge range of "4 - 3/0". I assume this means I cannot connect #6 wire to it? I don't want to size up the feeder wire/breaker, so what are my options? Are there 100amp sub-panels that will accept smaller wire? BTW, the inspector mentioned that I might run into this issue, but I didn't really follow his recommended solution. Best I could tell, he was suggesting shimming the wire somehow at the 100amp breaker/connecter. That doesn't seem right to me... Is there some sort of adapter available for this situation?

    Thanks.

  2. #2
    DIY Senior Member Chad Schloss's Avatar
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    i just wired the same panel in my garage with 6/3 using the 100a siemens panel. worked for me.
    Last edited by Chad Schloss; 11-13-2011 at 11:56 AM.

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    Electrical Contractor Jim Port's Avatar
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    I just wired the same panel in my garage with 6/3 using the 100a siemens panel. worked for me.
    Just because it works does not make it ok or a code compliant installation.

    You should splice a short piece of #4 onto the #6 and terminate the #4 on the breaker lugs.

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    DIY Junior Member seattle_steve's Avatar
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    Quote Originally Posted by Jim Port View Post
    You should splice a short piece of #4 onto the #6 and terminate the #4 on the breaker lugs.
    Thanks Jim. By "splice" do you mean simply twist-with-wire-nut as you would with smaller gauge splices?

    Steve

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    General Engineering Contractor ballvalve's Avatar
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    I think you need a panel without a main and infeed thru a 50 amp breaker.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Quote Originally Posted by ballvalve View Post
    I think you need a panel without a main and infeed thru a 50 amp breaker.
    That would be good, but as long as the wire feeding the subpanel is protected to the size of the wire, it doesn't really matter.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by seattle_steve View Post
    Thanks Jim. By "splice" do you mean simply twist-with-wire-nut as you would with smaller gauge splices? Steve
    Use a split bolt or a Polaris


    Quote Originally Posted by ballvalve View Post
    I think you need a panel without a main and infeed thru a 50 amp breaker.
    That would be backfed and that is what is being done with the 100 amp breaker
    What Jim said

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    DIY Senior Member Chad Schloss's Avatar
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    so you use a split bolt then? so electrical tape over that is supposed to be safer than terminating #6 on the main breaker??!!? this would be the first post of over 100 that i have read that would choose this route. strange..

  9. #9
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by Chad Schloss View Post
    so you use a split bolt then? so electrical tape over that is supposed to be safer than terminating #6 on the main breaker??!!? this would be the first post of over 100 that i have read that would choose this route. strange..
    It is about time you learned something
    If the breaker says that a #4 is the smallest conductor then a #6 would not be compliant. To use a split bolt of a polaris is the best choice at that time.
    So yes i suppose that I am saying that to use the proper size conductor is safer than using something that is non-compliant.

    EDITED TO ADD:

    I got to thinking while driving to school this morning about a statement you made here;
    Quote Originally Posted by Chad Schloss View Post
    so electrical tape over that is supposed to be safer than ..
    I would hope that someone would not just use electrical tape over a split bolt. First one should cover the split bolt with the backing that comes off rubber tape and then cover with a couple of layers of rubber tape before using 3M on the outside.

    Vinyl electrical tape by itself is almost useless in most cases simply because it will dry out and under heat turn to carbon. Just as the carbon that we use in our grills to cook hamburgers the tape will smolder for days before igniting something in its surroundings.
    Last edited by jwelectric; 11-15-2011 at 05:14 AM.

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    General Engineering Contractor ballvalve's Avatar
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    I think you left out the putty before the rubber tape. Whats with using the backing? It doesnt stick to anything, so saran wrap might be better. Putty takes the bumps out, tapers out and makes a clean shot. Now the tape lays clean. And I have never seen scotch 33 dry out and peel off, even after 12 years underwater. If we are talking harbor fright, I agree.

    I would think seeing a 100 amp breaker will cause the next guy to hook up his 80 amp welder in that place. Seems unsafe if not unreasonable to do that. Lot of ado and time for not buying the right breakerlesss panel in the first place.

    Our 'lately' mexican made breakers I have seen trip at 40 amps and some at 60 amps, so 2 would be a good backup.

    by the way, if he used an 'inline' set screw connector made for #6, it would likely slip right into the 100 amp terminals made for up to 3/0. That would be quick and clean and he need only insulate any part protruding.
    Last edited by ballvalve; 11-15-2011 at 10:58 AM.

  11. #11
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by ballvalve View Post
    I think you left out the putty before the rubber tape. Whats with using the backing? It doesnt stick to anything, so saran wrap might be better. Putty takes the bumps out, tapers out and makes a clean shot. Now the tape lays clean. And I have never seen scotch 33 dry out and peel off, even after 12 years underwater. If we are talking harbor fright, I agree.
    Using the backing keeps the rubber from getting into the threads of the split bolt and makes for a cleaner disassembly but of course someone without experience wouldn’t know this. There is no need for rubber putty if using the rubber tape.
    Spoke like a true well man. The installation is not going into a hole in the ground but instead is going in a panel exposed to the rise and fall of the temperatures or its environment. Without a doubt there will be dust and other flying’s in and around the tape. All this will dry out any tape but it takes experience to know things like this.

    Quote Originally Posted by ballvalve View Post
    I would think seeing a 100 amp breaker will cause the next guy to hook up his 80 amp welder in that place. Seems unsafe if not unreasonable to do that. Lot of ado and time for not buying the right breakerlesss panel in the first place.
    and anyone with experience would know that the welder would trip the 50 amp breaker supplying the 100 amp panel and then the next guy with the welder would know that the panel would not carry the load.

    Quote Originally Posted by ballvalve View Post
    Our 'lately' mexican made breakers I have seen trip at 40 amps and some at 60 amps, so 2 would be a good backup.
    are they not supposed to trip when they exceed their ratings?

    Quote Originally Posted by ballvalve View Post
    by the way, if he used an 'inline' set screw connector made for #6, it would likely slip right into the 100 amp terminals made for up to 3/0. That would be quick and clean and he need only insulate any part protruding.
    What is protruding?

  12. #12
    Moderator & Master Plumber hj's Avatar
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    quote; I would think seeing a 100 amp breaker will cause the next guy to hook up his 80 amp welder in that place. Seems unsafe if not unreasonable to do that.

    What is "unsafe" about it? The 50 amp breaker in the main panel will protect the #6 wire, and as soon as he tries to use the 80 amp welder and the 50 amp breaker trips he will have to reconsider his installation.
    Licensed residential and commercial plumber

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    General Engineering Contractor ballvalve's Avatar
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    Why not skip the suprise phase of the next guy in? And you have redundant safety for the installation and not a big wad of rubber in the box.


    are they not supposed to trip when they exceed their ratings?
    Are not 1.78$ Vi-agara tablets from india supposed to be legitimate and safe? Been to India? Is not the steering wheel on my jeep Patriot not supposed to fall off, as stated in my recent recall? Are not certain Firestone tires not supposed to delaminate at high speed and kill several families?

    What is protruding?
    I'll take that as agreement for a clean repair. But some are long and might protrude well out of the terminals.

    Maybe you dont use scotch 33, but its the gold standard, and as a topping over putty and rubber tape its fairly ornamental anyway. Over time it welds into a impenetrable mass and does not fall off. Hot, wet or cold. I cant imagine not using 15 cents of putty to get rid of all the sharp protrusions and bumps in the splice - makes the tape lay flat and clean. Makes the 'wrap' quick and easy. If you really want to get safe, brush on a coat of abs cement over the vinyl tape top coat.
    Last edited by ballvalve; 11-16-2011 at 11:25 AM.

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    Electrical Contractor/Instructor jwelectric's Avatar
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    All this time I thought that the Jeep was made in Belvidere Illinois here in the good ole USA.

  15. #15
    General Engineering Contractor ballvalve's Avatar
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    Toyota had more recalls last year than Dodge, so its a universal failing.

    The issue on the Jeep are a few rivets, most likely sourced from China or Mexico. Because we sold our machine tools to them, and closed our high school shops.

    Scotch 33 IS made in America.
    Last edited by ballvalve; 11-17-2011 at 05:05 AM.

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