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Thread: Can a load center have a breaker as large as its main?

  1. #1
    DIY scratch-pad engineer leejosepho's Avatar
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    Default Can a load center have a breaker as large as its main?

    I have a 30-amp feed going back to my detached workshop, and here is the load center in the workshop ...

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    I have a great-working old 120V arc welder that needs 30 amps ...

    http://books.google.com/books?id=8v2...welder&f=false

    Question: Can I put a 120V 30A breaker in my shop's loader center that has a 240V 30A main breaker?

    If I do that for the welder, I would use a NEMA L5-30P plug and receptacle just for the welder.

  2. #2
    Electrician ActionDave's Avatar
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    You can install the breaker, but you have what appears to be another problem. Is there a green screw next to the white wire in the top right corner of the panel in your photo?

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    DIYer, not in the trades LLigetfa's Avatar
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    Around here we were not allowed to mount a panel directly against wood and must put a layer of sheetrock in between.
    Last edited by LLigetfa; 09-29-2011 at 05:32 AM.

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    DIY Senior Member BobL43's Avatar
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    Quote Originally Posted by LLigetfa View Post
    Around here were are not allowed to mount a panel directly against wood and must put a layer of sheetrock in between.
    That's funny because around here the electricians nail a plywood sheet to the concrete foundation to mount the panel
    I am definitely not a pro plumber, but I am a pro crastinator

  5. #5
    DIYer, not in the trades LLigetfa's Avatar
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    Oops... I stand corrected.

    Question
    Does the Code require the installation of drywall behind an electrical panelboard?


    Answer
    No. This requirement was removed in the 2002 Edition of the Ontario Electrical Safety Code.

  6. #6
    DIY scratch-pad engineer leejosepho's Avatar
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    Quote Originally Posted by ActionDave View Post
    You can install the breaker ...
    That is good to know, and I thank you.

    Quote Originally Posted by ActionDave View Post
    ... but you have what appears to be another problem. Is there a green screw next to the white wire in the top right corner of the panel in your photo?
    No, but you definitely got me up out of my seat to go take a look! That screw is silver and just happens to appear green in that picture, and it holds the commons bar to that lug. The bonding screw is laying in the bottom of the panel, and it would go in the spot just above the screw you have asked about.

    Edit: Here is the rest of my story ...

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    The house has an old 60A XO panel directly behind the meter, and then the former homeowner added the exterior panel with 240V breakers for the workshop, dryer, AC and stove with everything still being fed by the original 60A service with #8 wire at the eave!

    We are presently on an electrician's project list to have our service entrance upgraded, and I will likely wait until then before doing very much with my welder even though all is well in the workshop.
    Last edited by leejosepho; 09-29-2011 at 06:04 AM.

  7. #7
    Electrical Contractor/Instructor jwelectric's Avatar
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    The back fed 30 amp breaker needs to be tied to the panel.

    You are correct your service needs attention

  8. #8
    DIY scratch-pad engineer leejosepho's Avatar
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    Quote Originally Posted by jwelectric View Post
    The back fed 30 amp breaker needs to be tied to the panel.
    You are talking about some kind of retainer for the main in the workshop, correct? I do not know what part I need to do that, but I do plan to ask the electrician about that when he comes out to update our service entrance.

  9. #9
    DIY Senior Member dlarrivee's Avatar
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    Quote Originally Posted by LLigetfa View Post
    Around here we were not allowed to mount a panel directly against wood and must put a layer of sheetrock in between.
    Sounds bogus to me, around HERE we're required to have a plywood for the panel to mount upon.

  10. #10
    DIY scratch-pad engineer leejosepho's Avatar
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    Default A question about my galvanized-steel ground rod

    I added a lighting circuit to the panel at the beginning of this thread, and I inadvertently shorted the black wire to the panel when I apparently over-tightened the clamp holding the wire at the top of the panel. The clamp was not really all that tight, but the "bump" on its plate was more of a sharp "V" than just "gently round" like I usually see, and the insulation on the new 12-2 w/G wire I used seems to me to be relatively light. In any case ...

    I was standing barefoot on the concrete floor of the workshop, and I felt a very light tingle through one of my fingers touching the end of one of the screws while I was wiggling the wire a bit (to check its tightness) and tightening that clamp. At that point, and since the box is not bonded, I soon discovered 120V between white and ground (since the ground was now hot), and nothing at all between black and white. It took me a while to realize the pinching clamp was the problem, but I eventually figured that out after checking all other connections in/at every box in that circuit.

    Question: Why/How did/could I feel a small trickle of voltage between ground and the concrete floor?

    My only guess is that my new 5/8" X 6' galvanized ground rod is in soil too dry for it to work properly. We have had virtually no rain here in NW Louisiana for some time now ...

    ... and it is a good thing I was barefooted today or I might not have caught that problem so quickly!
    Last edited by leejosepho; 10-07-2011 at 05:32 PM.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    That tickle could just as easily been enough to stop your heart! Never work on electricity in your bare feet. The ground rod is primarily for protection during lightening strikes...don't count on it for an effective ground. Neutral is on the center point of a 240vac transformer...and, it may not be exactly in the center. The current is trying to return to the source generator. Ground is sort of relative.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  12. #12
    Electrical Contractor/Instructor jwelectric's Avatar
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    There is no equipment grounding conductor installed with the feeder to that panel and no bonding in the panel so therefore any and all equipment grounding conductors in the small panel is mute.

    Either install an equipment grounding conductor with the feeders or bond the neutral and equipment grounding conductors in the small panel to give the fault current somewhere to go. Personally I would install an equipment grounding conductor with the feeders

  13. #13
    DIYer, not in the trades LLigetfa's Avatar
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    I think you mean "moot". Obviously the metal conduit did not provide a ground path sufficient to trip the breaker. I'm surprised you went so easy on lee with such a blatantly hazardous situation.

  14. #14
    DIY scratch-pad engineer leejosepho's Avatar
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    Quote Originally Posted by jadnashua View Post
    That tickle could just as easily been enough to stop your heart! Never work on electricity in your bare feet.
    I do understand the safety issues there, and my bare feet in this case had to do with my assumption the ground rod was doing more than it is apparently doing.

    Quote Originally Posted by jadnashua View Post
    The ground rod is primarily for protection during lightening strikes...don't count on it for an effective ground.
    I actually knew it was for lightning, and I am going to have to get the idea of it being an overall catchall out of my head. I thank you.

    Quote Originally Posted by jwelectric View Post
    Either install an equipment grounding conductor with the feeders or bond the neutral and equipment grounding conductors in the small panel to give the fault current somewhere to go. Personally I would install an equipment grounding conductor with the feeders
    I understand, and I thank you.

    Question #1: What about this from early-on here ...
    Quote Originally Posted by ActionDave View Post
    You can install the breaker, but you have what appears to be another problem. Is there a green screw next to the white wire in the top-right corner of the panel in your photo?
    ??

    If I am understanding correctly, bonding that small panel in my workshop is not a good idea since a problem at the house could send stray current on down the line and leave a heart-stopping tingle waiting on my metal switch cover.

    Question #2: Would an equipment grounding conductor along with the feeders actually be any better than what I already have? It seems to me that the problem I had yesterday would still be possible since the ground rod at the house is likely no better than the one at the workshop.

    Quote Originally Posted by LLigetfa View Post
    I'm surprised you went so easy on lee with such a blatantly hazardous situation.
    We used to have that kind of problem here, but he has learned there is just no need!

    Quote Originally Posted by LLigetfa View Post
    Obviously the metal conduit did not provide a ground path sufficient to trip the breaker.
    The conduit coming into the workshop is plastic, and it goes to a junction box since the feed was too short to reach the panel. So, the metal conduit you see is only grounded to the workshop's new ground rod ... and all of this work got started because I was getting a tickle from the table saw. When I first got to this house a little over a year ago, only one leg of the feed and the feed's neutral came into a receptacle on the wall and then there was a spider's nightmare going out from there. I ultimately discovered three of four receptacles with the black and white reversed, and someone had used a 3-way switch with one terminal going to ground (even though there really was no ground anywhere) for the old fluorescent light over the workbench.
    Last edited by leejosepho; 10-08-2011 at 07:52 AM.

  15. #15
    General Engineering Contractor ballvalve's Avatar
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    work on electricity barefooted and you'll look worse than that photo you post.

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