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

Discussion in 'Electrical Forum discussion & Blog' started by leejosepho, Sep 28, 2011.

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  1. leejosepho

    leejosepho DIY scratch-pad engineer

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

    shoppanel.jpg

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

    http://books.google.com/books?id=8v...nepage&q=twentieth century 115 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. ActionDave

    ActionDave Electrician

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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?
  3. LLigetfa

    LLigetfa DIYer, not in the trades

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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: Sep 29, 2011
  4. BobL43

    BobL43 DIY Senior Member

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    That's funny because around here the electricians nail a plywood sheet to the concrete foundation to mount the panel
  5. LLigetfa

    LLigetfa DIYer, not in the trades

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    Oops... I stand corrected.

  6. leejosepho

    leejosepho DIY scratch-pad engineer

    That is good to know, and I thank you.

    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 ...

    service.jpg

    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: Sep 29, 2011
  7. jwelectric

    jwelectric Electrical Contractor/Instructor

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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. leejosepho

    leejosepho DIY scratch-pad engineer

    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. dlarrivee

    dlarrivee New Member

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    Sounds bogus to me, around HERE we're required to have a plywood for the panel to mount upon.
  10. leejosepho

    leejosepho DIY scratch-pad engineer

    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: Oct 7, 2011
  11. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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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.
  12. jwelectric

    jwelectric Electrical Contractor/Instructor

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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. LLigetfa

    LLigetfa DIYer, not in the trades

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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. leejosepho

    leejosepho DIY scratch-pad engineer

    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.

    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.

    I understand, and I thank you.

    Question #1: What about this from early-on here ...
    ??

    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.

    We used to have that kind of problem here, but he has learned there is just no need!

    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: Oct 8, 2011
  15. ballvalve

    ballvalve General Engineering Contractor

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    work on electricity barefooted and you'll look worse than that photo you post.
  16. Cookie

    Cookie .

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    Lee, wear rubbersoled shoes while working on electricity and standing on especially, concrete. Believe it or not, while concrete appears to be a very dense material, it is in fact quite like a blotter. It can and does absorb water. You can actually see this happen on a hot summer day. Sprinkle some water on your sidewalk or driveway and look very closely. You can actually see the water penetrate the surface of the concrete. I don't think it would be much diffferent in the basement or you would not had felt that tingle. Concrete soaks up water from the soil.
    Last edited: Oct 8, 2011
  17. leejosepho

    leejosepho DIY scratch-pad engineer

    That photo you mention is not bad at all if you might happen to know and acknowledge the actual facts of the matter ...

    IM000448.JPG

    Yes, concrete is porous. In this particular case, however, I am concerned now that I know full voltage can go to ground without tripping a breaker ... and it is actually a good thing that I happened to be barefoot at the time or else I would not have even known there was a problem ... and so now I am thinking about installing a ground-fault breaker for the circuit in question. I just happen to have two of them on hand in the used panel the electrician is going to install in our house. My father-in-law had added an outlet out in the yard, and now I need to use GFI somewhere before reconnecting that wire anyway.
    Last edited: Oct 9, 2011
  18. leejosepho

    leejosepho DIY scratch-pad engineer

    Now baffled and needing some education ...

    Okay, here is my present dilemma helping me be grateful this is a DIY forum ...

    I have two QO120AFI breakers, and I have installed one of them in my workshop panel ... and now any attempt to place any kind of load on either circuit connected to the QO120AFI trips it. Why? I have the breaker's built-in "Panel" wire going to the panel's ground bar, and I have a second wire running from the breaker's "LOAD (N)" screw to the panel's Neutral bar ... and note: Disconnecting that second wire does not make any difference here.

    After turning off the main breaker in the workshop panel and checking for any possible continuity that should not be there, I have no continuity between any black and neutral or any black and ground ...

    ... however, I do have continuity between the panel's neutral bar and ground even though the panel is not bonded, and that suggests to me that the workshop's ground rod is working well and interacting with the ground rod about 80' away at the house where things likely *are* bonded.

    Other than my not knowing how to solve my present problem, what actually *is* my present problem?

    My goal here is to protect anyone and everyone from any kind of stray current while s/he might be standing either barefooted or with shoes on the workshop's concrete floor.

    Am I trying to use the wrong kind of breaker or something?
    Last edited: Oct 9, 2011
  19. LLigetfa

    LLigetfa DIYer, not in the trades

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    Any load, even a light bulb?
  20. leejosepho

    leejosepho DIY scratch-pad engineer

    The itty-bitty charger for my iPod does not trip it, but yes, the lights (two 60W bulbs) or even just the larger AC adapter for the computer speakers I have there for my iPod will trip it.

    I just tried the second AFI breaker in place of the first, and it does the same. My only guess here is there must be a problem at the house and the AFI in the workshop is picking it up ...

    Is that possible?
    Last edited: Oct 9, 2011
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