Load Center Wiring Questions

Discussion in 'Electrical Forum discussion & Blog' started by Lakee911, Jan 23, 2008.

  1. Lakee911

    Lakee911 I&C Engineer (mostly WWTP)

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    Am I allowed to double lug (a circuit breaker) for a hardwired secondary surge arrestor?

    Considering the fact that the main disconnect is a suitable overcurrent protection device, I could connect the device to the bus bar lugs. The wire size is too small, so how could I fit a #12 wire into a lug designed for something like #1 wire?

    Are wire connectors allowed in a panel? I'm replacing a panel and would like to know how to lengthen existing wires if the connectors are not allowed.

    Panel is mounted against the wall and the ceiling is low (6.5 or 7ft). Can I bundle the cables (with wire wraps) coming in overhead through one large 2in. knockout and through one cable clamp, or must I bring them in seperately, in conduit? The distance to the ceiling will only be a few inches.

    If I mount a 3/4" piece of plywood directly on the masonary block wall with powder actuated fasteners, will 3/4" long fasteners in the plywood alone be adequete to carry the weight of the panel?

    Thanks,
    Jason
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    The supressor I have on my panel specifically states in the installation instructions that it must be on its own breakers (either one 220 or two 110 on separate legs).
  3. Chris75

    Chris75 Electrician

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    What did the instructions that came with the surge protection say? ;)

    and no, you cannot have two wires under one screw...
  4. Lakee911

    Lakee911 I&C Engineer (mostly WWTP)

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    It didn't say anything about dedicated breakers on the instructions.

    I thought I couldn't have two wires under one screw but an electrician told me otherwise (not that it makes it right). He's a friend, so I didn't want to ask for a code reference.

    Jason
  5. Bob NH

    Bob NH In the Trades

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    All of my new breakers have connections that are designed for one or TWO wires. You can tell if the connection has a small plate under the screw with a place for a wire on each side of the screw.

    If your surge protector has wires coming from it and no terminals for mating to the lugs of the panel, then it is made to be wired into a circuit. I would just follow the instructions.

    Wire nut connections in the service panel are PERMITTED if there is room, and there is in any modern service panel.
  6. Alectrician

    Alectrician DIY Senior Member

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    689

    Sure you can...if the breaker is designed/rated for two conductors ie. SquareD QO style.
  7. Lakee911

    Lakee911 I&C Engineer (mostly WWTP)

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    Ok. Well, that's the panel in question.


    What do you all think of the other questions?

    Thanks
  8. Cass

    Cass Plumber

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    What you can't / shouldn't do is put 2 different size wires on the same breaker like taking a #12 and #14 wire and putting it on a 15A breaker. I have found a few situations like this and the #14 becomes loose because of uneven applied torque due to the wire size difference.
  9. Chris75

    Chris75 Electrician

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    I knew it had to be listed, just did not know sq. D had allowed it.. thanks...
  10. lampman42

    lampman42 New Member

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    Re: Panel Questions.

  11. Lakee911

    Lakee911 I&C Engineer (mostly WWTP)

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    Well, you're a few days late, since I already used the pins! I put in seven 1-1/2" pins. I don't think it's going anywhere. I'll keep an eye on it. I'll add tapcons if they start to move.

    Jason
  12. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

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    Last edited: Feb 8, 2008
  13. Chris75

    Chris75 Electrician

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    No, each cable shall be secured to the cabinet. Some connectors will allow two cables in each connector...



    ONLY IF you meet the following... (which you probably don't... I have yet to see a code compliant installation of this section)

    Cables with entirely nonmetallic sheaths shall be permitted to enter the top of a surface-mounted enclosure through one or more non flexible raceway not less than 18 in. or more than 10' in length provided all of the following are met:

    (a) Each cable is fastened within 12" of the outer end of the raceway
    (b) The raceway extends directly above the enclosure and does not penetrate a structural ceiling.
    (c) A fitting is provided on each end of the raceway
    (d) The raceway is plugged or sealed
    (e) The cable sheath is continuous through the raceway.
    (f) The raceway is fastened at its outer end
    (g) you meet the allowable cable fill
    Last edited: Feb 8, 2008
  14. Chris75

    Chris75 Electrician

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  15. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

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    May be very hard, but very common, and have apparently passed inspection. Can you give me the chapter & verse on that citation? There must be a loophole...
  16. Chris75

    Chris75 Electrician

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    check out 312 .5(C) You dont need a loophole, you just need to follow the code, and its usually hard to meet the requirements
  17. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

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    Thanks for the cite. I've spent some quality time on Mike Holts' forum and, as usual, find the discussions fascinating and the Code in desperate need of work beyond the normal revision cycle.

    312(5)(C)(b) immediately rains out the parade by prohibiting penetration of a structural ceiling, which is the reason for using the conduit in the first place. I can't believe that any reasonable person would prefer 30-40 individual cables making their way out of the attic space into individual knockouts on the panel to running them through several large conduits. But, is a garage ceiling "structural"? At least one NEC expert says no. If there's no drywall on the ceiling and the conduits pass between the joists, are they "penetrating" the ceiling? Maybe, maybe not.

    312(5)(C)(g) says to use Table 1 of Chapter 9 to determine conduit fill; Note 2 to Table 1 says Table 1 is "not intended to apply to sections of conduit or tubing used to protect exposed wiring from physical damage", which seems to be the case here, since 312.5 starts out by saying "conductors... shall be protected from abrasion...".

    Finally, the entire Exception under 312.5(C) applies to a "surface mounted" enclosure. If the service panel is mounted between 2 framing members, is it "surface mounted"? What if the panel is mounted on the surface of a masonry wall, on which a finish wall is later constructed so that the panel is ultimately flush with the finished surface?

    Bottom line, as usual, seems to be that the Code is pretty vague and conflicting in may instances; ultimately, if your AHJ likes it, it's OK. There seem to be lots of conflicts in both directions -- one inspector mentioned on Mike's forum, for example, will not accept plastic boxes with the integral cable clamps, even though they're UL approved, Listed, and still have a few drops of holy water on them.
    Last edited: Feb 10, 2008
  18. Chris75

    Chris75 Electrician

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    Location:
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    You get used to it, its really not that hard, to me it would be harder later on to add/remove circuits that were all installed in a conduit.

    Definition: The overhead surface in a room, made from any of several materials, as wood or plaster.

    Yes. BUT, 312.5(C)(g) is telling you to use the table...



    It means what it says, the panel MUST be surface mounted...

    I dont worry about what if's... cross that bridge when it happens...

    Listen, I have never met an AHJ, only inspectors, they can only inspect, not change the rules as they go, so if there is no state amendment, then they are making their own rules which is so wrong.... and its not OK if an inspector thinks its OK, its a code violation and they are not doing their job....
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