Metal framing

Discussion in 'Electrical Forum discussion & Blog' started by frenchie, Nov 20, 2007.

  1. frenchie

    frenchie Jack of all trades

  2. jwelectric

    jwelectric Electrical Contractor/Instructor

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    North Carolina
    If you are using metal boxes and the boxes are mounted to the metal frame and the boxes are properly bonded the metal studs are bonded through the process.
  3. 480sparky

    480sparky In the Trades

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    149
    Why would metal framing need to be grounded? Look at all the other metal stuff in buildings that aren't: Steel doors, aluminum storm doors, aluminum window frames, gutters & downspouts, metal drywall corner beads, copper roofs, aluminum & steel siding, metal cabinets, iron railings, garage doors, cast iron plumbing ......
  4. AZ Contractor

    AZ Contractor In the Trades

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    I have no idea why they should be grounded. Then again, I have no idea why they shouldn't be grounded.

    So why should they be or why shouldn't they be grounded?

    :rolleyes:
  5. Verdeboy

    Verdeboy In the Trades

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    2,051
    The difference is obvious: The metal frame is all linked together, unlike the other examples you cited. Thus, if any one part of it becomes energized, the entire frame of the house would become "hot."

    I recently ran into a situation where a metal staple had punctured the sheathing on some romex cable behind a wall. The wooden stud had burned slightly during the short, but the breaker never tripped!

    I don't know how the wiring is affixed to metal studs, but if something similar occurs, where the frame comes in contact with a hot wire, and if the breaker didn't trip, that would be bad.
  6. Alectrician

    Alectrician DIY Senior Member

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    689
    If you were using metal studs with NM and plastic boxes I can see where it might be an issue.
  7. Chris75

    Chris75 Electrician

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    Location:
    Litchfield, CT
  8. Verdeboy

    Verdeboy In the Trades

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    Damn. I guess my instincts were right. Too bad for that guy and his family.
  9. Chris75

    Chris75 Electrician

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    608
    Location:
    Litchfield, CT
    What was up with the hack install? And the comment about being a homerun? Where do they find these guys?
  10. frenchie

    frenchie Jack of all trades

    What I said, sorta - in NYC all the wire's BX, so anywhere it goes through the framing... this afternnon on the train I was thinking "and duh, the boxes are all screwed to the studs!" Because it's all metal boxes here, too.

    But then there's jurisdictions where metal framing goes with NM, and bushings, and (I assume) plastic boxes (?).

    LOL. Neither of you followed my link, huh? I brought up all the hurricane strapping and filch plates and joist hangers and shear panels in a coastal house.

    But then I considered that none of that's all connected to each other, like framing...

    I'm hoping you will click on Chris' link, I'm curious to get your views. How about it? Should there be a provision for grounding metal framing?
  11. BrianJohn

    BrianJohn DIY Senior Member

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    Location:
    VA
    In commercial applications it is "almost" impossible for the metal studs not to be grounded, due to the use of metal boxes, anchoring the track to the concrete and other metal structures in the building coming in contact with the framing members. In residential applications the only reason I can see why they are not grounded, is there have been no incidences that have brought this issue to the attention of the Code making panels.
  12. Alectrician

    Alectrician DIY Senior Member

    Messages:
    689
    Obviously.

    There MAY be something now , I don't know.
  13. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

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    A real freak accident. It's not clear to me why "bundling" the cables would have prevented the accident, as implied in the video. I've always felt the opposite way -- that leaving cables loose allows them to move out of the way of wayward screws and nails. Something had to have held that wire in place while the screw advanced... I would like to know why that cable was being held in place less than 5/8" from the backside of the drywall with no protection? Isn't there a 1 1/4" minimum requirement somewhere in the Code?
  14. Chris75

    Chris75 Electrician

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    608
    Location:
    Litchfield, CT

    When the used the word "bundling" I believe they meant strapping the wire... (it was just an example they were showing of other wires done correctly, the wire that got hit was just free flowing in the wall...)

    as far as the 1 1/4 rule, it would fall under 300.4 (D)
    Last edited: Nov 24, 2007
  15. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

    Messages:
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    Location:
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    My point exactly. Couldn't have been "free flowing", or it would have moved when the screw hit it. Probably was hit close to a fastened point, so the cable wasn't truly free. I've experimented a little with screw guns and nail guns going through 1/2" sheetrock into a stud cavity where cables were run -- never been able to pierce "free flowing" 14-2 or 12-2 cables with a screw, but nails are a problem due to their high velocity. Some of the heavier cables (e.g., 8-3) have enough mass that a nail will almost always pierce them before they've had time to move out of the way.

    Thanks for the Code reference; that's what I was thinking of. Interesting that the requirement is for cables running parallel to the studs only. In the video, it looked like the cable was perpendicular to an adjacent stud, but I may have misinterpreted what I saw. It was a 1 1/4" screw, not 1 1/8" as they said, but that's a nit.
    Last edited: Nov 24, 2007
  16. Chris75

    Chris75 Electrician

    Messages:
    608
    Location:
    Litchfield, CT
    I said it was free flowing only by watching the video, but I agree with you, seems like it would be 1 in a million for that screw to go through unless it was fastened in place...
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