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Accidentally drilled live wire.

Discussion in 'Electronic Basics' started by Chris, Jun 1, 2006.

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  1. Chris

    Chris Guest

    No harm done (to me, at least), but I accidentally drilled into a live,
    metal sheathed wire while hanging a tv bracket. (I happened to hit it
    right where it was stapled to the stud, so the sheathing didn't move
    and I drilled right into it. Other annoying thing is that I actually
    used a stud sensor with one of those wiring detectors, but it didn't
    pick it up). Weird thing is that it cut the power to my daughter's
    room, which is next door and on the same circuit as the room as I was
    in, but it didn't cut the power to the room I was actually in, nor did
    it blow the breaker.

    Anyhow, I cut into the wall, found the damage, removed a section (3
    inches?) of the metal sheathing, and spliced a piece of romex into the
    line. Functionally, this did the trick. My question, though, is how
    safe is this fix? The tie in is the same as for hard-wiring lighting
    fixtures, for example, but this is a power line we're talking about.
    Also, once I repair the wall, the splice will be essentially
    inaccessible. Also, assuming I need to have an electrician come in to
    replace the metal sheathed wire section, how big of a job would that
    be? I suspect the sheathing is "stapled" every couple of feet or so.
    Would he have to tear up the walls in both rooms to swap in a new wire?

    I'm less concerned about the cost than the hassle, but I also don't
    want to burn my house down. Any advice would be much appreciated.
  2. tombiasi

    tombiasi Guest

    You should not burry a splice in the wall.
    The proper way is to get enough slack before and after where you cut the
    wire to bring the ends out into a box.
    The splice is made in a box with a cover on it.
    The cover is accessible from outside the wall.
    If you don't like a blank plate on your wall, run new wire, but do not
    splice inside the wall.
    Electrician cost will depend on how much time this will take.
    I can't tell from here.
    Only one side of the wall needs to be disturbed.
  3. Bob Eld

    Bob Eld Guest

    In the US this "fix" probably violates the code. Splices are supposed to be
    in junction boxes not unprotected in walls. The wires should be joined on
    screw terminals or by use of wire nuts or crimps, but NOT soldered.

    The best way to do this is to put a metal junction box in the wall where the
    break is and splice the romex addition to the existing wires in the box
    using wire nuts. The box should be closed with a cover plate and may be
    walled up after the repair. There is no need to re-wire the whole length
    with a new sheathed cable.
  4. Jamie

    Jamie Guest

    its not up to code!
    not suppose to have boxes or wire attached to the studs, they are
    suppose to be 1.5 inches or more away from the studs. that is why they
    made the rule in the NEC book. you use wooden stand offs or metal
    brackets that can be attached to the studs if you want
    different rooms are suppose to be on their own circuit for the outlets
    and lights are on their own circuit etc....
  5. George

    George Guest

    Can you locate the place where this wire enters the wall in the attic
    or basement?
    if you can does it go directly from its point of entry down the wall to
    a switch or outlet?
    If so you could cut the wire there, pull a new section of wire down (or
    up) to the switch or outlet and set a box in which to make the

    I'm assuming your referring to a flexible metal conduit or sheathing
    was used
    I'm curious as to why someone used that in residential wiring.
  6. I'm more curious why the "live wire" sensor didn't detect the wire.

    Any idea how far away the wire was from the sensor? Did you move the
    sensor around the spot you were going to drill with several passes with
    the sensor orientated up/down and left/right?

    Can you verify the sensor is working by passing it around a known live
    electrical outlet?

    "Annoying" is an understatement.
  7. Chris

    Chris Guest

    I moved it all over the place--and the wire couldn't have been more
    than the thickness of a piece of drywall plus maybe an inch or so from
    the sensor. Also, because I saw there was an outlet more or less in
    line with where I wanted to drill, I did it a few times and the only
    reading I got was right by the outlet itself. So I
    assumed--incorrectly, obviously--that the wiring went down through the
    floor instead of up the wall.
  8. bad. I misses the part about it being in a metal sheath. That
    would explain the sensor not picking it up. It would pick it up around
    the outlet as it has a plastic cover.

    But I would also wonder why the metal stud detector of your stud sensor
    didn't see it.

    When cutting or drilling into walls, I don't like to assume there is
    nothing behind them - especially with residential work. So I use my stud
    sensor and Greenlee live wire sensor, followed by a magnetic stud sensor.

    Now someone up with a fresh water in a PVC pipe detector - they already
    have (bull)sh*t detectors for the sewage lines. <snicker>
  9. JeffM

    JeffM Guest

  10. Jasen Betts

    Jasen Betts Guest

    it could be that your live wire detector only detects wires that aren't
    encased in metal. If it has a metal detector setting that may get you
    what you want.

  11. Chris

    Chris Guest

    That would be my fault--I knew the wall had wooden studs so it never
    occurred to me to flip the stud finder over to "metal" mode. Of
    course, I wasn't counting on the armored electrical wiring. Live
    (luckily) and learn, I guess.
  12. <BIG SIGH OF RELIEF> at least its not a mystery now. Undetected wires
    are evil.
  13. Alan B

    Alan B Guest

    I'm betting on this explanation. The metal sheath will "suck up" any
    magnetic field that the detector might be looking for. Permeability is the
    magic word.
  14. ehsjr

    ehsjr Guest

    It is neither safe nor up to code.
    If you can get enough slack (not likely), you can
    splice the wires in a new junction box at the site
    of the break. The box must be accessible after the
    wall is repaired. Sometimes it works well to put
    a receptacle in the new box.

    If you don't have enough slack, you either need
    to tear into the wall (bad news) or do a bit of
    rewiring. That means disconnecting the cable
    at the last outlet before the break so that the
    section of wire in the wall is dead, and running
    a new cable from the basement or attic to the
    first dead outlet that died as a result of the

    Since you are less concerned with the cost than the
    hassle, hire an electrician. They are good at this
    kind of repair with minimal disruption.

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