Breaker Won't Trip, Is It Bad?

Discussion in 'Electrical Forum discussion & Blog' started by PM5K, Feb 28, 2009.

  1. PM5K

    PM5K New Member

    Messages:
    154
    Location:
    San Antonio, TX
    Recently some wires in the light for our ceiling fan started arcing, it generated so much heat that it burned through the metal (Aluminum?) of the light fixture itself. You could hear very loud popping noises when it was arcing.

    I took care of it by removing the light fixture (For now until we either get a new ceiling fan or a new light fixture).

    My question is, why didn't the breaker trip, and is that an indication that it may be bad?

    TIA
  2. Scuba_Dave

    Scuba_Dave Extreme DIY Homeowner

    Messages:
    885
    Location:
    South of Boston, MA
    Arc fault breaker will detect arcing & shut off
    If you know what else is on that circuit load it up to test
    Make sure it trips when capacity of the breaker is surpassed
  3. TedL

    TedL New Member

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    604
    Location:
    NY Capital District
    What's the brand of breaker/service panel?
  4. PM5K

    PM5K New Member

    Messages:
    154
    Location:
    San Antonio, TX
    I don't know off hand, I just assumed that normal operation of a circuit breaker is that it would trip if something connected to it arced.

    It sounds like you are saying proper operation is for it simply to trip it the load is too great for the breaker.
  5. maintenanceguy

    maintenanceguy In the Trades

    Messages:
    107
    Location:
    Pennsylvania
    I certainly can't tell from here what was going on inside the fan but it's possible that you had arching that wasn't drawing more current than the breaker was designed for and therefore the breaker should not have tripped.

    A high resistance fault will cause a spot that can get very, very hot but still won't trip a breaker. The only way to know is to use an amp meter and let it arc while you check the current draw.

    If I was worried, I'd swap out the breaker when I replaced the fan.
  6. PM5K

    PM5K New Member

    Messages:
    154
    Location:
    San Antonio, TX
    That sounds about right.

    I took out all of the sockets from the fixture and the insulation around the wires was gone near the sockets, which caused the arcing.

    Am I correct in assuming this is from the heat generated by the bulbs?

    I've always assumed that which is why I consider the fact that CFL's run much cooler than standard incandescent bulbs to be another advantage of using them.
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,820
    Location:
    New England
    If you don't exceed the wattage specified for the bulb sockets in the fixture, you should not be generating too much heat to create a problem. Putting say a 100W bulb where it says 60W max could create a problem. The wiring is rated at a specific temp, and there's a safety margin if you follow the instructions, nothing should happen.

    Think of an arc welder...lots of sparks, won't trip the breaker. Depends on how much current is being drawn. As mentioned, that sort of thing can still create a fire hazard, and is one reason why they now specify arc fault detector breakers for bedrooms - they are designed specifically to trip when that sort of thing happens.
  8. PM5K

    PM5K New Member

    Messages:
    154
    Location:
    San Antonio, TX
    For as long as I can remember they (my in-laws) have been using 60 watt bulbs which is the max recommended. I suppose it's possible that something else was used at some point in the past.

    Other than that, what else could cause this:

    [​IMG]
  9. Scuba_Dave

    Scuba_Dave Extreme DIY Homeowner

    Messages:
    885
    Location:
    South of Boston, MA
    Green - looks like corrosion/oxidation too
    Is this really old?
  10. PM5K

    PM5K New Member

    Messages:
    154
    Location:
    San Antonio, TX
    I just assumed that was bound to build up since the insulation was gone.

    It's probably about fifteen years old but that's just an educated guess.
  11. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,820
    Location:
    New England
    Looks sort of like it got wet.
  12. TedL

    TedL New Member

    Messages:
    604
    Location:
    NY Capital District
    Standard circuit brakers will not trip simply due to an arc. That's why there are the relatively new Arc Fault Circuit Interrupters, which do trip in that circumstance.

    You want to make sure that you do not have Federal Pacific Electric (FPE) breakers and panel. A high % do not trip when they should; they also have other well documented problems. Serious stuff. Please take the 60 seconds to look at the panel.
  13. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,292
    Location:
    Cave Creek, Arizona
    arc

    An arc is not a short circuit. That is why arc welders can work as long as you do not touch/weld the electrode to the workpiece.
  14. maintenanceguy

    maintenanceguy In the Trades

    Messages:
    107
    Location:
    Pennsylvania
    From the picture of the socket, I'd say the wires got too hot. Either too big a bulb was used, air flow around the wires was restricted, or the fixture was designed and manufactured poorly. Since it's only melted on the very end, near the terminal screws, it could be a loose, corroded, dirty connection at a screw. Bad connections causee high resistance and hot spots that will heat up the copper wire within a couple of inches of the bad connection.

    Once the insulation is gone, the copper is exposed to the air and pretty hot so it oxidizes quickly.

    If you're married to this fixture, there's high temperature wire available to re-wire it. I'm not sure what the covering is now but it used to be a fabric asbestos material. I still ask for "some of that asbestos high temp wire" and they know what I want.
  15. Alectrician

    Alectrician DIY Senior Member

    Messages:
    689
    It MAY be an indication of a bad breaker but probably not.

    A standard breaker is designed to take a bigger load for a short time. I have seen many temporary shorts that didn't trip the breaker.

    The burned wiring is simply from the heat from the lamp over the years. It's a very common occurance.
  16. PM5K

    PM5K New Member

    Messages:
    154
    Location:
    San Antonio, TX
    Thanks for the heads-up, I just didn't understand exactly how breakers work, but now I do.

    Does anyone know if arc fault breakers will work with ceiling fans? I was reading that they don't work with electric motors such as treadmills, or dishwashers.
  17. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,820
    Location:
    New England
    Many motors have brushes in them, and those will cause some arcs. I think they'd be problematic on an arc-fault breaker.
  18. thefonz

    thefonz New Member

    Messages:
    3

    Sometimes known as "Federal no blows" :D
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