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very shocking ceiling fan install

Discussion in 'General Electronics Discussion' started by jackorocko, Jun 25, 2011.

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  1. jackorocko


    Apr 4, 2010
    So I took on the job of putting in a new ceiling fan today. Not completely thinking I just turned off the switch on the wall and figured good enough. Well was I mistaken, as I started to pack up the light fixture wiring and current regulator, I felt this shock and next a spark with a loud bang.

    Interested look on my face, I couldn't understand what just happened. So I got out the meter and took a closer look, hot to ground 120V???

    So my question is why would someone switch the neutral leg in a circuit? What are the advantages of switching the hot or neutral side, disadvantages? I was surprised to see that it arced through the plastic box that the current limiter was installed inside of... Still kinda confused on why it is safe now with the hot side switched?

    I did call the inspector and asked if there was a specific way the code states, and he said NO, but usually switch the hot and on rare occasions the neutral. What rare occasions would those be?
  2. davenn

    davenn Moderator

    Sep 5, 2009
    thats a bit freaky, bet that gave you a fright with the bang huh

    I couldnt think of any rare occassions, All gear I have ever seen either switches just the hot or both

  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    My guess is that the "technique" in use was either unintentional or uninformed.
  4. shrtrnd


    Jan 15, 2010
    I've seen that happen when a do-it-yourselfer does part of the installation.
    Usually happens when somebody ties the ceiling fan power into some other device on
    the same leg. A second ceiling fan, another light or socket in the room, or multiple
    on-off switches for entry and exit from two ends of the room.
    *steve* pegged it, if somebody isn't careful, you can inadvertantly switch a neutral.
  5. jackorocko


    Apr 4, 2010
    Well I did learn a lesson out of this situation. So all was not lost on that electrician 40 years ago.
  6. daddles


    Jun 10, 2011
    Good for you jackorocko, it could have been a much more tragic story.

    For others that read this, the fundamental rule is to not work on wiring that has power to it. While that seems obvious, it's not to hard to make a mistake. Here's what I recommend when working on your home's wiring:

    Get a digital multimeter. Measure the AC voltage of a known working outlet to verify the meter is working. Then measure the AC voltage on each wire to every other wire in the area you're planning on working; also measure to any exposed metal. If there are n wires, you have n*(n-1)/2 measurements to make (you only need to measure one polarity). You should measure no more than 1 or 2 volts on a circuit to consider it safe. You may run in to phantom voltages; get an older VOM if you can or put a 47 kohm resistor in parallel with your meter leads.

    After making the measurements, measure a known good outlet again to verify your meter is working. This ensures you aren't electrocuted by a false negative.

    BTW, when I'm working on an unknown black box, I'll also make checks by measuring DC voltage. Your AC measurements might look safe, but there could be 100 VDC on some conductors and you want to know about that too. Again, check the meter before and after with a known-working voltage source.

    Now, I'm even more anal than that. I use a non-contact voltage detector after doing this to check each wire. Years ago this saved me from getting electrocuted, as a wire was hot but my multimeter said it wasn't (I believe the probe didn't punch through the oxide layer). Of course, check the non-contact detector on a known-good working outlet before and after too.

    If you get anal like this, you'll live long enough to terrorize your grandkids. :p

    Oh, one other thing. I can't lock out my circuit breakers, but if I'm working on a circuit, I turn the breaker off and put red or orange tape over it with a message not to turn it on, as the circuit is being worked on. Family members have all been warned to never touch a breaker so marked.
  7. duke37


    Jan 9, 2011
    I always check with my magic screwdriver.
  8. markalic


    Jun 27, 2011
    They just don't know :)
  9. jackorocko


    Apr 4, 2010
    Well this story got a little more interesting... After having the fan and light in working order for just a few hours a day over a ten day stretch, yesterday things got rather interesting again.

    So I turned on the switch and the breaker kicked immediately. I have added a few more appliances to this branch so I figured what the hell, maybe a weak breaker. Left the light off and went to bed, woke up the next morning and all the appliances where off so I turned on the fan/light and more sparks and bangs.

    Turns out the manufacture, which I will name here Harbor Breeze pretty much shipped a defective fan/light by even an idiots standards. They left a clipped wire with bare copper showing close to the end of the pull switch. Apparently when I pulled it a few times it must have moved the wire closer to the case or it was the fans vibrations.

    Fire waiting to happen and people wonder why others have trust issues
  10. jackorocko


    Apr 4, 2010
    The more I think about it this is why the original current regulator blew, being rated for around 1.5 amps. This also explains why Nothing happened until I plugged in the light fixture which contained the hidden disaster.
  11. jcurrie


    Feb 22, 2011
    a light pen is a must if your working around 12 (ac or dc) or above i use one all the time to check if voltage is present the only time i have seen interuptors on the nutral side is in computer controlled stuff(cuts down on voltage spikes) . the safest thing is to assume that a wire is HOT till proven otherwise.
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