electrical safety, lightbulbs used for testing, and probability

Discussion in 'Electrical Forum discussion & Blog' started by Thatguy, Aug 25, 2011.

  1. Thatguy

    Thatguy Homeowner

    Messages:
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    Location:
    MD
    I have been called back from the grave to respond to a private message on the subject above. Do not send me any more private messages or I will do my best to pursue a legal action against you for harassment.

    While it is not 0.0000, the likelihood of
    a light bulb used for test purposes
    harming anyone during the short test period of use
    due to a power surge
    is probably between
    dying from a shark attack [~55 deaths/yr]
    and being hit by an object from outer space [1 person in 50 years?].

    Does anyone know of anyone being harmed by a light bulb exploding due to a power surge while they were handling it?

    I am continually surprised that most people have trouble with this concept even though probability governs our decisions from birth to death, whether we want it to or not.

    To the author of the PM; study up on risk, decision theory, and game theory. I certainly have. DV Lindley is one author I recommend, as well as Baruch Fischhoff.

    Against my better judgement I will post some of my background -
    BSEE, MSEE, some computer science credits, worked as an elec. eng. for 37 years.

    For God's sake. . .:(
    Last edited: Aug 25, 2011
  2. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
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    Location:
    North Carolina
    The probability of being shot while playing Russian roulette is one and six, wanna play? We are not talking about the laws of probability but the safety of the members of this forum.

    It is a closed minded person that would only think of the bulb exploding as the total danger involved with a light bulb tester. There is a lot more than the blub exploding to contend with. What about a surge causing the bulb to open and give a false reading. The bulb burns open and does not come on, user thinks the circuit is dead, accident occurs. What caused the accident? As any good forensic investigator would find; improper use of testing equipment. Yes it is guaranteed that there will be an investigation if insurance is involved.

    This bulb could burst exposing live filament to the user. This bulb will need to be attached to the test probes somehow, how do you suggest? Would you suggest a festoon light? Mount a keyless to a box? Cut the end of a cord for a table lamp and use the cord for test leads?

    Wonder why all these safety regulations was put in place for?
    Wonder how the consensus standards are formed?

    Just what role does American National standards Institute (ANSI), National Fire Protection Association (NFPA), Occupational Safety and Health Administration (OSHA) and various other organizations? Wonder just how many Electrical Engineers make up the various committees of these safety organizations?

    Still to be asked and more important than all those above is; Why would someone who holds a Masters in Science of Electrical Engineering tell someone to work with something capable of delivering 10,800 watts for at least .033 seconds and as long as two full seconds to work with light bulb voltage tester for. Another question I have for you is just what makes you think the bulb will explode and not just burn out. I don’t believe I have ever seen a blub explode due to overvoltage.

    By the way the charge would be cyber stalking a Class 2 misdemeanor not harassment and as moderator of the site gives me the right to send you warning notices.

    If you would like I will be glad to post the message so all can see but what we won’t do is hash the discussion between us out on an open thread.
    I will leave it open for everyone to discuss the safety issues but statements aimed at either of us will be deleted.
    If you want to discuss this future please do it through PM just as it was started.
    Last edited: Aug 25, 2011
  3. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
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    Location:
    North Carolina
    The reason why I used the reference to Russian roulette is at age 60 should I receive second and third degree burns to 50% of my body the probability of me surviving would be about 10% that I would live or a 90% chance I would die.

    Here is a link where an electrician was using one of those cheap analog meters set at 1000 volts and died. This was a meter that without a doubt safer than something rigged using a light bulb.
    http://ecmweb.com/ops_maintenance/defective-test-equipment-20100101/

    There is a reason why meters have category ratings.
  4. BobL43

    BobL43 DIY Senior Member

    Messages:
    1,794
    Location:
    Long Island, NY
    Chance

    Although the chance of winning the lottery is exremely slim, someone often does. As an electrical person myself, I would have to agree with JWElectric. Most of us have done stupid things and taken stupid chances during our lifetime, but risking human life is not a good thing.

    However, in the link posted ( I did not read the entire PE's report), what was the transient voltage up to, and would, for instance, a good Fluke meter rated at 1000 volts been sufficient to not have been destroyed by this gross overvoltage and created the plasma, which is oh, SO dangerous? One time I had the local power company out to the house because of low voltage (96VAC) that I had measured. He said well, what kind of cheap meter do you have, anyway. I showed him, and it was a much higher end Fluke model than the one the power company gave him. Turned out the low voltage was due to too many houses on the same pole transformer (13 houses). I'm not sure what the primary voltage is on the poles in the neighborhood but maybe 13.6K.
  5. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,542
    Location:
    North Carolina
    There is no way of knowing what magnitude this transit voltage reached or which type transit it was.

    Being that this incident happen shortly after an electrical storm I would believe that it was an impulse instead of a oscillatory simply due to the switching of grids introduces impulse transits to the system.
    The impulse transit exists in every single phase residential system throughout our nation. These impulse transits are a very high energy event that can cause a very large explosion should they be shorted.
    A broke light bulb tester where the filament post are touching is more than enough to start this bolted fault which could end up being catastrophic. What are the probabilities of this happening? I don’t care because I am not going to put myself nor anyone else in that situation.

    The meter he was using at the time should have been at least a category III meter but it was a non-category meter. The meters that do not have a category rating are for use on low level energy items such as electronic equipment and are not designed to be used on line voltages such as the premises wiring of our homes.

    When there are over 32,000 lost time accidents in a seven year period due to electrical accidents I think that the laws of probability that during the short testing time someone could be hurt can be thrown out the window especially if that person is me or you.
  6. ballvalve

    ballvalve General Engineering Contractor

    Messages:
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    Location:
    northfork, california
    If it was a lightening strike, a category 100 meter would not have saved him. The burst came out of the breaker, not the meter. They could still read the writing on the meter. It looks like he was an unlucky Ben Franklin.

    While the protective gear would have been helpful, I don't go in panels during lightening storms, malls be damned. They can sell clothes tommorow.

    That reduces your plasma blast to odds of a comet hitting your bed. Better than the russian 1/6 plan.
  7. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,542
    Location:
    North Carolina
    You need to reread the link. The investigator said it was the fault of the meter not lightning.

    If the accident was due to a direct strike from lightning then there would never have been one word about the failure of the cheap meter.

    Yes things would have turned out a lot different should they have been wearing their PPE and Yes he should have been wearing rubber gloves and been using the proper category meter.

    Once again it has nothing to do with the odds. If you don’t believe me ask his family and see what they have to say.
  8. ballvalve

    ballvalve General Engineering Contractor

    Messages:
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    Location:
    northfork, california
    I instinctively disagree that a fault in a cheap meter could kill 2 people, especially when one of them must have been standing aside of the "explosion"

    A careful reading of the text tells us that the lawyers will not reveal the ACTUAL cause of the deaths, so to keep their fees higher. This is a great disservice to us who wish to know the details of a disaster of this sort.

    It seems to me that in the sparse and legally protected information given, that the breaker dispersed the plasma blast that caused the injuries. Or an outside "input" of high voltage at a very unfortunate moment.

    If you have any OSHA links to standard meters killing 2 or three persons in similiar conditions, please post them for our safety.
  9. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,542
    Location:
    North Carolina
    This would be due to your lack of understanding of what happens during an arc flash. During an arc flash the temperature can rise to as much as 35,000 degrees F which is almost 4 times the temperature of the surface of the sun. The blast can reach out as far as 10 feet.

    It doesn’t matter if you can conceive the accident or not but the facts remain the same.

    Want more
    http://www.iaei.org/magazine/2008/0...plan-an-electrical-inspectors-survival-guide/
  10. ballvalve

    ballvalve General Engineering Contractor

    Messages:
    3,261
    Location:
    northfork, california
    Interesting read, thank you, but adds that it is unsure if fused meters of any rating can provide adequate protection.

    And because of the lawyers, we will never really know what happened at that mall.

    And as a practical matter, no electrician is going to suit up to resist 35,000' F and stand 15' from the panel he is working on.

    I conceive of the accident and issues well, but for you as a teacher to change the existing procedures is a great uphill climb. Putting out these incidents is a good start.
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