[Jewelry making - Article 00244] - Re: [Orchid] Electrical question

[FrodoGem]

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>     Janet, The first thing I would do is find a new electrician. If
>     the plug on your kiln only has 2 prongs, it is NOT grounded, and
>     could pose an electrocution risk in the event of a fault in the
>     kiln. 

    Bravo!  Furthermore, if a new house has two prong outlets, it may
    not wired according to code.  Are all your outlets this way?  One
    thing to look for is what is called a "Grounding Electrode" outside
    your house near the meter or breaker box.  It is a metal rod
    approximately 1/2 to 3/4 inches in diameter that is driven into the
    ground.  There should be a wire clamped to the rod.  The wire
    ultimately should lead back to your breaker box.  (Some building
    codes may allow connection to a metal water pipe instead of a ground
    electrode  ) 

    The purpose of the grounding electrode is to ensure that the wires
    that should be at ground potential really are so.  It is there to
    ensure that it is the easiest path to ground, not you. 

    From your description, I would hypothesize (without testing, this is
    only speculation as a place I would begin investigating) that your
    Kiln has some contact between the metal and some wire inside that
    conducts electricty.  Possibly the white ("neurtal") wire.
    Furthermore, I would speculate that other outlets in your house did
    have three prongs but that you have no connection with a grounding
    electrode in your breaker box where all of the wiring from the third
    prong is connected together.  

    The third (middle) prong on a plug usually is usedt to connect metal
    housings of appliances to the grounding electrode.  If no connection
    exists, an electrical current from a short in one of your appliances
    could be carried back through the third prong.  Electric motors with
    "carbon brushes" are notorious for low level shorts.  As the carbon
    contact material wears away, it leaves dust to make a connection
    between the electric supply and the metal motor housing.  The point
    is that a household that does not have a physical connection to
    ground could produce low level shocks from touching all of the metal
    appliances.  (In fact, since code requires a grounding electrode,
    the green or bare ground wires and the white neutral wires are all
    connected together in your breaker box.  This means that either one
    could be the source of your phantom current.)  

    In my opinion it is a poor idea to use a water pipe instead of a
    grounding electrode.  If a water pipe is used, there can be any
    number of fittings used in the pipe that could break the connection
    with ground. 

    Finally, there is one other possibility that I can think of:  Some
    ruarl power grids rely heavily on the ground itself as one leg of
    the circuit that conducts electricty to homes.  This is a rare
    problem and to my knowledge, limited to ruarl areas.  In such areas,
    there can exist what are called "stray currents."  A stray current
    means that there is a difference in potential between one area of
    the earth and another.  In such a case, you can actually get a shock
    from a well grounded appliance merely by standing on earth that has
    a different potential from that where the ground electrode is driven
    in and then touching the grounded appliance. 

    This has been somewhat technical, but I hope it is a help.  Please
    note that I am not an electrician but have some college and trade
    school education in electrical theory.   Hopefully, this is
    understandable to you, but if not, an electrician educated in
    electrical theory should be able to understand what I am talking
    about and test to see if anything I described is happening. 
    Finally...it is OK to look around an see if there is a grounding
    electrode, however actual testing and wiring should be left to an
    expert.  Please don't attempt to do this yourself.  This is only
    intended to give you some ideas about what might be happening. 

Good luck...

Howard Woods
In the beautiful foothills near Eagle Idaho.


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