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Thread: Faulty Appliance - GFCI Not Working as It Should!

  1. #1
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    Faulty Appliance - GFCI Not Working as It Should!

    My Cuisinart Toaster Oven heat coil warped and eventually pulled out of the termination socket which in turn touched the metal case on the inside thereby energizing the entire toaster oven with 120V to ground. This was plugged directly into a GFCI outlet that had the green light lite showing that the GFCI should have been good. While visiting, my sister-in-law was making toast and touched the metal case of the toaster oven and the metal frame of the stove that was right next to the toaster oven. She received a shock because there was 120V between the case of the toaster oven and the metal frame of the stove. Shouldn't the GFCI has tripped? It is my understanding that when she received the shock, current would have come through the ungrounded conductor and b/c it returned through her and the metal of the stove (Equipment Grounding Conductor), the GFCI should have tripped b/c the current did not come back through the neutral conductor and the GFCI should have seen this differential?
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  2. #2
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    Quote Originally Posted by Jesse.Elliott View Post
    My Cuisinart Toaster Oven heat coil warped and eventually pulled out of the termination socket which in turn touched the metal case on the inside thereby energizing the entire toaster oven with 120V to ground. This was plugged directly into a GFCI outlet that had the green light lite showing that the GFCI should have been good. While visiting, my sister-in-law was making toast and touched the metal case of the toaster oven and the metal frame of the stove that was right next to the toaster oven. She received a shock because there was 120V between the case of the toaster oven and the metal frame of the stove. Shouldn't the GFCI has tripped? It is my understanding that when she received the shock, current would have come through the ungrounded conductor and b/c it returned through her and the metal of the stove (Equipment Grounding Conductor), the GFCI should have tripped b/c the current did not come back through the neutral conductor and the GFCI should have seen this differential?
    The outside sheet metal of the toaster oven should have been connected through the EGC in the cord back to the main bonding jumper and through there back to the transformer secondary neutral.
    That should have tripped a breaker if it was a good contact or a GFCI if it was not.
    So there is a missing or discontinuous EGC in the picture somewhere.
    When your sister-in-law made a connection to ground the GFCI should have tripped as long as the current through her was at least 6ma.
    But a current lower than 6ma can still be easily felt, so possibly the GFCI was fine.
    It is also possible that the incoming connection to the GFCI was made to the load side terminals or there was a jumper from line to load side.
    In either case older GFCIs might still appear to trip when tested but not actually disconnect the receptacle from power.

  3. #3
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    Our toaster oven does not have an EG, nor does our toaster. The case of the oven would have been energized but the GFCI should have tripped once the current level through your SIL reached 5-6 ma. Maybe it never got that high. Tell her if her hands had been wet from doing the dishes it would have been more likely to trip.
    Tom
    TBLO

  4. #4
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    Quote Originally Posted by GoldDigger View Post
    The outside sheet metal of the toaster oven should have been connected through the EGC in the cord back to the main bonding jumper and through there back to the transformer secondary neutral.
    That should have tripped a breaker if it was a good contact or a GFCI if it was not.
    So there is a missing or discontinuous EGC in the picture somewhere.
    When your sister-in-law made a connection to ground the GFCI should have tripped as long as the current through her was at least 6ma.
    But a current lower than 6ma can still be easily felt, so possibly the GFCI was fine.
    It is also possible that the incoming connection to the GFCI was made to the load side terminals or there was a jumper from line to load side.
    In either case older GFCIs might still appear to trip when tested but not actually disconnect the receptacle from power.
    I'm voting for the current being less than 6mA, because this appears to be the terminal off of one of the heater elements touching the case, so that element is likely in series with the line and it could be acting like a current limiting resistor. The Fluke meter in the picture is so low of a burden that it still reads it as 120V, but the circuit is such high resistance that there is less than 6ma of current flowing.
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  5. #5
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    If the current is less than 6mA, the shock should be very mild per general physical effects for various values of current. In a scale of 1 to 10, what is the severity of shock felt according to your in-law?


    In the worst case scenario any test lamp glows between the case of the toaster oven and the metal frame of the stove and trips GFCI, as you are saying there exists 120V there?

  6. #6
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    Quote Originally Posted by Sahib View Post
    If the current is less than 6mA, the shock should be very mild per general physical effects for various values of current. In a scale of 1 to 10, what is the severity of shock felt according to your in-law?


    In the worst case scenario any test lamp glows between the case of the toaster oven and the metal frame of the stove and trips GFCI, as you are saying there exists 120V there?
    I personally have not tripped a GFCI via my body. My brother has, twice in the same day while standing in mud. Once before he repaired his saw and once after. He said it hurt like hell.
    Tom
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  7. #7
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    One misconception people have is that a gfci will protect you from shock. Well, it won't but as mentioned above if the ma gets somewhere between 4 and 6 then the gfci should trip. You would still receive a shock but not enough to badly hurt or kill you.

    I also wonder whether that toaster oven has an equipment grounding conductor.

  8. #8
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    Quote Originally Posted by ptonsparky View Post
    it hurt like hell.
    GFCI does not limit fault current, only its duration. Were the fault current less than 6mA, say 5mA, the shock would have been very mild and gfci may take several seconds to trip, which may also explain OP query.
    Last edited by Sahib; 02-15-17 at 02:05 PM.

  9. #9
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    Quote Originally Posted by Sahib View Post
    Were the fault current less than 6mA, say 5mA, the shock would have been very mild
    That is not true. A < 5ma shock can still be painful and very startling.
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

  10. #10
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    I think one issue to remember is this: as electrical professionals, many (if not most) of us have experienced varying degrees of shock from accidental contact. I for one have been hit by 120V via a GFCI (which did trip), it felt worse than a bad static discharge, 120V no GFCI (ouch), and 480V (burns and intense pain from them for weeks, but barely felt the initial contact). So the degree of "mild" or "painful" is only meaningful in a context wherein someone has a point of reference. For the average person who has never been shocked before, ANY shock is going to be scary! But a decent point of reference, because MOST people have experienced it, is that static electricity shock you feel after walking on nylon carpet. If it's like that, changes are it was below the trip threshold of a GFCI, but I'd venture to say that anyone feeling that would still be very upset.
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