advice on wire gauge for built in oven

Discussion in 'Electrical Forum discussion & Blog' started by jono604, Nov 1, 2011.

  1. Electromen

    Electromen New Member

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    I taught high school for seven years after college. I quit because the income was too low. Teachers in my school district max out at $85,000 per year. I may teach part time in retirement just to keep busy but at this point I don't want to lower my income.
    Last edited: Dec 12, 2011
  2. Electromen

    Electromen New Member

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    I thought this discussion was about Ovens. Instead it's turned into an attack of one's experience.
    JW you are a hard headed individual and a self proclaimed know-it all. I feel sorry for you.
    I joined this forum to help some DIY'ers, not to defend myself.
    Have fun, I will not return.
  3. DonL

    DonL Banned

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    If You Google® "false gfci tripping" there is about 1,910,000 results.

    That tells me that many people are having the false triggering problems.
  4. DonL

    DonL Banned

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    Don't give up Electromen®

    Not all of us are as lucky as JW in this real world.

    I think You meant to say "Have fun, Ill be back."
  5. leejosepho

    leejosepho DIY scratch-pad engineer

    Before I knew the difference between AFCI and GFCI, I had an AFCI trip and never stay on and nobody here could ever explain why.
  6. DonL

    DonL Banned

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    I guess I missed out on that one.

    I do know that a GFI for an appliance is different than a Personal Protective GFI.

    Personal Protective GFIs trip in the 5 MA or so range

    and Appliance GFIs trip at around 30 MA.


    If you run a appliance on a Personal Protective GFI, You are Very Lucky if it Does Not Trip on occasion.


    If You really want to be 100% safe, Turning OFF the Main Breaker works much better than anything...
    Last edited: Dec 12, 2011
  7. BobL43

    BobL43 DIY Senior Member

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    Hi Don, sometimes it IS hard to just read and enjoy the discussion and remain quiet for long, even though you swore it off:p. Discussion is good; don't worry be happy. We can't win every argument, but we can put our $.02 in.
  8. leejosepho

    leejosepho DIY scratch-pad engineer

    That was just a little side issue in my workshop thread while we were all discussing/debating/arguing the matter of whether ground rods ever actually accept/conduct/convey any faulted current.
  9. leejosepho

    leejosepho DIY scratch-pad engineer

    Oops. Browser fault!
    Last edited by a moderator: Dec 12, 2011
  10. DonL

    DonL Banned

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    Sure they do.

    Most of the Current will take the path of Least resistance...
    Last edited: Dec 12, 2011
  11. Electromen

    Electromen New Member

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    I've never heard of ones that are for appliances. There is GFCI protection for large service entrances, like 800 amp and above which are different. For personal protection I only know of one type available in the receptacle and circuit breaker. If there are ones dedicated to appliances I'd like to learn about it.
  12. jwelectric

    jwelectric Electrical Contractor/Instructor

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    2,532
    Location:
    North Carolina
    Wow! Current takes every available path not just the path of least resistance. The earth being a high resistor will conduct little or no current from a 120 supply.
  13. jwelectric

    jwelectric Electrical Contractor/Instructor

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    There is the Ground Fault Circuit Interrupter that we install for those places outlined in 210.8 such as bathrooms, garages, outdoors, crawl spaces, unfinished basements, kitchens and other places that are installed to protect the user.

    Then there is ground-fault protection of equipment as outlined in 215.10 for feeders and 230.95 for services where these are 600 volts or less and more than 1000 amps.

    These are two different types of ground fault protection
  14. DonL

    DonL Banned

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    3,978
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    They Vary depending where in world that you are.


    United States

    GFI receptacles in the USA have connections to protect downstream receptacles so that all outlets on a circuit may be protected by one GFI outlet.

    In the United States, the National Electrical Code requires GFCI devices intended to protect people to interrupt the circuit if the leakage current exceeds a range of 4–6 mA of current (the trip setting is typically 5 mA) within 25 ms. A GFCI device which protects equipment (not people) is allowed to trip as high as 30 mA of current; this is known as an Equipment Protective Device (EPD). "RCDs" with trip currents as high as 500 mA are sometimes deployed in environments (such as computing centers) where a lower threshold would carry an unacceptable risk of accidental trips. These high-current RCDs serve for equipment and fire protection instead of protection against the risks of electrical shocks.

    GFCI outlets are required by law in wet areas (See National Electrical Code (US) for details.)

    In the U.S., the National Electrical Code requires GFCIs for underwater swimming pool lights (1968); construction sites (1974); bathrooms and outdoor areas (1975); garages (1978); near hot tubs or spas (1981); hotel bathrooms (1984); kitchen counter receptacles (1987, revised 1996 and specifically excluding the refrigerator outlet, which is usually on a dedicated circuit); crawl spaces and unfinished basements (1990); wet bar sinks (1993); laundry sinks (2005).[7]

    This link has some more info;

    http://en.wikipedia.org/wiki/Residual-current_device


    Sorry about the MA error on my part "equipment (not people) is allowed to trip as high as 30 mA of current"
    I think I put 50MA, I stand correcting Myself.
  15. DonL

    DonL Banned

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    Let me get my book out...
  16. DonL

    DonL Banned

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    If this is the case, Then why can I go outside and take an extension cord, connect the Hot (Black /small blade) side to a light bulb and connect the other side of the light bulb to a Ground Rod (Connected to nothing but earth), and it lights up ?

    (I do not recommend trying this, unless you are an electrician)

    Please Tell me where the Voltage / Current return path is coming from ? Sounds like FM.

    I think that you could learn more from some Experimenting.


    If Earth Ground is that bad then why does the NEC even require it ?

    And if you are correct (as You must be) then a GFI for outdoor use is Useless, is it not ?


    I would like to learn something new because Theory only works in a Vacuum,
    That is, unless you know every single variable...
    Last edited: Dec 12, 2011
  17. DonL

    DonL Banned

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    We are not even getting this Oven Fixed, lol...
  18. jwelectric

    jwelectric Electrical Contractor/Instructor

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    Location:
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    ,Do you understand the difference between parallel and series connected resistance?

    I do this experiment several times a year. I am having different results than what you are having.
    The answer is found in 250.4. There are four reasons to connect a wiring system to earth, 1- lightning, 2- Power surges, 3- unintentional contact with higher-voltage lines, and 4- stabilize the voltage
    Using the requirement of 250.56 of the NEC of 25 ohms and 120 volts Ohm’s Law says if I connected a 15 amp breaker directly to an 8 foot rod then only 4.8 amps of current will flow.
    Most residential transformers across the US are supplied on the primary by 7200 volts. Using the same 25 ohms this high voltage will push 288 amps of current through the earth. (Unintentional contact) A lightning strike will have a very high voltage and in the event of a strike earth will allow a magnitude of current to flow with that kind of a push. Should lightning strike the high voltage lines the secondary will have a “surge†of 1/30 of whatever the lightning strike was but it will be high enough to push a lot of current through the earth. (power surge)
    The power company does everything it possibly can to achieve at the most 10 ohms on their grounding electrodes. Look at the pole holding any transformer and see their conductor going to their electrode.
    In most cases across the US the resistance of grounding electrodes on homes will be 300 ohms and upwards. To drive an 8 foot single rod anywhere in America and you will be darn lucky to have less than 100 ohms.

    If you really meant what you said in your last sentence of this post you would have been listening when I explained how a GFCI device works. The connection to earth plays no role in the equation. What makes one open is when there is a difference of .004 to .005 amps between the black and white conductors connected to the device.
    A human with a resistance of say 10k ohm and using 25 ohms for earth this would be a total of 10025 ohms. Divide 120 volts by 10025 ohms and there will be about .012 amps flowing. This is just shy of the “let go threshold†but more than enough to trip a GFCI device, almost three times the amount of current to open the GFCI device.

    Your light bulb experiment above done with math will be as follows;
    120 volts with a 100 watt light bulb and the resistance of the rod at school that averages ~500 ohms. To find the resistance the test was done with a three point reading for a more accurate reading by an engineer three years ago.
    To find the resistance of the bulb we will square the voltage and divide by the wattage which gives us 144 ohms
    Add the resistance of the rod and bulb and forget the resistance of the conductor being that it is so small will give us a total resistance of 644 ohms.

    Now to see how much wattage this circuit will allow to flow we will square the voltage and divide it by the resistance and the total wattage this circuit will allow to flow is just over 22 watts. Yep late at night one might see the bulb glow.
  19. mtcummins

    mtcummins In the Trades

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    Pittsburgh PA
    Y'all can talk theory till yer bleu in the face...

    I know for a fact that GFCIs do trip w/o reason. There's probably a good 100 million people in this country who could confirm that they've had random trips.

    As for your comments about what work I do, no I don't do new construction. I hate it. I do historic renovations and restorations. My contractor... not sure how (or why?) you made any random assumptions about the kind of work they do, but they do massive amounts of new construction. He'll tell you the same thing... the damn things trip on their own. Not all the time, not always with the same tools, just randomly. You're still operating under the assumption that they act 100% consistently, so that a tool that trips one once would always trip them. This is false. So no, they aren't running to the GFCI all day, that would assume consistent failure, which would indicate either a faulty GFCI or a faulty tool.

    If your head is too far up your arse to deal with reality, that's your problem. Theory or no theory, calculate all you want. Think about it for another few years, run the calcs, read your textbooks. Keep telling people the "facts" based on books. Fact is, in the real world the things do trip, and its not always for a good reason. Many thousands of people can confirm this. Therefore, GFCIs should not be put on appliances such as refrigerators, freezers, cooktops, D/W, disposals, etc.
  20. DonL

    DonL Banned

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    Very Well Put...
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