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Thread: does this make any sense

  1. #16
    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    Quote Originally Posted by leejosepho View Post
    I might be wrong, but I believe that is actually required when the subpanel is in a detached building. When I ran power out to a garage a few years ago, I was told to run 220 (2 hots) and a neutral, and to connect the subpanel to a ground rod at the garage and with the subpanel not being bonded.
    That's all in 250.32. I get a headache every time I read it.

  2. #17
    Electrician Chris75's Avatar
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    Quote Originally Posted by Mikey View Post
    Not sure what you mean by that. As far as I can see, no matter what kind of circuit problems we dream up, only the GFCI will recognize that some of the current supplied to the load is not returning and will open the circuit before that "lost" current reaches a potentially fatal level. You don't need an EGC for that, and adding an EGC doesn't help. It doesn't matter if the GFCI is in a main panel, sub panel, or outlet, with or without an EGC, ground rod, or what-have-you.

    This is the kind of discussion that needs a blackboard and beer.
    What I mean is a EGC is much better than a gfi, unless like your scenario something happens to the EGC, but its all what if's at that point. IMO, the reason we install GFCI receptacles is because we have no control over what someone is going to plug in, (ie: extension cord with the ground pin missing).

    One good example is pool motors, if they are hardwired, then no gfci protection required, but add a cord and GFCI is now required.

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    Electrician Chris75's Avatar
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    Quote Originally Posted by Mikey View Post
    That's all in 250.32. I get a headache every time I read it.
    Why? its pretty cut and dry. I think the biggest confusion is what people think a ground rod actually does, or the earth for that matter.

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    In the Trades kencaz's Avatar
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    Quote Originally Posted by leejosepho View Post
    I might be wrong, but I believe that is actually required when the subpanel is in a detached building. When I ran power out to a garage a few years ago, I was told to run 220 (2 hots) and a neutral, and to connect the subpanel to a ground rod at the garage and with the subpanel not being bonded.
    The grounding Electrode system is for lightning protection not fault clearing.

    If your detached building has no metal connection to the main building, water, gas, conduit, etc, it was acceptable to install only un-grounded and grounded conductors with no EGC. In this case you WOULD bond the neutral to the subs enclosure and the enclosure to the grounding electrode system. This would allow the Neutral to carry ground fault current back to the transformer.

    It is, however, required as of 2008 NEC to always run an ECG for an outbulding, (which is always a good idea anyway). Then there will be no issue of wheather bonding is required.

    KC

  5. #20
    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    Quote Originally Posted by Chris75 View Post
    Why? its pretty cut and dry. I think the biggest confusion is what people think a ground rod actually does, or the earth for that matter.
    It sure is dry... Agreed on ground/grounding/earth/bonding issues. I admit to being hazy in this area as well, but the haze is slowly lifting. But as long as you've provided the opening, what DOES a ground rod actually do? It looks like different ground rods do different things, as well. Poking around my house, I see a ground road at the base of the pole supporting the transformer; at the main service entrance below the meter; at an outbuilding with a subpanel; and at the dock (with a subpanel). I hope the local crack addicts don't decide that these are all copper.

  6. #21
    DIY scratch-pad engineer leejosepho's Avatar
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    Quote Originally Posted by kencaz View Post
    If your detached building has no metal connection to the main building, water, gas, conduit, etc, it was acceptable to install only un-grounded and grounded conductors with no EGC. In this case you WOULD bond the neutral to the subs enclosure and the enclosure to the grounding electrode system. This would allow the Neutral to carry ground fault current back to the transformer.
    Okay, maybe somebody told me wrong several years ago ... but now I need to run wire to a subpanel in an attached workshop at the back of the garage and house, and I understand that to need four (4) wires and no bonding, correct?

    Quote Originally Posted by kencaz View Post
    It is, however, required as of 2008 NEC to always run an ECG for an outbulding, (which is always a good idea anyway). Then there will be no issue of wheather bonding is required.
    I am a DIY handyman working on my own stuff. What is an ECG?

    PS: "ECG" just reminded me of a great brain teaser for nurses: Ask a nurse what an EKG is, and he or she will tell you it is an electrocardiogram (sp?). Next ask what an EEG is, and he or she will say it is an electroencephelogram (sp?). Right after that, ask what an EGG is and you will get a blank stare ... then say it is an egg to be eaten for breakfast.
    Last edited by leejosepho; 05-11-2008 at 05:31 AM.

  7. #22
    Electrician Chris75's Avatar
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    Quote Originally Posted by Mikey View Post
    It sure is dry... Agreed on ground/grounding/earth/bonding issues. I admit to being hazy in this area as well, but the haze is slowly lifting. But as long as you've provided the opening, what DOES a ground rod actually do? It looks like different ground rods do different things, as well. Poking around my house, I see a ground road at the base of the pole supporting the transformer; at the main service entrance below the meter; at an outbuilding with a subpanel; and at the dock (with a subpanel). I hope the local crack addicts don't decide that these are all copper.

    A ground rod is simply for limiting the voltage imposed by lighting, line surges, or unintentional contact with higher-voltage lines. It has NOTHING to do with the little hole you see in a receptacle.

    In a nutshell, hopefully it will prevent surface arcing from higher voltages.

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    Last edited by Chris75; 05-11-2008 at 05:45 AM.

  8. #23
    Electrician Chris75's Avatar
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    Quote Originally Posted by leejosepho View Post
    Okay, maybe somebody told me wrong several years ago ... but now I need to run wire to a subpanel in an attached workshop at the back of the garage and house, and I understand that to need four (4) wires and no bonding, correct?
    Correct


    Quote Originally Posted by leejosepho View Post
    I am a DIY handyman working on my own stuff. What is an ECG?
    That was a typo, should have been EGC, Equipment Grounding Conductor.

    The wire that connects to a ground rod is a GEC, Grounding Electrode Conductor.

    THis is why electricity is not really a DIY type of job, too much basic theory required even for the simplest jobs.

  9. #24

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    Quote Originally Posted by Mikey View Post
    ...no matter how well-planned, code-compliant, and well-built, we can imagine a scenario where the guy holding on to the appliance gets zapped...
    I think those who write the electrical and other codes go by history and what has actually happened in the past. Not what might happen in the future.

    If there is one rare freak accident, I don't think that would carry much weight as to changing the electrical code. BUT if there are say hundreds of cases each year of people being electrocuted from the same situation, then they do what they can to change the code to prevent these things from happening in the future.

    Then there is the probability that a situation will occur. Is it likely that a lot of people will have situations where there are say 4 electrical problems all at once? Or is it more likely that most people who have electrical problems will have just 1 or 2 problems at a time?

    Problems being; neutral which is loose and becomes disconnected, ground wire gets cut, hole drilled in wall severing neutral wire only, an appliance which has a hot wire which is touching the metal case, etc.

  10. #25

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    Another situation I forgot to mention is that with large wires, it is common for there to be a smaller ground wire than the current carrying wires...

    We all know that breakers are designed to cut off the electricity if the amperage being used exceeds the capacity of the wire size. (If there is too much amperage flowing through a wire, it can become hot and start a fire.)

    There can be a situation where the neutral is bonded to the ground in a subpanel. And the ground wire in the main cable going to the subpanel has a smaller diameter wire than the other wires...

    Say the neutral on this cable is loose at one end and becomes disconnected. Then the ground wire would carry the load of the neutral, would not be correctly protected by the size breaker installed, and could become hot and start a fire.

  11. #26
    In the Trades kencaz's Avatar
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    Quote Originally Posted by leejosepho View Post
    Okay, maybe somebody told me wrong several years ago ... but now I need to run wire to a subpanel in an attached workshop at the back of the garage and house, and I understand that to need four (4) wires and no bonding, correct?
    Correct, The Neutral/White (Grounded Conductor), and the EGC/Green (Equipment Grounding Conductor), should ONLY be bonded at the Main Panel.


    I am a DIY handyman working on my own stuff. What is an ECG?
    Sorry, my bad. I meant EGC [Equipment Grounding Conductor]. The green wire.

    KC

  12. #27

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    i spoke to a licensed electrician who addmitted it makes no sense to him either.
    It took me a while to "figure it out" too.

    If you lose the neutral, the current will find it's way into/thru water pipes, gas pipe etc.

    Of course if this happens at the service, the same thing will happen but they are tring to minimize the risk.

  13. #28
    DIY scratch-pad engineer leejosepho's Avatar
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    Quote Originally Posted by Chris75 View Post
    ... electricity is not really a DIY type of job, too much basic theory required even for the simplest jobs.
    Yes, and a lot of common sense. My wife told me her fan did not work in a kitchen receptacle, and it sparked when I tried it to check it out. What I ultimately pried out of the box was a stabbed receptacle packed in foam with a neutral wire that had turned black. I have never done anything anywhere near that bad, but I certainly agree that some people should never do any electrical work at all. Or, maybe a license should be required for applying foam ...
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  14. #29
    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    Well, at least they had air infiltration under control. I sometimes wonder if box fill calculation methods will be changed to derate when dealing with foam-filled or otherwise really-sealedup-well boxes.

  15. #30
    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    Default So THAT's why I'm confused...

    "In North America, much of the confusion regarding grounding has its roots in the National Electrical Code of the United States."

    This is from a technical note from APC which actually is pretty decent:

    "Neutral Wire Facts and Mythology"

    http://www.apcmedia.com/salestools/S...NQYQ_R0_EN.pdf

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