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Thread: Ideal dock wiring Questions?

  1. #16
    Retired Defense Industry Engineer jadnashua's Avatar
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    If the wiring is installed properly, and you don't have a defective device, you won't get shocked. Even if you did have a defective device, the safety circuits should trip, preventing any harm. A solid wire back to the source will provide the means for any safety device to work. A ground rod won't, even as a backup - there's just too much resistance back to the source to prevent harm. Failing to understand this has killed many people. A good pro should be able to provide you with a system that will be safe. It appears you are an example of a little knowledge results in the wrong conclusion...
    Jim DeBruycker
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  2. #17

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    Quote Originally Posted by LLigetfa View Post
    Now I have respect for your knowledge but I must take exception to your using this absurd analogy to ridicule the OP. The earth as a ground can be an alternate path on a residential service if there is improper wiring exposing an individual to a potential. A lantern battery has absolutely no affiliation with earth ground unless explicitly grounded. An electric fence comes to mind.

    In Ontario the electrical utility always runs a neutral alongside a hot so there is always a minimum of two conductors on a single phase pole line. When I was driving through Alberta, I was surprised to see miles of pole line with only a single conductor on it. I can only imagine that the earth in Alberta is not a suitable conductor for the return path and that there must be a buried neutral.
    Mr LL... I think you figured it out... "alternate path" is the exact thing that electrons/electricity takes when a shorted circuit happens. If a metal floating dock is not grounded the path of electrons from a ground or neutral wire connected a long distance away in a switch box can and does have a difference of potential and the path of least resistance will become the person in the water who comes into contact with the metal dock. If anyone wishes to take me up on this scenario I'll invite them down and drag out my Wal Mart volt meter to show them some interesting things when it comes to boat docks and electricity. If there is no ground on that dock you can actually grab a hot wire and not even feel a tickle... that's why wires are insulated and code calls for them to be in conduit or completely enclosed.
    Something similar happens which I am not familiar enough with the explanation to give it but the galvanic reaction is why boats/marine engines are equipped with sacrificial anodes. Okay... I'll probably get bashed for that statement too but I'm cool with that too....
    Last edited by Randyj; 03-22-2011 at 07:18 PM.

  3. #18

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    Quote Originally Posted by jadnashua View Post
    If the wiring is installed properly, and you don't have a defective device, you won't get shocked. Even if you did have a defective device, the safety circuits should trip, preventing any harm. A solid wire back to the source will provide the means for any safety device to work. A ground rod won't, even as a backup - there's just too much resistance back to the source to prevent harm. Failing to understand this has killed many people. A good pro should be able to provide you with a system that will be safe. It appears you are an example of a little knowledge results in the wrong conclusion...
    Jim... this is where lots of people get screwed up. In effect this is not just one circuit. The electical wires running to and from the switch box back up at the lake house is one circuit. The dock itself and it's ground rod which it is bonded to is in effect another circuit (especially when it becomes the alternate path of electricity). If you want to try an experiment... go look in your power meter box. There is a neutral wire from the pole/transformer. There is also a ground wire connected to a ground rod or some other earth grounding provision. Now... and get out your volt meter, put one lead on the neutral wire and one lead on that same ground wire... then disconnect the neutral and put one lead on the neutral from the pole and one lead on the ground wire to earth..Do the same with either "hot" leg in your meter box/switch box...then tell me what happens. I've run across several old houses where the ground was substitued for the neutral wire and amazingly things still worked but a volt meter gives a reading of around 64 volts. I never tried to explain it but I know what the problem is when I see this reading. This is where practical applications are useful and theory is what you learn in school. Oh yeah, nice meeting you back in '07 in Anderson, SC
    Ever wonder why (in my switch panel) the earth ground is bonded to the box but the uninsulated neutral wire from the pole is insulated from the box? Funny how they have no difference in potential until they are disconnected.
    Last edited by Randyj; 03-22-2011 at 10:34 PM.

  4. #19
    DIYer, not in the trades LLigetfa's Avatar
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    Years ago I was working as service tech for a computerized fuel pump control system. The system was blowing boards left. right, and centre. I called in an electricial contractor when I confirmed the service to the building was faulty. It turned out the neutral was open and all the current was being carried by the ground to the copper water pipe serving the building.

    One of the guys had commented to me that the cold water was warm. There was so much current going through the copper water supply line that it was heating the water.

  5. #20

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    EXACTLY LL.... and that's why codes nowadays stir people away from using water pipes as earth grounds since the popularization of plastic water lines. I'd bet those circuit boards were getting fried because the electricity was being thrown out of phase and you got some crazy voltages.... regardless of how "proper" the wiring was installed. Sounds like your electric wires sprung a leak and some of it's energy was being dissipated/lost as heat.
    Last edited by Randyj; 03-22-2011 at 07:43 PM.

  6. #21
    General Engineering Contractor ballvalve's Avatar
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    http://www.google.com/search?q=equip...8&sourceid=ie7

    Try reading the first PDF article, if you can.

    Looks like a real can of worms here.

    If the docks are being wired by licensed electricians and every year a few die, seems like we need better electricians or better maintenance.

    The Mod should note that there are many opinions about the NEC and its bible, and try and be a bit more of a moderator rather than an executioner.
    Last edited by ballvalve; 03-22-2011 at 09:47 PM.

  7. #22

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    I'll concede that there was more than one part to my o.p. The suggestion that loads should be calculated for wire and breaker sizing is absolutely correct where it applies to well pumps and other high demand appliances/equipment. However, when it comes to the general type of outlets and a couple of standard 2 or 4 lamp fluorescent fixtures used on docks this is a very general application. I do know that I am not equipped with the knowledge to calculate large loads, but for general purpose outlets and appliances this is very basic and for a 200-300 foot run for simple lighting and a few outlets this should be something that could be answered in a very straight forward manner. The part about GFCI's is simply whether or not a GFCI breaker should be in a switch box and that breaker supply power to GFCI outlets... should both be used or only one. JW did in fact say that he recommends only the breaker in the switch box if my understanding of his reply is correct. The article referred to in another reply concerned a wooden dock's ground in which the neutral wire failed and there was no safety ground. Had the dock been a metal dock which had an earth ground that kid would not have been electrocuted simply by touching the metal boat lift. If properly wired every piece of equipment on that dock would have been bonded to the dock. Thus, the path would have been through the dock to earth ground rather than through the kid to the water to the earth ground. I might be dumber than I look but I don't think so....
    Last edited by Randyj; 03-22-2011 at 11:42 PM.

  8. #23

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    Quote Originally Posted by LLigetfa View Post
    Years ago I was working as service tech for a computerized fuel pump control system. The system was blowing boards left. right, and centre. I called in an electricial contractor when I confirmed the service to the building was faulty. It turned out the neutral was open and all the current was being carried by the ground to the copper water pipe serving the building.

    One of the guys had commented to me that the cold water was warm. There was so much current going through the copper water supply line that it was heating the water.
    Hey LL.... this same kinda sorta thing happened to me recently when a limb fell across my power lines and pulled the neutral wire from the transformer on the pole. It blew one of them fancy little pig tail looking screw in fluorescent light bulbs I had in a lamp in my kitchen/livingroom/den/bedroom. I went out to my switch box with my walmart volt meter and found that I had 220 volts to one leg of my switch box and something crazy like 64 volts to the other ... or was it 64 volts between them and 120 from neutral to something?...or maybe from the ground wire to a hot wire?... at any rate it was some crazy voltage I was reading. That's when I got out my coon hunting light and followed the wires back to the pole with the transformer and saw the limb across the wires and the neutral wire dangling and not attached to the transformer. I called the power company and eventually a service guy came out and 'splained to me how that neutral wire is necessary to balance current/voltage. Thangs like this happen in the trailerhood 'specially when it's several miles out in the boon docks.... and if you ain't figgered it out yet, besides tinkering with this handyman stuff I tend to get into a bit of creative writing at times... hehehe
    Last edited by Randyj; 03-22-2011 at 10:50 PM.

  9. #24
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by LLigetfa View Post
    Now I have respect for your knowledge but I must take exception to your using this absurd analogy to ridicule the OP. The earth as a ground can be an alternate path on a residential service if there is improper wiring exposing an individual to a potential. A lantern battery has absolutely no affiliation with earth ground unless explicitly grounded. An electric fence comes to mind.

    In Ontario the electrical utility always runs a neutral alongside a hot so there is always a minimum of two conductors on a single phase pole line. When I was driving through Alberta, I was surprised to see miles of pole line with only a single conductor on it. I can only imagine that the earth in Alberta is not a suitable conductor for the return path and that there must be a buried neutral.
    Ever hear of a SWER distribution system? This will be a system that is supplying a power grid at somewhere around 20,000 volts. Use Ohm’s Law to see how much energy this much push could muster through earth. Was it a lot more than a 120 volt circuit that is being discussed in this thread?

    To compare the utility to our branch circuits would be like comparing an apple to a lemon or a freight train to a horse drawn carriage.

    In residential wiring the earth cannot be used as any type of return path and would not carry enough current with 120 volt push to make a 100 watt light bulb glow at all.

    Oh by the way I am not trying to ridicule anyone. When someone is wrong they are simply wrong and I have posted two code sections and the math that prove that the idea of the earth carrying fault current is not true for a 120 volt branch circuit.

  10. #25
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by Randyj View Post
    If you want to try an experiment... go look in your power meter box. There is a neutral wire from the pole/transformer. There is also a ground wire connected to a ground rod or some other earth grounding provision. Now... and get out your volt meter, put one lead on the neutral wire and one lead on that same ground wire... then disconnect the neutral and put one lead on the neutral from the pole and one lead on the ground wire to earth..Do the same with either "hot" leg in your meter box/switch box...then tell me what happens.
    WOW!!!!!!!!!!!!!!!!
    I CAN’T BELIEVE MY EYES

    Why haven’t I ever thought about doing this before?

    Here we stand at the panel of this school building and making these readings from the ungrounded conductors and the disconnected grounding electrode system and we are getting a reading of exactly zero. We are now checking the voltage from the utility neutral to the electrode conductor with a voltage reading of zero.
    Something is very wrong with our dirt as it just don’t seem to want to play fair. Why are we not getting these funny readings? We are using an analog meter instead of a DVM, does that matter?
    Has anyone else tried this? What did you get?

  11. #26
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by LLigetfa View Post
    One of the guys had commented to me that the cold water was warm. There was so much current going through the copper water supply line that it was heating the water.
    Quote Originally Posted by Randyj View Post
    EXACTLY LL.... and that's why codes nowadays stir people away from using water pipes as earth grounds since the popularization of plastic water lines. I'd bet those circuit boards were getting fried because the electricity was being thrown out of phase and you got some crazy voltages.... regardless of how "proper" the wiring was installed. Sounds like your electric wires sprung a leak and some of it's energy was being dissipated/lost as heat.
    The 2011 Edition of the NEC in section 250.52(A)(1) still requires that a metal water pipe in contact with earth for more than 10 feet be used for a grounding electrode. Just where does this statement of the codes now days leading people away from using the metal water pipe for an electrode come from?

  12. #27
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by ballvalve View Post
    http://www.google.com/search?q=equip...8&sourceid=ie7

    Try reading the first PDF article, if you can.

    Looks like a real can of worms here.

    If the docks are being wired by licensed electricians and every year a few die, seems like we need better electricians or better maintenance.

    The Mod should note that there are many opinions about the NEC and its bible, and try and be a bit more of a moderator rather than an executioner.

    Ballvalve

    The equipotential bonding grid is different than the grounding electrode such as being discussed here although what Randyj is describing with his ground rods at the pier is almost a equipotential grounding grid.

    It is his conception that the branch circuit supplying the pier is somehow losing current to earth that is wrong.

  13. #28

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    What you get is resistance and stray voltages/currents. You need to read Mike Holt's paper mentioned in ballvalve's post. Equipotential planes are a huge no no and definitely not the way to ground a barn for milk cows. That paper specifically supports and explains everything I've been saying about stray voltages/currents, voltage drops, resistance in wires... all that stuff. Work all the ohms laws mathematical computations you want but if you don't take into account resistance due to the length of wire you're gonna get very erroneous results. if you do recall your physics class there is this thing called loss of energy due to friction in mechanical devices. This same principle applies to loss of energy when electrons move through wires. Being arrogant will not save lives. I never really dove in deep enough to understand it but I've been told that it's not the voltage that kills but the current. Edison, Tesla, and all the old guys described current... DC and AC. Do you know why? Why not DV and AV?

  14. #29

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    Quote Originally Posted by jwelectric View Post
    The 2011 Edition of the NEC in section 250.52(A)(1) still requires that a metal water pipe in contact with earth for more than 10 feet be used for a grounding electrode. Just where does this statement of the codes now days leading people away from using the metal water pipe for an electrode come from?
    MR JW... I can't tell you what number it is in any book. However, last year I put a new switch box on my rental house and had it inspected by an electrical contractor who pulled a permit and had it inspected by the city inspector. I was told to remove the old ground to the water pipe because that is no longer acceptable and I had to go to the big box store, purchase a ground rod and drive it in the ground then attach the ground wire from the switch box panel to that ground rod using an acorn clamp. I know these things from experience, practical applications and some rudimentary class room work which included a few thousand ohm's law calculations. You may be able to prove your theories mathematically but can you prove everything you say by practical applications in the real world? I can do both and have done both but still do not claim to be an electrician which is why I came to this forum to ask a few simple questions. What I do claim to be is a plumber and very good handyman who repairs things, virtually any thing.
    Now, what I have done to satisfy my curiosity and for my own edification, I called my electrical contractor concerning the ground rod issue and was told that it is required to connect a ground rod and metal water pipes together. However, I know the inspector required me to remove the ground to the old water pipe and install a ground rod bonded to my switch box.
    Last edited by Randyj; 03-23-2011 at 07:33 AM.

  15. #30
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by Randyj View Post
    What you get is resistance and stray voltages/currents. You need to read Mike Holt's paper mentioned in ballvalve's post. Equipotential planes are a huge no no and definitely not the way to ground a barn for milk cows.
    Although the equipotential grounding grid is required to be installed by the NEC no matter what Mike Holt wrote. But then again if you read his paper you will see he is only repeating what someone else has said.

    Quote Originally Posted by Randyj View Post
    That paper specifically supports and explains everything I've been saying about stray voltages/currents, voltage drops, resistance in wires... all that stuff.
    This paper does not in any way support anything you have said.

    This paper address the installation of a grid underground that keeps the potential between the surface on which one is standing and any metal that is exposed that could be touched at the same time at the same potential.
    What you are saying is that the rods you are installing are to give current somewhere to go and this just is not true. You are trying to say that the ground rods are installed to let “leaky current” have somewhere to go, again this is not true. You are saying that current will travel the path of least resistance, this is not true. You are saying that the installation of ground rods at the pier are to make a path of low resistance so the current can go back to earth, this is not true.

    This paper is addressing SWER type distribution systems where there is a large voltage pushing current through earth. Of course if one uses Ohm’s Law it is easy to see that a voltage of 19,000 volts can drive more current through earth than a 120 volt circuit and in neither case is any current being lost in earth. With the SWER system earth is the return path and in our 120 volt circuit the neutral is the return path.

    You on the other hand are trying you best to prove that driving all these ground rods at the metal pier somehow makes the pier safer and this is far from the truth.

    Quote Originally Posted by Randyj View Post
    Work all the ohms laws mathematical computations you want but if you don't take into account resistance due to the length of wire you're gonna get very erroneous results. if you do recall your physics class there is this thing called loss of energy due to friction in mechanical devices. This same principle applies to loss of energy when electrons move through wires.
    The loss of energy or the I squared R losses of a circuit has nothing to do with grounding and this unheard of “leaky current” you keep talking about.

    Quote Originally Posted by Randyj View Post
    Being arrogant will not save lives. I never really dove in deep enough to understand it but I've been told that it's not the voltage that kills but the current. Edison, Tesla, and all the old guys described current... DC and AC. Do you know why? Why not DV and AV?
    At least you do say a few things that are correct. It is indeed the current that kills and not the voltage but there are such things as DV and AV. If the sine wave of the current is direct then the sine wave of the voltage will be direct. If the sine wave of the current alternates then the sine wave of the voltage will alternate.

    You say in this statement that you never dove deep enough to understand so pray tell me why you refuse to listen to those who swim in this knowledge on a daily basis. Having knowledge is in no way being arrogant. Not having knowledge but refusing to listen to those who do have knowledge is most definitely being arrogant. Having said this I agree with you that being arrogant will not save lives.

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