Ideal dock wiring Questions?

Discussion in 'Electrical Forum discussion & Blog' started by Randyj, Mar 20, 2011.

  1. ballvalve

    ballvalve General Engineering Contractor

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    http://www.google.com/search?q=equi...rlz=1I7DKUS_en&ie=UTF-8&oe=UTF-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: Mar 22, 2011
  2. Randyj

    Randyj Master Plumber

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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: Mar 22, 2011
  3. Randyj

    Randyj Master Plumber

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    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: Mar 22, 2011
  4. jwelectric

    jwelectric Electrical Contractor/Instructor

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    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.
  5. jwelectric

    jwelectric Electrical Contractor/Instructor

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    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?
  6. jwelectric

    jwelectric Electrical Contractor/Instructor

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    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?
  7. jwelectric

    jwelectric Electrical Contractor/Instructor

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    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.
  8. Randyj

    Randyj Master Plumber

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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?
  9. Randyj

    Randyj Master Plumber

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    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: Mar 23, 2011
  10. jwelectric

    jwelectric Electrical Contractor/Instructor

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    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.

    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.

    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.

    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.
  11. Randyj

    Randyj Master Plumber

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    You got pretty close there JW but I'm not saying that the circuit supplying power to the pier is losing current to earth. I'm saying that it loses voltage due to the distance from the switch box panel. If the ground wire comes all the way from the switch box hundreds of feet away there is a difference in voltage between the ends of that ground wire and a difference between that ground wire and the ground rod at that distance. This is why that ground wire back to the main switch panel must be cut and a ground rod installed at the walkway entrance. If this is not done then there is a very measureable voltage between the dock and the water. I have in fact touched one lead of my volt meter to a dock then dropped the other end in the water and got an 8 volt reading but when I disconnected the ground wire going back to the switch box panel the reading dropped to zero. The ground rod configuration may or may not protect equipment/appliances and may not even throw a breaker but it will save lives because the current path is then through the metal dock bonded to the ground rod. I may not understand the description of equipotential grounding but I do understand zero voltage and zero current and I know how to detect them.
  12. Furd

    Furd Engineer

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    I'm reminded of a few old sayings like, "You can lead a horse to water..." and, "There are none so blind as those that refuse to see." Keep up the good work, JW.

    Randy, there are all manner of "electrical inspectors" and some are not worth the powder to blow them to hell. I would be VERY leery of any contractor that was also authorized to do inspections. I once dealt with a municipal inspector that couldn't have found any code citations if he was given the book opened to the correct page. It isn't unlike doctors that send you to an imaging center in which they have a financial stake. The "inspector" that required you to disconnect the grounding electrode conductor from the metallic water piping was WRONG! Now to give benefit of doubt it may be possible that he wanted you to upgrade the GEC rather than completely remove it and then failed to inspect the entire system on the re-inspection...if there WAS a re-inspection.
  13. jwelectric

    jwelectric Electrical Contractor/Instructor

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    In 44 years of field experience, 11 years of classroom experience, 4 years of college training, the one thing I have never seen nor heard tell of until your post is a grounding conductor that has a difference in voltage between the ends if the conductor. As a matter of fact I have never seen a grounding conductor that had voltage on it unless there was a fault condition.
    Please explain what kind of grounding wire you have that carries a difference in voltage between the two ends.

    Let me make sure that I understand just what you are saying here. You cut the grounding conductor and drive a ground rod to which you attach the equipment grounding conductor and all faulted current then flows into earth, is this correct so far????

    Now was this before you installed the ground rod or after you installed your ground rod?

    and this is nothing short of bull droppings. These ground rods does not save any lives at all and in fact puts lives in danger

    It is very obvious that you do not have any understanding of grounding and bonding at all. If you are going to try to convince me that by removing a grounding conductor from the system’s grounding electrode and it removed fault current to the water you are going to have to do a lot better job than you have done here.
  14. ballvalve

    ballvalve General Engineering Contractor

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    The OP said a few people a year die from shocks at this lake. Seems thats like having a serial killer in the neighborhood, and someone would have done a 'study' as to its causes.

    I have never worked on a dock and hardly been on one, but I fail to see why this is any different than a pool deck or waterscaped yard with lights and pumps and outlets - except that its always in motion.

    Such areas utilize GFCI's and normal grounding wires, and no one in planning or in the trades has ever suggested they have a equipotential ground plane installed. I think you mentioned 3x3 feet.

    And RAJ, surely no one would consider the 'voltage drop' contributing to shocks and breaking the ground wire at the dock foot and adding ground rods. Thats a bit of hallucination.

    I would guess your serial killer at the lake is old wiring that has wiggled up and down for many years in waves and storms and rubbed itself bare in conduit, to various values of danger. Attached to old standard breakers, perhaps without any ground at all.

    I would wire my dock with some mine rated SJ 3 or 4 wire cord in pvc conduit with pvc flex and loops at the dock joints connected to modern GFCI breakers. Then I would liberally use silicone inside the boxes to partially encapsulate the wires to preclude motion. And all connections would be covered with an anti corrosive paste-grease.

    A lot of work, which is why I dont have a dock and why people die at them.

    Frankly, a standard extension cord zip tied to the dock rail and plugged into a GFCI would likely be safer than some old wires in flex or conduit that cannot be inspected for chaffing from motion. Ask Boeing, they worked this out years ago.
    Last edited: Mar 23, 2011
  15. jwelectric

    jwelectric Electrical Contractor/Instructor

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    Ballvalve

    Any and all bodies of water, be it pool, pond, lake or fountain requires an equipotential bonding grid. Even the whirlpool tub installed in bathrooms requires bonding of any metal pipes that are in contact with the tub water.

    Each and every one of these bodies of water will require an insulated equipment grounding conductor to be installed all the way back to the service equipment except that portion of the circuit that is inside a dwelling unit.
  16. ballvalve

    ballvalve General Engineering Contractor

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    From what I have seen, no inspector has ever uttered the word equipotential bonding grid at a pool [especially an above ground pool] or yard fountain. Of course they will require a ground wire. Have not seen it spec'd into plans either, on a residential level. Seems to have variable regional enforcement based on web research.

    Bonding pipes at a whirlpool tub does not seem to be related to EPB grids.

    And how do we account for the millions of portable hot tubs that have only GFCI's and a standard plug?

    What are the 'mechanics' of these dock deaths? Is it the motion that causes shorts?

    http://www.erico.com/public/library/fep/LT1242.pdf

    At this site, they claim even above ground pools need a perimeter EPB grid around it. Anyone ever seen that installed?

    If the OP ever comes back after being tossed to the lions, I would like to know the details of these regular dock deaths.
    Last edited: Mar 24, 2011
  17. jwelectric

    jwelectric Electrical Contractor/Instructor

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    680.26 requires the equipotential bonding grid for in ground pools

    680.42 for hot tubs installed outside but there is a TIA out for these installations

    680.74 for the whirlpool tub which must be bonded with a #8 just as any equipotential grid

    682.31 for the insulated EGC and 682.33 for the equipotential bonding grid for natural
    or artificially made bodies of water which the pier would fall under.

    Sorry that you have never heard of them but they are a very important component to wiring around bodies of water where someone is going to come in contact with the water and metal objects at the same time.

    As to the OP I would be inclined to say that instead of him being tossed he jumped in on purpose.
  18. ballvalve

    ballvalve General Engineering Contractor

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    I said that I never saw them spec'd in on residential plans, not that I have not heard of them.

    It appears that many consider them foolish or ineffectual at best.

    Could you answer my question as to what is the practical answer to the mechanics of dock electrocutions? Am I correct in assuming that a dock in motion is prone to compromising wire insulation?

    Obviously, if the NEC were the bible, you would be in a top post at the Vatican research library. But as you know, each religion has its own flavor of bible.

    Some of us just need practical answers without page and paragraph quotes if we are to help you actuate the 'death and electricity' sticky to save lives.
  19. Randyj

    Randyj Master Plumber

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    Looks like we're gonna beat this horse to death. I can tell you that I learn a heck of a lot about things from people who know a heck of a lot less about them than I do. I NEVER have claimed to have all that education in electricity nor to teach it or all those other wonderful things. But I do know a few things about it and learned it by experience and OJT and have worked in a multitude of different kinds of residential, commercial, and institutional maintenance. I couldn't begin to tell you much about 3 phase wiring but I've worked on lots of 3 phase equipment. I've been around delta wye's and worked on 440 volt vacuum forming machines but can't tell you how a delta wye is configured or how that electricty comes out of it... but I can find a broken wire and replace a burned out element, switches and all kinds of things that run on 440 on a vacuum forming machine and have done lots of maintenance on cad/cam's and CNC's but still can't operate either.
    I can tell you that offshore equipment and boat docks are far from the same as residential wiring. They have special and abnormal issues from earth bound structures. If you're gonna get to know something about dock wiring you need to read this...
    http://www.highport.com/electricalHazard.php
    Here is an except from it....It is worth repeating that shore-power based AC circuits never have the neutral grounded on board...

    NEVER think you know more about something because you have more notches in your belt.... I'm the first to tell you I don't know everything and can learn from any body. If I knew it all then I would have never come to this forum to ask questions.... I have learned that marine electricity is not the same as terrestrial electricity. And yes, two ground rods hundreds of feet apart can have voltage and current between them and not even be connected to a power source. This is not class room stuff. It is field experience. There's still lots I don't know.
  20. Randyj

    Randyj Master Plumber

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    Ballvalve...et.al. Here's another link that discusses the exact same thing and in this discussion a "qualified" electrician is saying the very same thing about the tingle that I said way back there concerning voltage drop.
    ://www.electrical-contractor.net/forums/ubbthreads.php/topics/167411/2.html
    Here's the part that I noticed in the thread...
    Quote:
    With the mains to the house, garage and dock off I still have the same current flow, yet neither the new copper ground rod at the meter, nor the poco ground, nor their guy wire show any current flow.

    Did you remove the main bonding jumper for this test? The utility primary and secondary grounded conductors are connected together. In many cases like this the source of the voltage is the voltage drop on the utility primary neutral.
    Don
    _________________________
    Don(resqcapt19)

    As for some details on the electrocutions on this lake I would say that most have been due to frayed wires as you described. I know one was a construction worker who dropped his saw in the water and he automatically reflexed to get it. One had something to do with some idiot had a hot tub on his dock when 240 volts came through the dock into the water via a swimmer who grabbed the metal dock. I would bet that the dock was not grounded properly to a ground rod. To me the key here is that electricity does not take the shortest path to source but takes the path of least resistance. From what I've read the NEC is somewhat at conflict with applications in non-conforming locations. Personally, I live on the lake but don't even have a dock and if I did I would rather it not be wired for electricity but still would have a ground rod bonded to it. This would be to prevent shock to swimmers in the event someone used an extension cord for a battery charger, light, or any other appliance.
    The idea that there's no such thing as voltage leaks is just wrong. There is no such thing as an absolute insulator. All an insulator does is offer a very good or acceptable amount of resistance. If glass and ceramics (very good insulators) did not conduct electricity then we would not have resistors and transistors, i.e. they leak electricity. In a sense even rubber is a very good conductor of electricity if you remember the old experiment with static electricity and pocket combs... and that Tesla thingy with the big rubber band can give you a hell of a few thousand volts shock.
    You'd be surprised at how many docks I've seen with no more protection than ordinary house wiring and far worse. Read the links I've posted concerning docks. I may get some terms wrong or confuse current and voltage but the detail is not in the current/voltage from the distribution point. The important item is in the ground to the dock. The voltage drop causing the tickle is from the losses due to the distance these wires travel, (especially if the earth ground wire goes hundreds of feet back to the switch box. Suppose this were dc. An electron would have to travel from the battery on the "hot" all the way back down the neutral wire to the panel where earth ground is connected then back down the "ground wire" to the dock. It would have to travel 3 times the distance as it would on only a single wire. This difference in travel time and the losses due to whatever causes those losses... I'll call it friction as an analogy to a mechanical device... would result in a difference in potential or current or whatever the correct term is. This results in a measurable difference in voltage just as I have proven to myself when I put one lead of my volt meter in the water and touched the other to the dock I worked on. For all I know it could have been differences due to stray voltages between the dock and distribution panel but the fact is that there was a voltage difference and I've seen it and heard of this several times. I am not new at this.) The "voltage drop" I'm seeing is in the earth ground wire when it goes back to the panel, not the wires carrying the service voltage/current to and from the dock.
    At the dock the potential will be different than it will be at the other end. I can only explain this in layman's terms because I am not accustomed to the technical jargon. See the link I posted to the electrical-contractor.net thread. It is a very "techy" discussion. I have to strain a little to follow but I do understand it.
    Last edited: Mar 25, 2011
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