Ideal dock wiring Questions?

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

  1. jwelectric

    jwelectric Electrical Contractor/Instructor

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    I think that a lot of the confusion about earth grounding of a premise wiring system such as our homes comes from the methods used for connecting an electrical component to an automotive system.

    In the automotive system we have a 12 volt system that is powered by a 12 volt battery. This battery has two post one positive + and one negative -. We all call the negative terminal of the battery the ground terminal. If one was going to wire a light to this system we would take a hot wire + and place a fuse (overcurrent device) inline to a switch to control the light. Another wire would be connected to “ground†or the negative – terminal of the battery which is connected to the body of the automobile.
    In the automobile the negative – side of the battery is “grounded†or connected to the frame of the automobile. In reality what we are really doing is connecting this “ground wire†to the negative terminal of the battery by using the metal path of the automobile as the negative wire. Just as with the rusty trailer hitch should this negative – path (the ground) be broken the light would not work. The current path back to the negative post of the battery would be broke and there would be no complete path for the current to follow.

    In a premise wiring system such as our homes we can connect a light by installing a breaker (overcurrent device) to the bus bar of our panel and installing a conductor to a switch. From the switch to the light and then the other wire is connected to the neutral terminal bar in the panel. This terminal bar is connected back to the transformer through a neutral wire. Both of these circuits use only two wires in order to work, in the automobile a hot and a ground (negative) and in our home a hot and a neutral.

    The major difference between the term used in an automotive circuit and the wiring system installed in our homes is the term “groundâ€. In the automobile the term “ground†is used to define the negative terminal of the battery. In our homes the term ground is used to define earth which an automobile does not have. Our negative wire (a bad use of the word negative) is the neutral wire.
    In both cases the return path will carry current the negative (ground) wire in the automobile or the neutral of the house wiring. In both cases the current that leaves the source, in the automobile the battery and in our homes the transformer, returns to the source. No current is leaking out of the circuit into anything or being dumped through the grounding conductor to earth.

    In the wiring systems installed in our homes we install a grounding electrode system which must be bonded to our service neutral. Then we install a third conductor called the equipment grounding conductor which is also bonded to the grounding electrode and the neutral conductor at our service.

    Unlike the “ground wire†installed in our automobile which will be carrying current, the equipment grounding conductor, this third wire, will not carry any current at all unless there is a ground fault. The purpose of this grounding wire in the circuits of our home is in case a hot wire comes in contact with any exposed metal. This equipment grounding conductor will carry this faulted (hot touching the metal) current back to the neutral in the service equipment and back to the transformer causing a high draw of current that will open the overcurrent device. It would be just like taking the hot conductor in our automobile and touching the ground (body of the automobile) the current would be carried back to the negative of the battery causing a high current draw thus blowing the fuse.

    As outlined in 250.4 of the NEC this earth grounding is done for four reasons and the opening of the overcurrent device is not one of them. Ground as defined by the NEC for the wiring systems installed in our homes is a connection to earth. Ground as defined in automotive wiring is defined as a connection to the negative post of the battery. There is a big difference between the two definitions. In our homes the second wire is called a neutral and the grounding is a connection to earth which an automobile does not have.

    If earth grounding would work for a return path then the utility companies around America would not install the neutral conductor from the transformer to our homes, business, and industrial plants. There would be no need for this conductor and the utilities would save millions of dollars.
  2. Randyj

    Randyj Master Plumber

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    I'm good with discussing the theories of automotive electricity and comparing to utility company supplied power to it's customers. I'm also good with comparing the term "ground" in those cases. It appears to me that the term "ground" should be completely thrown out except to refer to a wire or circuit connected to the earth, dirt, ground... Seems the term introduces much confusion. So, a term should be used to describe the negative side of a DC circuit and another term or equivalent term to describe the neutral side of an AC circuit. In dual circuits such as 240 volt AC a similar delineation is made by saying L1 and L2. IMO, to compare a utility to an automobile is totally like discussing apples and oranges because the automobile is like a completely self contained utility and all of it's users/customers. Another big difference is that the modern automobile contains RF circuits, AC circuits, and DC completely self contained.. if compared to a dock that's like installing a gasoline engine powered generator on a dock rather than running electrical wires from a service panel hundreds of feet away... no more need for an earth ground than installing a ground rod to an automobile. It would then have it's own electrical source and the green wire would lead directly back to the generator without the earth contributing anything, no voltages, no currents, no resistance of earth. In common vernacular just about everyone uses the term "ground" for "neutral". In my posts I have tried to avoid this confusion. If we get particular about the correct use of the language then we should refer to it as a "neutral connection or neutral side of the circuit".. a short cut is to simply say "neutral (for continuous connection to the neutral of the transformer)" or "ground (for continuous connection to earth)". As a professional multi-skilled laborer I have to know the difference. A discussion of all the different professions encompassed in the field of maintenance should be a different thread (more apples and oranges). There is no doubt in my mind whatsoever that the NEC as well as all plumbing codes are totally devoted to safety and health. In medicine it is the field of preventive medicine (health inspector) (one of my previous occupations/Military) that is the first line of defense. Same as in buildings/structures/utilities.. it is the maintenance man who is the first line of defense.
    Back to dock wiring.. Wouldn't it or would it not be... safest to simply NOT directly connect any earth ground at all to a metal dock? All earth ground wires terminate at receptacles. All wires in insulated (PVC) and all outlet & switch boxes be made of a non-conductive material? All switch box panels on the dock insulated from contact with the dock? .. .this would be comparable to how any appliance is wired, everything insulated from human contact and totally avoids any possibility of even a tickle voltage from the difference in stray voltages, voltage drops and any kind of electrical currents. It appears that this would certainly satisfy the NEC requirement that the green wire/ground be a continuous connection all the way back to the service entrance. No need for epg's, grids in the earth, buried hamster cages, ground rods... nothing except circuit wires to provide electricity and protection from faults. KISS... Keep it simple suckah. For one thing... wiring a dock is the big time equivalent of running an extension cord to the dock. You would not connect the ground wire of an extension cord to a dock or metal building....
    Last edited: Mar 31, 2011
  3. Randyj

    Randyj Master Plumber

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    I just got back in from trying this to verify once again what I've done several times before. It appears that my dirt is a very good conductor. I completely disconnected the wire from the ground rod the got out my walmart voltmeter to check the voltage between the "hot" wires in my switch box and the ground rod. I got a full 123 volts AC. I have done this at other places and got only 64 volts. If a hot wire hit the dirt around here it would trip the breaker. It is right at 200 ft to the transformer and it's ground rod.... of course, the ground is wet after all the rains we've had lately.... and the neutral wire is properly connected to the transformer unlike the time it got jerked out of the transformer when a limb fell across the line.
    The nature of the dirt here is a bit different than other places. If you drag a strong magnet across the ground you pick up lots of rocks and dirt due to the high ferrous content.
    Last edited: Mar 31, 2011
  4. jwelectric

    jwelectric Electrical Contractor/Instructor

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    As to the generator at the dock it would depend on the type of generator being used as to whether or not a grounding electrode system would be required. A self contained portable generator would not require a grounding electrode but a permanently installed generator would require a grounding electrode system.

    There is no way on earth to make stray voltages disappear. It would require that there be no more electrical storms and both the north and south poles would have to be neutralized to stop all stray voltages or gradients voltages through earth’s crust. The temperature would need to be constant over the entire earth with no cold fronts colliding with warm fronts.
    All theses combined causes the earth’s crust to have voltages without there ever being any type of electrical current produced by the utilities or any other man made current.

    The thought of comparing the 12 volt DC system to a 120 volt AC system as being like comparing apples to oranges is untrue. The only two things that change are the type of voltages and the numbers. The equations are the same.

    As to calling the neutral the ground conductor is not exactly correct either. The neutral conductors that supply our homes are a current carrying conductor just as the ungrounded (hot) conductors. In a 120 volt circuit the neutral carries just as much current as the hot conductor. The equipment grounding conductor never carries current unless something bad goes wrong.
    The reason the neutral is called the groundED conductor is because the utility connects this conductor to earth. In most cases for a dwelling unit the return or neutral of the high voltage supplying the transformer is connected to the neutral of the secondary (the one coming to our homes) and to the grounding electrode conductor at the utility pole or pad mounted transformer. It is called groundED by the NEC because by the time the electrician gets to wire the building this earth connection is already established or past tense.

    The electrician installs the equipment groundING conductor at the time of the installation therefore in the present tense. This grounding conductor is then bonded to the grounded conductor and the grounding electrode conductor at the service. The grounded neutral is earth grounded twice, once by the utility and again by the electrician at the service equipment and can be earth grounded for the third and more times each time the conductors leave the service equipment and go to another building or structure on the outside.
    The purpose of bonding this metal dock to the grounding electrode for the panel supplying the metal dock is in case one of the circuits supplying equipment such as lights, receptacles, boat lifts, and the such on the metal dock should come into contact with the metal dock there would be a low impedance path back to the source supplying power to that dock in order to open the overcurrent device thus stopping the flow of current.
    This bonding is not to relieve the voltage gradients between the water and the metal or wooden dock. A ground rod will not relieve this current. An equipotential grid does not relieve these stray voltages but instead brings everything to the same or equal potential therefore no current flow.

    Even if everything was installed in non-metallic enclosures and raceways it would not relieve the stray voltages. There would still be the step potential between the water and the dry ground.
  5. jwelectric

    jwelectric Electrical Contractor/Instructor

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    Deleted as it was a duplicate
    Last edited: Mar 31, 2011
  6. Randyj

    Randyj Master Plumber

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    I think this may be where our difference or argument is getting confused. If there is a fault current to a dock connected to a ground rod then a swimmer contacting the metal dock does not become PART OF A SERIES CIRCUIT... That swimmer becomes PARALLEL to the return path of that earth ground circuit. Those electrons traveling through a metal dock, as you point out, seek a path back to the transformer through the earth... with all of it's resistance, stray voltages and sine waves and straight waves and curly waves....and all the salts of the earth... if there is no continuous route to the neutral of the transformer or power company's generator. If the POCO had never driven a ground rod this danger would not exist.... right???
    Last edited: Mar 31, 2011
  7. Randyj

    Randyj Master Plumber

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    Now that's silly.... I ain't never in my life seen dry ground unner a boat slip... 'cept in the drought of 2007.

    I'd be willing to bet a fair amount of money that if you cruise all 500 miles of shoreline of this lake you'll not find the first EPG. And if a compliance officer or inspector did the same thing looking for code violations he/she would spend the rest of his days writing citations and going to court for this lake alone.... much less all the river and tributaries between here and Mobile bay in the Gulf of Mexico.
    Last edited: Mar 31, 2011
  8. jwelectric

    jwelectric Electrical Contractor/Instructor

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    No that person is in series with the earth
    True if the electrical was not ever connected to earth how could it return
  9. jwelectric

    jwelectric Electrical Contractor/Instructor

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    go just a few inches from the water and what do you have? dry ground

    The reason why there would be no grounding grid is because there is no requirement to install one under a metal dock. Most people with a little common sense know better than to go swimming in waters such as these in the first place
  10. Randyj

    Randyj Master Plumber

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    Wrong... ya got MUD... water 'n dirt.
  11. ActionDave

    ActionDave Electrician

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    Dude, look at the keyboard on your computer. Two rows up from the space bar on the far right is a key labeled "Enter". Help some of us out and hit it once in a while.
  12. jwelectric

    jwelectric Electrical Contractor/Instructor

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    Randy

    After a discussion with one of my students I have been ask to find out just what you mean by this statement.

    Would you mind taking a few minutes and explain what you are saying for the benefit of those who are reading this thread?
  13. DonL

    DonL Jack of all trades Master of one

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    Hello Group,

    Lets not let this thread die, It is good, and long lived. (Thanks to Terry and the Group)

    Did the problem ever get resolved ?

    Real Ships connect to ShorePower when they pull up to the docks.

    Not only does it put the boat at the same potential as the Power Ground it also discharges any Static Electricity,
    that the sacrificial anode does not.

    Look at how boat docks that have gas pumps are wired, They have the same threat as Humans when it come to safety.

    And also "Theory only works in a vacuum" , there are just to many unknown variables in every day life.

    Here is a question for You, Does a light give off light or does it suck up dark ?

    I would like to see a thread on RF, where the Earth Ground is everything, And it can carry big time Current. (Must be FM)

    Have a Great Day.

    DonL
  14. Randyj

    Randyj Master Plumber

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    To answer your question dark and light would have to be defined in terms that relate to sucking up darkness or giving off light. In my opinion, light invades darkness like pouring water on something. Actually, astronomers consider light in many cases to be contamination of darkness...In this line of thinking I would assume total darkness to be devoid of any kind of radiation.... so what do you call vacuum?

    Want a thread on RF, grounding, FM ... start one!
    Last edited: Apr 12, 2011
  15. Randyj

    Randyj Master Plumber

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    Sorry for the delay in replying to this question...
    If the POCO had never connected neutral wires to ground rods then the stray voltages from the power company sources would not be entering earth. As I understand it, some power companies are running only one wire but depend on the earth to carry the return current. I've not been concerned enough about it to think about this very hard...
  16. DonL

    DonL Jack of all trades Master of one

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    Hello Randyj and the group,

    Very good on your answer Randy. Light does interfere with astronomy, That is why stargazers go to the county for a good view.
    City lighting is a big problem. Light Clutter is one name for it.

    I have seen the bashing that you have gotten.(Call it what You will, I am not a book worm, Nor want to be.) Don't think nothing of it. Some people have Book Smarts but No ability to apply what is in the book, In the World we live in. They are smart, but contrary to popular belief, They do Not know it all.

    Nobody knows everything, Or their Head would be so big for the brain to hold all the information, That is needed to be a Mister Know It All.

    The fact is that Opposites attract.

    Grounds can kill, If your potential is Above OR Below Ground, when you come in contact with something. Only takes Milli-amps, but also
    Voltage is needed (for Your skin to Conduct). A good example is to go across a 12 Volt car battery and you don't feel a thing, even tho it can produce many hundreds of amps. Increase the voltage and it can grab A-hold of you even if you do not touch it. (I hate when that happens)

    Ground Loops are very common in many electronic systems. (Electric , electronic, call it what you want, Flow of electrons)
    Simply a difference in potential. You don't need to be a Rocket Scientist to figure it out.

    A Vacuum is mostly available in outer space, and it is very cold. And electron theory is based on ideal conditions, In a Vacuum, Where
    electriciy can travel at the speed of light, But only in theory, Not on Earth, Yet.

    Electrons will flow mostly in the path of least resistance, but also takes other paths that are in their electric connections.

    Lightning take the quickest path that it can find, And will blow something apart if the current get to high for it to be dissipated. (Heat gets involved)

    I know that a lot that I am saying, You know first hand, I just wanted to refresh your memory and the others that need too be Refreshed.

    Have a great day.


    DonL...


    "Theory only works in a vacuum" , there are just to many unknown variables in every day life.
  17. ballvalve

    ballvalve General Engineering Contractor

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    If a tree falls in the forest, and no one is there, does it make a sound?
  18. DonL

    DonL Jack of all trades Master of one

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    LOL

    Yes the trees do make a sound, And the birds and squirrels say O-Shit, and run for cover.
    But there is no one but God that ever hears them...
  19. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    FWIW, you can't measure cold...you can measure the amount of heat (energy) (the less energy, the less heat, the more cold)....similar to light, dark is the lack of light....
  20. Randyj

    Randyj Master Plumber

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    Well DonL... the thread was everywhere from very serious to highly entertaining for me. I learned a little and refreshed a lot of things I haven't seriously studied in many years. However, the principles of electron behavior still applies just as it did back then. There is some difference in interpretation in several things. One being the idea that electricity takes the path of least resistance or takes the shortest route to source. I think that though lightning is not the same as generated AC or DC since it is static electricity it still shows the fact that electricity can and will take several paths and is analogous to stray voltages... and as far as I'm concerned shows the path of least resistance. The only time I know of that electricity takes the shortest route to source is when it is in a wire and that is the only time it will follow a straight line unless maybe you want to consider an arc such across a spark plug gap or getting zapped by an electric fence... and that is also an example of one wire carrying a current or charge while the ground acts like a conductor. Speaking of electric fences, they work by using a capacitor to store electrons and a 12 volt source can and will knock you on your ass when a capacitor discharges through you in which an electric fence does just that. When I was a kid we used to have fun by charging up a condenser out of a car then handing it to a buddy and telling him to see if it's any good.... It was fun to watch'em jump... pee in their pants if they were drinking..
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