Ideal dock wiring Questions?

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

  1. Randyj

    Randyj Master Plumber

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    Posting for a friend because I want to know other's opinions and tho' I'm a very good and very experienced maintenance/handy man I'm still not an electrician.

    I live on a lake and most of the floating docks here are wired for electric lights, air pumps for floating boat lifts, and usually a provision for battery chargers. Also, many docks will have well pumps to use the lake water for washing down boats. Generally a boat dock will have 2 to 6 outlets and a couple of 8 ft florescent light fixtures and maybe some kind of light out over the water. The distance to the main switch box in a lake house is typically 200 ft from the dock.

    Generally the docks are wired with 12/2 WG in conduit. Also, if the ground comes from the switch box rather than a ground rod at the walkway to the dock you can get a 6 to 8 volt "tickle" when you climb upon a metal boat dock... So, I've installed several ground rods at the walk way and cut the safety ground from the switch box to stop this "tickle" voltage which is a result of voltage drop from the long distance of wiring to the dock. A typical walkway to the dock is 65 ft.

    Here's some questions... what size/type of wire would you run to the dock?

    Would you use a GFCI breaker, GFCI outlets, or both?
  2. jwelectric

    jwelectric Electrical Contractor/Instructor

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    First you can drive all the ground rods you want to but it will do nothing to remove the “trickle shock” hazard between the shore and the water. There is not a motel somewhere underground that electrons retreat to nor is there some kind of electron party that take place underground. Every one of those little electrons are doing their best to return to their source and the improper installation is forcing them to seek a path back through earth.

    The size of the conductors supplying the dock disconnect will be determined by the load served. To size these conductors everything being served will need to be calculated. Without the size of the pump motor, lift motor and other items it is impossible to say what size these conductors need to be.

    If 240 volts is needed for items such as the water pump and boat lift then a four conductor feeder will need to be installed to the dock disconnect. ALL conductors supplying the dock will need to be insulated something that won’t be found using a UF cable.

    The disconnect for the dock will need to have its own grounding electrode system established with the neutral being isolated from the insulated equipment grounding conductor. This equipment grounding conductor should be size 12 or larger.
    An Equipotential Plane will need to be installed at this dock panel that reaches out no less than three feet in all directions.

    Everything at the dock will need Ground Fault Circuit protection. I recommend GFCI breakers in the dock panel.

    This code compliant installation is the only way to stop the “trickle shock”
    Remember that people die every year from shocks received from dock electrical power.
  3. Randyj

    Randyj Master Plumber

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    I do definitely appreciate your reply tho' it is a bit over my head with all the theory. I do know for a fact that the way I've done the ground rod does stop the tickle and insures a safety ground. I found out how to do this from an Alabama Power company engineer. As for An Equipotential Plane, I don't have a clue what you're talking about but can kind of decipher that one. There are probably 20,000 docks on this lake that have electricity and I doubt there is a single one wired as you have described. Most are wired pretty much as you would wire a garage or hobby shop out building.... some are extremely dangerous and there is usually one or more reported electrocutions every year on this lake from improperly wired docks tho' most are wired by electrical contractors. After reading your reply I still don't know if I would simply install GFCI breakers in the breaker panel or do that and also install GFCI outlets.???? Where is that motel you mentioned?

    I would imagine that a ground plane has been established since the dock is framed with steel and the roof and utility closet is enclosed in sheet metal. The walkways are also of the same material, generally all I-beam or tubular steel construction. All points that are hinged or on a pivot have jumper wires for grounding purposes which are bonded.
    Last edited: Mar 21, 2011
  4. ActionDave

    ActionDave Electrician

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    If you do not understand what JW is saying you need to enlist someone who does. A "tingle shock" can be deadly. Driving a bunch of ground rods is not the answer and does not ensure a "safety ground".
    Click HERE to read a case of dock wiring gone bad.
  5. drick

    drick In the Trades

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    It absolutely does not provide any measure of safety except in the event of a million volt lightning strike. And in that event the ground rods are attempting to minimize the damage to the electrical distribution system and have nothing to do with protecting you. Electrical power wants to return to where it came from which is your distribution panel, not the center of the earth. The way to get fault current back to the panel is with a properly installed ground wire. And if you have a GFCI installed in the panel it will detect the current imbalance between the hot and neutral wires and open the circuit breaker before you are killed.

    -rick
  6. jwelectric

    jwelectric Electrical Contractor/Instructor

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    There is not one word of my post that contains theory. Every word is fact and backed up from the NEC

    Now here is a bunch of theory that is totally unfounded and contains absolutely no fact. As has been pointed out all ground rods do is dissipate lightning and has nothing to do with clearing a fault.

    If you don’t understand the equipotential grounding then it would be best for you not to do any wiring around water.

    Yep as you pointed out none are wired as I describe and there is a couple killed each year. Does that sound right to you?

    once again a good reason for you to not be messing with this wiring. Have you got a code book??

    There aint one

    Well my friend it is very clear that you have no clue of what a equipotential grounding plane is so please save a life and stay away from doing electrical work around docks. It is also clear that you have no understanding about grounding and bonding. The hinge points are bonded not grounded

    Last edited by a moderator: Jul 24, 2012
  7. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

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    It absolutely amazes me that someone who can afford all this will not hire a pro to do a professional's job.
    I guess it is yet another case of more money than brains. :rolleyes:



    And I can assure you, like the others, that this with 100% certainty, does NOT provide you with the "safety ground" that you are needing.
    LISTEN to JW, then have your friend HIRE A PROFESSIONAL.
    Last edited by a moderator: Mar 30, 2011
  8. Randyj

    Randyj Master Plumber

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    Gee thanks guys. I keep hearing "hire a professional" and being told that I don't know what I'm doing. But, many of these docks which were wired by "professionals" leave TINGLES and people are getting killed because the docks are NOT PROPERLY GROUNDED. I do understand the "source" is at the switch panel. The shortest distance to ground is through the metal of the dock structure. The conductance should be greater and a shorter distance to ground when grounded at the dock walkway entrance rather than a smaller wire which runs hundreds of feet back to ground. Granted, this is not a balance of potential. However, a voltage drop due to distance which results in resistance makes the metal dock the shortest distance to ground. Thus, it becomes more conductive which also will throw that breaker if there is a shorted wire. If what you guys are saying is true then why would there be a ground rod required at a switch box rather than relying solely on the neutral wire coming from a pole? Grounds do not go all the way back to the power plant, routes of neutral wires do. Bash me all you want... it helps me understand. Balance of potential is thrown out of balance when the wires (the potential in wires) are not balanced and grounding is not equalized in some way.

    When the ground shifts from the neutral to safety ground the shortest distance is through the dock. There is a difference in potential between the switch box hundreds of feet away from the dock when that electron route is provided by a wire. Removing the tickle happens when this difference of potential is removed. If you cut the neutral wired running to a power pole you will throw the voltage to a switch box out of balance. When it happened at my house I was getting 220 on one leg. A safety ground and a neutral wire are simply not the same. The neutral is to provide a balance of potential.
    If you want to experiment with this you can measure the voltage between ground at source to a ground and at the end of a small wire hundreds of feet away from that source. This is why I don't wire docks and do not install wiring to docks tho' I will replace outlets and switches and do maintenance on them. It is a matter of liability, not capability.

    When a person in the water grabs a metal dock they become the shortest distance between ground and source if the dock is not grounded at the walkway and the dock is sitting on rubber floats which act as isolators. This is not theory... it's more like a road map.
    Last edited: Mar 22, 2011
  9. jwelectric

    jwelectric Electrical Contractor/Instructor

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    There are four reasons to connect a wiring system to earth or ground if you please. These four reasons are outlined in 250.4(A)(1)
    Nowhere in this code section does it say anything about the earth being a conductor for current flow. In 250.4(A)(5) it clearly states that the earth is not a return path or part of the conductor of a return path,
    This leaves your concept that the earth somehow relieves current flow an absolute falsehood.

    It does not matter who makes the installation if it is not done correctly then it is not safe. If you or anyone else thinks that driving ground rods or grounding a metal dock somehow makes it safer then you or whomever is badly mistaken.

    A simple flashlight is one of the best training tools that I use. The flashlight has a power source a load and a complete path, the three things needed for current flow. To connect the batteries of the flashlight to an eight foot ground rod would serve no purpose and in no way would cause the batteries to go dead.

    To drive a ground rod in the middle of my yard and connect this ground rod to a 20 amp breaker in my home and turn the breaker on would not trip the breaker even if I fulfilled the requirements or 25 ohms as outlined in 250.56,
    This can be proven using Ohm’s Law of current is equal to the voltage divided by the resistance, 120 divided by 25 equals 4.8amps and nowhere enough to trip even a 15 amp breaker. To cause enough current to flow from the ground rod through earth back to the ground rod installed at the utility pole or pad mounted transformer there would need to be less than 8 ohms of resistance in the earth path. I just don’t believe this can be achieved with 100 eight foot ground rods installed in any given spot on earth in order to have an instantaneous trip of a 15 amp breaker. For this breaker to trip the second it was turned on the resistance between the grounding electrode system and the utility ground would need to be less than 1 ohm.

    The resistance of 100 foot of #6 copper is about .04 ohms and would draw around 3000 amps of current at 120 volts. This is enough proof using math to prove that the earth will not clear a fault as quick as a properly installed equipment grounding conductor.


    If a person is in the water and grabs a properly installed metal dock that is floating in water then there would be no path through that person and earth for current to flow as the metal dock would be bonded back to the source with a low impedance conductor that would clear any current imposed on the metal dock. This is not theory nor a road map but plain old physics.

    Again you display a complete lacking of knowledge of current flow and what you purpose is nothing short of a death trap for anyone coming into contact with an installation as you outline. Again this is not theory but fact as outlined in the physics or current flow.

    So in closing I respectfully ask you to listen instead of throwing out all this bull about ground rods that has no foundation at all.
  10. Randyj

    Randyj Master Plumber

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    Thanks for your reply to my bull... but if you insert a human into a circuit you're going to get someone killed. Power source-human-ground... that's what kills people. Theory and code books work great when everything is perfect. When there the system fails is when the safety ground and ground rod take over and some idiot like me has to come in to figure out that a professional failed to realize that a floating dock is insulated from ground and that the person in the water becomes the shortest distance to ground. BTW, I aced physics and basic electronics. Originally, my question was about using GFCI breakers and GFCI outlets in series... not about ground planes or code books.
    Last edited: Mar 22, 2011
  11. jwelectric

    jwelectric Electrical Contractor/Instructor

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    When you make a code compliant installation then everything is prefect including theory. The thought pattern of a person being in a circuit causes death is true but the earth plays no role in this death nor does it take away the chance of death.

    I agree that when there is a fault to ground the equipment grounding conductor is what clears the fault. This is true simply due to the fact that the equipment grounding conductor is bonded to the grounded neutral at the service equipment not because there is a ground rod installed. It is the low impedance path through the equipment grounding conductor to the neutral at the service equipment that causes the breaker to trip and the ground rod plays no role in this tripping.

    It is due to people like you that think that connecting something to earth clears fault current that kills people. The people that understand that the bonding of the equipment grounding conductor to the neutral at the service equipment that establishes a low impedance (resistance) path back to the source is what removes fault current are the ones who save lives.

    If you are that good at math it should be easy for you to understand that it is through the low impedance that clears faults not a earth ground. It is a simple math problem that any fifth grader can understand as I have outlined in my last post. If you had a good understanding of grounding and bonding that you seem to think you have then you wouldn’t have to ask anything about Ground Fault Circuit Interrupters. You would already have the knowledge to answer your own question.

    I am not trying to be rude to you in any manner but am speaking the truth. In your comments of earth ground or ground rods if you please you display a total lack of knowledge of physics as it concerns electrical current flow. It is through your own comments that leads me to believe the last two statements you made in your last post are untrue.

    As to your question about GFCI devices I have already answered your question several times but maybe not to your liking.

    The bottom line here is plain and simple, you have displayed a total disregard to safety and put your misconceptions of earth grounding in place of someone’s life. I suppose you think that everyone that has replied to you misconception of earth ground is nothing short of a lunatic even though we are trained in our fields but on the other hand by your own admission are not;
    Last edited: Mar 22, 2011
  12. Randyj

    Randyj Master Plumber

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    Sorry... I don't mean to argue here. But, the one thing that seems to be unclear is that when a floating dock is energized by contact with a wire then the dock becomes a part of the circuit and the power source. Electrons, like water, do not follow the shortest distance to their source but they follow the path of least resistance thus if the dock is not grounded then the path of least resistance becomes the person in the water who grabs hold of the metal dock.... 4th grade 4-H club....
    To carry the theory/analogy a little futher... if the return path has more resistance than the provided (pipe for water, wire for electricity) can handle then a leak develops and a little of that stuff flow out which is where the tickle comes from when a dock is grounded to the panel hundreds of feet away and not to the earth. The neutral wire is provided for a return path to source. The ground is provided for an emergency escape route to safety. Rudimentary logic/theory.
    Last edited: Mar 22, 2011
  13. jwelectric

    jwelectric Electrical Contractor/Instructor

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    If what you say about electricity taking the path of least resistance then use all the physics and electronic knowledge you can muster and explain a parallel resistive circuit to me.
    Here are some laws of physics concerning current flow. 6.25 times 10 carried to the eighteenth power of electrons passing one point equals one coulomb and one coulomb per second equals one amp. This is what is moving through the conductor.
    100 million lines of magnetic flux being cut for one second generates one volt. This is the amount of pressure it takes to push one amp through one ohm of resistance.

    Every one of those electrons that leaves the power source be it a DC battery or a nuclear power plant generator or the transformer supplying our home MUST return to its source. Not even one of these electrons are allowed to be detoured or “leak out†anywhere in its path. This is basic electric 101 and part of the first day of the classes I teach.

    If the wiring circuits installed on this floating metal dock are installed in the proper manner and the metal dock becomes energized then the over current de vice will open. The current will flow from the metal dock to the bonding conductors that bond the equipment grounding conductor back to the service equipment where the equipment grounding conductor is bonded to the service neutral conductor back to the transformer supplying the house.

    This path will have a lot less resistance than the path from the point of contact back to the utility grounding to return to the transformer which is the source supplying this branch circuit.

    But wait a minute------------- you said that current will always take the path of least resistance so the person in the water wouldn’t feel a thing.
    I think you are somehow confused about what role the earth plays in current flow. You seem to be convinced that current flows to earth and not back to the source. If this were true then I could take the 6 volt battery from my lantern and connect one side of the battery to earth and the battery would go dead. Simple test you can do at home and let us know how many years it took for the battery to go dead.
  14. LLigetfa

    LLigetfa DIYer, not in the trades

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    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.
  15. Randyj

    Randyj Master Plumber

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    Maybe I am confused and pretty stupid for a dumb ol' southern fried country boy who doesn't teach school.. and so are all those other stupid people who put ground rods and ground wires to switch boxes. BUT, you should drag yourself down to Alabama where if you're standing bare footed in your bathing suit and dripping wet with water you'll get the do do knocked out of you if you're standing on dirt and grab a hot wire or any wire or metal structure with a sizable difference in potential than the earth. Too, if you're teaching this stuff you might have studied something a bit different than I did because there is such thing as voltage drop and resistance on wires which run long distances and this voltage will "leak" or dissipate in some form of energy whether it is electrons escaping through a ground wire into a metal dock or in the form of heat. This loss of energy accounts for a significant amount of loss of produced energy from power plants even if they're nuclear, coal fired, oil fired or hydro electric. If for any reason a wire grounded to a switch panel hundreds of feet away has a difference in resistance, conductance or voltage that pressure you refer to is gonna push them electrons rat down to the dirt iff'n dem dang electrons don't be jump'n rat off into the crick through some dang fool grabb'n holt of that there metal dock with all them voltages stuck to it. I don't know what number it is in that dang book of yours's but I bet it's in air sum whares...
    Last edited: Mar 22, 2011
  16. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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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...
  17. Randyj

    Randyj Master Plumber

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    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: Mar 22, 2011
  18. Randyj

    Randyj Master Plumber

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    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: Mar 22, 2011
  19. LLigetfa

    LLigetfa DIYer, not in the trades

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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.
  20. Randyj

    Randyj Master Plumber

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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: Mar 22, 2011
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