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Thread: Ideal dock wiring Questions?

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  1. #1

    Default Ideal dock wiring Questions?

    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. #2
    Electrical Contractor/Instructor jwelectric's Avatar
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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. #3

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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 by Randyj; 03-21-2011 at 06:40 PM.

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    Electrician ActionDave's Avatar
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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. #5

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    Quote Originally Posted by Randyj View Post
    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.
    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. #6
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by Randyj View Post
    I do definitely appreciate your reply tho' it is a bit over my head with all the theory.
    There is not one word of my post that contains theory. Every word is fact and backed up from the NEC

    Quote Originally Posted by Randyj View Post
    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.
    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.

    Quote Originally Posted by Randyj View Post
    As for An Equipotential Plane, I don't have a clue what you're talking about but can kind of decipher that one.
    If you don’t understand the equipotential grounding then it would be best for you not to do any wiring around water.

    Quote Originally Posted by Randyj View Post
    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.
    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?

    Quote Originally Posted by Randyj View Post
    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.????
    once again a good reason for you to not be messing with this wiring. Have you got a code book??

    Quote Originally Posted by Randyj View Post
    Where is that motel you mentioned?
    There aint one

    Quote Originally Posted by Randyj View Post
    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.
    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 Terry; 07-24-2012 at 02:52 PM.

  7. #7
    Licensed Electrical Contractor Speedy Petey's Avatar
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    Quote Originally Posted by Randyj View Post
    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.
    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.



    Quote Originally Posted by Randyj View Post
    I do know for a fact that the way I've done the ground rod does stop the tickle and insures a safety ground.
    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 jwelectric; 03-30-2011 at 03:01 PM.

  8. #8

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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 by Randyj; 03-22-2011 at 06:54 AM.

  9. #9
    Electrical Contractor/Instructor jwelectric's Avatar
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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)
    (1) Electrical System Grounding. Electrical systems that are grounded shall be connected to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation.
    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,
    The earth shall not be considered as an effective ground-fault current 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,
    250.56 Resistance of Rod, Pipe, and Plate Electrodes. A single electrode consisting of a rod, pipe, or plate that does not have a resistance to ground of 25 ohms or less shall be augmented by one additional electrode of any of the types specified by 250.52(A)(4) through (A)(8). Where multiple rod, pipe, or plate electrodes are installed to meet the requirements of this section, they shall not be less than 1.8 m (6 ft) apart.
    This can be proven using Ohmís 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 donít 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. #10

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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 by Randyj; 03-22-2011 at 08:42 AM.

  11. #11
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by Randyj View Post
    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 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.

    Quote Originally Posted by Randyj View Post
    When there the system fails is when the safety ground and ground rod take over
    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.

    Quote Originally Posted by Randyj View Post
    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.
    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.

    Quote Originally Posted by Randyj View Post
    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.
    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;
    Quote Originally Posted by Randyj View Post
    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.
    Last edited by jwelectric; 03-22-2011 at 09:23 AM.

  12. #12
    DIY Junior Member skdaddle's Avatar
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    Default Boat Lift Electrical Shock


    I experienced a slight electrical "tingle" when I was working on a boat cradle on a boat lift wired for 240V operation. My fingertips felt like they were humming on the aluminum lifting beam. I was straddling the beam with my feet in the water at the time as I tightened the boat cradle bolts. The lift was about 1' above the water in a fresh water lake. The lift was connected to a dock panel box with a 240v 20 amp Ground fault breaker installed. Lift operation was thru a remote control with a limit switch. The lift has two 3/4hp motors and the distance from the house to the lift is approx. 200'. I opened the dock panel box and noticed the GF breaker did not have a neutral wire from the house. A 10 gauge UF 2 conductor wire with copper ground energized the box from the house, coming from a non-ground faulted 30 amp breaker located on the outside of the house. It also had a 30 amp dbl pole GF breaker circuit going to a hot tub on the outside deck of the house. The dock panel box also has a 120V line coming from the house, but I could not locate its source. This line powers a 120V GFCI receptacle that was added to the outside of the panel box by bolting a metal outdoor weatherproof sgl gang box thru the side of the dock panel box. The boat lift wiring from the remote control has a UF 3 wire with ground cable in 3/4" plastic electrical conduit that runs down the boat lift piling, along the bottom of the lake and up the nearest pier piling, where it then continues under the wooden dock to the dock panel box, the white and copper wires were attached to the neutral/ground bar. There does not appear to be any breaks or wiring malfunctions in this part of the circuit. The GF breaker at the dock panel box has its neutral wire attached to the neutral/ground bar in the box, shared with the ground and neutral wires from the house 240V and 120V wiring. The house 240V wiring uses the black and white wires to energizes the load terminals, while the copper ground goes to the neutral/ground bar in the box. When the lift was lowered into the lake and the lifting beams were allowed to touch the water, the ground fault breaker did not trip and the lift appeared to operate properly.
    The dock system is a wooden pier with an aluminum gangway ramp that rolls on top of a pvc foam filled floating dock. The water depth at present is about 9' at the boat lift location, but will drop as the lake is lowered during the winter months.
    Why do we get this shocking sensation when we touch the lift and the water? It is alarming, but not painful.

  13. #13
    Licensed Electrical Contractor Speedy Petey's Avatar
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    I have to say, I am having a hard time following all this, but I will say for certain, the GFI breaker at the dock DOES need a line side neutral, so the 10/2 run to that panel is NOT proper or safe. Since the load is straight 240v it does not need a load side neutral.
    Also, the fact that a separate 120v wire was run to the same panel is not correct. There should have been one feeder, with two hots, a neutral and a ground, run to the panel and the branch circuit breaker feeding the dock equipment in that panel.

    I would have a qualified electrician come out and look at this mess. Not much sounds like it is right.

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    DIY Junior Member skdaddle's Avatar
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    Default Thanks, Speedy!

    We took your advice and enlisted the help of an electrician, it turned out that there was 247 volts on the line coming from the house as well. The local power company was being notified to have an engineer come and check the transformer on the line pole coming in to the house. Another dock service line is being trenched down to the dock with the correct number of wires in it also. Hopefully, this will correct the problem!

  15. #15
    Licensed Electrical Contractor Speedy Petey's Avatar
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    There is NOTHING wrong with 247 volts. That is pretty typical in my area.

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