Ideal dock wiring Questions?

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

  1. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,301
    Location:
    Houston, TX
    Hey Randy, and the group,

    Fence chargers make a lot more voltage than 12 Volts using Switching supplies. If you charge a cap on a 12 V battery it will not shock your normal
    dry skin, Put it on Your tongue and you will feel it, like testing a 9 volt batt to see if it is good.

    Pee on a Electric fence and the flow gets shut off Quick. (You will only do that once, then You learn)

    Electric fences limit the current, but Capacitors can be very dangerous, If they are not discharged before testing or touching.

    You can Light a Florescent Tube by just getting RF near it, with no connection at all. Will light as if it was in a fixture.

    Electricity is your friend, Only if you respect it.

    Kind of like Human Life and People.

    And Yes Jim the absence of Heat = Cold.

    Have a nice Evening.

    DonL.
  2. Randyj

    Randyj Master Plumber

    Messages:
    1,047
    Location:
    Alabama
    DonL.. here's something that may interest you. Actually, light comes from dark (just like the Bible says)...

    From Wikipedia, the free encyclopedia
    (Redirected from Black body radiation)
    As the temperature decreases, the peak of the blackbody radiation curve moves to lower intensities and longer wavelengths. The blackbody radiation graph is also compared with the classical model of Rayleigh and Jeans.
    The color (chromaticity) of blackbody radiation depends on the temperature of the black body; the locus of such colors, shown here in CIE 1931 x,y space, is known as the Planckian locus.

    A black body is an idealized physical body that absorbs all incident electromagnetic radiation. Because of this perfect absorptivity at all wavelengths, a black body is also the best possible emitter of thermal radiation, which it radiates incandescently in a characteristic, continuous spectrum that depends on the body's temperature. At Earth-ambient temperatures this emission is in the infrared region of the electromagnetic spectrum and is not visible. The object appears black, since it does not reflect or emit any visible light.

    The thermal radiation from a black body is energy converted electrodynamically from the body's pool of internal thermal energy at any temperature greater than absolute zero. It is called blackbody radiation and has a frequency distribution with a characteristic frequency of maximum radiative power that shifts to higher frequencies with increasing temperature. As the temperature increases past a few hundred degrees Celsius, black bodies start to emit visible wavelengths, appearing red, orange, yellow, white, and blue with increasing temperature. When an object is visually white, it is emitting a substantial fraction as ultraviolet radiation.

    Blackbody emission provides insight into the thermodynamic equilibrium state of cavity radiation. If each Fourier mode of the absolutely stable equilibrium radiation in a cavity with perfectly reflective walls were considered as a degree of freedom, and if all those degrees of freedom could freely exchange energy, then, according to the equipartition theorem in classical physics, each degree of freedom would have one and the same quantity of energy. This approach led to the paradox known as the ultraviolet catastrophe, that there would be an infinite amount of energy in any continuous field. The study of the laws of black bodies helped to establish the foundations of quantum mechanics.
  3. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,301
    Location:
    Houston, TX
    Very Interesting Randy.

    Thanks for sharing that Far Out Information.

    Have a Great Day.

    DonL
  4. ebob1

    ebob1 New Member

    Messages:
    2
    Location:
    Lynchburg, VA
    need help with dock wiring please

    Please help. I have been reading the thread and there seems to be disagreement on the proper way to wire the dock.

    My dock has an outlet and light that are wired to a GFI breaker at the panel in the house (100 ft away). There is no disconnect at the dock. The ground wire also goes to the panel in the house. Wiring is AGW 12 I think. The dock is wood, however it is supported by huge steel I-beams that are driven down through the water into the lake bottom. I think that the ground for the lights is also connected to the steel I-beams in some manner. I imagine that these I-beams make pretty good grounding rods. ( I think I read in the code that is posted on this site that metal parts of the dock should be grounded to the switchbox - but in this case it seems to be grounded to both earth and box.) Question 1 –is this proper wiring?

    BTW -The only time I have felt a â€trickle†is when the water was high (over the docks) and I touched a metal part on the dock. My GFI breaker was turned off, so I suspect that the trickle was from a neighbor’s submerged wiring that was returning through my ground?

    Question 2 is related to the copper plumbing in my house. I am getting “blue water syndrome†from corrosion of the copper pipe. I have read that this can be caused by electrolysis from differences in potential between the cooper pipe (also bonded to the ground at the switch box) and ground causing small currents. My question: is it possible that the ground at the dock is causing these currents that are corroding my pipes? If so, what should I do about it.
  5. DonL

    DonL Jack of all trades Master of one

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    Location:
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    Welcome to Terry's Forums ebob1.

    You might want to start a new thread to get a good answer, as this one got blown out of the water.

    I think that static electricity causes issues with boats moving across water.

    As you said your power was off and still felt a ”trickle”, or maybe a electrical box was under water.


    Good Luck on your project.

    Have a great day.

    DonL
  6. ActionDave

    ActionDave Electrician

    Messages:
    351
    Location:
    Colorado
    The problems you have can be a Power Company problem or a problem after the POCO transformer at your house. You need to make sure the problem is not your electrical system first.

    I don't go straight to the "Need qualified help" answer very often, but in these cases I do.

    You need a good electrician, one that understands grounding and bonding, not just one that is good at running circuits or bending pipe.
  7. DonL

    DonL Jack of all trades Master of one

    Messages:
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    Location:
    Houston, TX
    ebob,

    Often times Ground and neutral are not at the same potential, especially when you have a better Ground than the electric company provides at the power pole, Like yours in the water, Then you could have problems.

    You need to have all your neighbors install GFI's also, in order to make the whole dock safe.

    If you "Need qualified help" then maybe JW can help you.


    DonL
  8. ballvalve

    ballvalve General Engineering Contractor

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    Location:
    northfork, california
    I will simply never go to a lake or dock again. Too much murky water in this thread. Get an ATV - no shocks there, maybe a branch in the face.
  9. ebob1

    ebob1 New Member

    Messages:
    2
    Location:
    Lynchburg, VA
    thanks - the electricians that wired my house and dock were definately of the "running circuits and bending pipe" types. The original wiring had no GFI and wires connected with wire nuts nailed up under the dock with no enclosure. (amazingly the building inspectors approved this). I put in the GFI and a water proof connection myself.
    Last edited: May 25, 2011
  10. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,540
    Location:
    North Carolina
    Not grounded to the switch box but bonded to the switch box. There is a big difference between bonding and grounding. Grounding is simply connecting to earth but bonding is a connection between the exposed metal parts and the source (service neutral).

    This is known as stray voltages and can come from many different places

    Not a plumber so I will leave this to one
  11. skdaddle

    skdaddle New Member

    Messages:
    4
    Location:
    sc
    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.
  12. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

    Messages:
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    Location:
    NY State, USA
    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.
  13. skdaddle

    skdaddle New Member

    Messages:
    4
    Location:
    sc
    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!
  14. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

    Messages:
    996
    Location:
    NY State, USA
    There is NOTHING wrong with 247 volts. That is pretty typical in my area.
  15. DonL

    DonL Jack of all trades Master of one

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    Location:
    Houston, TX
    It is close enough for Government work.


    3.1 Utility Voltage Levels

    Anyone receiving power from an electric utility will see the nominal incoming voltage level (e.g. 120V) change over the course of a day to a small or large degree. There are many factors contributing to the amount of voltage level fluctuation observed including: 1) location on the local distribution line, 2) proximity to large electricity consumers, 3) proximity to utility voltage regulating equipment, 4) seasonal variations in overall system voltage levels, 5) load factor on local transmission and distribution system, etc.

    Voltage levels are often highest during the nighttime hours and weekends when the electrical demand is minimal and are lowest weekday afternoons when the demand for electricity peaks. Most electric utilities in the U.S. try to maintain the voltage level within plus or minus 5% of the nominal voltage level (e.g. 480V +/-5%), however for short periods the voltage level may be as much as 6% high or 13% low (according to ANSI Standard C84.1). On the nominal 480V system, this would translate to incoming voltage ranging from 509V (480V +6%) to 420V (480V-13%). Larger deviations from nominal voltage are also permissible on a momentary basis or may simply be unavoidable.


    Enjoy Your Day.


    DonL
  16. jwelectric

    jwelectric Electrical Contractor/Instructor

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    2,540
    Location:
    North Carolina
    You would feel this even if thee was no power to the dock at all. It is due to earth voltages
  17. hj

    hj Moderator & Master Plumber Staff Member

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    Location:
    Cave Creek, Arizona
    quote; do know for a fact that the way I've done the ground rod does stop the tickle and insures a safety ground.

    NO IT DID NOT. What it did was supply a path for that electricity to go into the ground, which is wasting power. It is NOT enough to trip the breaker, but there is enough resistance so the power THINKS it is doing something useful.
  18. HenryOhm

    HenryOhm Electrical Engineer

    Messages:
    1
    Location:
    Washington
    Randyj,

    Too be honest, when I first saw you state, "...and cut the safety ground from the switch box..." I immediately cringed. I am an electrical engineer, degreed from a major university and with a state license, and I find myself having to walk very carefully through the types of things you describe before I change anything like an existing safety ground.

    I have seen some references elsewhere to a long distance distributed system like this having multiple grounding rod locations. Perhaps this is what you refer to. But, I would think that the ground rods back at the house should still be connected to the ground wiring, just the dock ground rods added to the system. If you have any neutrals at the dock tied to ground, than perhaps you have the neutral-to-earth voltage differences due to voltage drop across the neutral return as you seem to want to describe. But, perhaps you have a short somewhere on the dock using only the ground wire. Or maybe a nearby dock has a short with your dock's ground providing the return. Tread carefully, there could be a number of reasons why you could see this tickle voltage. And, lifting grounds could be the worst solve for them. ActionDave's link is very sobering (http://ecmweb.com/design_engineering/electric_case_floating_dock/index.html).

    Maybe upsizing the cable back to the house above what would otherwise be required by code may be part of the solution. But, I think you really need some expertise to figure this all out. With so many docks on the lake, maybe there is a really sharp electrician locally who specializes in this. Ask around.
  19. Randyj

    Randyj Master Plumber

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    Location:
    Alabama
    Thanks Henry. I typed a long reply about all kinds of things peculiar to lake homes and these being very remote locations but must've hit the wrong key and wiped it all out... but, yes, I do believe you have a reasonable solution that probably would work and makes sense.... either a second or much heavier safety ground wire returned back to the source of the switch panel and it's ground rod. The fact that many of these docks are set up with a 12/2 WG from the switch panel at the house and run 100-200 ft to the walkway then another 60 ft or more of walkway and several twists & turns after that gives a good 200-400 ft of 12 ga wire and not uncommon to have a couple of splices along the way... definitely going to present some resistance and imbalance of ohms and volts. I just enjoy learning to troubleshoot these types of things but I'd rather avoid the liablity and let somebody else tackle the problem. I don't know if it makes sense or is logical to others or not but to me a ground rod connected to the walkway entrance does make sense to balance voltages between the dock, water, and earth so there is a return path other than dock to water to earth.
    Last edited: May 16, 2012
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