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Thread: Ideal dock wiring Questions?

  1. #136
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by skdaddle View Post
    I experienced a slight electrical "tingle" when I was working on a boat cradle on a boat lift wired for 240V operation.
    You would feel this even if thee was no power to the dock at all. It is due to earth voltages

  2. #137
    Moderator & Master Plumber hj's Avatar
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    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.
    Licensed residential and commercial plumber

  3. #138
    Electrical Engineer HenryOhm's Avatar
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    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...ock/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.

  4. #139

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    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 by Randyj; 05-16-2012 at 06:35 PM.

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