? Solution to bonding freshwater surrounding floating dock

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luckylerado

luckylerado

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Lake of the Ozarks
I am struggling to come up with a way of creating an equipotential between a floating steel dock and the green freshwater surrounding it. The idea would be to minimize the gradients immediately surrounding the dock and provide a low resistance path to ground for stray fault currents.

The best I can come up with is turning down into the water from the steel structure something similar to an air terminal use for lightning protection and creating a counter poise so to speak by joining the submerged rods together underwater with a heavy conductor. The cons I see with this method would be :1 creating a new swim hazard, and 2 what materials to use for the submerged components to avoid oxidation, corrosion, and algae buildup.

I also considered bonding to and sinking sections of galvanized chain-link fencing around the perimeter of the dock but unless the depth of the water is relatively shallow I do not think that I will get the effect that I am after.

Another idea I have tossed around is tethering a floating buoy with a metal bottom to the steel structure with a heavy flexible conductor at various points along the dock. This, however, has its own set of issues in areas of heavy wave action.

Any ideas on means and methods to accomplish this goal would be greatly appreciated.

Thanks.
 
Unless you have low level GFP protection, you will never be able to provide enough bonding to clear faults. I don't think that water is any where near conductive enough to let you eliminate the voltage gradient.
 
I agree that there is not going to be a way to "eliminate" the voltage gradient. However supplying a low resistance path to ground for those stray currents provides me a place to monitor those currents via the main grounding conductor with a CT set to respond in the mili-amp range and now I have a control circuit that can be wired to do what ever I want weather it be a shunt trip breaker or strobe, buzzer etc. The idea would be to make "visible" a potential electrical hazard from adjacent boats or docks that do not have adequate ground fault protection.
 
Are you doing this for pay? Keep in mind that if it fails in its protective function, you are on the hook for the multiple millions of dollars that the inevitable law suit will decide the dead person was worth.
 
I agree liability is a fact to consider but that is not an insurmountable task. But someone has to do something 3 dead here in my area due to improper wiring of docks in the past few weeks and 2 close calls requiring CPR. And the problem continues to get worse every year. Until 2006 it was acceptable practice to wire your dock with romex with no GFI protection, and all of those structures permitted before that time have been grandfathered in.

That being the case, for any structure inspected after that time the electrocution risk from your neighbors dock is much more likely then from a fault to ground on your own dock. ANY jackass with 50 dollars can purchase an electrical license in this area from the city and the inspectors are no better trained most times. If they can check off all the boxes on the inspection form it passes. They would never know if someone grabbed the steel structure for a neutral some where on the dock say for a submersible pump that only runs 15 minutes a day. And currently 30 and 50 amp shore power recepts are not required to be GFI protected. Balderdash if you ask me.
 
luckylerado said:
I agree liability is a fact to consider but that is not an insurmountable task. But someone has to do something 3 dead here in my area due to improper wiring of docks in the past few weeks and 2 close calls requiring CPR. And the problem continues to get worse every year. Until 2006 it was acceptable practice to wire your dock with romex with no GFI protection, and all of those structures permitted before that time have been grandfathered in.

That being the case, for any structure inspected after that time the electrocution risk from your neighbors dock is much more likely then from a fault to ground on your own dock. ANY jackass with 50 dollars can purchase an electrical license in this area from the city and the inspectors are no better trained most times. If they can check off all the boxes on the inspection form it passes. They would never know if someone grabbed the steel structure for a neutral some where on the dock say for a submersible pump that only runs 15 minutes a day. And currently 30 and 50 amp shore power recepts are not required to be GFI protected. Balderdash if you ask me.
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It seems to me that someone that wants to be cheap is never going to buy your system.

Just how would this system protect you from a neighboring dock that had an issue? Or from a boat?
 
I would choose to say "make you aware of" rather than "protect you from". Stray currents in the water when shunted to the grounding electrode via a properly grounded steel structure will provide enough current to be read by a current sensing switch on the grounding conductor. Then you just use that switch; now responding to ground fault currents which go unnoticed by your GFI protection, to annunciate that fault with a latching relay and an alarm of some kind. At very least it would promote investigation.

My line of thinking in creating this post was to find a way of expanding somehow the range at which those fault currents can be detected by expanding the equipotential plane out into the water as freshwater is not a good conductor and when given no other alternative will prefer to travel through a swimmer to get to ground. Removing the difference of potential between the steel dock and the water to a reasonable distance is key.
 
It appears to me that the proposed solution would be a lot more expensive than providing GFCI or low level GFP protection for all circuits near the water.
 
The problem is, if you have stray voltages from the circuits that have functional ground fault protection, the ground fault protection will trip. It is the other voltage sources that are not ground fault protected, such as utility feeds, feeds to other buildings and the like that is the problem. Turning off the ground fault protected circuits will not remove the other hazardous voltages.
 
hillbilly1 said:
The problem is, if you have stray voltages from the circuits that have functional ground fault protection, the ground fault protection will trip. It is the other voltage sources that are not ground fault protected, such as utility feeds, feeds to other buildings and the like that is the problem. Turning off the ground fault protected circuits will not remove the other hazardous voltages.
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Yes, the GFP would only provide protection for the actual dock circuits, but most of the incidents involve power to boats or dock equipment. It is true that stray voltage from other sources could be an issue, but in most cases that votlage is being introduced into the water by the EGC for the boats or dock equipment. Maybe the GFP protection for the docks needs to disconnect the ungrounded conductors, the grounded conductor and the grounding conductor.
 
jxofaltrds said:
What I mean is if it (the dock) is sitting in the water the same way a bird sits on a line shouldn't it be safe?
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While the person on the energized dock would be safe, a person in the water touching the enegized dock would not be. There would be voltage gardient in the water, just like there is around an energized grounding electrode. I don't know what it would be in the water but around a grounding electrode, if you are touching the energized electrode and the earth 3' away from the electrode, you would receive about 85% of the voltage that is on the electrode.
 
don_resqcapt19 said:
While the person on the energized dock would be safe, a person in the water touching the enegized dock would not be. There would be voltage gardient in the water, just like there is around an energized grounding electrode. I don't know what it would be in the water but around a grounding electrode, if you are touching the energized electrode and the earth 3' away from the electrode, you would receive about 85% of the voltage that is on the electrode.
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OK help me out and maybe I wasn't clear. If a metal dock is isolated from the shore how can it be at a different potential than the water surrounding it?
 
jxofaltrds said:
OK help me out and maybe I wasn't clear. If a metal dock is isolated from the shore how can it be at a different potential than the water surrounding it?
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I am assuming that there is electrical equipment on the dock and there some type of connection between the electrical grounding system and the dock.
 
don_resqcapt19 said:
I am assuming that there is electrical equipment on the dock and there some type of connection between the electrical grounding system and the dock.
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OK. I assumed no electrical connections per the OP. Again 'assumed' that he just wanted to eliminate any stray voltage.

If it does have electric could it be bonded similar to a pool but 'drape' a 3' curtain around it?

The reason I say drape is because, first less apt to get tangled in it and second would/should most of the current rise from the bottom of the body of water?
 
don_resqcapt19 said:
Yes, the GFP would only provide protection for the actual dock circuits, but most of the incidents involve power to boats or dock equipment. It is true that stray voltage from other sources could be an issue, but in most cases that votlage is being introduced into the water by the EGC for the boats or dock equipment. Maybe the GFP protection for the docks needs to disconnect the ungrounded conductors, the grounded conductor and the grounding conductor.
Click to expand...

But if the GFP is powering the boats or dock equipment, it will trip if it is causing the voltage. A Properly bonded dock is creating a return path, not the potential. Most likely the problem if it is from the GFI protected circuit is one or more of the following (a) Failed GFI (b) Miswiring by not protecting the entire circuit by GFI (c) Dock is not properly bonded, just to name a few.
 
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