boat dock shocks swimers

[hvf1118]

What is the code on boat docks and grounding docks?

 

[K8MHZ]

What is the code on boat docks and grounding docks?

If you know about people getting shocked from boat docks you are dealing with a potentially lethal problem. If you have to ask about code requirements on the Internet I, personally, do not think you are qualified to address the problem and strongly suggest that you should immediately hire someone that knows grounding and bonding like the back of their hand to make a safe repair.

Also, just being able to recite the code will not lead you to a safe solution.

Sorry about being so brash, but this is literally a life or death ordeal if left uncorrected.

 

[G._S._Ohm]

And salt water is slightly more safe because it shunts the current around the swimmer's less conductive body.

 

[hvf1118]

Power Plant on water way

Power Plant on water way

This is not something Iam working on. But the power co that is generating power told a guy to take the ground wire lose to stop the shock. The ground around the house is all rock and the power plant ground puts power in to the lake. with very little dirt to ground, this is a promblem all around the lake. The land around the lake is very rocky.

 

[fisherelectric]

At Smith Mountain Lake in southern Virginia they have the same problem. My brother had a boat lift that was made with guard steel rails to lift his pontoon boat and people were getting slight shocks off of them. I drove down and checked it out. Was reading 2 or three volt from the rails to the water. Disconnected the lift motor and still got voltage. Finally I disconnected the equipment ground for the lift motor and got no more voltage on the lift. All grounding was done properly from the service to the dock and everything at the dock was GFI protected. Called in the power company and their rep said that this was a problem common around the entire lake and that no one had ever been hurt because it wasn't enough voltage to cause a "problem". Apparently the grounding for the system was at a slightly higher potential than the lake. My brother got rid of all the guard rails and replaced with wood, coated the lift cables and covered them in plastic, replaced steel ladders at the dock etc. and doesn't allow any swimming around the boat lift anymore. I was down there last year and checked the voltage from the lift to the water again and got zero volts, so maybe the PoCo has fixed the problem, if it is fixable.

 

[G._S._Ohm]

it wasn't enough voltage to cause a "problem".

The current determines the harm.
Try measuring the voltage across a 300 ohm resistor wired from the water to the ground. A chunk of hardware cloth with the surface area of a human body attached to the submerged end of the resistor may give you a different reading.

There are laws about "quiet enjoyment" but I don't know if they apply to this situation for the lakeside residents.

 

[George Stolz]

This is not something Iam working on. But the power co that is generating power told a guy to take the ground wire lose to stop the shock.

That is not the solution. If there are no wiring violations on the premises, and the problem is found to be that the utility neutral is the source of the voltage, then that needs to be addressed. The POCO should merit a lawsuit suggesting removing the EGC.

The current determines the harm.
Try measuring the voltage across a 300 ohm resistor wired from the water to the ground. A chunk of hardware cloth with the surface area of a human body attached to the submerged end of the resistor may give you a different reading.

Why in God's name would you guess around at what could potentially kill someone, and what you reckon would probably just hurt like hell, and shoot for just hurting people?

 

[GeorgeB]

I'm not up on my electroplating knowledge, but a friend had a problem that the (about 3 volts in his case) difference was rapidly removing the zinc galvanizing from his dock. He tried the marine typical "zincs" which helped a little, but not much.

He rigged an isolated DC source using a 6V battery and transformer isolated charging system with something in the water (not zinc, I don't think) as anodic (not cathodic) protection for his dock. He had to replace the sacrificial (anode/cathode?) every 6 months or so, but the loss of galvanizing stopped. IIRC, he could adjust the voltage limited constant current source to actually build up the dock zinc layer.

Again, IIRC, the dock to water potential was reduced to near zero. His sacrificial thingy was not safe to touch, and was some 40 feet below water connected by insulated conductor.

 

[Dennis Alwon]

There was an article awhile ago about this in EC&M I believe or Electrical Contractors

 

[G._S._Ohm]

Why in God's name would you guess around at what could potentially kill someone,
and what you reckon would probably just hurt like hell,
and shoot for just hurting people?

I don't guess around unless I say "I'm guessing."
The effect of current levels on the human body are well documented.
I'm not shooting for anything.

Your comments are not "ad hominem", but they may be "straw man" or they may be just plain
http://en.wikipedia.org/wiki/Eristic

 

[K8MHZ]

CODE VIOLATIONS

1. January, 1994 Oklahoma State Department of Health (OSDH) inspected eleven commercial docks and five private docks, and an earlier (1989) inspection of 116 commercial docks, found 96% not in NEC compliance; most common fault was open ground.

http://www.facebook.com/topic.php?uid=117494761627517&topic=97

Wow! I never thought that there would even be a fraction of the NEC issues found. The link has a plethora of reports and information on the topic being discussed.

 

[George Stolz]

I don't guess around unless I say "I'm guessing."
The effect of current levels on the human body are well documented.
I'm not shooting for anything.

Your comments are not "ad hominem", but they may be "straw man" or they may be just plain
http://en.wikipedia.org/wiki/Eristic

When you suggested measuring resistance various ways, it seemed evident to me that you were suggesting fixing the problem just enough to avoid killing someone who's resistance happened to be 300 ohms or more to ground.

It didn't occur to me that you weren't interested in fixing the problem at all, but performing experiments to pass the time until someone else came along to actually fix the problem. Mea culpa.

 

[don_resqcapt19]

...
The effect of current levels on the human body are well documented.
...

While in general that it true, but it is not true for people in the water where the current is applied across most of the body. This issue if the reason for the pool perimeter bonding...to make sure the water and the surface around the water is at the some voltage. Small voltage differences can prevent people from getting out of the water. Voltage differences that you normally can't even feel.

 

[jmellc]

Maybe I'm a little slow, but where is the voltage coming from? Is the equipment picking up voltage from the motors or lights? I've never done any work at docks or boathouses, so this is foreign to me. If gounding is the problem, can ground rods not be driven into the lake or river bottom? Or would that worsen the problem in the event of a fault current?

 

[readydave8]

You shouldn't be able to see, smell, or feel your electricity unless something is wrong.

 

[K8MHZ]

You shouldn't be able to see, smell, or feel your electricity unless something is wrong.

I nominate this for (by far) best post of the year.

 

[don_resqcapt19]

You shouldn't be able to see, smell, or feel your electricity unless something is wrong.

In cases of pools, docks and other like locations I don't agree. We are required by the code to energize the water. The voltage that energizes the water is not always from a problem in the electrical system.
Often it is nothing more than the normal voltage drop on the utility primary grounded conductor and on the service grounded conductor. This normal voltage is very difficult to eliminate and is the very reason that we have the perimeter bonding rule for pools. We have to energize the pool perimeter to the same voltage as the water to make it safe to get out of the water.

 

[readydave8]

In cases of pools, docks and other like locations I don't agree. We are required by the code to energize the water. The voltage that energizes the water is not always from a problem in the electrical system.
Often it is nothing more than the normal voltage drop on the utility primary grounded conductor and on the service grounded conductor. This normal voltage is very difficult to eliminate and is the very reason that we have the perimeter bonding rule for pools. We have to energize the pool perimeter to the same voltage as the water to make it safe to get out of the water.

I know you're right but I usually get a laugh when I say that line to a customer, thought I'd try it on the internet.

 

[Matthew_B]

Maybe I'm a little slow, but where is the voltage coming from? Is the equipment picking up voltage from the motors or lights? I've never done any work at docks or boathouses, so this is foreign to me.

Most often the problem is from the utility neutral. They use the same conductor for neutral and ground. It results in the dock becoming part of the neutral return path.

If gounding is the problem, can ground rods not be driven into the lake or river bottom? Or would that worsen the problem in the event of a fault current?

That would work, but the most common solution on the utility side is to pull in another phase which reduces the neutral current.

 

[George Stolz]

That would work, but the most common solution on the utility side is to pull in another phase which reduces the neutral current.

Adding a ground rod would put another resistor in parallel with the one we're trying to protect (the person). It may have the appearance of working (if it has much effect), but it would be more accurate to say it would "mask the problem somewhat."