Lake dock safety

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Wacko

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Smyrna, GA
The dock at the lake house is some how electrified. Or maybe not. I hooked the branch circuit wiring directly to the metal frame of the dock and the branch circuit breaker tripped immediately.

While the kids are swimming and try to climb out they receive what appears to be a clear electrical shock.

I am a licensed electrician. I have examined the wiring thoroughly. Including an insulation test on the branch circuit wiring. There is an equipment ground wire in the conduit supplying the dock and the dock has a good earth ground.

Could static be causing this issue?

I have done some research and read where several kids have been killed by this problem.

I know this is a code forum. Just thought I would ask.

Thanks ahead.

Wacko
 
Do not let anyone swim around a dock with any connection (including grounding conductors) to the electric utility system.

Even if nothing is wrong on your premises this can put voltage between anything connected to the EGC and the water as a result from voltage drop on POCO's primary neutral.

Swimming pools are safe because of all the equipotential bonding we put in them, but large bodies of water are just about impossible to do this with.
 
Wacko said:
The dock at the lake house is some how electrified. Or maybe not. I hooked the branch circuit wiring directly to the metal frame of the dock and the branch circuit breaker tripped immediately.

While the kids are swimming and try to climb out they receive what appears to be a clear electrical shock.

I am a licensed electrician. I have examined the wiring thoroughly. Including an insulation test on the branch circuit wiring. There is an equipment ground wire in the conduit supplying the dock and the dock has a good earth ground.

Could static be causing this issue?

I have done some research and read where several kids have been killed by this problem.

I know this is a code forum. Just thought I would ask.

Thanks ahead.

Wacko
Click to expand...

is there a boat connected to shore power nearby?
there was once an 80' sailboat in the marina near here,
that was leaking 15 amps into the water nearby.

it was eating up everyone's zincs, and doing a number on
propellers as well.

the floaty thing i posted a link to might be a good idea....
swimming off of anything with power running to it is a
very bad idea. very bad. if i had to enter and leave the
water at a dock that has shore power, in violation of the
code, i'd probably have a 3 pole disconnect opening every
single conductor to that dock. and it would be back at the
source, not on the dock.

an air gap on every conductor. including the ground.
padlocked off before anyone goes swimming.
 
To amplify the answer somewhat, you can try to diagnose the problem by measuring the voltage between the metal of the dock and an insulated wire with the stripped end six feet or more away from the dock.
Then compare that to a voltage measurement from the main bonding point at the service disconnect and a screwdriver driven into the earth 20 feet or more away from the building.
Chances are you will see that there is a similar voltage in both locations, and the most likely cause is a problem with the service neutral or the POCO multiply grounded neutral.
If it is a POCO problem you may or may not get any help from their engineering section when you make a trouble call about it.
If you disconnect the POCO neutral from your building and the voltage on your grounding conductor goes away but the POCO neutral is still offset from remote earth it is pretty much guaranteed to be a POCO problem.
If you open the main breaker at the service disconnect and the voltage goes away the problem could still be in a variety of places, including the service neutral itself.
 
You might also want to look at the requirements of 555.3
Starting in '14 Marinas had to have supplies with a 100ma maximum GF protection.
This won't necessarily prevent shock but it helps identify boats with significant leakage problems.
 
Just for the record, I would like to state unequivocally that there should be no swimming at the dock while any wiring is connected to it (including just the EGC by itself) until the problem has been diagnosed.

In the situation of a marina rather than a residential private dock, swimming absolutely should be prohibited within a certain distance which will vary between fresh and salt water.
 
2017 NEC 555.24 requires a sign on a dock to warn of shock
(3) The signs shall state “WARNING — POTENTIAL SHOCK
HAZARD — ELECTRICAL CURRENTS MAY BE
PRESENT IN THE WATER.”

And the scope of 555 now includes docks for dwelling units. Also required is a 30 MA GFPE on the feeder...

Even though you may not be under the NEC, it shows how serious the NEC is about preventing electric shock drownings
 
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