electric leakage - marina boat dock

Fitzdrew516

Senior Member
Location
Cincinnati, OH
The higher conductivity of saltwater may protect against electric-shock drownings (ESD) in the water, but increases the hazard of incidental contact such as grasping an energized handrail or wire rope dangling from a winch.
Right, I hear ya - I was specifically talking about ESD. I think that phenomenon is harder for people to understand/not as well known.
 

mgookin

Senior Member
Location
Fort Myers, FL
The higher conductivity of saltwater may protect against electric-shock drownings (ESD) in the water, but increases the hazard of incidental contact such as grasping an energized handrail or wire rope dangling from a winch.
And that's where the confusion was throughout the thread. Many were talking about a gradient in the water causing death while I was talking about the water having potential to something bonded and that causing death.

We can see clearly now, the rain is gone.... Gonna be a bright bright sunshiney...
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Best answer IMO. You have no control over what voltage to ground may be on the utility side of your service, and because it is bonded to the customer side grounded conductor it is on all equipment grounding conductors.

No one needs to be swimming in the area around the docks for other safety reasons anyway, especially public dock areas.

As far as salt water - the fact it is more conductive means voltage gradients that do exist are in larger zones and it is harder to physically reach across enough zone to be exposed to enough potential to be a problem.
New section 555.24 for the 2017 code requires a sign reading "WARNING--POTENTIAL SHOCK HAZARD---ELECTRICAL CURRENTS MAY BE PRESENT IN THE WATER". Signs are required to be posted so as to be clearly visible from all of the approaches to the marina.

I think this sign stopped short of being a legal warning sign, because, as I recall, a legal warning sign must tell you what you must do to avoid the hazard.
 

fmtjfw

Senior Member
Yes. Exactly. The only possible way I could think of ESD occurring in anything other than freshwater is if it were to occur in brackish water - Especially brackish water with a low salinity. But in true "salt water" I can't see this happening due to the high conductivity of the water itself. In saltwater applications the current running through the water, when it reaches a would be victim, the vast majority of the current would travel through the water instead of the human (water is the less resistive load).
So again thinking of this - I think maybe if it was a small child in brackish water (depending on the salinity) it may pose a risk due to the child having a lot less resistance than the normal human. Can anyone else think of instances where saltwater could harbor the effects of ESD?
Electrically, people are essentially a conductive bag of salt water.
 

ghostbuster

Senior Member
http://www.mikeholt.com/newsletters.php?action=display&letterID=777

This is a link to an article published in 2009 and republished on this website.

Thought it maybe of interest.

The last time I spoke to the author:
1.the utility has refused to pay the court ruling
2 the people that own property on this lake with the underwater power cable are having a hard time selling

3.The utility has also refused to fix the cable problem---- according to their lawyers it would be an admission of guilt

What a mess !
 

exoticmagneto

Member
Location
Austin
two girls drowned at a local lake ?

two girls drowned at a local lake ?

We just had a sad Incident where two girls drowned at a local lake and it was determined that it was due to electrical leakage from faulty wiring on a boat dock. I have several friends on that lake and some of them have been asking me the best way to test/prevent this. my main suggestions were

the power is fed from a Gfci breaker at the source vesus using gfci receptacles at the doc.
test the gfci regularly especially during the summer months
make sure all the wiring is uf and rated for outdoor or wet environments

what is the best way to test for problems ,
what other advice would you give a home owner with a boat Dock.
Would you please post what lake in what city / town ? I'm searching for a news article about this unfortunate incident.
 

exoticmagneto

Member
Location
Austin
Please point me to NEC on this

Please point me to NEC on this

GFCIs on marinas (for boats) need not be 6ma, they are allowed to be up to 100ma. 100ma can kill you, but has fewer nuisance trips.
General purpose receptacles are still at 6ma. The "service" (main ocpd) must have 100ma or below. Some places try for 30ma on feeders or branches.

The main thing is to stay out of the water. Neither swim nor fall in.

GFCIs on marinas (for boats) need not be 6ma ??? Guess that depends on who is interpreting a marina as solely a commercial entity or not.

I was under the impression that in any residential application (like a residential boat dock), 6 ma is the standard NEC requirement.

Please point me toward where in the NEC there is an allowance for 100 ma (or more than 6 ma) at a residental boat dock, if you are aware of one.
 

rippledipple

Member
Location
New Jersey
Occupation
Electrical contractor
elect. leakage

elect. leakage

GFCIs on marinas (for boats) need not be 6ma ??? Guess that depends on who is interpreting a marina as solely a commercial entity or not.

I was under the impression that in any residential application (like a residential boat dock), 6 ma is the standard NEC requirement.

Please point me toward where in the NEC there is an allowance for 100 ma (or more than 6 ma) at a residental boat dock, if you are aware of one.
did this lake have an alum.floating dock by any chance??
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
GFCIs on marinas (for boats) need not be 6ma ??? Guess that depends on who is interpreting a marina as solely a commercial entity or not.

I was under the impression that in any residential application (like a residential boat dock), 6 ma is the standard NEC requirement.

Please point me toward where in the NEC there is an allowance for 100 ma (or more than 6 ma) at a residental boat dock, if you are aware of one.
A residential occupancy would not have a marina...it may have a boat dock. The rule for the 100mA trip is in Article 555 and does not apply to residential boat docks.
 

kwired

Electron manager
Location
NE Nebraska
GFCIs on marinas (for boats) need not be 6ma ??? Guess that depends on who is interpreting a marina as solely a commercial entity or not.

I was under the impression that in any residential application (like a residential boat dock), 6 ma is the standard NEC requirement.

Please point me toward where in the NEC there is an allowance for 100 ma (or more than 6 ma) at a residental boat dock, if you are aware of one.
555.3, and it is for the main feeder to the marina, not for branch circuits or individual outlets, you still may need a class A GFCI for some of those.
 

exoticmagneto

Member
Location
Austin
gfci on the feeders

gfci on the feeders

gfci all dock circuits
may increase nuisance tripping but that is the price you pay

we hadvan issue where people got shocked
all dock ckts had gfci
the main feeder did not, from shore to dock on messanger
it abraded and fell in the water
we put gfci on the feeders after that
Depending on the distances involved with those feeders, I have been informed there very well may be constant tripping issues due to capacitive phenomena in long runs of parallel conductors.
As an example, if you had 300 feet of wiring from main panel to reach the subpanel near or at the water's edge on a GFCI, then <another> GFCI in the subpanel where downstream of the GFCI out in to the lake (another 300 feet) was a submersible pump - - - seems like that would be unworkable for nusciance tripping and capacitive issues ?
 

kwired

Electron manager
Location
NE Nebraska
Depending on the distances involved with those feeders, I have been informed there very well may be constant tripping issues due to capacitive phenomena in long runs of parallel conductors.
As an example, if you had 300 feet of wiring from main panel to reach the subpanel near or at the water's edge on a GFCI, then <another> GFCI in the subpanel where downstream of the GFCI out in to the lake (another 300 feet) was a submersible pump - - - seems like that would be unworkable for nusciance tripping and capacitive issues ?
Good design would put the ground fault protection near the water's edge so this is not as much of an issue. Also remember that a 100mA trip device will tolerate a lot more capacitive effects then a 4-6 mA trip device.
 
A 130,000 pF capacitor will draw 6 mA at 120 volts.

I don't have a reliable spec, but an Internet search suggests that Romex cable has a capacitance between 15 and 100 pF/foot, which suggests that capacitive nuisance tripping won't occur in runs of less than 1300 feet.
 

kwired

Electron manager
Location
NE Nebraska
A 130,000 pF capacitor will draw 6 mA at 120 volts.

I don't have a reliable spec, but an Internet search suggests that Romex cable has a capacitance between 15 and 100 pF/foot, which suggests that capacitive nuisance tripping won't occur in runs of less than 1300 feet.
Now put 6 mA GFCI on the main feeder to a building and you have the feeder, the branch circuits, appliances, anything connected to the system as potential capacitance.
 

iwire

Moderator
Staff member
Location
Massachusetts
A 130,000 pF capacitor will draw 6 mA at 120 volts.

I don't have a reliable spec, but an Internet search suggests that Romex cable has a capacitance between 15 and 100 pF/foot, which suggests that capacitive nuisance tripping won't occur in runs of less than 1300 feet.
It does not have to be what trips it, it simply removes some of the headroom for other leaks.
 

brantmacga

Senior Member
Location
Georgia
Occupation
Electrical contractor
that article linked doesn't say, but I was pretty certain the first time I read about this, it said the shock occurred when a powered metallic ladder was lowered into the water.
 
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