Step Voltage?

I think DC would work... AC I have a hard time thinking it would work.

The one fly in the ointment in the above scenario happens when someone uses a UL approved appliance having the green safety wire and the white neutral connected. Although everything else is compliant to code this one connection while required on land is not approved on a boat especially a metal hulled boat.

Return current in the white wire splits at the point where the plug in appliance has the green and white wire joined as required by UL.

The part of the return current which follows the green wire is not sufficient to trip a breaker.

Furthermore if the metal hulled vessel is new and compliant with best practices it may have an isolation transformer. This means a GFCI on the dock will never trip either. However stray current in any vessel will circulate in the green safety wiring and the code compliant 'bonding' wiring that connects thru hulls in the vessel. A step potential can easily be set up - especially in fresh water.

Which electrocutions are we talking about? It didn't make the news here.

http://www.bbc.co.uk/news/world-us-canada-18725859

Thanks

So if the wiring on a mobile platform (house boat) is defective, how will a stationary device be able to detect a problem that can be moved at random??

That sir is one of the question(s) I posed. What are your thoughts?

And I don't know that it was a houseboat, in fact one took place in a marina. The articles didn't state whether or not a vessel electrical system was involved, only that an investigation is ensuing.

As I stated, with the advent of high power inverters and generators that are not marine rated, all things are possible. Marine rated devices are available, but are 3 times the cost. It seems that people feel the marine rating (USCG approved) is nothing more than a license to raise prices.

Another poster stated something about DC. While there are documented cases of electrocution with 28 VDC, DC is a self correcting. If the DC leakage is not corrected, the offending vessel will sink.

I work in the marine electrical field and this kind of problem is not as easy to fix as some posters imply. It can happen even when proper marine grade and type approved equipment is used. Even the experts cannot agree on one solution.

It is regrettable that these fatalities occurred and as always people are quick to start a witch hunt to nail someone with blame. I intend to track this story because I work in the field. I suspect the accident investigation will uncover a few surprises.

Dock-side equipment without a GFCI appears to have been the problem at at least one site:

http://articles.kspr.com/2012-07-05/electrocution-death_32555705

"...Officials say there was no ground fault interrupter to monitor the current and trip the electricity if there was a problem. They say the electricity could have come from several sources, including a boat lift or a pump used to power a water slide...

Sad that not using a $15 device caused this tragedy, hopefully others will learn from it.

Use of a 5ma GFCI may not have been the solution. The report I linked to said the boys were swimming between two house boats and would be rescuers felt a strong paralyzing tingle until power on the boat was shut off.

One possibility as a cause would be the plugging in of an approved household device in the houseboat system.

This reaches into an area where even the experts sometimes disagree as to the solution.

I once encountered a shock hazard in a government installation only two years old. The work was done by qualified contractors using approved work practices and mostly certified equipment. A GFCI did nothing to prevent the problem. The problem location was located upstream of the GFCI.

Sometimes the wiring itself leaks current despite being fairly new. Outdoor equipment normally uses SJOW grade of wiring. This is rated for outdoor use and as such is UL approved. unfortunately many people mistakenly think 'outdoor' means water proof. It is and it ain't. For submerged continuous use you need to use 'submerged cable' not outdoor rated. I have tested 18 month old UL approved outdoor grade wire and found it failed the megger test. Plastic wiring insulation will permit electrons to migrate through the insulation. As the wire ages some of the plasticizer molecules evaporates leaving a void in the plastic structure. Water molecules migrates through these voids and eventually leads to leakage current.

If you submerge SJOW wire full time it will fail in a couple of years but not enough to trip a circuit breaker.

We all know what happens when nuisance trips keep occuring. Somebody finally bypasses it when they cannot find an obvious cause. Not finding the cause and no cause being present is not the same thing.

Unfortunately land based electricians do not get in-depth training as marine electricians so they may not be fully conversant with the finer details.