Originally Posted by jacwjames
~ a couple years ago in East TN there were a couple kids that had drowned from the causes you detail. Since then new regulations have been passed that marina's have to abide by regarding proper wiring.
Thanks for the information.
The real problem is on the boats themselves. The current carrying neutral conductor of the boats wiring is bonded to the engine block of any inboard engine as well as to any metallic portions of the hull. That connection is not broken when the power from the shore connection is connected. The most common transfer arrangements do not switch the neutral conductor. They leave it connected to any on board power source such as a generator or inverter. Since the neutral conductor of the on board system is bonded to the engine block the balancing current flow on the neutral conductor takes all available pathways back to the utility transformer from whence it came. That includes that additional pathway through the water and all of the other grounded metal on all the other boats to the Grounding Electrode System of the Marina's electrical service, via the main bonding jumper back to the Service Equipment's neutral and back to the center point of the utility's transformer.
That is why this problem will be so difficult to eliminate. It will require that all of the existing boats be retrofitted to isolate their neutral conductors from ground when the power is transferred to a shore connection. In many cases their AC distribution panel will have to be reconfigured or replaced. As long as any boat is still wired with the neutral bonded to ground on the boat when receiving shore power the danger will remain.
Local and State electrical authorities having jurisdiction could require that all of the shore connections be protected by Ground Fault Circuit Interrupters (GFCIs). Then the imbalance of current returning on the neutral conductor of the shore line would cause the disconnect of the shore line power source. The boats owner would have to rewire or do without shoreline power.