Pre-Purchase Inspections
January 2010 - Shore Power

Leakage current, it's a phenomenon that's rarely identified and poorly understood, even by many professionals in the marine trades. Make no mistake about it; however, its consequences can be both costly and lethal.

Leakage current may occur or be measured in many places aboard a vessel; however, the location that's the most telling is your shore power cord. All of the electricity that flows to your boat via the black and/or red wires contained within the shore power cord should also return to its source, typically a transformer at the head of the dock, via the white wire, which also resides under the familiar yellow jacket of a shore power cable.

If the vessel's AC shore power system is wired incorrectly, or if it's damaged, then current will return to the source via multiple paths, through the white wire within the shore power cable and through the water via the vessel's bonding system. The insidiousness of this fault is that you'll never know it's happening until equipment is damaged or, worse, someone is injured.

If the shore power wiring aboard your vessel is properly designed and installed, then the current flowing through the cable should be at equilibrium. That is, the meter should read zero or near zero. If current that's coming aboard is returning through the water, an imbalance occurs, which the meter, pictured in this month's ad, records. Ideally, leakage current in shore power cables should not exceed 30 milliamps, that's 30 one thousandths of an amp, less is preferred. This vessel, undergoing a comprehensive Steve D'Antonio Marine Consulting Systems Inspection, is reading over ten times that amount, all of which is flowing through the water in which the vessel is floating. Faults of this sort are an electrocution hazard for both swimmers and those aboard.

If you're interested in finding out more about Pre-Purchase Inspections like the one described above, system inspections, vessel selection assist, the Captains’ Club (simply click on these words to be taken to the relevant sections of this website) or other services offered by Steve D'Antonio Marine Consulting, email or call 804-776-0219.