April 7

Understanding Marine Electrics: Protecting Your Boat from a Shorepower Cord Arcing Fault

Today we'll be discussing one of the leading causes of fires on boats: arcing faults. An arcing fault occurs when there is a loose connection in an electrical circuit, but not enough current to trip a circuit breaker or blow a fuse. This can result in sparks, which can burn surrounding materials and eventually lead to a fire. The danger lies in the fact that these faults can occur without any visible sign of a problem, making them difficult to detect until it's too late.

Shore Power Cords

Shore power cords are particularly susceptible to arcing faults. This is because of the plug-style connections at both ends (as opposed to bolted connections), the potential for boat movement (loosening the connections), and the marine atmosphere (promoting corrosion). In the U.S. the standard marina outlets are 30 amps and 50 amps, while in Europe it's often 6 or 16 amps. These relatively high amperages combined with the potential for loose and corroded connections increases the risk of arcing faults. This is one of the more common causes of boat fires.

To prevent arcing faults, it's essential to regularly check both ends of your shore power cord and the power inlet on your boat for any signs of burning, scorch marks, or other damage. If you notice any of these, it's crucial to replace the cord and fittings immediately to avoid further risks.

Importance of Using Locking Plugs for Secure Connections

When plugging in your shore power cord, make sure to use a locking plug that screws or clips into place. This is especially important if your boat is moored in a marina where it may be subject to rocking and rolling. Loose plugs result in arcing faults and a potential fire hazard.

Insurance Claims: Negligence and Prevention

It's important to note that insurance companies may deny claims related to arcing faults if negligence is deemed a factor. Failure to properly secure shore power connections and cords or neglecting to regularly check for signs of damage have been construed as negligence. Taking proactive steps to prevent arcing faults, such as using locking plugs and conducting regular inspections, will help to protect your boat.

If you're interested in learning more about AC systems on boats and how to prevent arcing faults, be sure to check out the modules in our Advanced Marine Electrics course! Our comprehensive course covers various topics related to marine electrics, including shore power connections, grounding, and electrical safety.

About the author 

Nigel Calder

Nigel is often referred to as THE guru when it comes to technical systems on boats.

He is a long-time member of the American Boat and Yacht Council (ABYC) electrical Project Technical Committee (PTC) which writes the standards for recreational boat systems in the USA, and has also been involved in European standards development.

Nigel is best known for his Boatowner’s Mechanical and Electrical Manual (now in its 4th edition), and his Marine Diesel Engines (in its 3rd edition), both considered the definitive English-language works in their field.


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