Over-Current Protection

Thermal Breaker

Today's high loads make proper installation critical

By Michael Kelly, Bayland Enterprises
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Electrical systems on boats are becoming more complex with heavy loads – such as inverters, bow and stern thrusters, and windlasses – and the addition of many new accessories, from electronics to entertainment systems.

One thing we see in the field is improper placement or even a lack of fuses and breakers on electrical circuits. It is not uncommon to see multiple conductors connected directly to battery posts without fusing to supply devices such as bilge pumps, stereo memory or other electrical items.

People tend to think the purpose of the fusing or breakers is to protect the equipment or appliance connected to the circuits when, in fact, they are over-current devices. Meaning they protect wire insulation from melting and starting fires in the event of current overload and also prevent short circuits that can cause more current to flow in the conductor than the conductor is rated to carry. The American Boat and Yachting Council (ABYC) states that every positive conductor in the Main DC Power Distribution System (except those intended to carry starting currents) must be protected by a fuse or circuit breaker.

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