Aerial Photo of a Marina

DC Circuit Protection

Protecting the electrical circuits and your boat.

Looking at the wiring on your boat can either be neatly managed, correctly terminated, cable tied and fused, or chaos of a bunch of cables and poor connection! If it is the latter, then you need to contact us today!

When we break it down to the individual circuits, there is quite a bit to consider in order for your boat to comply with regulations, but most importantly, for your boat to be safe. For more information on installation standards, the most commonly known is the ABYC E-11 of the American Yacht and Boat Council (ABYC) and the NMEA 0400 of the National Marine Electronics Association (NMEA). Throughout the EU we have ISO-9001 standards and these are currently only enforced at construction and not for any installation after the boats CE Approval.


The Circuit


Without going into too much detail, a DC Circuit can be though of as everything connected to your batteries. In order to create a circuit, you need a source of power, a conductor, a fuse and a load. The fuse is designed to protect the entire circuit from damage caused by excess current from an over load or short circuit.

In a survey done by BoatUS Marine Insurance, between 2008 and 2012, electrical short circuits were the number one cause of fires on board. It was reported that 55% of fires were caused by electrical faults, and 43% of those were found to be in the boats DC electrical system.

On your boat, you will find cables carrying power to and from each piece of equipment, note that we are saying 'to and from', because when we calculate the cable or conductor size for an individual piece of equipment we use the distance from the power source and back.

Choosing the right wire size for your DC electrical project is important, since a wire that is too small can overheat and possibly start a fire. The American Boat and Yacht Council (ABYC) publishes charts with valuable detail to help experienced boatbuilders and installers determine what wire size they need. Although these charts are an excellent resource, they can be a bit intimidating to the DIY boater.

In order to rate the conductor size Blue Sea Systems have a very handy online tool to assist with choosing the correct cable size. (Also available on iOS and Android) As well as cable size, it will also suggest a suitable fuse or circuit breaker, based on information entered into the circuit wizard.


Fuse Rating


Fuses are rated in amperage and regulation require every ungrounded wire except those in the engine starting circuit to have circuit protection.