What's the reason for having a breaker on the 12V negative DC supply?

[RIN]

Our boat has a circuit breaker for the engines (actually I think just one of them), one for domestic positive 12V and one for negative. What is the advantage of having a breaker on the -ve side of the battery? I would have thought grounding a good idea.

 

[superheat6k]

Current flow in and out of the battery travels along both wires, so having a breaker on the -VE simply provides additional overcurrent protection, and to all ciruits at once, assuming they share a common -VE return. Some like also to completely isolate the batteries, and this would allow this.

 

[noelex]

Isolating the - supply reduces the possibilities of stray current corrosion. It is a good feature.