I want to install some circuit breakers in a new panel (Spring project) The old ones currently on the boat are stamped 120v /240v 15amp. This confused me given that it is a 12 volt circuit but I discovered that it is common. An Electrician told me that "Amps are Amps, it doesn't matter what voltage they are rated for." Another told me that is not quite true. If those circuit breakers are built for AC circuits (As the 120v /240v voltage stamp on them seems to indicate) Then they will be effected differently by low DC voltage. Logically if I had a massive circuit breaker for a 3000 volt industrial 'thing' that was rated at 30Amps, there is no way a 40 amp load at 12 volts will trip it! Is there a formula for adjusting the rating? Are the circuit breakers they sell to us boaters simply re-purposed? I have noticed that often- after the breaker there is an in line fuse (Radio) so I guess that the breaker protects the wiring but is too crude to guard the Radio?
