Circuit breaker sizing

[Realgun]

I have a new issue. Since I am trying my best to rewire the boat to the Correct color codes and such I need a Circuit breaker or fuse less than 7 inches from battery. Actually I can go 40 inces as the wire is in a duplex wire already.<br /> <br />So the wire I am running is 6 guage. The wires Ampacity is 102 Amps. The maximum amps in the wire is going to be about ~30 amps and the length is also 30 feet total. Now the Wire itself is whats being protected the other circuits from the wire is in a fuse block and has fuses for all other wires. So do I use a 100 amp circuit breaker or a 45 amp?<br /><br />I am thinking a 60 would do what I want with no issues.

 

[jlinder]

Re: Circuit breaker sizing

The fuse can be no larger than the capacity of the weakest link. That means that even though the wire is 102 amps if the main bus of the fuse block is only rated for 60 amps then 60 amps would be the largest fuse you could use.<br /><br />You don't have to work about the current capacity of any circuit on the other side of any of the fuses in the fuse block.<br /><br />That said you should not just fuse at the maximum. If you are going to draw 30 amps max then 60 would probably be fine (as long as you past the tests above).