Wire sizing question (1 Viewer)

[workingdog]

I'm doing some rearranging of the main power at the batter while I'm replacing my alternator. The conversion never got cleaned up and I had no protection at the battery. I'm putting one of those 100 amp Bussmann breakers in the two circuits that goes to the cab - one is the original harness and the other is the computer and post conversion equipment. The headlights, ARB compressor, and starter all have their own leads from the power distribution box. My question is, what size cable should I run from the distribution box to the Bussmann breaker? It's supplying both the orignal and post conversion circuits, but there's not much there. ECM, radio, heater, interior lights... Doesn't seem like much. But it must be supplying the coils as well.

Peter

 

[4x4veteran]

I'm doing some rearranging of the main power at the batter while I'm replacing my alternator. The conversion never got cleaned up and I had no protection at the battery. I'm putting one of those 100 amp Bussmann breakers in the two circuits that goes to the cab - one is the original harness and the other is the computer and post conversion equipment. The headlights, ARB compressor, and starter all have their own leads from the power distribution box. My question is, what size cable should I run from the distribution box to the Bussmann breaker? It's supplying both the orignal and post conversion circuits, but there's not much there. ECM, radio, heater, interior lights... Doesn't seem like much. But it must be supplying the coils as well.

Peter

10 gage?

 

[Solace in Solitude]

10ga is good... 8ga is better.

 

[73FJ40]

The standard FJ40 starter is rated at 1.2 kilowatts, which converts to 100 amps at 12 volts. What are you protecting with 100 amp breakers?

 

[Solace in Solitude]

@73FJ40 is correct...

100amp is pretty big for your standard FJ40.

I have two breakers, one 30amp and one 40amp.

If you use a 100amp breaker to protect a circuit that carries less than 100amps, you are wasting your money and not protecting anything.

I have noticed that local auto parts carry only 50 & 100amp... but, you can easily buy smaller amperage breakers online.

 

[1969FJ]

Following standard design, you must first determine what is on the circuit and its rush current and full load current. Then, the correct breaker can be sourced.