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Discussion Starter #1 (Edited)
I have 2 amps one takes 2x70 amp fuses and the other takes 2x30 amp fuses. I am currently running 4 gauge wire but will upgrade to 0 gauge.
Do I add up the amps to use a 200 amp fuse?
Thanx any help is appreciated
 

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Fuses at the power source are to protect the wires from getting to hot to start a fire. Fuses in equipment are meant to protect the insides, from fire or damage.

A 0 gauge wire in home applications is rated for 150-170 amps depending on the insulation type/rating to keep it safe. Automotive may handle more if not near combustible material or insulation rating is higher, eg 105 deg C
 

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Discussion Starter #3
I understand the why.
It's that some say use a rated fuse to match the load others say us a rated fuse to match the wire.
So which is it? If I go by wire I here use a 100 or 125 amp fuse. If I go by load use a 200 Amp fuse.
 

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And, if your load really is 200 or whatever, get wire that can handle the load. And to complicate it a little, amps don't typically pull the rated amps continuously, so you might not really need a 200 continuous amp capacity.
 

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I'm not sure if you have this situated yet, but I've got a similar setup power wise. I've got 4 20 amp fuses in my mono amp and 4 20 amp fuses in my 4 channel amp. I've got a run of 1/0 to a fused distribution block in my trunk with #4 coming off the distribution block for each amp. My cable is fused at the battery with a 150 amp MANL fuse. The NEC has specifications for 60 C, 75 C, and 90 C rated conductors, 125 amps, 150 amps, and 170 amps, respectively. I'm running Streetwires with a rating of 105 C. Together, my amps have a total current draw of a possible 160 amps, according to your logic. EE principles tell me my 105 C wire is rated for at least 170 amps (I don't care to get into the math to adjust it; I know it works). I have never blown my 150 amp inline fuse. I have blown the 80 amp fuse I had protecting my mono amp twice. It ended up being a gain setting issue after I went from a 4 ohm load to a 2 ohm load after changing my subs.

So, in short, your 1/0 is probably okay for the amps and fusing should be based on the conductor rating of your wiring. Hopefully you have a higher rated copper wire rather than aluminum. Aluminum is rated much lower for the same gauge. Assuming you have similar wiring to mine, I'd fuse it at 150 amps to 170 amps.

Should your amps actually draw close to 200 amps continuously (damn near impossible), your 1/0 won't suffice. A parallel run of #2 would work or a single run of 3/0 would work. 2/0 would work if you can find it rated higher than 90 C. Also, keep in mind, the NEC bases their information with 30 C ambient temperature. It's hotter than that under the hood. Heat increases the resistance of the cable therefore lowering it's current handling capabilities.

I am an electrical engineer.
 
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