I have a crossfire 1000d and a concept 4 channel total 1350RMS and 4ga wire what size of fuse should I have 100Amp?
in reality you'll probably draw no more than that but if you wanna do it the way everyone else says....add up the on-board fuses for the amps and get one around that size....
There's a flaw in the "sum your amp fuses and buy something that size" logic.. Two of them, actually First off, understand what that fuse up front is there for. The fuses in the amps protect the amps if something goes wrong... or if someone hooks things up wrong, so the amp doesn't die. The fuse up front is there to protect the wire... or rather the car, should something happen to the wire... say, you put a screw through the power wire.. or the insulation is cut where it is routed through the firewall, or near something sharp.... in that case, the wire comes in contact with ground... and you have an instant short circuit. A heck of a lot more than 125 amps worth of current could flow... in fact, the current that could flow in that situation has nothing to do with the amps that you have in your car... Considering the amps that you have in your car is a consideration... but only to help establish a minimum fuse size that you will need. Generally going larger won't hurt, at least to a point. The second flaw in the logic is that resistance in the wire is not being considered. The amps might be able to draw up to their fuse-ratings worth of current... but that's just how much current actually gets INTO the amps... What isn't considered is how much current got burned up in the process of drawing current through the wire, as heat! I'd leave at least a 10% overhead for this figure... maybe more, if you are pushing the gauge wire that you have for the amps that you have... Bear in mind... larger power wire, less resistance, less current wasted. But by default, I'd generally recommend a 150amp fuse for up front... that's usually bigger than the amps that you have and the current burned in the wire, but less than the amount of current that would be violently drawn in a short circuit scenario. Good luck!
