I'm getting a hifonics amp that produces 640 watts nominal. What size inline fuse should I buy?

 

200

 

Well, I wasn't expecting that.

 

If you are trying to protect from a dead short, I'd install a fuse about 1.5-2x the total fuse rating from the amp itself.

 

ah, well that makes sense.

 

the amp determines the size of the power wire needed, the size of the power wire will set what size fuse you will need. What size is the fuse in the amp? That fuse is made to protect the amp and that will also help determine what size cable to use. Are you planning on adding or upgrading the amps? This is important to know before you start running power wire or installing fuses

 

I haven't gotten the amp yet. I was gonna go with 4 guage wire. I don't plan on upgrading the amp or adding another amp any time soon.

 

This shows you all the things you need to know for (properly) calculating the fuse size along with power wire...
http://www.realcaraudioreviews.com/Articles/Fuses.jsp

Basically, your amp's current draw will determine what fuse to use. That draw, along with the length of wire you plan to run, will determine the wire's gauge.

Also check this one for properly fusing your system:
http://www.bcae1.com/fuses.htm

Edit: Can't spell to save my life today...

 

I have 2 amps. One for subs and one for highs and they have far diff. fuse characteristics so I have the fuses on the amp, two seperate inline fuse holders between the amps and the main fuse on my firewall.

For the basic one amp install, with 600 or so watts and 4 guage power wire, 100-120 amp fuse is more than suffiecient. Besides that amp will probably only produce 400watts peak on a good day.

 

100 amp is too big for 4 awg, I don't like to go above 80.