Fuse Required?

The wiring debacle continues! I've read various threads regarding amplifier wiring and referenced a number of different sites (ie: BCAE) in an effort to acquire all the necessary parts to install my car audio system. Some two months later (with many lessons learned), I've come to another fork in the road and have received conflicting information yet again.

For my installation, I'm running a 0 gauge power wire to a distro. block; from there, 4 gauge wire to a mono and four channel amp. My questions are as follows:

1) Do I need a fuse to protect the 4 gauge wire running from the distro. block to the amps? I've read that when you decrease the wire size (O gauge to distro., 4 gauge from distro. to amps), you need to fuse the wire to protect it.

2) My mono amp. manual (under specs.) states that a 90 Amp (ANL) power fuse is recommended. Does this refer to the size of fuse I should protect the 4 gauge with?   I already have a large fuseholder for install at the battery.

Part of my confusion stems from the fact that my old set-up had smaller wire running from the distro. block to the amps and the smaller wire was not fused.   Thanks in advance to anyone who can provide assistance.              

putting a fuse on the 4-gauge wire certanly won't hurt. The idea is that if one of the wires shorts out, then the fuse for that wire will blow before the main fuse blows. If the main fuse off the battery blows, then that 4-gauge wire will be carrying a lot of current, and could heat up & bad things happen.

If you're ever wondering if you need a fuse or not, it's best to put one. They are cheap and can save you a lot of money.

-Drew

IMO you should always fuse the wire to protect the wire not the load.  The amps have their own fuses in them to protect the inner electronics.  Fuse the 0 gage at the battery with anything you like up to a 350 amp fuse and yes, fuse the 4 gage at or just after the distru block for up to 150 amps.  (This is the location for the 90 amp fuse your amplifier is recomending.) 

Choose your fuse sizes to 1) at least equal the fuse sizes of the amps, while 2) not exceeding the capacity of the wire.  The numbers I used above are the wire capacities.  Anything lower that those numbers will still protect the wire as long as the fuses are sufficient to meet the amplifier's demands.

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Thanks for the clarification, Drewt. Given how long this has taken, I can wait another week and order a couple of fuses.

Thanks as well, DYohn. I'll reference both amp manuals and install the recommended fuses to protect the 4 gauge wires.