proper power wiring

Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=118684
Printed Date: May 09, 2024 at 10:55 PM

Topic: proper power wiring

Posted By: 08canyon
Subject: proper power wiring
Date Posted: December 20, 2009 at 3:23 PM

After searching this site to no avail, here I am once again looking for your expert advice. I am in the process of wiring two amps. One requires a 100 Amp fuse, the other a 50 Amp fuse. I am running 1/0 from the battery to a fused distribution block. I know it is wise to mount a fuse within so many inches of the battery for safety's sake. My question is... What rating does the fuse near the battery need to be? The combined total of the two amplifier's fuse ratings (Again, I am using a fused distro block)? Or does it need to be the amperage rating of the cable it's self? Does it really matter as long as it is at least rated at what I need for my amplifiers?

Thanks again...

-josh

Replies:

Posted By: oldspark
Date Posted: December 20, 2009 at 4:25 PM

The fuse is normally to protect the wiring - ie, the maximum that the cable can handle.
But a size that handles both loads is acceptable (assuming it does not exceed the cable rating). This might be 100+50 = 150A, or 120A, or 200A etc.

Fuses are often sized to be no smaller than ~70% of normal load current, sometimes 90%.

Posted By: j.reed
Date Posted: December 20, 2009 at 4:48 PM

Recommended power and ground size.

I fuse for the wire at the battery and fuse again for the amp at the amp or let the on board fuses do there thing at the amp. Thats what there for. You can fuse your 0 gauge at no more than 350A. Thats all it can carry. Seeing as you have a total of 150A fusing from the amps. a 150A would be the minimum to fuse at the battery for the wire. As said above, the fuse at the battery is to protect the wire and should be no more than 12" from the battery. The fuses at the amp or on the amp are to protect the amp. So you can fuse anywhere from 150A to 350A at the batt for your 0 gauge.

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Posted By: oldspark
Date Posted: December 20, 2009 at 6:23 PM

Just to clarify, my 120A fuse assumed that the 100A & 50A fuses were for downstream cable or load protection as opposed to an indication of load currents.

For high current loads, I prefer to have overrated cabling all the way with a single fuse that handles the load(s) at the battery end. (That assumes the loads have their own protection, otherwise I add a load-protection fuse at the load.)
That's based in a minimum voltage drop philosophy.

Fusing at the battery end to me means as close as possible to the battery whether it be 1, 4, or 12 inches from the battery post.
The assumption being that the unfused portion is physically secure - ie, negligible risk of shorts etc, and of course at least equal to downstream fuse & cable ratings.
The latter assumes that battery-post fusing is impractical. (Battery post fusing is considered by some to be dangerous - unless ofcourse it is the -ve post that is fused LOL!!)

Posted By: 08canyon
Date Posted: December 20, 2009 at 9:26 PM

oldspark wrote:

The fuse is normally to protect the wiring - ie, the maximum that the cable can handle.
But a size that handles both loads is acceptable (assuming it does not exceed the cable rating). This might be 100+50 = 150A, or 120A, or 200A etc.

Fuses are often sized to be no smaller than ~70% of normal load current, sometimes 90%.

Thanks again! Thats what I though... just wanted to be sure.

-josh