i have a question about fuses....

[SocialStealth]

Point well taken. I know you're not the average when it comes to knowledge on this website, your posts prove otherwise. I didn't intend to belittle you by any means. The ampacities that are posted (by others) FAR EXCEED the code maximums. Using a lesser rated fuse can never hurt (other than annoying blown fuses killing your tunes). Every amp I've ever owned was fused from the factory. If those fuses blow, Houston we have a problem (in the amp most likely). You are absolutely correct in saying there is no need to fuse above expected current. I'm more concerned about people using too large a fuse. Your last sentence: Either way the point is that fuses are sized to be larger than the max load which I'm sure the average CA guy doesn't know, is of concern. It sort of implies that you fuse according to the load. You MUST fuse according to the wire size, not the load. I'm quite sure you know better, but some 16 year old kid will read it differently and burn down his Honda. For some strange reason, people here seem to think that a shorter wire can carry more currrent than a longer wire. I know (and I assume you do as well) this is total BS. The "car audio bible" sites are full of absolutely incorrect information these people seem to take as Gospel. They sell their wares that way. A salesman trying to sell you his goods is like a hawker at a carnival: he has his eyes on his mark. PT Barnum wasn't wrong.

SO WHAT FUSE DO I USE FOR MY 1/0g BIG 3 UPGRADE?

Sweet jesus, just tell me what to do, but if my honda burns down i'll devote my life to murdering your family

 

[McIntosh 10+ year member]

SO WHAT FUSE DO I USE FOR MY 1/0g BIG 3 UPGRADE?
Sweet jesus, just tell me what to do, but if my honda burns down i'll devote my life to murdering your family

1/0 (in free air) is rated for 260A maximum (at 86 degrees F ambient). The largest derating in the code book is .41 (for 176 degrees F ambient). 260x.41=106.6 amps. It obviously gets quite hot under a hood. How much conservatism is built into the national code? I have no idea. These numbers are also for the best commercially available insulation (that's what fails under overload conditions, followed by a short circuit usually). Chinese insulation --- who knows? Somewhat less I'm sure.

 

[McIntosh 10+ year member]

If only someone had the right equipment to bench test several car audio power wires. It would be interesting to see how much current they can run before they melt....

Yeah, but under what conditions? The insulation is what fails (due to I squared R heating). Combine that with high underhood temps which heat/soften the insulation without any current flow. Now run the wire across a vibrating alternator mount (or your hot vibrating grounded metal of choice along the wire's routing) and viola, short. In days of yore (non traverse engines with a clutched fan) you always had air flow over the alternator (and wiring). Most cars now use "on-demand" electric fans and the alternator is far from any airflow they may provide. A mighty hot place to be, especially at other than highway speeds. I'm guessing a real world test would have to take place in an oven at 300+ degrees (anal extraction, but seems reasonable for underhood temp, maybe too low). I routinely strip wire heated to 250 in my oven, the insulation is as soft as a banana peel. Its really not designed to withstand those types of temperatures. The wire doesn't melt, the insulation does.

 

[AlterEgo99 5,000+ posts]

Yeah, but under what conditions? The insulation is what fails (due to I squared R heating). Combine that with high underhood temps which heat/soften the insulation without any current flow. Now run the wire across a vibrating alternator mount (or your hot vibrating grounded metal of choice along the wire's routing) and viola, short. In days of yore (non traverse engines with a clutched fan) you always had air flow over the alternator (and wiring). Most cars now use "on-demand" electric fans and the alternator is far from any airflow they may provide. A mighty hot place to be, especially at other than highway speeds. I'm guessing a real world test would have to take place in an oven at 300+ degrees (anal extraction, but seems reasonable for underhood temp, maybe too low). I routinely strip wire heated to 250 in my oven, the insulation is as soft as a banana peel. Its really not designed to withstand those types of temperatures. The wire doesn't melt, the insulation does.

Did you NOT read my post!? //content.invisioncic.com/y282845/emoticons/wow.gif.23d729408e9177caa2a0ed6a2ba6588e.gif

 

[McIntosh 10+ year member]

Did you NOT read my post!? //content.invisioncic.com/y282845/emoticons/wow.gif.23d729408e9177caa2a0ed6a2ba6588e.gif

Yes i did. I failed to see any mention of insulation temperature or even the mention of the word insulation. Did I miss something? //content.invisioncic.com/y282845/emoticons/wow.gif.23d729408e9177caa2a0ed6a2ba6588e.gif