Fuse question...UNDER fusing?

[stuwad21 10+ year member]

Hey I have tried to search for this, but doenst look like any topic answers this question. Ok so here is goes (sorry for hte long post already)

My uncle and I have been arguing about how to fuse your system. He tells me to fuse for the equipment and I tell him to fuse for the wire. I even sent him to bcae and he still is arguing. He tells me this: "If you put that 150A at the battery with 1/0 wire, and your load is only ~80A (2 amps at 50 and 30 + headunit + relay) you will burn up everything else long before the wire goes and the equipment down the line" He thinks that I should be a 80A fuse at the battery which has 1/0 wire coming out of it. Is there a problem with this, say with UNDER fusing (bcae says the MAX fuse is something like 400A for 1/0 wire)? What will happen if I put that 80A fuse at the battery instead of 150A? Does limiting your fuse in thsi case limit your amp's performance?

Any help is greatly appreciated.Thanks in advance!

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[JimJ 5,000+ posts]

If you under-fuse, you're going to blow fuses.

 

[stuwad21 10+ year member]

So who is right in this case? I am putting a 150A at the battery, and he is telling me that it should be no bigger than a 80A. If he is right, then why does everyone say to fuse the wire and NOT the equipment? If that site is correct, then a fuse of 300A should be fine with 1/0 wire correct?

Maybe I am completely missing something, but he is a pretty smart guy and he seems really intent that he is right.

 

[JimJ 5,000+ posts]

If you fuse significantly under your equipment's current draw, you're going to blow fuses. That's a fact.

You fuse for the ampacity of the wire, not the load on the equipment - at least for the under-hood fuse. The fuses at the distribution block, if there are any, are fused for the equipment.

 

[xSomeguyx 10+ year member]

If you've got a maximum draw of 80a, and fuse it for 150a, there won't be any difference then if you were to fuse it for 80a. The only point at which it makes a difference is if somehow you manage to draw the maximum current, at which point you'd not only blow the fuse on the amp, but also the fuse on the wire. The idea isn't so much that you're fusing the amp, because it has it's own fuse to protect itself.

 

[squeak9798 5,000+ posts]

because it has it's own fuse to protect itself.

There you have it //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif The fuse on the amp is to protect the amp, the fuse on the wire is to protect the wire.

Unless you have an amp that DOESN'T have an internal fuse (a lot of high-powered mono amps don't have internal fuses), in which case you WOULD have to fuse for the equipment.

 

[skmfkr 5,000+ posts]

400a is the max fuse rating for 0awg wire, which means you would need bigger wire your pulling more than 400a, actually i think its more like 300a not 400a, but thats what you said. You need a 80a fuse not a 150a fuse...well actually this is whats gonna happen i had a 200a fuse on 4awg wire and a viper 1100.5 with 3 40a fuses and it blew all 3 fuses on the amp instead of the inline fuse cuz it was bigger. Just get an 80a fuse, then you only need to replace one fuse instead of multiple fuses

 

[ToyTundra 10+ year member]

My though is that as long as the wire's fuse will blow before the wire melts it's all good.

I personally take the smaller of the two (wire max current and amp's current draw) and match it at the battery, but im deathly afraid of an electrical fire //content.invisioncic.com/y282845/emoticons/uhoh.gif.c07307dd22ee7e63e22fc8e9c614d1fd.gif