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What size fuse for amp?

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Old 02-03-2009, 01:49 PM   #1
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What size fuse for amp?

I know there's alot of threads on it, but I'm still a little unclear. So I'm going to have about 1200 wts rms for my sub amp. I'm going to use 1/0 gauge wiring anyways, I know it's overkill but if I upgrade later on it'll be easier. Plus, isn't it better to go overkill anyways?

I know you want to pick a fuse based on wire size, not the amp. Most sites say to use a 300-350 amp fuse for 0 gauge wiring. But that wouldn't be necessary for me right? Couldn't I go with something about half that size since I'm not pushing the high wattage that most 0 gauge systems are? Oh, and how far away from the battery should the fuse be placed? Any help is great, thanks!
Old 02-03-2009, 02:19 PM   #2
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Re: What size fuse for amp?

http://www.the12volt.com/info/recwirsz.asp

1/0 is way overkill for the sized system you are planning.
Old 02-03-2009, 03:32 PM   #3
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Re: What size fuse for amp?

Hm, well it's going to be at least a 12 ft run of wire, and 1000-1200 watts. So I guess it's saying 2 gauge is what should be used. I don't really see many places selling 2 gauge though...I want to go with knukonceptz, and they only have 4 or 0 gauge.

I was planning on going with the copper/aluminum mix or copper clad aluminum wire in 0 gauge. Mainly because it's way cheaper, and it'll just be a step down from actual 0 gauge 100% copper wire. Wouldn't that be about the right size I'm looking for?
Old 02-03-2009, 09:38 PM   #4
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Re: What size fuse for amp?

its easy

watts / volts = amps
so....
1200 / 12 = 100 amps
there's your answer
Old 02-03-2009, 10:12 PM   #5
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Re: What size fuse for amp?

Quote: Originally Posted by raven2510
its easy

watts / volts = amps
so....
1200 / 12 = 100 amps
there's your answer
That's assumes 100% amplifier efficiency. Generally speaking, you should multiply that number times 1.2 (80% eff) to get input draw.
Old 02-04-2009, 01:42 AM   #6
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Re: What size fuse for amp?

Alright, so 120 amp fuse then? Does it change with what size of wire I want to run? Thanks.
Old 02-04-2009, 11:51 AM   #7
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Re: What size fuse for amp?

not always. your trying to protect your car's electrical system from being damaged by putting the fuse inline with the amp's power wire. you dont want the fuse to be so large that even if the amp acts up or has a short that the main fuse doesnt blow. you also dont want to run too small of wire. too small of wire creates resistance, which is heat, which can lead to tons of problems. get my gist?
Old 02-04-2009, 12:13 PM   #8
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Re: What size fuse for amp?

Well I don't want to go 4 gauge, I think that would be pushing it. Where can you get some cheap 2 gauge, since knukonceptz doesn't carry any?
Old 02-04-2009, 12:42 PM   #9
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Re: What size fuse for amp?

Quote: Originally Posted by geraldwp
not always. your trying to protect your car's electrical system from being damaged by putting the fuse inline with the amp's power wire. you dont want the fuse to be so large that even if the amp acts up or has a short that the main fuse doesnt blow. you also dont want to run too small of wire. too small of wire creates resistance, which is heat, which can lead to tons of problems. get my gist?
The fuse being added to the power wire is not to protect your car's electrical system, its to protect the wire its connecting to.

Your 'not always' answer is incorrect. Fuse size should always change with wire size.

When determining the proper fuse size, it should be greater than the maximum current draw possible from the amplifier, while being smaller than the maximum ampacity rating of the wire. So obviously you size the wire first, making sure its capacity is larger than the maximum current draw of the amp.
Old 02-04-2009, 01:12 PM   #10
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Re: What size fuse for amp?

your wrong buddy.

this is the only part that is true.

"When determining the proper fuse size, it should be greater than the maximum current draw possible from the amplifier, while being smaller than the maximum ampacity rating of the wire. So obviously you size the wire first, making sure its capacity is larger than the maximum current draw of the amp."

the wire size is determined also by the current draw. as is the fuse size. the fuse is to protect both the car and the amp. im sorry that i left out the amp part.

Last edited by geraldwp; 02-04-2009 at 01:14 PM.
Old 02-04-2009, 01:48 PM   #11
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Re: What size fuse for amp?

Quote: Originally Posted by geraldwp
your wrong buddy.

this is the only part that is true.

"When determining the proper fuse size, it should be greater than the maximum current draw possible from the amplifier, while being smaller than the maximum ampacity rating of the wire. So obviously you size the wire first, making sure its capacity is larger than the maximum current draw of the amp."

the wire size is determined also by the current draw. as is the fuse size. the fuse is to protect both the car and the amp. im sorry that i left out the amp part.
The 'car' doesn't need fused, only the wire does. Now if you want to say the fuse is protecting the 'car' in case the 'wire' catches fire and burns the car down, you could. But then I guess we could also say the fuse is there to protect your garage as well...? The point is when people start misunderstanding what exactly the role of the fuse is in their system, mistakes in sizing start to happen. You can disagree with me all you want, but I notice you didnt explain exactly HOW I was wrong. Id be glad to listen while you attempt to do so, then I'll be glad to correct you once you've finished.

Cheers.
Old 02-04-2009, 02:22 PM   #12
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Re: What size fuse for amp?

Yeah, I've heard the same thing, fuse is there for the wiring protection (and car I guess). Always have it just slightly above the amp rating, and below the maximum rating of the wire.

So technically, I can have a fuse anywhere between 90 amps (my amp fuse total) and 250-300 amps (the 1/0 gauge wire rating)? I'm guessing it's better to stick closer to the amp rating, like a 100-120 amp fuse? Thanks.

Last edited by onecrazyfoo4u; 02-04-2009 at 02:25 PM.
Old 02-04-2009, 03:31 PM   #13
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Re: What size fuse for amp?

I'm running 3000 watts in my El Camino, I have 4 gauge wire with 100 amp fuse.
Old 02-04-2009, 03:38 PM   #14
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Re: What size fuse for amp?

Is that 3000 wts rms or peak? I'm going off of rms. You're probably use underrated wiring if it's rms. 3000 watts recommends 1/0 gauge.
Old 02-04-2009, 03:46 PM   #15
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Re: What size fuse for amp?

its 3000 peak sorry my bad.
Old 02-04-2009, 04:01 PM   #16
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Re: What size fuse for amp?

Its 4 guage wiring that came with 100 amp in-line fuse.
Old 02-04-2009, 04:20 PM   #17
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Re: What size fuse for amp?

So rms is probably 1500 watts then? Still seems a tiny bit underrated depending on how long the wire runs are. This chart from above says it should be 2 gauge for 1400 watts rms: http://www.the12volt.com/info/recwirsz.asp
Old 02-04-2009, 04:38 PM   #18
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Re: What size fuse for amp?

My amp is 2400 watts, 1200 RMS. I guess I am running around 2700 watts I am running my 6x9's off my cd player and it is 300 watts peak. not 3000.
Old 02-04-2009, 04:41 PM   #19
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Re: What size fuse for amp?

Tsumani is my brand wiring they put the 100 amp fuse in there so I am going to trust them, because they know more about it than I do. I been running it for about 7 years with no problems.
Old 02-04-2009, 04:47 PM   #20
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Re: What size fuse for amp?

www.cardiscountstereos.com is a really good website that is cheap to get anything and everything is brand new. Thats where I buy everthing. If they dont have what you need just contact them they might be able to get it for you. They respond to emails pretty quickly.

Last edited by customchevys; 02-04-2009 at 04:50 PM.
Old 02-04-2009, 05:42 PM   #21
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Re: What size fuse for amp?

OKay, yeah, 1200 rms watts is right on the border....you should be just fine with 4 gauge. That's the exact same amount I'll be using, but I still might go 2 gauge or 0 gauge if I can't find 2 gauge.
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