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What size Fuses???

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  • What size Fuses???

    I am getting ready to install a complete carputer sytem in my new car and i had a question about what size fuses to use. What wattage spec should i be looking at when deciding on fuse size for a particular amp. For instance one of my amps is the Polk C300.2. It's 4ohm wattage (wich i will be using) is stated at 150watts per channel so a total of 300 watts. At that rating i would want about a 25amp fuse.

    But what is the other wattage spec? Total Dynamic Power (all ch. driven) 850 watts

    At that rating i would need a wopping 70 amp fuse for one amp!

    Now this is my first system i am setting up in a car, i am a home audio person. So those numbers may sound normal for you but a 70amp fuse for one amp sounded excessive to me, but i could be way off. ANy help would be great.

    On a side note, my ps for my carputer is the opus 150w... what size fuses have you guys been sucesfull in using for hooking that guy up.


  • #2
    your lookin at the wrong numbers.
    Your seeing Wattage, as in how many watts the amp puts out. You need to know how much it takes to power the amp.

    A 50-130A fuse would not be out of the question at all on more powerful amps. Personally, I prefer the circuit breakers as they are a one time purchase.

    EDIT: Polk recommends a 60A "Vehicle protection" fuse for that amp. Check the instructions, thats where i found it.
    2005 Ford Focus ST


    • #3
      Well how many watts it puts out is going to be directly connected to how mnay watts it takes to power it. You cant have an amp that puts out say 500 watts but only needs 200 watts to power it.

      Thanks for the 60A tip for that amp i was able to find that too after you pinted it out to me.

      How about the opus though, what size fuse for that. It ias a 150W ps but i am sure it is not 100% effecient so i know it needs at least more than a 12.5A fuse. What have you guys used on your opus's


      • #4
        Originally posted by BrentMcGhee
        Well how many watts it puts out is going to be directly connected to how mnay watts it takes to power it.
        Sounds easy, huh. If only it were that easy. Your best bet is to always go with the manufacturers suggestions. I bet Opus has a manual with the info.

        EDIT AGAIN: Opus manual states it has a 15A input fuse. That tells me a 20A vehicle protection fuse sounds about right.
        2005 Ford Focus ST


        • #5
          What ever size fuses are on the side of the amp is the size of the fues that you need under the hood (or circuit breaker if thats your method).
          Trying is the first step toward failure


          • #6
            Brent, you need to do two things:
            1) Read the manuals, they'll tell you what fuses you'd need
            2) realize there are two fuses you need per device: onef or the power wiring and one for the actual device itself. Don't try to calculate their factor of safety or whatever, just follow directions. 15 amps rating is so that the wire that can only take 15 amps worth of impedance that you dont' see isn't goign to melt away and cause a fire, frying your PSU. Power wiring is simple because for each gauge there is a fuse rating. Devices are simple too because the manufacturers will provide you with the fuse ratings in their manuals. If they don't, contact them. Just don't second guess them. I think Old school Rockford Fosgate Amps are the only things you amps you can do that with.
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