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Fuse ratings and Power Wire Gauge

Discussion in 'In-Car Entertainment' started by sharma, Nov 25, 2009.

  1. sharma

    sharma Member

    Mar 27, 2007
    Likes Received:
    [Nov 25, 2009]
    Hi guys,

    I have 2 amps, one is 220 rms max and the other is 200 rms max. The power wire i have in the car is 8 guage and the fuse up front is 40 amps. There is a small distributor block in the back which splits the power wire for the 2 amps. That wire is 10 guage (and very short) and the fuses in the distributor block are both 20 amps.

    I just wanted to confirm if this sounds fine. My previous amps were less powerful but i never had any problems with the setup.

    I was just wondering because i looked at the fuses in the new amps, one had a 30 amp fuse and the other had two 40 amp fuses. So i read somewhere that the total ampage for the fuse up front should equal the total of the amp fuses (which would make 70 amps, this in turn would require a lower guage power wire). However i assume the fuse up front being 40 amps is the better option to keep things safe and that the power wire should be fine for this wattage?

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  3. AndyMac

    AndyMac Moderator Staff Member Moderator

    Jun 10, 2003
    Likes Received:
    [Nov 25, 2009]
    As a rule of thumb you divide the RMS wattage by the voltage to give you the amperage. However in a car this is usually way too conservative as it does not include the huge inefficiencies and losses suffered when running car hifi from a puny 12v.
    The setup above should be fine, if it isn't all you will suffer is continuous blown fuses, however what you must never do is put in a bigger fuse than the cable can handle, as this can result in the cable failing or getting very hot. 8 gauge is 40amp, so your current setup is protected. Personally I would run a second 8 gauge cable for the second amp, but unless both amps are going to be used for subs then this is probably overkill.

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