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Fuse ratings and Power Wire Gauge

sharma Nov 25, 2009

  1. sharma

    sharma Member

    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?

  2. AndyMac

    AndyMac Moderator Staff Member Moderator

    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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