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  • Wiring / Fuse question

    I'm fairly new to the scene. I've been doing a lot of reading and am about to install my PC. I believe I have the wiring / fusing worked out, but thought I should get a double-check on my calcs.

    I have an Opus 150W ATX (the old version) and an Alpine amp. This is a no head unit install. The Alpine uses a 50A (2 x 25A) fuse. The Opus has a 15A fuse on board. If I put a 60A fuse on the power line, close to the battery, will that be OK?

    The PC is running a Centrino Mobile processor that draws about 25W. I figured 25W for the MB, 10W for the Xenarc and another 40W for HD, DVD, USB, etc. So, I'm at 100W, peak. At 12V, that translates to a little over 8A.

    So, I've got 8A + 50A = 58A. A 60A fuse should work, right?

    FYI, I'm running a 4 ga. cable to a fused distribution block (which I'll fuse at 50A & 10A) and then 8 ga. to the amp and the Opus.

  • #2
    Fuses are to protect the wiring not the devices, they have their own protection. If you run cable for 60A yes if you dont then no you need to split the fuses to supply all the different cables. You need a separate fuse at the start of every change in gauge of wire. For example if you run a large cable to a distro block you need to fuse from the distro block to suit your cables. Make sense?
    60A isnt large enough for the main fuse either as you have a potential draw of 65A. 5A is a lot of difference in a low voltage car environment. Personally I would use a 70A for a bit of head room and wire accordingly.
    Visit my site V8 Scimitar

    SP13000, 300GB SATA HD, 1GB DDR. Opus 150, K301 screen, Cisco WIFI, AQmax GPS, RoadRunner and FreeDrive, Sony MEX-R5 head unit. 4 years installed and it just keeps running!

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    • #3
      OK, I understand that the fuses in the distro block are for protecting the wiring. So, how do I figure out what fuse size to use?

      Say I put an 80A fuse on the power cable by the battery. (I had the amp fuse size wrong in the original post. Its drawing 60 A. Add 15 A for the Opus and some "head room".) I'm running a 4 ga. cable to the distro block and then 8 ga. to the Opus and amp.

      According to the things I've seen, the 8 ga. wire should be able to handle the 60 A of the amp. The 8 ga. run is only about 3 ft. If I use a fuse smaller then 60A, won't it blow before the amp maxes out (at 60 A). Same for the Opus. Am I missing something? I would think that if I have an 80 A fuse on the battery, I could do 60 A + 20 A fuses in the distro block. Thanks for all the help.

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      • #4
        I work in metric wire size but from what I see 8ga can take 60A so you can use a 60A fuse you don't need to use smaller.
        Visit my site V8 Scimitar

        SP13000, 300GB SATA HD, 1GB DDR. Opus 150, K301 screen, Cisco WIFI, AQmax GPS, RoadRunner and FreeDrive, Sony MEX-R5 head unit. 4 years installed and it just keeps running!

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