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Thread: Wiring question...

  1. #1
    Join Date
    Feb 2006
    Birmingham, UK

    Lightbulb Wiring question...

    Hi all,

    I have started a fibreglass project for a custom sub build for my Mitsubishi Galant estate boot. Build is going ok, slowly, but in preparation for the wiring phase of the project, I was wondering if there was anything wrong in using domestic electrical cables to the system.

    I'm a domestic electrician by trade, so have plenty of wiring about and have looked around at a number of wiring kits. I'm looking to run a 600W max amp with a suitable low powered sub, and not looking to upgrade from this at all (I had the same system in a HUGE ported box in my previous Toyota Corolla, but as I need the boot-space for work, I'm going for a small custom build.

    The amplifier has a 20A fuse and the wiring for this is just huge! In domestic cables, 20A can easily be carried by a 1.5mm or 2.5mm CSA cable, but in car wiring kits they are usually 5-6mm CSA wide! Speaker cables also have too much CSA. A 1mm CSA cable could easily take up to 12-15A.

    So I was wondering, if I could simply use some domestic wiring in my car (all suitable insulated and protected throughout obviously)? It'll mean I dont have to force a load of super thick wires under my door sill, I can have all my wires take up the same space as an average power lead from a wiring kit!


  2. #2
    Join Date
    Apr 2008
    how long have you been an electrician? i to have wiring needs. as for using big wire it may be conductivity, like my welder, you need bigger cable the longer you go to take the power, so it dose not melt your wire using high current.

  3. #3
    Join Date
    Apr 2008
    Norfolk, VA
    The thing to remember is the voltage difference. Domestic houses use 120 V, while a car uses 12 V. That means for the same power, a car will draw 10x as many amps, therefore bigger wire is necessary. Once that is accounted for, domestic wiring should be fine, though it may be stiffer and harder to work with.

  4. #4
    Low Bitrate benedums's Avatar
    Join Date
    Jan 2007
    Eagan, MN


    The Sketch is correct!

    20A on 120AC is way different than 20A on 12DC.
    A 100 watt light bulb will draw about 0.8 amps on 120AC.
    Where as a 100 watt amp will draw about 8 amps on 12DC.

    Amps = Watts/Voltage

    Copper is copper, so 12AWG domestic wire will have "roughly" the same current caring capability as 12AWG speaker wire...
    And as HisSketchiness said the domestic wire will be a lot more rigid than and stranded speaker wire.
    CarPC Status:
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  5. #5
    Constant Bitrate golfguy's Avatar
    Join Date
    Nov 2006
    Fort Worth, TX
    Check out this reference site, it was very helpful to me and I'm sure it will be to you, as well. Remember to always fuse your power runs as close to their source (battery or distribution block) as possible. It's really easy to short something out if you forget to disconnect the battery. You can make some really big sparks and do some real damage if you don't have a fuse on your power line. The fuse in the amp won't protect your battery or car. You should use at least a 12 or maybe 10 AWG wire (sorry, I don't know the Euro equivalent) for your amp.
    Any day is a good day for golf.

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    (Check Speedy's Install)

    Speedy was traded for a 2004 350z - Install complete except for permanent screen installation.

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