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Thread: 18 awg max amp

  1. #1
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    Default 18 awg max amp

    I googled a lot, bit found no real answer. I need to run a 2 wire power cable 66 feet from PSU to RGB amp, max amps that amp will pull is 4.5, I would like to T off the same line at 33 feet to an additional RGB amp. This would keep me from using so much wire. However, I cant seem to find if this will work.

  2. #2
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    Default Re: 18 awg max amp

    I know this works on my 100 count tombstones, but that is only 20 feet of wire and 2 tombstones on 1 wire

  3. #3
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    Default Re: 18 awg max amp

    Do a google search for "resistance per foot chart". You will find a table that gives you common resistance per foot of wire for a given gauge of wire. Using that and your estimated current values you can predict the voltage loss in the wire. If you loose more than is allowed for your application then you need thicker or shorter wires.

    Data from the table (NOTE: This is for solid wire, use a different table for stranded):
    Common Wire Gauges
    AWG wire size (solid) Diameter (inches) Resistance per 1000 ft (ohms)
    18 0.0403 6.385
    16 0.0508 4.016
    14 0.0640 2.525
    12 0.0808 1.588


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  4. #4
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    Default Re: 18 awg max amp

    It all looks like it will handle it, but I think the one thing I did not take into consideration is that I am unsure how many amps the traces on a distro board can handle. I can always out in a larger fuse but not sure the trace will handle it.

  5. #5
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    Default Re: 18 awg max amp

    If this is a matter of delivering power to the prop, oversize the feed.

    DC has a terrible propagation over distances compared to AC. In the field, @ 50' to maintain acceptable voltage drop, double the wire size or at minimum, the next size up. If I need 15A at the end of a 50-100' run, minimum wire size I use will be a #10 to maintain DC voltage/current and to minimize voltage drop.

    AC and DC characteristics are different. Most people assume the voltage drop in DC is the same as AC, nothing could be further from the truth.

    That is why Westinghouse won against Edison. AC vs DC. AC is easier to control and distribute over long distances. End of history lesson
    -Eddie

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  6. #6
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    Default Re: 18 awg max amp

    Ampacity is not just based on a wire size. It is rated for each specific wire type, and it's application. For example, 18AWG SPT1 an SPT2 have different ampacity ratings. So you really need to look at the datasheet for the specific wire you're using to know. That will account for conductor material like copper, aluminum, or a combination. It'll also account for insulation type and thickness. Then it'll likely show tables for each application, single conductor in free air, in raceway, bundled in a control panel, etc...

  7. #7
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    Default Re: 18 awg max amp

    Quote Originally Posted by jchuchla View Post
    Ampacity is not just based on a wire size. It is rated for each specific wire type, and it's application. For example, 18AWG SPT1 an SPT2 have different ampacity ratings. So you really need to look at the datasheet for the specific wire you're using to know. That will account for conductor material like copper, aluminum, or a combination. It'll also account for insulation type and thickness. Then it'll likely show tables for each application, single conductor in free air, in raceway, bundled in a control panel, etc...
    I thought the difference of SPT1 and SPT2 was the thickness of the insulation.

    Sent from my SM-G960U using Tapatalk

  8. #8
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    Default Re: 18 awg max amp

    I thought the difference of SPT1 and SPT2 was the thickness of the insulation
    it is

  9. #9
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    Default Re: 18 awg max amp

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  10. #10
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    Default Re: 18 awg max amp

    Quote Originally Posted by Strawberry View Post
    I thought the difference of SPT1 and SPT2 was the thickness of the insulation.

    Sent from my SM-G960U using Tapatalk
    It is, And that does affect ampacity. More insulation means it can safely carry more power. (until you get to higher temperatures)

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