Wire Gauge Sizing

Discussion in 'Instruments / Avionics / Electrical System' started by GESchwarz, Sep 6, 2019.

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  1. Sep 6, 2019 #1

    GESchwarz

    GESchwarz

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    I am 10.5 years into my build and I am about to start doing some wiring for the first time. What wire gauge do I need to power my navigation lights out at the wingtips?

    Does anyone have a table of wire gauges for typical systems of a general aviation aircraft?
     
  2. Sep 6, 2019 #2

    N804RV

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  3. Sep 6, 2019 #3

    TFF

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    A.C. 43-13 has some charts. My guess is probably 18g for most of a 12v system 22 if it was 24v.
     
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  4. Sep 6, 2019 #4

    N804RV

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  5. Sep 6, 2019 #5

    pictsidhe

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    It depends on the current and voltage. What are light specs?
     
  6. Sep 6, 2019 #6

    GESchwarz

    GESchwarz

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    Thank you! I have A C 43-13. I've always thought of it as a mechanic's reference than an engineer's.
     
  7. Sep 6, 2019 #7

    BJC

    BJC

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    I think of it as "Here's what we (the FAA) think works …"


    BJC
     
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  8. Sep 6, 2019 #8

    N804RV

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    Wire guage vs amps vs length is pretty standard stuff. It’s like building code, you’re either in compliance or not. Even experimental aircraft builders are expected to to use “acceptable methods and practices”.
     
  9. Oct 11, 2019 #9

    wktaylor

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    AG CASA AC 21-99 AIRCRAFT WIRING AND BONDING [AUSTRALIAN]
     
  10. Oct 12, 2019 #10

    Daleandee

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  11. Oct 12, 2019 #11

    Daleandee

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  12. Oct 13, 2019 #12

    Winginitt

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    Going to use LED lighting ?
     
  13. Oct 13, 2019 #13

    AdrianS

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    Why would you not?
     
  14. Oct 13, 2019 #14

    dtnelson

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    Other things to consider when selecting wire gauge:

    - Intermittent use or full time use? Intermittent means the wire has less time to get hot, so you can often get away with a smaller gauge.
    - Will the wire run be in a bundle? If so, it will transfer heat too/from other wires in the bundle. Don't cheat on gauge for a full time use wire in a bundle.

    Keep in mind that the wire tables are intentionally very conservative. Some would say very, VERY conservative. And that you'll be carrying around that weight whether the wire is carrying current or not. So don't add your conservative to the wire table conservative... keep to the minimum recommended gauge.
     
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  15. Oct 13, 2019 #15

    Aerowerx

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    Use a wire with a high melting point insulation. Teflon is higher than Tefzel.

    If you have a short, you don't want the insulation melting and causing more problems. Of course, you do have a proper size fuse on the circuit, don't you?
     
  16. Oct 13, 2019 #16

    mcrae0104

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    Get Nuckoll's book. He discusses Teflon, Tefzel, PVC, and that mystery wire you have in a drawer in the basement. The short story, though, is this:

    Capture.JPG
     
  17. Oct 13, 2019 #17

    Winginitt

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    Winginitt: Going to use LED lights ?

    My simple understanding is that LEDs use less current, and most wire sizing on airplanes was done prior to the invention, or at least common availability of LEDs. Having said that, I think that concerns over the weight of wiring is often overblown. You have a few long wires, but most are short runs. A slightly larger wire may prevent melting and resists vibration better. I know weight is a preminent consideration in airplanes, but I don't think the wiring in most of the simple airplanes that are the product of homebuilders will suffer because of a little overcapacity sizing. The builders who are building aircraft with $50k instrument panels most likely have a pro doing their wiring.....but their airplanes probably have enough power to offset minor wire sizing changes.

    On another website (automotive), there is a discussion about using "amp" meters. The thing is, they were fine in their day, but today there is a lot more amps being used than there were back in the 50s, and amp meters simply cannot handle the current requirements of todays cars. Somewhat the same thing with airplanes. If you are rebuilding a certified airplane, you know exactly what component you "HAVE" to use, and what wire size circuit it takes. With a homebuilt you are using "non-certified" items and allowing the manufacturers recommendation to guide you. You don't always know how correct this information is, or how well the component is made.....so allowing for a little extra variation in its operation seems like a prudent choice to me.

    The results of even one wire overheating can be catastropic, so for myself I would always want to err on the side of increased safety rather than worry about a miniscule increase in weight.;)
    But thats just my opinion.......

    Here is a nice reference site. http://www.eaa162.org/files/1377/File/experimental_electrical.pdf
     
    Last edited: Oct 13, 2019
  18. Oct 13, 2019 #18

    BJC

    BJC

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    Regardless of the wire size selected, proper over-current (overheating) protection (fuse, breaker, fuse-able link, thermistor, etc.,) needs to be used.


    BJC
     
  19. Oct 13, 2019 #19

    rv7charlie

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    I suspect that it will be difficult to even find teflon insulated wire today, because teflon 'flows'. The wire will eventually work it's way through the insulation at stressed locations. Besides, who fries bacon on their a/c wiring? :)

    Let me cast another vote for the Aeroelectric book. If you can't shell out for the print, you can download it for free. It will 'teach you to fish' instead of buying you a fish dinner.

    Charlie
     
  20. Oct 13, 2019 #20

    BJC

    BJC

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    PTFE (“Teflon”) insulated wire is widely available. I would bet that it is used in type-certificated aircraft. I know that it is used in E-AB aircraft. Just choose your applications appropriately.


    BJC
     

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