Electrical Wiring: Amps vs Wire Gauge

Discussion in 'Hacks' started by dholaday, Nov 8, 2012.

  1. dholaday

    dholaday Been here awhile

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    I'm looking to update some of the electrical stuff [a highly technical term] on my rig and came across the following. Thought others might find it useful.

    http://www.offroaders.com/tech/12-volt-wire-gauge-amps.htm

    It's a chart showing wire gauge and amps and distance. Also has links to other useful hints.
    #1
  2. Ron_Ces

    Ron_Ces Aging Hacker

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    Just remember,
    Resistance is NOT futile.. It's Voltage divided by Current.

    Ron
    #2
  3. Mechanista

    Mechanista manic depressive

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    Nice! Thanks.
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  4. DaveStockwell

    DaveStockwell Rock Fodder

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    To anyone using this chart, note that the resistance numbers are related to length measured in FEET, not inches. You'd be hard pressed to find more than 3 feet in any single wire run on your bikes. This isn't a big deal since resistance in a short distance is much less. Just didn't want anyone getting too far into their project before they discovered they were using super fat wires.

    Also, there is the additional issue of abrasion, especially in the wire bundle that runs past the steering head. Lots of flex + lots of dirt in a tight space can equal abrasion. My father is learning this lesson on his recently purchased KLR. He definitely has his winter project laid out for him this year.
    #4
  5. dholaday

    dholaday Been here awhile

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    We have longish runs between bike and car in a hack setup.

    Also note that you need to count total circuit length, including distance to ground. For instance, if your device is 3 feet from battery, total distance is 6 feet.

    One of the things I'm [probably for no reason] worrying about is the extra load we put on a bike's wire when we tap into it to feed a circuit on the hack. That is, if we tap into the bike tail light wire to feed the tail light on the hack, will we over-stress the bike's wire? I have no idea how much safety margin is built into the bike's wiring, especially on a canbus system.

    Duncan
    #5
  6. XL-erate

    XL-erate Been here awhile

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    I appreciate the link but in my opinion their specs are extremely light for wire gauge in some examples. I'd never run a 30 amp circuit through an 18 ga conductor, much less 50 amps through 16 ga as suggested there!

    I never run anything less than 14 ga anywhere in vehicle/bike wiring. Also vehicle specific wire is different than residential or commercial/industrial wire, being more strands of finer gauge conductors.

    Please note the instructions above the graph, to include the full length of the ground/return to chassis ground in your length calculation. A 5' current-carrying conductor could have a 5' ground return, so you'd need to calculate for 10' length, not the 5' length!

    Also want to be real careful about sticking in a short piece of light gauge wire in a circuit that's primarily heavier gauge, as the lightweight piece can cook like a fuse element because the larger wire it's patched into has higher ampacity. Similar to patching a 1' long section of 1/2" garden hose into a 100' run of 2" high-pressure fire hose, not altogether good.
    #6
  7. davebig

    davebig Another Angry Hun !

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  8. XL-erate

    XL-erate Been here awhile

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    I was typing and didn't see your replies, Duncan and DHoladay!

    Very good point on the extension of an existing run of wire. That must be calculated into the total. That's also a place where one may accidently choke a circuit by patching in a little piece of light gauge wire, not knowing that the rest is one or two gauges larger! Just as bad, a circuit run in 18 gauge that then has a device added that pulls a lot of amps and is wired in 12 gauge is going to stress the whole run of light gauge.

    Just like everything else, there are premium grades of wire and junk stuff out there too. In general Marine spec'd wire is going to be good stuff, soft pliable copper instead of cheap brittle alloys. Of course the coating type and quality matters too.

    Though slightly off topic: wherever possible except in emergency repairs, solder and seal ALL connections.
    #8
  9. davebig

    davebig Another Angry Hun !

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    Though slightly off topic: wherever possible except in emergency repairs, solder and seal ALL connections.[/QUOTE]

    Now considered a nono Military spec wiring and virtually every bit in a modern welder or plasma cutter is crimp only poor solder joints are often overheated prone to breaking, sealing more than heat shrink traps moisture,tinning is still cool but no one keeps a pot on the stove anymore, assembly lube and dielectric grease are handy.DB
    #9
  10. grisezd

    grisezd Been here awhile

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    And now further off topic. I run a lot of wire in vehicles (test equipment in cars), and I've entirely stopped soldering where I can use a crimp instead. I've seen too many soldered connections break right at the end of the solder. I'm thinking it's the effects of heat. We beat the hell out of the cables driving around like idoits, but the soldered joints fail inside strain relieved plugs!

    That said, I do enjoy soldering. I just limit it to circuit boards and un-crimpable connectors.
    #10
  11. XL-erate

    XL-erate Been here awhile

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    I'd suggest the breakage is due to one of three things: the alloy content of the wire i.e. quality, the alloy of the solder, or the amount of heat used - how- for what period of time.

    Top quality marine grade wire solves #1, proper marine spec solder #2 and type of torch/technique solves #3.

    Too cool of a torch or iron means more prolonged heat traveling far away from the confines of the soldered joint while waiting for solder to melt. That typically ruins the wire coating as well. There's pre-tinned wire available too, so that as soon as solder breaks an instant bond is made as solder flows quickly.

    Check out the marine stores for the better quality stuff, but of course at a slightly higher price. Ancor, Packard, Belden are some trustworthy names in wire and components. Just some examples of providers, do your own search for pricing of course:

    http://www.jamestowndistributors.co...freeText=Tinned_Primary_Marine_Wire&page=GRID&

    http://www.shipstore.com/search?cat=electrical

    http://www.iboats.com/Primary-Marine-Wire/dm/view_id.216631
    #11
  12. davebig

    davebig Another Angry Hun !

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    That is some very nice wire also very expensive but again no one solders if there is anyway to avoid it, as it's not reliable, you don't see any soldering in a Tig torch capable of delivering 200 + amps continuous but there is allot of elegant crimps.I do know where to find nice wire now though,thanks.DB
    #12
  13. XL-erate

    XL-erate Been here awhile

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    Yeah, I'm not Mr. Electron Wizard anymore. Plenty of my wires get crimped, depending on the project and the moment. Building looms is far different from patching in a new gizmo. Don't want to insult your or anybody else's intelligence or experience which may exceed mine by light years.

    I'll correct myself and say, nothing wrong with a proper crimp!
    #13
  14. Bobmws

    Bobmws Curmudgeon At Large

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    Posi-lock and posi-tap connectors are a good alternative to crimping, alot easier to use in tight spaces.
    #14
  15. DRONE

    DRONE Dog Chauffeur

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    Hey XL-erate, I'm OK with my crimper--I got it from Eastern Beaver-- but I have one of the more expensive soldering guns from Radio Shack and . . . . it SUCKSS! Any links to what you consider to be a gun that will heat up the wire quickly to conserve the insulation?
    #15
  16. XL-erate

    XL-erate Been here awhile

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    I've had my stuff for years so haven't looked lately. What you want to know is an iron's actual tip temperature, plus wattage rating and heating time. If a mfgr. can't tell you that [but you may have to contact mfgr. directly] then one may assume it's not top notch stuff or it's outsourced or both. I consider 30 Watts the bare minimum, prefer higher like 40-50W, but care required not to overheat when soldering. In a quality iron the watts rating may not be as important as actual tip temperature. I prefer a small squared tip for some work, or a pointed tip for other more precise joining jobs.

    You can use tie wraps as temporary fixtures when soldering to hold wires, in order to free your hands and more easily and quickly concentrate heat, flux and solder where it's needed.

    Some decent irons are Antex - made in England. They have quick change tips. Their 18 Watt [actual] is equal in performance to a rated 30W, providing just under 750*F/400*C tip temperature. I'm pretty sure they make higher wattage irons as well.

    http://www.minute-man.com/acatalog/Online_Catalog_Standard__Antex_Soldering_Irons__23.html

    Eclipse [MADE IN CHINA] has a dual wattage iron station for their irons: http://www.minute-man.com/acatalog/Philmore_Soldering_Irons.html

    Philmore is another decent name in irons & soldering tools, but probably made in China to their specs now. S4140 is 40W, temp compensating professional tool. S4240 is their temp controlled soldering station to adjust wattage as desired, S4240R is the replacement iron for that station. Philmore has every configuration & size of tip you'd need.
    http://www.starkelectronic.com/pes4240.htm

    Other names are Weller [pro stuff preferred over hobby] or Wahl.
    http://www.starkelectronic.com/wahl.htm

    What we prefer for vehicle wiring are the piezo - flameless butane soldering irons requiring no power cord. Of course one must exercise care around flammables!

    For example: http://www.starkelectronic.com/nteirons.htm

    Or:

    125W 1,000*F -
    http://www.amazon.com/dp/B000ICGN38?tag=starkelect-20&camp=14573&creative=327641&linkCode=as1&creativeASIN=B000ICGN38&adid=0JFB7HNWNR87PK0RMB60&&ref-refURL=http%3A%2F%2Fwww.starkelectronic.com%2Fwhlpro.htm

    75W -
    http://www.amazon.com/Weller-P2KC-P...000WOHSHM/ref=pd_sim_hi_2/189-5912784-6491842

    Portasol - Made in Ireland 125W 600*F tip
    http://www.amazon.com/Portasol-0105...003H6NN2Q/ref=pd_sim_hi_1/189-5912784-6491842

    Whatever you're looking for, study the fine print on specs of course. Many end providers out there, these above just picked out of the hat. Be real careful with butane tools around your fuel system & vapors.

    Top quality solder & flux and pre-tinned wire can make all the difference in the world in your soldered connections. Just as important is control of the wiring system.

    Wire ties, shrink tube, wire wraps etc. are required in order to reinforce and prevent flexing of wires which breaks connections.

    Most often the soldered connection will break as a result of wires moving and flopping around or from extreme vibrations. This work hardens individual soft copper strands making them brittle, so that the strands break right next to the rigid soldered joint.

    Because copper naturally work hardens the less movement of wires the better, including while building looms, moving wire locations, adding new devices etc. Absolute minimum movement and a gentle hand plus super secure wiring really pays off.

    .
    #16
  17. XL-erate

    XL-erate Been here awhile

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    Another really important consideration is the Stripper and Crimper. I use Klein Tools.

    Unfortunately with out sourced mfg. the wire may not be what it's described as being. The actual diameter of half a dozen different brands of '12 gauge stranded copper' may vary considerably. Just picking the '12 ga' slot on a stripper is no guarantee that it's correct for the wire. Aslo there's two different types of strippers, one for Solid wire and one for Stranded wire! They're nowhere near the same outer diameter in the same gauge number! A practice run is needed to identify exact diameter, relative to the strippers in addition to knowing what tool you have.

    A close look at freshly stripped wire may reveal a very slight cut in all or some of the outside conducters, setting it up for premature failure. I'd rather work harder to use a larger stripper jaw and 'pull' insulation than get a quick strip that nicks the strands.

    Also important that the crimper fits the particular terminal as closely as possible. Some will over-crimp, damaging the conductors but its invisible inside crimped terminal. About the same as nicking them, they're crushed or scarred or whatever which again starts the work hardening, along with a weakened area of concentration right next to or inside opening of terminal.

    Proper tool for the job always applies whenever possible. I knew a guy out in the field that could strip wire and crimp terminals faster and better with a Klein Electricians Knife and standard crimper than anybody else could do with an automatic stripper! He got top bucks and was specially imported on the big jobs thanks to 35 years experience.

    Technigue is often lacking in electrical wiring simply because most guys rarely do it and haven't really studied the principals at work.

    .
    #17
  18. rmhrc628

    rmhrc628 Long timer

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    Hi guys

    Is there any guide on what gauge wire we should use when adding accessories ?

    Is 12 gauge the universal across all the brands ?

    I want to add in some wiring and can't seem to find what size wire is stock on my Hondas
    #18
  19. DRONE

    DRONE Dog Chauffeur

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    12 gauge? Whoa! That would be fine if you're adding a microwave oven!

    Frankly, most accessories on a bike can be fed just fine with 20-gauge or 22-gauge but that size wire is not robust enough for the physical abuse it goes through on a bike. Ya know, vibration, wind, rain, hail, rider fiddling, etc. I use 18-gauge for most everything, and bump up to 16-gauge for anything likely to pull 10 amps or more, like a horn or heated grips. Here's a typical AWG chart and you can see it says 18-gauge is fine for 3-foot connections up to 40 amps (that's 480 watts!)

    [​IMG]

    So, 18 and 16 gauge works fine, I'm also careful to use lots of wire ties to hold everything in place, and I wrap electrical tape around my wires if they are going to be routed over anything with an edge or corner -- to protect them from rubbing damage. But electrically, the amount of copper in an 18-gauge wire is plenty for bike accessories.

    The only exception I'd note would be the connection between the battery and a aux fuse panel, if that's what you plan on having. For a 60-amp aux fuse panel, I'll use 12 or 14 gauge, just for overkill.
    #19
  20. XL-erate

    XL-erate Been here awhile

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    There are a few things on a bike that can draw high current, like some light arrays and above mentioned heating items. An important factor I wanted to mention is to stay with the same gauge wire throughout an individual circuit. That is, to identify the existing wire and maintain that size, or be sure when creating a new circuit that all components are the same gauge.

    If you start out with 14 gauge and you're wiring something with a fairly heavy current draw, and you then patch in a piece of 18 ga or 20 ga between the 14 ga wiring and the new device, you've created a dangerous bottleneck. There's a chance of an electrical fire in the section that's smaller gauge because current is being choked down and it will convert to heat, which is the path of least resistance.

    Somewhat the same is true if you start out with 20 gauge, patch in a section of 14 ga, then install a device that can draw high current. The bottleneck is now at the other end of circuit, the beginning, but results can be the same: FIRE!

    In these cases you're actually better off from a safety standpoint to mantain a circuit in a slightly smaller gauge throughout, less chance of fire. As DRONE said, most bike stuff isn't going to draw huge current, but it's still important to maintain continuous wire size in any given circuit.
    #20