Electrical Wiring: Amps vs Wire Gauge

[dholaday]

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-vo...gauge-amps.htm

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

[Ron_Ces]

Originally Posted by dholaday

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-vo...gauge-amps.htm

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

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

Ron

[Mechanista]

Nice! Thanks.

[DaveStockwell]

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.

[XL-erate]

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.

[davebig]

[QUOTE=XL-erate;20009218]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.

I think you are so right and quality of wire is also a real issue as its hard to find it retail, I hang out in a welding shop all winter with a guy who repairs welders and is an excellent electronics tech. The reason long battery cables end up 4 awg are wholesale welding supplies are only ones with decent affordable cable.Motorcycle harnesses are much better than they where a decade ago http://www.easternbeaver.com/ helps allot also, I'm a Ducatisti in another life I never expect to see 12v to the headlight circuit that's 4 yrs old ?

[XL-erate]

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.

[davebig]

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

[grisezd]

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.

[dholaday]

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

[davebig]

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

[XL-erate]

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!

[DRONE]

Originally Posted by XL-erate

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!

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?

[XL-erate]

Originally Posted by DRONE

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?

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/O...Irons__23.html

Eclipse [MADE IN CHINA] has a dual wattage iron station for their irons: http://www.minute-man.com/acatalog/P...ing_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?...m%2Fwhlpro.htm

75W -
http://www.amazon.com/Weller-P2KC-Pr...912784-6491842

Portasol - Made in Ireland 125W 600*F tip
http://www.amazon.com/Portasol-01058...912784-6491842

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.

.

[XL-erate]

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.

.