Electrical Wiring: Amps vs Wire Gauge

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.

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

 Ron_Ces 11-08-2012 07:04 PM

Quote:
 Originally Posted by dholaday (Post 20003136) 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 11-08-2012 07:14 PM

Nice! Thanks.

 DaveStockwell 11-08-2012 07:57 PM

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.

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

 XL-erate 11-09-2012 02:32 PM

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 11-09-2012 02:52 PM

[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 ? :lol3:lol3

 XL-erate 11-09-2012 03:28 PM

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 11-09-2012 03:39 PM

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 11-09-2012 04:43 PM

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.

 XL-erate 11-09-2012 08:16 PM

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.com...Wire&page=GRID&

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

http://www.iboats.com/Primary-Marine...view_id.216631

 davebig 11-09-2012 08:29 PM

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 11-09-2012 09:20 PM

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!

 Bobmws 11-10-2012 05:31 AM

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

 DRONE 11-10-2012 10:09 PM

Quote:
 Originally Posted by XL-erate (Post 20011749) 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?

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