bdosborn wrote:Joe G wrote:
I made a few wire gauge charts to use at work, and thought I'd post them for the benefit of everyone here as well.
Joe G
30 Amps through an 18 AWG wire? Your chart looks badly undersized, what kind of wire are you using?
Bruce
Keep in mind that would be for a run of no longer than 5 feet - the first chart (10% voltage drop) is based on the recommendations of my wire supplier (Waytek). Their 18 ga. has a resistance of 6.9 ohms per 1000 ft, so that's 0.0345 ohms in 5 feet - 0.0345 ohms at 30 amps would drop the voltage 1.035 volts or 8.6% in a 12 volt system. According to them, that's within industry accepted standards. In fact, according to that, you could go as high as 34 amps for 5 feet.
I agree with you that 18 ga seems too small for the job, and a 10% loss is a lot, so that's why I use the second chart (5%) which calls for 14 gauge for a 5 foot run at 30 amps.
The charts show what a dramatic effect the length of the wire has on it's ability to carry current.
I use high temp polyethylene coated (GXL) wire, but these charts apply to vinyl coated wire as well.
I know you know your stuff, Bruce. You do fine work and I respect you for that. I'm not in any way trying to be combative here. I just wanted to let you know where I'm coming from on this.
Joe G
P.S.
I encourage you to check my math on this, because I have been wrong before. If my figures are incorrect, I will gladly revise the charts immediately.
Here is the data I was working with:
Wire resistance per 1000 ft:
18 ga = 6.9 ohms
16 ga = 4.7
14 ga = 2.8
12 ga = 1.8
10 ga = 1.1
8 ga = 0.7
6 ga = 0.4
4 ga = 0.3
2 ga = 0.2
amps x ohms = voltage drop