Minimum Wire Gauge Requirements

[2Big4a3Series]

I am running a pair 15A and 20A circuits in my car for additional accessories using 14 and 12 gauge wiring respectively based on my knowledge of of 120VAC household/commercial electric service.

Does the same principle apply for 12VDC as well or could I get away with smaller gauge wiring being that the voltage is lower?

[archemedes]

same basic principle, I prefer to go a bit bigger myself just so I don't have to run a new line when I decide to add a circuit to it. Voltage isn't what will do damage , amperage will.

[twistednut]

The 15 amp = #14 wire and 20 amp = #12 wire doesn't apply in this case. Maximum ampere ratings for wire are based on table 310.16 of the NEC. But, you are probably going to be using cheap ass wire from Napa so it's ampere rating should be based on table 402.5 To figure out the size of wire you need use Ohm's Law, P=IE. P=watts I=amps E=volts.
#18, 6 amps 6x12=72 watts
#16, 8 amps 96 watts
#14, 17 amps 204 watts
#12, 23 amps 276 watts
#10, 28 amps 336 watts
If you are only going to use the accessories while the car is running you can use 14 for the voltage multiplier.
Because you are dealing with a 12 volt system try and keep your wire runs less than 12" and ground the accessory as close as you can to the body otherwise you will have to deal with voltage drop.

[2Big4a3Series]

Thanks! This is exactly what I needed to know. :up: