Airbag wiring kit

[fixit-p]

14 ga. is too small, at 30 amps and just 10' of wire the voltage drop is 1.5 volts at 15' it's 2.3 volts (too much resistance) 10 gauge would be better or 12 gauge for short runs.

[crakarjax]

Originally Posted by fixit-p

14 ga. is too small, at 30 amps and just 10' of wire the voltage drop is 1.5 volts at 15' it's 2.3 volts (too much resistance) 10 gauge would be better or 12 gauge for short runs.

Not quite true, for 14 gauge at 10' and 30 amps the voltage drop would be 0.774 volts.

However, since the compressor will never reach 30 amps (peak 23 amps -- probably will happen only upon startup, as the 150psi amperage is actually less than 19 amps) the actual PEAK 10' voltage drop that you can expect with 14ga wire at 10' is about .6volts, at 15' .9 volts. For continuous duty, to voltage drops are .5v and .73v.

source: http://www.stealth316.com/2-wire-resistance.htm

Now, the question here is really, "what is the allowable voltage drop for this compressor?" The part we need to worry about is the DC motor.

So to reiterate what we care about:
- MAX 19 amp continuous
- MAX 15' wire run
= .73v drop at 14 AWG
= .3v drop at 10 AWG

So yes, you will end up having a .4v increase in voltage at the compressor with 10AWG vs 14AWG. The difference is a 2.5% voltage drop vs. 6% voltage drop. Typically 6% is acceptable and that's why 14AWG is acceptable -- keep in mind this is a 15' run, which is really not going to happen. I will probably go with 12AWG myself, since 12 gauge speaker wire is very readily available, and I have a 150' spool left over from wiring my home theater speakers.

[fixit-p]

I used the calculator on here yesterday http://www.powerstream.com/Wire_Size.htm it was linked in this thread yesterday but not today. I don't know what assumptions went into the calculator but according to ohms law your figures are correct but either way it still confirms that bigger is better 6% as opposed to 2.5% voltage loss