...voltage drop is not related to I^2, rather just I. Power dissipation in the wire is usually not a problem.
Hi DDW,
I think you misunderstood my point -- I'll take the blame for that.
It's true that voltage = current x resistance, so voltage drop is proportional to resistance and current...but
voltage drop is not the problem here. The problem is
power loss in the wiring.
Power = [current^2] x Resistance (aka I-Squared-R)
The power dissipated in any circuit is equal to the current
squared times the resistance. Hopefully there is no argument here. This is true for a simple resistor, and it is true for a wire as well. Therefore, wiring size is dictated by
I-squared-R (which is why power losses in wiring are called "I2R" losses).
You don't need a BSEE to prove this to yourself. Download any wire sizing table from anywhere you like (ABYC, etc.) Next, size the wiring for any load you like, in
watts (recalling that watts = current x voltage). Finally, look up the wire size on the table.
The Blue Sea Systems Circuit Wizard app (for Android or iOS) makes this really easy.
Circuit Wizard - Blue Sea Systems
You will find that (for example):
1) 4,800 watts @ 24V = 200A, and this requires AWG #2.
2) 4,800 watts @ 12V = 400A, but this requires AWG 0000.
That's a savings of
five AWG sizes difference for the same 4,800 watts... just by doubling the voltage!
If you're really interested, check the AWG standards tables and you'll see that the
weight of the copper in AWG 0000 is more than
four times the weight of the copper in AWG 2.
Worldwide...the trend overall is toward higher voltages, because this means less copper is needed. When you double the voltage, you reduce the copper needed by 75%. Yes...this is eco-friendly.
Just for fun, carry this forward to 240V, you will see you only need 20A to deliver 4800 watts...and now you only need AWG 16 wire to supply a 4800 watt load.
Now...in case you ever wondered why almost every country in the world (except the U.S.) uses 220-240v instead of 120v...it's because it needs only 25% as much copper to deliver the same watts.
For you techno-historians out there, it's Edison vs. Westinghouse all over again....
Edison vs. Westinghouse: A Shocking Rivalry
Are we having fun yet?