Originally Posted by Jim Bennett
I am curious as to what loads you expect to want #10 wires, and are the outlets rated for 30 amps?
The AWG 10 request is more about voltage drop over the length of the wire.
I requested AWG 10 for the 12 volt drops after reading a report of some plug in inverters having problems using AWG 16. See Plug in inverter
The inverter that I might get, if I ever need it, is the 200 watt Wagan EL2600 Elite. I read the manual on this inverter and found that it will give an audible alarm if the voltage drops to 10.5 volts plus or minus 0.5 volts, so in theory it could sound an alarm if the voltage reached 11 volts.
My farthest outlet at the front of the trailer on the upper cabinet is about 21' from the converter. At that distance, with AWG 10 wire and 20 amps, the voltage drop is about 0.42 volts. The lead acid batteries should reach 11.42 volts when they are about 75% discharged. If the batteries are more discharged that that, the alarm could sound. I consider this level reasonable.
AWG 16 wires have significantly more resistance, in fact almost exactly 4 times the resistance of AWG 10. This leads to a drop of 1.68 volts in the same conditions. The battery would have to be above 12.68 volts in order to see more than 11 volts at the outlet. This is about equal to the full charge voltage of a lead acid battery, which isn't going to work very well.
Also, with AWG 16, the wires are wasting about 13% of the power being provided just to heat the wire when drawing 20 amps. Your battery is effectively 13% smaller if this is your main load. With AWG 10 that reduces down to a little more than 3%.