Extension Cord

I have a rooftop a/c on a TM 3124. I need to run an extension cord from the farthest reach of the power cord of the trailer to a 30 amp outlet 125 ft. away. The trailer power cord is 10/3 at 30 amps. If I run an extension cord 10/3 rated at 30 amps does anyone know if I will have a voltage drop that might hurt the a/c especially on start up? What if I used an 8/3 rated at 50 amps? Thanks for your advice .

[ShrimpBurrito]

I think I'd use either 8 gauge aluminum or 10 gauge copper.

If you pull 30 amps through a 10 gauge aluminum cord 125 feet long, you're going to lose about 15 volts. If you use 8 gauge, you'll lose 9.5 volts, which will probably be adequate, depending on the voltage of your source. Copper has less resistance, but is much more expensive. If you use 10 gauge copper, you'll only lose 7.7 volts.

I've found this site to be a nifty source for these sorts of calculations:
http://www.powerstream.com/Wire_Size.htm

Dave

[Wavery]

Just remember....you can't cheat Mother Nature....

If the distance from your AC to your power cord is 25' and the length of the trailer power cord is 30' and the distance to the outlet from the power cord is 125', you have a total run of 180' that would make the round trip 360' .

With 10AWG copper wire, that would give you a voltage loss of 10V and that's if all of your connections are perfect (which they aren't, I can assure you). You may expect an additional 2V loss through all of the various connections in this configuration.

That may bring you down to 108V (from 120V). This may still be within tolerances for your AC. It depends on your "Start-up" amps.