A couple of suggestions:
1. Use copper wire.
2. Both Lowes & Home Depot sell a weather proof metal box with the 30 Amp outlet already inside the box. Made for RVs @30 amps and 120 volts
3. Spoke to Tiffin Motor Homes yesterday and a local RV park owner. All 30 Amp RV outlets are 120 volts.
4. You should also consult with someone that knows about voltage drop. If the 30 Amp outlet that you are going to plug your RV into is over 100 feet away (the distance between the fuse block and the plug you may need to increase the wire size to more than a # 10 gauge. The longer the
distance between to fuse panel and the motor home the greater the chance that your voltage will drop below the 115v to 120v needed to run your appliances such as refrigerator, tvs, microwave, heat pump etc and you could burn them out.