Bobbo wrote:
I agree. If you are going to run 4 wires, install the outlet and breaker that takes all 4 wires. Done once and finished.
That is what I did. I have a 30 amp RV. For now. When I ran my power, I pulled three 6g wires (black, red, white) and one 10g wire (green), put in a 50 amp breaker, and a box with 50amp/30amp/20ampGFCI outlets and breakers. I will never have to touch that wiring again, no matter what I may buy in the future. It did not cost THAT much more to do than a straight 30 amp setup would have been.
(While doing this, I also ran a second conduit and installed a separate box with telephone line and satellite/cable coax. Like I said, done once and finished.)
This is only code compliant is you have a 20, 30 and 50 amp breaker at the box at the trailer. Otherwise you could overload the 20 amp and 30 amp between the trailer and the box.