After we built our new home in northeast Texas, I built a long level concrete RV pad with full hookups for friends and relatives to park their RV when visiting us. Along with water and sewer connections, I installed a 30-amp and a 50-amp RV electric receptacle box In the attached photo, the box on the left is a 50-amp connection and on the right is a 30-amp. I wired the 50-amp with 4-gauge and the 30-amp with 8-gauge wiring in separate conduit and on separate circuits. In addition to being wired with a ground back to the main circuit breaker, each of the RV outlets are grounded to earth with a ground rod at the post. The main circuit breaker box is about 30 feet away and mounted on the service entrance meter pole.
Bill