wa8yxm wrote:
How about this.. Put a 50 amp outlet in that box. Feed it with the 30 amp breakers and wire.. Then you use a dogbone to plug in the RV, but if you ever get a bigger RV... Well my 50 amp rig, if you are just a little careful.. gets by just fine on a 30/30 120/240 volt outlet.. You just need to be a little careful is all, and to know what is on each leg,
But that might be the best use of your existing resources and will counter those code talkers in this thread since you will be delivering all 4 wires, properly to an outlet more than heavy enough to take what 30 amp berakers can give 'em.
Mixing components in a circuit of different ratings and capacities is a bad idea at best and a disaster at worst. The OP needs to run either a 30A service with 30a breakers and #10 wire, or a 50A service with 50A breakers and #6 wire