50 Amp Service has to be 240v
Since I'm not aware of any 240 volt requirements in an RV (such as for a clothes dryer outlet), I had been wondering if it was ok to just bring in two 120v, 50-amp circuits. It seems like nothing in the RV would know the difference.
I figured out why that is NOT an acceptable approach.
In summary, it's because the neutral wire in your RV isn't sized for 100 amps of current.
In order to maintain 50 amps or less in that neutral wire, it's necessary that the two circuits have opposite phase across that neutral. This means that when one circuit is moving electrons into the neutral, the loads on the other circuit are taking at least some of those electrons out of the neutral. Neglecting minor phase-shifts (which happen when motors are involved), if each circuit is drawing 30 amps, the current in the neutral wire back to the pedestal has zero amps. The worst-case current in the neutral occurs when one circuit is pulling 50 amps and the other is pulling 0 amps.
I just thought this was interesting. I wonder if any of the "surge protection" devices actually check that there is ~240v between line-1 and line-2, because that is really important! I think I'll find out.