Some good, and not so good, responses here.
The RV 50 Amp service is limited to 50 Amps of current total from each branch as supplied by the service entrance.
The supplied voltage is split phase 240 Volts - each voltage is 180 degrees out of phase with each other and equal in amplitude.
This is accomplished by the transformer neutral which center taps the 240 volts and provides the return path back to the service entrance - the neutral always carries the difference current between the 2 branch currents.
If no neutral exists, and if the 2 loads are unbalanced in reference to their current draw, then each 120 V branch will assume an unknown voltage due to loading with the sum of the 2 voltages equal to 240 volts. This is very bad...
The ground connection back at the service entrance is not designed to carry current and will not balance the voltage when the neutral is disconnected.
You must run a 4-wire circuit or you run the risk of serious equipment damage and/or shock...
