House power is normally 120/240/120 volt at 100, 150 or 200 amps.
What that 120/250/120 means is you have 3 (+safety ground) wires, I will call them L-1, N and L-2 L-1 to N=120 L-1 to L-2 = 240, N to L-2 is 120 again.
RV power comes basically in two sizes
30 amp: This is 120 volts, at 30 amps Pick an L and Neutral (Plus safety ground) and that's it. only 30 amps though
50 amp is identical to the house, save for the 50 amp breaker.
NORMALLY there is either nothing in the RV that needs 240 volt or just one thing, that one thing is a device that determines (Automatically) if you are on 30 or 50 amp (or at least tries to) it is called an Energy Management System by some companies (Intelletec for example) Other companies use that name for other stuff.
But all it uses the 240 volt is sensing a 50 amp supply. If it does not see that it assumes 30 amps.
