Can A 30A MH Plug Into A 50A Outlet (with a plug converter of course)

[Kiawah]

The purpose of a circuit breaker, is to protect the downstream wiring. The problem you will have, is you are connecting a 30 amp wire to a 50 amp protector. Will it work electrically to provide power, yes. Is it safe to protect a fire in that cable, no.

Your coach circuit breaker box would have a 30 amp breaker, so under normal circumstances that breaker should trip if you try to draw too much current. However, the wire from the breaker box to transfer switch, the transfer switch, and then shore power cable and connectors are only capable of 30 amps. Any problem in those three areas, they could burn up.

If you're going to do this on a regular basis, you should build a 50 amp male plug, a 50 amp rated wire, a 30 amp circuit breaker, then a 30 amp female socket.....in a waterproof box. Alternatively you can build that in your coach and use a 50 amp shore power cable to the coach. The Advantage to this last alternative, is you now would also have the second 120v leg at the coach to use for other purposes if you wish.

[Isaac-1]

While it is sort of true that the purpose of the breaker is to protect the downstream wire, there are few situation where a 30 amp 10 GA cord plugged into a 50 amp breaker is any more of a fire hazard than a 6 GA 50 amp cord would be. The 50 amp breaker will trip nearly instantly if there were a direct short in either size cord, only overloading over a period of time would make a difference, and with a 30 amp main breaker downstream the chances of this are slim.

A lot of what a breaker does is prevent damage to insulation cause by long term overheating of a wire that is drawing more amps than it is rated for and in this case that downstream 30 amp main breaker will tend to prevent the vast majority of things that would cause this.