I use that exact adapter(yellow one) when we are at a park that only has 50 amp service on the pedestal. Since I have 2 shore cords, (one for my 2nd a/c, and one for my standard 30 amp shore cord) I plug my 30 amp shore cord into one of the 30 amp plugs of the adapter (which is protected by the main breaker 30 amp circuit) and I plug the 2nd shore cord(for my 2nd a/c) into the 2nd 30 amp plug on the adapter (using the 30-20 amp adapter). My 2nd shore cord is protected by its own 20 amp circuit breaker. Works GREAT