I had a 75 foot 12 gauge extension cord running to my RV and did the 120VAC to 30 AMP to 50 AMP connections. Had the RV plugged into this configuration during the entire off-season and ran the AC, TV, DirecTV wireless modem system, DVD player, and the RV's 12 volt system with no problems what so ever.
Just make sure that the 120VAC connection from the house doesn't have anything else drawing off that circuit. Since it is tripping, it may be that you're running something else off that circuit that is exceeding the breaker. Also, make sure it's a 20 amp circuit, not a 15 Amp. If it is 15 amp, you're AC's peak draw (normally on start-up), might be exceeding 15 amps.
