[Bob Landry]

OK, I'm confused. The OP said he had a 50-30-30 cheater box but the 20A breaker at the pedestal was tripping. My interpretation of that box would be that you plug it into 50A service and it splits each leg to provide two 30A services to the trailer. If that's not the case, then it's not a 50-30-30. Also, why would he be trying to plug a 20A cord in a 30A service? You would not be able to plug the 30A cord into the 20A outlet without an additional adapter. I think I have read of splitters that combine a 20A & 30A service to provide one 50A, but that would only be one 50A leg, not two like you would get with regular 50A service. I personally would not ever depend on one of those to work. The two outlets may not be in perfect phase, you could get a voltage drop from the difference. If they work, great, I just don't see how they do it.