The circuit breakers on the inverter will monitor and trip if overloaded as you have found out. This will occur in pass through as well as invert. Do you know if you have more than two "Romex" cables connecting to the inverter? If there are three, then you have the model with one line in (30 amp) and two out. There should also be two breakers. One can be 20 amp and the other can be 15 amp.
Mike, RVIA & RVSA Certified Master RV Technician
Amy, Dr. Assistant - Roxie & Mei Ling, four legs each
2000 Gulf Stream Scenic Cruiser 450 hp & 1330# torque
06 Saturn Vue, 06 Chevy Z71 4x4 & 2014 Corvette Z51 M7