Breaker Keeps Tripping

Hello,

I have a 27' travel trailer, and the circuit breaker supplying power to my water heater and microwave keeps tripping.

When I hook up to shore power, the breaker trips right away, and I cannot reset it because it will trip again. I have unplugged the microwave, still trips. I replaced the on/off switch on the wall, still trips. I replaced the circuit breaker as well and it still trips.

This is occurring plugged into two different 30 amp plugs; the campground and a buddy's house. When camping, I played around resetting the breaker and the on/off switch (switches from microwave/off/water heater), and I blew the pedestal breaker. Resetting the pedestal breaker only tripped the trailer breaker, so I just left it tripped during my last outing.

During my troubleshooting I disconnected the battery to cut out that variable. When on battery power, the hot water heater does not work at all.

I am now not sure what it could be. The converter? Any help you can provide would be greatly appreciated.

Thanks!

Jeff