Your coach may not be wired like mine, but this is how mine works. The batteries are the sole source of DC power. The inverter/charger keeps the batteries charged. I have a house fuse and a self resetting circuit breaker between the house batteries and the DC fuse panel.
Here is how my batteries are wired. You should take a photo of yours and share it here so we can verify the connections. Also, you can test for voltage from ground to the post where your positive house cables connect. You should measure 13-14v.