I recently installed a Xantrex Freedom 10 (1000 watt) Inverter/Charger. The installation calls for another breaker box for a total of two.
(1) The main breaker box has two breakers, on 20amp breaker for the Air Conditioner and another 15 amp breaker for the Inverter/Charger INPUT.
(2) The secondary breaker box has one 15 amp breaker for the Inverter/ Charger OUTPUT which feeds all of the 110v electrical outlets in my Sovereign
The Freedom 10 Inverter/Charger has a built in relay. When the relay detects 110v current it passes the current directly to the secondary breaker box feeding all of the outlets in my trailer. As you can see, there is no way to feed the Air Conditioner via the Inverter. I never use the Inverter for the microwave or the wife's hair dryer (I use the genny for that). Pictures of my installation can be found in my blog.
The Freedom 10 is also an effective charger, putting out 14.45volts and 50amps. I have large 2 guage cables connecting the Inverter/Charger to my batteries. It works much better than my old Magnetek 55amp charger.