David, here's PART 2: HOW TO DO IT
WARNING! A REAL ELECTRICIAN SHOULD DO THIS, NOT SOME DUMMY LIKE ME.
#1 DO IT SAFELY AND HAVE THE SYSTEM BE COMPLETELY FOOLPROOF AND SAFE.
#2 See #1 above...
1. Find a suitable DPDT relay with 115 vac coil WARNING! MAKE SURE THERE IS A LOT OF CONTACT SPACING SO THAT BOTH CONTACTS OPEN BEFORE ANY CONTACTS CLOSE. This relay has to be rated for the high startup current from the A/C.
2. Disconnect the incoming shore power cable from the main circuit breaker in the load center.
3. Wire the incoming shore power through a suitable circuit breaker to the relay's Normally Open contacts (IMPORTANT). and also connect the shore power to the existing converter if you wish to keep it. You really can't feed the converter from it's existing circuit breaker because it's also tied into the breaker box common bus. You can just leave the existing converter breaker in place disconnected.
4. Wire the relay's Normally Closed contacts to the output of your inverter.
5. I THINK you can just wire the relay's armature (moving contacts) to the same input circuit breaker which was connected to shore power. An electrician should figure out what amperage the breaker should be rated at. Fortunately the inverter will have it's own overcurrent protection built-in.
6. Ask an electrician if it's ok to tie all the grounds (green wires) together at the load center.
1. As you said, the inverter needs to be pretty close to the battery, or the 12 vdc cables must be really large gauge. I'd guess that the wire gauge and length should be such that you lose less than 0.5 vdc at maximum current draw.
2. The inverter would fit under the fridge in place of the original converter, I'd think. BUT if it generates more heat than the converter, that might be problematic. Also, the inverter will have a cooling fan which might be pretty noisy. Mounting the inverter on the tongue would be better for heat dissapation and noise, but the on/off switch would net be easily accessable.
3. Wherever the inverter is, you would like to have easy access to it's on/off switch, as you would want to shut it down overnight to save battery.
4. Sounds like this would require a whole lot of battery power, so you'd want to calculate how many amp-hours of battery you'd need for a weekend.
YOUR MILEAGE MAY VARY, CONTENTS MAY HAVE SETTLED IN SHIPPING, BUYER BEWARE..... CONSULT AN ELECTRICIAN TO BE SURE THIS IS SAFE.
I hope it works out for you! Let us know how the project progresses!