Finished installing today and all is working as expected. The fridge was a little bit of a bear to get in as the sidewalls for the fridge opening were not 100% straight (vertical) and it was getting tight at the top. The fridge is 23 1/2" and the opening is 24" at the bottom, but closer to 23 3/5" at the top. I was worried I might pop out the top horizontal support of the cabinet, but wife just said give some more umph.. I did a few times and it got in. Thinking about it now, she had nothing to loose at it would something for me to fix..
I don't even really need to secure it down its so tight, but I'll still put something in place.
I used the existing DC battery wires (4 awg) leading to the existing inverter (1000W) and connected them to the new 1500W inverter. I pulled the fridge 120v circuit from the breaker panel and combined it with the existing 14-2 romex feeding outlets originally tied to the inverter/transfer switch. So now the transfer switch feeds the original outlets (which was way more than I thought; each side of the master bed, both bunk beds, under dinette and above cab) and the fridge 120v outlet. I plugged the transfer switch into the new inverter. I also added a switch to the fridge circuit/outlet as we don't always use the fridge. This way we if we need an outlet (turn on inverter) we don't have the draw of the fridge. I also added a 30amp breaker between all the outlets powered by the transfer switch and the transfer switch itself. I could go lower, but its what I had on hand.
Getting the new inverter arranged was painful. Its 2x the volume (size) of the previous. I had to pull a laminate side off in the storage area to get it to fit and moved the transfer switch over to opposite side.
The RV has OEM Precision Circuits power manager. There is a power monitor/relay in the 120v breaker panel. The 30amp shore feed goes through the monitor, picking up amperage usage. The water heater/fridge hot side connects to relay posts on the front of this monitor. The unit has relays so it can turn off the outlets if power usage gets too high. I removed the hot water from the monitor and connected the hot directly to the breaker. The biggest part here was keeping the power monitor working, which shows 120v shore power amp usage on the front panel. Very helpful determining what can be run simultaneous but still keep total amps under 30 (or 27 for that matter). Relay pic is before I removed the circuits. It still needs a hot and neutral (L1/N) to monitor amp usage.
I tested everything out and its working as expected. Pop the breaker for the shore power and the transfer switch kicks over to the inverter without any fridge flicker. Turn the breaker back on and a few seconds later the transfer switch goes back to shore power.
Now I just need to monitor power usage and confirm. Today I saw 1 amp draw on 120v and 60W on 12v/inverter. Seems a little low, but I could hear the fridge running and it was cooling. Perhaps the compressor was not running 100% since I was turning things off/on while testing or not. I'll leave that testing for another day where I can sit and watch.