Originally Posted by mitiempo
There is no reason to over-complicate this.
The inverter has a built-in transfer switch so it makes sense to use it.
There are 2 ways to easily wire it, one good one excellent.
1. Shore power to main double pole breaker. Remove jumpers from double pole breaker and run output to inverter input. Run inverter output to main panel hot and neutral bus. On shore power the panel is fed from the inverter's pass through. The downside is that any AC item on the boat can be powered by the inverter when away from the dock, such as the water
heater, so it is important to make sure high draw items are left off.
2. Shore power to main double pole breaker as normal. One 15 amp breaker on the panel is wired to the inverter input along with the neutral. The inverter output goes to a small sub-panel that is only composed of the items desired to be powered when away from the dock, typically the AC outlets. Away from the dock only the outlets can be powered by the inverter. The inverter can be turned off with it's own breaker. This method has only the downside of the cost of a small panel for the outlets.
My installation is for an inverter/charger, not just an inverter. It is not a common thing to find and not recommended for the majority of boaters, and certainly not for someone who is not experienced with AC circuits.
It is possible to damage most inverter/chargers by "backcharging" them via shared neutral - when the AC and input and output of the inverter are not separated. The many boats that I wired with split panels
I cut the main hot bus on the main AC panel so that the loads were separated by whether they were powered by shorepower or by the inverter. The neutrals have to be kept separate as well.
Just because something has a feature is no reason to use it. However, the transfer switch can really simplify the installation and most people would probably use it. It's drawback is that the inverter and its transfer switch has to work to have any AC on the boat. I had to remove many a unit off of customers' boats to get them repaired and to keep AC on the boat the incoming AC had to be connected to the AC out on a temporary basis.
That is the reason I wired my boat the more complicated way. I can use shorepower to power the Main AC panel and still send AC In to the charger function on my I/C. The AC Out of the I/C is disconnected so that forgetting to turn off all AC in the winter won't lead to dead batteries from space heaters/dehumidifiers left on from AC outlets if the inverter switches on. I try to keep it turned off but it requires constant checking and I have left it on at times.
Splitting off high current
loads, like water heaters, air conditioners, etc., can still be done but that is a separate issue.
My more complicated setup is so I can have AC to the main panel even if the I/C or its transfer switch dies without doing any rewiring at the I/C. This rewiring is minor so this is a tradeoff of complexity and cost for convenience. Most boaters will not want to do this but some might.