I have a question based on the layout in Post #3 above. If the inverter goes out, you would switch to to the grid using the transfer switch. It looks like the grid input on the inverter would still be hot based on the polaris tap connection. Could that introduce any backfeed that might further harm the inverter?
I couldn't find a polaris connector for use with 4/0 wire. Does anyone have a link to this or perhaps another brand if there is not one from polaris?
I might be able to get some Southwire 4/0 4/0 4/0 2/0 feeder cable (MHF) for about $2.50 per foot. I was thinking of using this for running between switch, fuse panel, inverter, and tap connectors (original SER cable will still come in from the meter). Any issues with using the MHFcable in this case. MHF can be used inside provided it is in conduit.