I think I found a case where I NEED to turn OFF power assist when using a generator (shore power) to ensure our vans RCD's connected to the inverters AC out, continue to function.
1) Obviously when on inverter the Multiplus II turns ON its MEN's relay so our vans RCD safety switches function as normal.
2) Shore Power (GRID) aka caravan park.
Even with power assist ON and working, The Multiplus sees the shore connection and correctly assumes its using the shore power (grid) Earth and so MEN's relay OFF and RCD safety switches function as normal
THE PROBLEM
When we plug our generator into our vans shore power connection the inverter will assume its grid shore power and so turn OFF the MEN's relay thinking there is a shore power earth.
This is actually fine as I have a 16A RCD safety switch on our shore power connection BEFORE the inverter feeding shore power to AC IN and it's a special product that does trip the RCD even when on generator. It's made by a company called PowerSafe and called an RCD DUO.
The issue is if I turn ON power assist while using the generator.
I assume the Multiplus thinks it has a shore power earth, and so if power assist kicks in all the vans RCD's coming off the Multiplus AC output will NOT have an inverter MEN's, rather the multiples assumes a shore power MEN's earth and there is not any earth as its the generator plugged into the shore power connection.
So in this case if a fault occurs the 16A shore power "PowerSafe RCD DUO" should trip which will disconnect the generator (shore power), but the inverter will continue to operate and the vans RCD's will not trip. Now as shore power was just disconnected, the multiples I assume will now turn ON the MEN's relay and now the vans RCD's will trip.
BUT not too sure all that delay helps the person being shocked.