Have you experimentally verified this? What is the control mechanism used, i.e. how does it do that?
For that matter, when multiple PWs are running off-grid, how do they interact--is one of them running as a grid forming inverter, while the others stay in grid following mode? If that's the case, I could see it working as you describe. The Gateway and the grid forming PW would just need a protocol for confirming that the Gateway's local side of the MID is seeing the AC the grid forming PW is creating.
Cheers, Wayne
You pose a good question I could not answer because I didn't fully know. I could turn off my main breaker, then one of my 5 powerwall breakers and verify for myself. (goes and verifies)
Interesting result, and you are right again Wayne. If a system was in backup mode, any single breaker disconnected from the bus (or turned off) is still live from the Powerwall end of the circuit. I just tested with my system in backup mode, and turned off individual breakers. There was still 240 vac being created at the Powerwall side of the turned off breaker.
This is interesting and good to know, that unless all of the Powerwall are shutdown at once any number shutdown that is less than the total could remain energized from the Powerwall end of the circuit, despite a breaker in the off position.
Slightly disturbing, and one more reason why adding a button to shut all of them down at once is much better. I did confirm that this button trips the internal relay and disconnects all ungrounded conductors in the Powerwall(s).
I have to say now that I was wrong, and I think the Powerwalls need a breaker retainer as well, though I still think the code doesn't require them. Good thing the Gateway 2 internal panelboard retains the breakers as a standard.
Not sure what the retaining clip looks like for the BR1224L400R but I think it is designed to be at one of the 4 corners of the distribution bus, at least that's what my notes say. It could be there is a different retainer for a 30A breaker besides the BRPHDBJ2 and the BRPHDBJ needed for larger breakers depending on where on the bus they are located.