Using a generator interlock on an essential loads panel


New Member
Jun 3, 2022
New York
I am looking at installing a grid backup solution with or without PV attached, and noticed that many schematics show an inverter bypass circuit to operate the essential loads panel as a normal subfeed in the event that the inverter is down.

Since my main panel is a Square D Homeline, I was thinking of installing a subfeed in the same type. The main breaker of this subfeed would then be the load-side of a hybrid inverter, which would interlock with a direct connection to the main panel.

Is such an arrangement necessary, since the inverter would most likely detect grid on the load side and throw fault?
What circumstances does code usually allow these interlocking plates? It seems to me like it would be too easy to defeat compared to a dedicated double pole double throw transfer switch that physically cannot have both main and aux connected at the same time.

For overall system, I plan on installing at least 1500w of grid backup capacity. My roof can support around 9kw theoretical, but is not north-south aligned like many buildings and so probably won't yield more than 6kw actual. If I do allow the inverter to export to the grid side at all, I plan on using CTs on the incoming service for meter-zero mode when conditions are favorable.
Western NY with National Grid by the way, which adds even more overhead to the setup if I did attempt meter-zero. I have little interest in net metering due to the ripoff rates offered.