Backfeeding Generator Subpanel with PV solar

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This seems like such a simple question, but I'm unable to find the answer.

For a PV solar system, according to the NEC, on the main panel you can backfeed to 120% of specification. So 200 amp main with a 40 amp maximum backfeed. I can understand that. I guess it is also OK as an alternative location to the main panel to backfeed a 100 amp subpanel with a 20 amp backfeed too, if somebody for some reason chose to do that.

This inverter is set up to backfeed the main panel when the grid is up. It is also set up to output power when the grid is down, but over a different line. This alternative power will be output to a generator subpanel with a manual transfer switch. So the only way the inverter will supply power to this subpanel is when the grid is not supplying power. Also, there will be no ability to connect a generator to this subpanel, it will be strictly with the inverter.

So if it is a 100 amp generator subpanel, where in the NEC does it say that it is OK to backfeed (if that is the correct word) at 100 amps instead of limited to 20 amps as NEC says for a PV system?

To me it isn't any different than a generator supplying the power to the subpanel, but with PV the rules seem somewhat confusing.

George Stolz

Staff member
Windsor, CO NEC: 2017
Service Manager
Sub3marathonman, according to your profile you are not an electrician or an engineer. Therefore, I am closing this thread.

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