NEC 230.71 PANEL

[cola]

I have a Eaton 400 amp HP404040SHF W/split mains in Riverside County California.
I'm using the second sub breaker @ 150 amp. Back feed only from solar and 15kw batters. (grid tied)

230.71(B)
In general, a service should have a single disconnecting means.
However, one set of service entrance conductors is permitted to
supply two to six service disconnecting means in lieu of a single
main disconnect. Both single-occupancy and multiply-occupancy
buildings can be provided with one main service disconnect or up
to six main disconnects for each set of service-entrance conductors.
Conductors from renewable energy sources, such as photovoltaic
systems and wind generators, are feeder conductors.

Would this still be a non-compliant install.

 

[jaggedben]

If it's an existing service the AHJ may or may not give you grief. The 2023 NEC has an exception that explicitly allows this, but the 2022 California Electric code (based on the 2020 NEC) does not, so if the inspector wants to be a jerk about it then they could be a jerk about it. You may want to make sure the customer agrees to the cost of a backup plan, such as a 'Hawaiian Tie-In" with a new subpanel on the existing feed, or a load side tap.

If it is a panel that's being installed as a new service panel then you should probably find another plan.