This question is about whether "circuits" can be grandfathered if the breaker or panel is changed but the circuit is otherwise not disturbed.
Code is NEC 2017. My existing main panel has plenty of ampacity but few spaces, and thus, is totally full. I have several potential paths for an upgrade.
One involves fitting a subpanel and moving 4 circuits (2 double-stuff breakers) there, and adding circuits there.
The other involves outright replacing the main with a very fine 60 space main panel. No more space problems!
But what happens with AFCI and GFCI requirements? If this were a new house, nearly all my circuits would require it, but I am grandfathered. Will the "new main" scenario void the grandfathering and require that nearly all circuits be upgraded to that protection? Or can I just move over my old breakers and call it good?