Wow, spent the afternoon searching the archives re 100A subpanel. Bazillions of posts, opinions, and interpretations, but no consensus, but the safe way(s) to go are either:
1) Install 90A cb on feeder panel for #4 CU;
2) Use #3 CU.
(BTW, I plan on THHN).
Question about option #2- the neutral & grounding bars on the main panel are only rated for up to a #4 CU. What do I do with my grounded & grounding wires if I use #3?
Yes, I've removed the bonding jumper from my sub. Will make sure that neutral bars get only grounded conductors, and grounding bars get only grounding counductors.