I have a question about sizing a feeder. For sake of discussion, assume a 100 amp sub-panel within 40 feet of the service panel. The ampacity charts say #3 copper or #1 aluminum but I read somewhere that indicated that as a feeder the size could be smaller. Of course, now I can't find the reference.
And while I'm asking and given most of my experience involves conduit, what cable types would be acceptable for wiring said sub-panel.