Re: wire size
jioman-wire temperature ratings are one of the first thing an electrician learns. If you are installing a luminaire, er fixture, that requires 90 c wire, and you only have NM, not NM-B, you will eventually cause the NM wire insulation to overheat and fail. You should either install a different fixture, or get a qualified electrician to help. I have had many of my students tell me horror stories about melted and damaged NM in homes with incandescent fixtures due to heat.