NM vs. NM-B Cable: Ampacity, Code Rules, and Selection
NM and NM-B cable look similar. Both are non-metallic sheathed cables used for dry indoor wiring. Many project teams treat them as interchangeable—until inspection reveals a problem. The difference is conductor insulation temperature: Type NM is rated 60°C, while Type NM-B is rated 90°C. This difference affects not only code compliance but also long-term reliability […]