NEC requires junction boxes to meet size (box fill), material, accessibility, and grounding rules (per Articles 314 & 300). Non‑compliance risks safety or code violations. NEC Article 314 establishes requirements for the installation and use of electrical boxes, conduit bodies, fittings, and handhole enclosures. A conduit body is a removable-cover section of a conduit system that provides access at junctions or termination points. 16 Box Fill capacities, and critical environmental ratings (such as UL 94 V-0 fire resistance and -10°C cold weather resilience). This guide breaks down the actual rules inspectors check — with calculations and real-world examples. If you remember nothing else, these are the five things that.