NEC Requirements for Outdoor Distribution Boxes: Complete specification guide for outdoor electrical distribution boxes covering NEC Article 312 requirements, NEMA ratings, sizing calculations, and selection criteria for commercial and residential applications. 💡 Specification Insight: NEC 312. 2 requires outdoor distribution boxes to have rain-tight enclosures when installed in. It takes the incoming power and safely distributes it to different circuits throughout your building. Whether in a home or an industrial facility, this box keeps your electrical setup organized, functional, and efficient.