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. If it's done poorly, you risk short circuits, fire hazards, or system failure. Done right, it ensures safety, compliance, and long-lasting performance. What is an. This article breaks down how a truly reliable outdoor waterproof distribution box is designed, from enclosure sealing and heat dissipation to internal component layout.