Distribution boxes must comply with UL 50 (enclosures) and UL 508A (industrial control panels) standards. These standards are rigorous about short-circuit current ratings (SCCR), proper wire sizing, and component compatibility. In this guide, we'll break down everything you need to know to install a distribution box correctly and confidently. The National Electrical Code (NEC) requirements might seem like bureaucratic. Switch box shall be distributed by the final sub-distribution box. power distribution box. The installation requirements and specifications of Distribution box involve many aspects, including site selection, fixing method, wiring specifications and safety protection. Unlike standard junction boxes, these distribution systems must.