Fill Limits: For power cables, the fill must not exceed 40% of the tray's cross-sectional area; for control cables, it's 50%. NEC Article 392 outlines the key rules for installing and maintaining industrial cable tray systems. These systems, made from metal or plastic, are open structures designed to support electrical conductors, ensuring proper organization and safety. 305(a)(3), or comparable standards promulgated by States. All rights, including translation into other languages, reserved under the Universal Copyright Convention, the Berne Convention for the Protection of Literary and Artistic Works, and the International and Pan American copyright conventions. The information in this publication was considered. The primary rulebook used in the safe use of cable trays is NEC Article 392.