Cable tray systems are recognized as a wiring method by many national and international electrical codes. Typical requirements address: Tray construction, load ratings, and materials. Support spacing, mechanical strength, and. This publication is intended as a practical guide for the proper and safe* installation of cable ladder systems, cable tray systems, channel support systems and associated supports. The Cable Tray ng standards, performance standards, test standards and application in this document have been tested extens ompetent professional en completely installed, without damage either to conductors or. The primary rulebook used in the safe use of cable trays is NEC Article 392.