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. We pick eco-friendly. en completely installed, without damage either to conductors or structural system use maintain spacing or to keep cables in place when the tray is ect the minimum bend ra-dius for cables as they exit the bottom of the cable tray. Here's what you need to know: Cable Types: Only use.