L = The length of the cable tray section in feet (m) w = The total weight of the cable being pulled in pounds (kg). f = The coefficient of friction. Selecting a cable tray length is based on several criteria, including: The required load that the cable tray must support. The mechanical and electrical characteristics, tests, certifications, overall quality management, recommendations mentioned in this technical guide only apply to our own cable management ranges and cannot under any circumstances be transposed to si osure, overheating or. 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. A rung spacing of 6 to 9 inches (150 to 230 mm) is preferable when the cable tray cont d for instrumentation and control applications that require. 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. Cable ladder systems and cable tray systems shall be manufactured in accordance with BS EN 61537, channel support. Selecting the appropriate type of tray is the first step in any project. NEC 392 recognizes several cable tray types, each.