Annex C is used to determine the maximum number of conductors or fixture wires that can be placed inside a conduit, tubing, or cable tray when all conductors are of the same size and insulation type. The mechanical and electrical characteristics, tests, certifications, overall quality management, recommendations mentioned. During the design of a cable management system, one of the most important questions is the cable tray capacity. A rung spacing of 6 to 9 inches (150 to 230 mm) is preferable when. A Cable Tray Capacity Calculator is an essential tool for electrical engineers, contractors, and project managers involved in the installation and management of electrical cables. 16, tray fill, ampacity adjustment, voltage-drop checks, grounding, and IEC design cross-checks. Use NEC 392 for tray rules, but still size conductors from NEC 310.