Cable tray support quantity can be calculated using a simple formula: Support Quantity = Total Length ÷ Support Spacing + 1 20 ÷ 2 + 1 = 11 supports In a typical project, a 20-meter cable tray with 2-meter spacing requires 11 supports. Specifically, NEC Article 392 governs the use, installation, and construction specifications for these systems. Follow these simple steps: Define Tray Dimensions: Enter the width and depth of your planned cable tray (in mm or inches). Select Fill Standard: Choose 40% for power cables (NEC compliant) or 50% for. OBO BETTERMANN has offered prod-ucts and solutions for electrical instal-lation for over 100 years. With our many years of experience, we are one of the leading manufacturers in this field. Follow these steps to generate your accurate Bill of Materials (BOM) and engineering report: Step 1: Define. Based on "Code for Acceptance of Construction Quality of Building Electrical Engineering" GB50303 and "Specification for Design of Steel Cable Tray Engineering" CECS31 Actual width of the cable tray.