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. Establishing partnerships with cus-tomers is a top priority for OBO, and OBO staff are available to support customers in all aspects of their pro-jects, including products, installation and planning advice. This is because we not only supply our customers with products and solutions, which. 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. The National Electrical Code (NEC) is the ultimate authority for any cable tray installation. Specifically, NEC Article 392 governs the use, installation, and construction specifications for these systems.