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. As a key structure supporting the cable tray, the accurate calculation of the support quantity directly affects construction costs, efficiency, and safety. In complex engineering environments, the. Article Summary: A compliant cable tray installation requires a thorough understanding of NEC Article 392, proper structural support, and precise installation techniques. Engineers often focus only on cable quantity while overlooking important factors such as tray span, cable weight distribution, and environmental conditions. Common values: 200, 400, 600, 800mm Actual height of the cable tray. A rung spacing of 6 to 9 inches (150 to 230 mm) is preferable when.