How to measure the dimensions of a cable tray tee to tee

Cable tray tee dimensions are specified by the widths of the three connecting sections, typically noted as W1 x W2 x W3, and can be equal or unequal depending on installation needs.

Understanding Tee Dimensions

A cable tray tee is a fitting that allows a main cable tray run to branch into two directions. The dimensions of a tee are defined by the widths of the three arms: W1: Width of the main run entering the teeW2: Width of the branch run exiting the teeW3: Width of the opposite side of the main run (if unequal) Tees can be equal (all three widths the same) or unequal (different widths for main and branch runs), depending on the cable load and routing requirements.

Standard Widths and Depths

Cable tray widths typically range from 50mm to 900mm, with common sizes including 100mm, 200mm, 300mm, 450mm, and 600mm. The depth (or side rail height) usually ranges from 25mm to 150mm, which affects cable stacking capacity and ventilation. When measuring a tee, the depth of each arm should match the connected trays to ensure proper cable support and fill compliance.

Measuring Tee Dimensions

Measure the inside usable width of each arm (W1, W2, W3), not the outside edge-to-edge dimension, as side rail thickness adds to the overall size. Check the depth of the tray arms to ensure adequate vertical space for cables. Confirm material thickness to match load requirements; heavy-duty trays often require 2.

5mm or more with reinforced side rails. Calculate cable fill: Determine the total cross-sectional area of all cables and ensure it does not exceed the allowed fill percentage (commonly 40% for power cables, 50% for control cables) to maintain ventilation and prevent overheating.

Ordering and Specification

When ordering a tee, specify the dimensions clearly as W1 x W2 x W3 and indicate whether it is equal or unequal. This ensures compatibility with the main and branch trays and avoids installation issues. Always consider future expansion, leaving 25–40% spare capacity in the tray system for additional cables.

By following these guidelines, you can accurately measure, select, and install cable tray tees that meet both code compliance and practical installation requirements.