How far should cable trays be spaced for fixed supports

Fixed supports for cable trays should generally be spaced every 3 to 5 meters for horizontal runs and less than 2 meters for vertical runs, depending on cable type, tray material, and load.

Horizontal Runs

For straight horizontal cable tray sections, supports should be installed at the start, end, and at intervals of 3 to 5 meters along the tray. This spacing ensures that the tray remains stable, prevents sagging, and avoids undue stress on the cables. Wider trays or heavier cables may require closer support spacing to maintain structural integrity and prevent excessive deflection . The recommended practice is to match the tray length to the support span and place only one splice plate between supports to minimize stress at joints .

Vertical Runs

For vertical cable tray sections, supports should be fixed to the building structure at intervals preferably less than 2 meters. Cables within vertical trays should be secured at the top and every 1.5 meters to maintain organization and prevent mechanical strain . For long vertical runs exceeding 32 meters, strain relief sections should be incorporated, often by offsetting the cable horizontally by at least 2 cable diameters to prevent tension buildup .

Cable Type and Material Considerations

The spacing of supports also depends on the cable type, insulation, and weight. Stiffer cables, such as MDPE-sheathed power cables, may require greater spacing between supports to achieve the same allowable deflection, while flexible LSOH cables may need closer support . Ladder tray rung spacing and tray width also influence support intervals; wider trays or larger rung spacing may reduce overall strength, necessitating shorter support spans .

Additional Guidelines

• Ensure adequate clearance for maintenance, inspection, and airflow (minimum 150 mm vertical spacing for floor-mounted trays) to prevent overheating .
• Horizontal spacing between power and signal trays should generally be no less than 0.5 meters to reduce electromagnetic interference, with shielding allowing reduced spacing .
• Supports should be made of fire-resistant materials to prevent premature failure in case of fire .
• For bends, supports should be applied on either side of the bend, and the internal radius should not be less than the cable's minimum bending radius . By following these guidelines, cable trays will maintain structural integrity, ensure safe cable installation, and allow for future expansion or maintenance.