Instrument cable trays and instrument cable tray spacing

Instrument cable trays should be sized and spaced to support small-diameter control and instrumentation cables safely, typically using 6–12 inch rung spacing for ladder trays.

Tray Selection and Sizing

Instrument cables, such as Type TC, PLTC, or ITC, are generally small-diameter multi-conductor cables. Ladder-type cable trays are preferred for these applications because they provide good ventilation and easy access for installation and maintenance. Tray widths commonly range from 6 to 24 inches for instrumentation cables, depending on the number of cables and future expansion needs.

Tray fill should be calculated using the actual cable outer diameters, not estimates, to ensure the tray is not overloaded. Industry best practice targets an initial fill of around 40%, allowing growth up to 50% for future cable additions. Proper fill ensures adequate cooling, prevents cable damage, and maintains neat installation.

Rung Spacing

For small-diameter instrumentation cables, rung spacing of 6, 9, or 12 inches is recommended. Closer spacing prevents cable drooping and maintains a neat appearance, while wider spacing may be acceptable for larger power cables but can reduce tray strength. Always check the cable manufacturer's minimum bending radius to avoid damage during installation.

Support and Installation

Cable trays must be supported at regular intervals to prevent sagging and maintain structural integrity.

IE

C 61537 and related standards recommend using compatible accessories and ensuring proper support spacing based on tray type, width, and load. Trays should be level, plumb, and securely mounted, with horizontal deviation ≤2 mm per meter and vertical deviation ≤3 mm per meter. Segregation is important: power and signal cables should be routed separately to minimize electromagnetic interference, using dedicated trays for instrumentation cables.

Sharp edges must be removed, and grounding jumpers installed at each connection point to ensure electrical continuity.

Additional Considerations

Material selection: Painted or galvanized steel for indoor use; stainless steel or aluminum for outdoor or corrosive environments. Future-proofing: Leave space for additional cables and thermal expansion. Compliance: Follow IEC 61537, NEC 392, and manufacturer guidelines for tray strength, fire resistance, and cable compatibility.

By following these guidelines, instrument cable trays will provide a safe, reliable, and maintainable pathway for control and instrumentation cables, ensuring long-term system performance and compliance.