Double-layer installation method for fiberglass cable trays

Double-layer fiberglass cable trays can be installed by stacking trays with proper support, spacing, and fastening, ensuring load capacity and safety compliance.

Planning and Support

When installing a double-layer system, each tray layer must be supported independently or with shared supports designed to handle the combined load. Trapeze supports or threaded rods are commonly used, with spacing not exceeding the distance between splice plates of the trays. Ensure that the design load safety factor is at least 3: 1 to account for the weight of cables and trays.

Center-hung supports allow easier cable installation from both sides.

Tray Alignment and Splice Placement

Each tray section should be equal to or greater than the support span. Splices should ideally be located at quarter-span points to reduce stress on the fiberglass. When stacking, ensure that the upper tray does not interfere with the lower tray's cable bend radius and that there is sufficient clearance for cable installation and maintenance.

Fastening and Torque

Use snug torque of 3–4 ft.-lbs. for all threaded rod nuts. Ensure full engagement of all-thread rods in clamps, such as B-Line BFPU751 series, to meet load ratings. For double-layer setups, verify that the combined weight does not exceed the maximum load per hanger (typically 318–340 kg per hanger for standard fiberglass trays),.

Material Handling and Cutting

Fiberglass trays can be cut with a circular saw with an abrasive wheel or a hack saw; drill with standard twist drills. Any cut or drilled surfaces must be sealed with compatible resin to maintain structural integrity. Support trays firmly during cutting to prevent chipping or damage.

Safety and Compliance

Follow NEM

A FG-1 guidelines for fiberglass tray support and installation. Avoid using trays as walkways or lifting points. Maintain minimum clearance between trays and supporting rods (typically 2 inches max) to prevent stress on the fiberglass.

Ensure that the installation complies with local electrical codes and manufacturer specifications. SummaryDouble-layer fiberglass cable tray installation requires careful planning of support spacing, load capacity, splice placement, and fastening torque. Proper handling, cutting, and sealing of fiberglass, along with adherence to NEMA FG-1 standards, ensures a safe and durable installation.