Cable trays shall be installed according to the latest revision of the NEC, NEMA VE 2, and manufacturer’s installation instructions.
Cable tray elbows shall be supported per NEMA VE 2 requirements.
Cable tray supports shall be located so that connectors between horizontal straight sections of tray fall between the support point and the quarter-point of the span. Cable tray installations shall be installed so connectors are not located in center points of span between supports or directly on supports. Cable trays shall be fastened to the support system using guides that allow for longitudinal movement.
Expansion connectors shall be provided at building expansion joints and in long runs of outdoor tray at intervals of 30 m (100 ft) or per NEMA VE 2. A bonding jumper shall be installed at each expansion joint according to standard approved document. All cable tray systems shall be bonded together with bonding jumpers.
Cable trays shall be grounded at least every 15 m (50 ft) and at both ends for Cable Tray Installation Guidelines for Engineers.
All cable tray conduit drop-outs shall be bonded to the cable tray according to with grounding bushing on conduit end and bonding wire bolted to the cable tray with a compression lug.
Cable Installation Guidelines for Engineers
Cables shall be installed in the proper cable trays as identified on the contract drawings. Cables shall be installed in a neat and workman like manner. Where drawing details dictate, laying of cables and spacing shall be maintained in trays as shown.
Pulling of medium voltage cable in cable tray shall be performed by using conductor for pulling, not insulation or cable jacket. To properly facilitate pulling a sufficient amount of cable jacket, insulation and any other material shall be removed to expose the bare conductor.
The installation of low voltage cable shall be performed using industry accepted methods and tools manufactured for the pulling of wire and cable.
A tension meter/recording device shall be used with all cable and wire pulls. Recorded data shall be made available for representative review.
Cable installation shall be performed per recommended methods and requirements of NEMA VE 2. Cable manufacturer data shall be used in the design of the cable pulls. Maximum tension and sidewall pressure shall be considered in the rigging of the cable pull. Proper radius pulling wheels shall be used and adequately supported. Care must be taken when rigging supports from existing structures. If necessary temporary supports shall be installed for rigging of the pulling equipment. It is the pulling contractor’s responsibility to ensure no damage occurs to the structure, other equipment, and/or personnel involved in pulling the cables. It is recommended that the rigging design be approved by a responsible engineer through calculation to avoid any such damages. Cable trays shall not be used to support any rigging for cable installation Guidelines for Engineers.
Cable clamps or straps suitable for outdoor duty and ultraviolet light shall be provided to limit the movement of conductors within the tray. Strapping shall be installed at maximum intervals of 1800 mm (6 ft) for horizontal runs and 900 mm (3 ft) for vertical runs.
Cables shall enter electrical equipment using only approved connectors suitable for the environment.
Cables runs outside of cable tray shall be installed in conduit or as otherwise shown on the contract drawings. Type MC cable shall be supported as permitted by the NEC. Cable runs must be protected from physical damage.