The cable tray system shall accommodate the weight of the horizontal and/or backbone cabling. 3 Provide horizontal elbows, end plates, vertical risers and drops, tees, wyes, expansion joints and reducers. Although BS 7671 touches on the subject of cable supports, it does not detail specifically what these support distances should be. 8 (Other Mechanical Stresses (AJ)) in that document provides requirements for cable support. Proper installation can significantly reduce electromagnetic interference, prevent fire hazards, and improve overall efficiency. Cable Management Tray Size: Choose a tray size.