Telecommunications Horizontal Cabling and Support Structure
The horizontal cabling is the portion of the telecommunications cabling system that extends from the telecommunications room to the work area telecommunications outlet. The horizontal cabling shall be installed in a home run, star topology. It is preferred that a telecommunications room should be located on the same floor as the work areas served. The maximum horizontal distance shall be 76 meters (250 feet). For ease of cable installation and future expansion in hallway or major distribution routes, cable trays are the preferred method for distributing the horizontal wiring from the telecommunications room to the communication outlets. When conduit runs are required a minimum 1” conduit shall be run to each jack; daisy-chaining jacks is not acceptable. J-hooks, spaced every 4 feet, may be used for distribution of small cable bundles above suspended ceiling spaces, from major distribution routes to room outlet locations. Cable trays shall be designed to accommodate a maximum calculated fill ratio of 50% to a maximum of 6 inches inside depth, to allow for future cable installations. Cable tray products shall be B-Line or Flex Tray brand. No cable may be attached to conduit, pipes, any other utility structure, or laid on top of ceiling tile.
J-hooks shall be attached to building members with fasteners appropriate for the material. Wood screws or lag bolts shall be used for wood, screws with plastic or lead anchors shall be used for plaster and concrete, self taping screws shall be used for sheet metal. Attachment to drywall alone should be avoided.
Unistrut or equivalent may be used where necessary to provide attachment points for conduit or cable tray. All Thread Rod shall be secured to threaded anchors.
Occasionally large hooks that will carry the weight of many cables may be used, and securely attached with lag bolts, metal concrete anchors, or metal anchors with epoxy.
Hooks shall be mounted no more than four (4) feet apart. Closer spacing may be necessary in areas where cables are routed around corners or are in close proximity to other mechanical or electrical systems.
Where raceway, cable tray and conduit are used it shall be sized according to the list below. The minimum size for raceway and conduit is 1 inch diameter or equivalent. Use Flextray or B-Line cable tray products. No more than two 90 degree bends are allowed between horizontal cable pull points, although no 90 degree bends is preferred. Use sweeping bend products when 90’s are required. The number of cables that can be installed in a conduit is limited by the allowed maximum pulling tension of the cables. A maximum fill of 40% is preferred to allow for future additions of cable.
Surface Raceway, Cable Tray and EMT Conduit
EMT Conduit Sizing Chart
|EMT Conduit Size||Maximum Cables|
|Cable Tray – B-Line Products|
|FT4X8X10||Flex Tray Cable Tray|
|FT4X4X10||Flex Tray Cable Tray|
No section of interior conduit shall be longer than 100 feet between pull points. No section of conduit shall contain more than two 90-degree bends, or equivalent between pull points. For conduits with an internal diameter of 2 inches or less, the inside radius of a bend in conduit shall be at least 6 times the internal diameter. For conduits with an internal diameter of more than 2 inches, the inside radius of a bend in conduit shall be at least 10 times the internal diameter. Conduit sizing is directly related to the planned diameter of the cable bundle, including known future installations, and the maximum pull tension that can be applied to the cable without degradation of the cable transmission properties. Conduits shall be reamed to eliminate burrs and sharp edges. Pull string or rope shall be placed in installed conduits.
- Flexible conduit (metal or plastic) is not permitted.
- Surface raceway systems shall not force cable into a bend radius less than 1.21 inches under condition of maximum fill.
When cables are installed in an un-insulated drywall wall, no box is required; instead a device mounting bracket can be mounted securely in the wall.
When a conduit and surface raceway box is used as both a jack and pull box, the minimum box depth shall be 3-1/8".
Cable in exposed finished areas (e.g., open ceilings) shall be installed in EMT conduit, or an appropriate raceway. The preference is not to use raceway which combines electrical and communications wiring; however, power poles may be used for this when necessary.