Media Distributing Methods for Structured Cabling Design
Media Distributing Methods
Selection of cable types and the type and style of information outlet to use is determined by the system designer based on an evaluation of the architectural and media distribution methods available to support the communications requirements on a floor by floor basis.
Media Distributing Methods consist of the supporting structures for concealing and/or supporting the wires or cables placed between the riser or telecommunication closet and the desired terminal location.
The plenum created by a ceiling or access floor is typically used as an air-handling plenum for conditioned air distribution. When the access floor plenum is used for air distribution in the office, check applicable local codes for electrical, voice and data wiring requirements (plenum cable may be required). In the general office, these requirements may differ from those in the room where fire suppression systems are typically used.
In the general office where access floor is not used as an air handling plenum, most codes allow low voltage (voice and data) wiring to run just as in a nonair handling ceiling plenum. Good wiring management would dictate, however, bundling of main runs or placement in cable trays with a parallel arrangement to each other.
Distribution Systems
There are five main types of Distribution Systems:
- Unlimited access (raised floor)
- Ceiling (zone and grid)
- Conduit
- Other miscellaneous – cable trays or racks
- Horizontal wiring is run in floors and ceilings in many ways. In ceilings, the following methods are used:
- Home-Run Method
- Zone
- Raceway
Home-Run Method
With the home run method, cables are routed directly from the serving telecommunication closet to the jacks at the work areas. This method is also
economical and offers the most flexibility for distributing cables in a ceiling. It also minimizes Crosstalk coupling, since pairs from different jacks are not in the same cable sheath.
Zone Method
Zone Cabling is a useful option for supporting open office work areas. Open office design is a practice based on modular furniture, flexible partitions, and project workgroups. This divides horizontal cabling into two parts:
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- A permanent section from the telecom closet to a consolidation point (the zone cables).
- An adjustable or flexible section from the transition point to the telecom outlets (extension cables). The consolidation point establishes a cluster or group of work areas (zone).Consolidation points must house and otherwise protect the interconnection of the zone and extension cables.
Raised Floor Method
The raised floor (also called access floor) consists of square plates that rest on locking aluminium or steel pedestals attached to the building floor. The plates typically consist of a steel bottom plate adhesively bonded to a laminated wood core covered by cork, carpet tiles, or vinyl tiles. Any square is removable for access to the cables beneath.
This approach provides complete flexibility and accommodates easy installation, high capacity, and easy fireproofing. Disadvantages include the sounding board effect created by walking on raised floors, high initial installation expense, poor control over cable runs, and decreased room height. When the space beneath the floor is used as an air plenum, plenum cables are necessary.
Baseboard raceways are metal or plastic channels that run along the baseboards of a building, DADO trunking is a common name for this type of infrastructure. They provide easy access to cables and are used for office areas where most jacks are placed against the walls. The front cover of the raceway is removable, and jacks are placed anywhere along the channel.
Power and communications cables are separated by partitions. If metallic partitions are used they must be grounded. These systems may also be applied at desk height, which provides convenient access to jacks if most desks are against the walls.