Information Technology Reference
In-Depth Information
drawing should be prepared and cable runs planned out and measured (on the draw-
ing) to be certain. Allow an extra 3.5 to 5 m for each vertical drop from the ceiling
to the wall outlet and 2 to 3.5 m for the drop from the ceiling to the patch panel.
Remember that the vertical drop must start well above the ceiling grid, because rules
forbid placing the wire directly on the ceiling grid. If your patch panel is not wall-
mounted, allow additional distance for the cable run to the rack or cabinet.
Remember also that cable is normally run at right angles on the wiring board
or in the rack. It is amazing how much extra cable all of these right angles require.
EIA/TIA-569-A specifies the minimum size and suggested locations for
“telecommunication spaces” such as TRs. It would be ideal if you could adhere to
those standards, but some buildings may not allow such luxuries. Keep in mind that
the network managers and technicians need to have quick and easy access to the
patches and hubs in the TRs. If you absolutely must share space, place the wire ter-
mination point in a corner of the room that will not be blocked by storage or office
equipment. Place it at an easily reachable level where there is adequate light, venti-
lation, and power. Several manufacturers make wall-mounted cabinets that conceal
and protect your wiring and hubs.
All LAN cables should be routed away from potential sources of interference.
Avoid fluorescent lights, motors, pipes, structural steel, and power lines. The
National Electrical Code
®
, TIA/EIA-568-C, and ancillary documents specify the
separation distances, both for safety and for interference. With the exception of flu-
orescent lights and electric motors, most interfering conductors can be crossed at
right angles, but you should still maintain a minimum separation for safety reasons.
Some authorities advocate direct physical support Category 5e/Category 6
LAN cables. This requires the use of cable trays, ducts, cable hangers, or conduit for
the entire route of each cable. In many situations, these extensive precautions are
simply impossible or cost-prohibitive.
However, in large buildings with suspended ceiling grids, it may be desirable to
use a cable tray routing system to help organize and protect the LAN cable. The key
element is to eliminate any deformation in the insulation or twist integrity of the
cable. That generally means that you must avoid long unsupported spans of wire,
sharp bends, kinks, binds, nicks, and tight tie-wraps.
To illustrate a basic data-only wiring system design, we will show a cabling plan for
a simple two-story building using the concepts we have covered in this chapter.
Our example will have 24 workstations per floor. We will use Category 5e
specifications, direct patch panel termination, and will have one TR per floor. We
