95 ANSI/TIA/EIA-569-A Though the ANSI/TIA/EIA-568-B Standard describes the subsystems of a structured cabling system, the TIA has published a more thorough document called ANSI/TIA/EIA-569-A Commercial Building Standard for Telecommunications Pathways and Spaces. The purpose of the ANSI/TIA/EIA-569-A Standard is to provide a flexible and standardized support system for a structured cabling system, along with the detail necessary to design and build these facilities. The detail pertains to both single and multitenant buildings. NOTE This 569-A document is especially important because network managers, architects, and even cable installers often don t give enough forethought to the spaces and infrastructure that will support structured-cabling systems or data-communications equipment.
96 Chapter 2 Cabling Specifications and Standards Though repetitive to large degree with respect to ANSI/TIA/EIA-568-B, ANSI/TIA/EIA- 569-A does define and detail pathways and spaces used by a commercial cabling system. The elements defined include: Entrance facility Equipment room Main terminal space Telecommunications rooms Horizontal pathways Backbone pathways Work areas WARNING When planning telecommunications pathways and spaces, make sure you allow for future growth. ANSI/TIA/EIA-569-A provides some common design considerations for the entrance facility, equipment room, and telecommunications rooms with respect to construction, environmental considerations, and environmental controls: The door (without sill) should open outward, slide sideways, or be removable. It should be fitted with a lock and be a minimum of 36 inches (.91 meters) wide by 80 inches (2 meters) high. Electrical power should be supplied by a minimum of two dedicated 120V-20A nominal, nonswitched, AC-duplex electrical outlets. Each outlet should be on separate branch circuits. The equipment room may have additional electrical requirements based on the telecommunications equipment that will be supported there (such as LAN servers, hubs, PBXs, or UPS systems). Sufficient lighting should be provided (500 lx or 50-foot candles). The light switches should be located near the entrance door. Grounding should be provided and used per ANSI/TIA/EIA-607 (the Commercial Building Grounding and Bonding Requirements for Telecommunications Standard) and either the NEC or local code, whichever takes precedence. These areas should not have false (drop) ceilings. Slots and sleeves that penetrate firewalls or that are used for riser cables should be firestopped per the applicable codes.
97 Separation of horizontal and backbone pathways from sources of electromagnetic interference (EMI) must be maintained per NEC Article 800.52. Metallic raceways and conduits should be grounded. Based on our own experiences, we recommend the following: Equip all telecommunications rooms, the entrance facility, and the equipment room with electrical surge suppression and a UPS (uninterruptible power supply) that will supply that area with at least 15 minutes of standby AC power in the event of a commercial power failure. Equip these areas with standby lighting that will last for at least an hour if the commercial power fails. Make sure that these areas are sufficiently separated from sources of EMI such as antennas, medical equipment, elevators, motors, and generators. Keep a flashlight or chargeable light in an easy-to-find place in each of these areas in case the commercial power fails and the battery-operated lights run down. NOTE For full information, consult the ANSI/TIA/EIA-569-A Standard, which may be purchased through Global Engineering Documents on the Web at http://global.ihs.com. Entrance Facility The location of the entrance facility is usually either on the first floor or in the basement of a building and must take into consideration the requirements of the telecommunications services required and other utilities (such as CATV, water, and electrical power). ANSI/TIA/EIA-569-A specifies the following design considerations for an entrance facility: When security, continuity, or other needs dictate, an alternate entrance facility may need to be provided. One wall at a minimum should have 3 /4-inch (20 mm) A-C plywood. It should be a dry area not subject to flooding. It should be as close to the actual entrance pathways (where the cables enter the building) as possible. Equipment not relating to the support of the entrance facility should not be installed there. WARNING The entrance facility should not double as a storage room or janitor s closet.
98 Chapter 2 Cabling Specifications and Standards Cabling @ Work: Bad Equipment-Room Design One company we are familiar with spent nearly a million dollars designing and building a hightech equipment room, complete with raised floors, cabling facilities, power conditioning, backup power, and HVAC. The room was designed to be a showcase for its voice and computer systems. On the delivery day, much of the HVAC equipment could not be moved into the room because of lack of clearance in the outside hallway. Several walls had to be torn out (including the wall of an adjacent tenant) to move the equipment into the room. Another company located its equipment room in a space that used to be part of a telecommunications room. The space had core holes drilled to the floor above, but the holes had not been filled in after the previous tenant vacated. The company installed its computer equipment but did not have the core holes filled. A few months later, a new tenant on the second floor had a contractor fill the holes. The contractor s workers poured nearly a ton of concrete down the core and on top of the computer equipment in the room below before someone realized the hole was not filling up. Many organizations have experienced the pain of flooding from above. One company s computer room was directly below bathrooms. An overflowing toilet caused hundreds of gallons of water to spill down into the computer room. Don t let this kind of disaster occur in your equipment rooms! Main-Terminal Space The main-terminal space is a facility that is commonly a shared space in a multitenant building. The main cross-connects are in this room. This room is generally a combination of an equipment room and a telecommunications room, though the TIA/EIA specifies that the design for a main-terminal space should follow the design considerations laid out for an equipment room. Customer equipment may or may not be located here. However, our opinion is that it is not desirable to locate your own equipment in a room shared with other tenants. One reason is that you may have to get permission from the building manager to gain access to this facility. Equipment Room Considerations to think about when designing an equipment room include the following: Environmental controls must be present to provide HVAC at all times. A temperature range of 64 75 degrees Fahrenheit (or 18 24 degrees Celsius) should be maintained, along with 30 55 percent relative humidity. An air-filtering system should be installed to protect against pollution and contaminants such as dust. Seismic and vibration precautions should be taken. The ceiling should be at least 8.0 feet (2.4 meters) high.
99 A double door is recommended. (See also door design considerations at the beginning of section ANSI/TIA/EIA-569-A. ) The entrance area to the equipment room should be large enough to allow delivery of large equipment. The room should be above water level to minimize danger of flooding. The backbone pathways should terminate in the equipment room. In a smaller building, the entrance facility and equipment room may be combined into a single room. Telecommunications Rooms Here are some design considerations for telecommunications rooms, suggested by the ANSI/ TIA/EIA-569-A: Each floor of a building should have at least one telecommunications room, depending on the distance to the work areas. The rooms should be close enough to the areas being served so that the horizontal cable does not exceed a maximum of 90 meters (as specified by the ANSI/TIA/EIA-568-B Standard). Environmental controls are required to maintain a temperature that is the same as adjacent office areas. Positive pressure should be maintained in the telecommunications rooms, with a minimum of one air change per hour (or per local code). Ideally, closets should stack on top of one another in a multifloor building. Then, backbone cabling (sometimes called vertical or riser cable) between the closets merely goes straight up or down. Two walls of the telecommunications room must have 3 /4-inch (20 mm) A-C plywood mounted on the walls, and the plywood should be 8.0 feet (2.4 meters) high. Vibration and seismic requirements should be taken into consideration for the room and equipment installed there. Two closets on the same floor must be interconnected with a minimum of one 78(3) tradesize conduit or equivalent pathway. The 78(3) trade-size conduit has a sleeve size of 78 mm or 3 inches. Horizontal Pathways The horizontal pathways are the paths that horizontal cable takes between the wiring closet and the work area. The most common place in which horizontal cable is routed is in the space between the structural ceiling and the false (or drop) ceiling. Hanging devices such as J hooks should be secured to the structural ceiling to hold the cable. The cable should be supported at
100 Chapter 2 Cabling Specifications and Standards intervals not greater than 60 inches. For long runs, this interval should be varied slightly so that structural harmonics (regular physical anomalies that may coincide with transmission frequency intervals) are not created in the cable, which could affect transmission performance. Shake, Rattle, and Roll A company that Jim worked for was using metal racks and shelving in the equipment rooms and telecommunications rooms. The metal racks were not bolted to the floors or supported from the ceiling. During the 1989 San Francisco earthquake, these racks all collapsed forward, taking with them hubs, LAN servers, tape units, UPSes, and disk subsystems. Had the racks been secured to the wall and ceilings, some or all of the equipment would have been saved. If you live in an area prone to earthquakes, be sure to take seismic precautions. NOTE Cable installers often install cable directly on the upper portion of false ceiling. This is a poor installation practice because cable could then also be draped across fluorescent lights, power conduits, and air-conditioning ducts. In addition, the weight of cables could collapse the false ceiling. Some local codes may not permit communications cable to be installed without conduit, hangers, trays, or some other type of pathway. WARNING In buildings where the ceiling space is also used as part of the environmental air-handling system (i.e., as an air return), plenum-rated cable must be installed in accordance with Article 800 of the NEC. Other common types of horizontal pathways include conduit and trays (or wireways). Trays are metal or plastic structures that the cable is laid into when it is installed. The trays can be rigid or flexible. Conduit can be metal or plastic tubing and is usually rigid but can also be flexible (in the case of fiber-optic cable, the flexible tubing is sometimes called inner duct). Both conduit and trays are designed to keep the cable from resting on top of the false ceiling or being exposed if the ceiling is open. Other types of horizontal pathways include the following: Access floor, which is found in raised-floor computer rooms. The floor tile rests on pedestals, and each tile can be removed with a special tool. Some manufacturers make cablemanagement systems that can be used in conjunction with access floors. Under floor or trenches, which are in concrete floors. They are usually covered with metal and can be accessed by pulling the metal covers off.
101 Perimeter pathways, which are usually made of plastic or metal and are designed to mount on walls, floors, or ceilings. A pathway contains one or more cables. Many vendors make pathway equipment (see Chapter 5 for more information). When designing or installing horizontal pathways, keep the following considerations in mind: Horizontal pathways are not allowed in elevator shafts. Make sure that the pathways will support the weight of the cable you plan to run and that they meet seismic requirements. Horizontal pathways should be grounded. Horizontal pathways should not be routed through areas that may collect moisture. KEY TERM drawstring A drawstring is a small nylon cord inserted into a conduit when the conduit is installed; it assists with pulling cable through. Larger conduits will have multiple drawstrings.