1 guide to network cabling fundamentals chapter 4

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Guide to Network Cabling Fundamentals

Chapter 4

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Chapter 4 - Installing Cables and Supporting Structures

Identify the different pathways and why they are necessary

Understand the layouts of equipment rooms and telecommunications rooms

Discuss proper cable installation procedures Identify good cable management practices and

understand their importance Document your network

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Pathways provide the means for placing cables between the equipment room, the telecommunications rooms, and work areas Two types of pathways exist: horizontal and vertical Choosing proper pathway components at the design

stage makes it easier to perform cable-related work and maintenance later

Generally, cabling choices do not dictate pathway choices; the pathway must accommodate all standards-compliant cabling and allow for necessary changes later

Pathways

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Horizontal pathway systems: Horizontal pathway systems are designed to distribute,

support, and provide access to the horizontal cabling, which is the cable that links the distribution field of the cross-connect system in the telecommunications room to the telecommunications outlet/connector in each work area

The horizontal distribution system includes the pathway itself (cable trays, conduit, and J-hooks),as well as related spaces such as pull boxes, splice boxes, and consolidation points that provideaccess to the cable and connecting hardware

Pathways

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Horizontal pathway systems (cont.): There are a number of methods for routing horizontal

cables to the work area; one of the most common methods is zone cabling, in which cable bundles are run to a particular area from the telecommunications room along J-shaped hooks suspended in a plenum or above a ceiling

Upon reaching the zone, cables are fanned out and dropped though interior walls, support columns, or raceways, and then terminated at the telecommunications out/connector (work area outlet)

Pathways

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Horizontal pathway systems (cont.): An underfloor duct system is a network of metal raceways

that are embedded in concrete The underfloor duct system includes the main feeder

ducts, which carry the cables from the telecommunications room to the distribution area, which in turn carry the cables to a specific floor area

The system also includes junction boxes, which permit the changes in the direction of the cable, and a splice box, which is an opening in the system providing access for making connections

Pathways

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Horizontal pathway systems (cont.): Conduits are pipes that cable is placed in and pulled

through; they are installed from telecommunications rooms to work area outlets in floors, walls, columns

The following conduits are rated as suitable for buildings: rigid metal made of steel; intermediate metal conduit; electrical metal tubing; PVC conduit

When using conduit for your pathways, observe these design and installation guidelines: run cable in the most direct route; continuous sections no longer than 30 m and no more than two 90° angles; each conduit must be bonded to ground

Pathways

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Horizontal pathway systems (cont.): Cable tray systems are commonly used as distribution

systems for cabling within a building They are often preferred to conduit and raceways Cable trays are prefabricated structures that route and

support telecommunications or power cables Cable trays are open and equipped with sides that allow

cable to be laid within the tray’s entire length When cable trays are used in the ceiling area, conduit

should be provided from the end of the tray to the telecommunications outlets

Pathways

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Horizontal pathway systems (cont.): Access (raised) floors sit above the existing subfloor and

provide access to the space under its panels; Access floors are most often found in computer and

equipment rooms There are two basic types of access flooring: standard

and low-profile floors Access floors consist of the following components: steel

footing which rest on the subfloor; pedestals support and interlock with lateral bracing and panels; modular floor panels rest on bracing and pedestals

Pathways

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Horizontal pathway systems (cont.): To distribute horizontal cable from the

telecommunications room to the work area, ceiling distribution systems use the open, interstitial space between the structural ceiling and an accessible grid ceiling hanging below it

Guidelines for ceiling distribution include: the ceiling space is only used for horizontal cabling serving the floor below; the areas used are fully accessible from the floor below; the ceiling tiles are removable

The ceiling zone method is commonly used

Pathways

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Vertical pathways: Vertical pathways are the spaces that provide distribution

access of backbone cabling between communications rooms in multistory buildings

Follow these vertical pathway design requirements: the pathways should be stacked above each other and be accessible from each floor; they must contain at least three 4-inch conduits, or sleeves; the pathways should have a 100-watt fixture with a bulb and a 20-amp, 100-volt electrical outlet, and the pathway entrances should be secured with a mortised combination lock

Pathways

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Vertical pathway installation guidelines: All installation personnel have adequate preparation Establish adequate spacing between cables and any

other facilities that use the same/adjacent pathway Remove any hazards from each floor Complete all necessary preparations before install Choose the raising or lowering method and then set up all

necessary associated hardware, including shoes, sheaves, and winches

Set up safety measures such as perimeters, cones, and reel and sheave blocks

Pathways

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Vertical pathway installation guidelines (cont.): When lowering cable, position the cable reel away from

the opening; use a shoe or sheave to direct the cable into the opening; ensure that adequate braking measures are set up; secure the cable once it is in position, starting at the bottom level

When raising cable, secure an opening sheave and power winch; lower the pulling line from the top floor; ensure that adequate braking measures are set up; use the manufacturer’s pulling eye or a core hitch; secure the cable once it is in position, starting at the bottom level

Pathways

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Choosing the right cable and documenting it before installation involves: Creating a detailed floor plan that identifies every

relevant piece of equipment Identifying floor plan elements with a unique ID Before running the cable, consulting the floor plan for the

cable ID number and apply this ID to the end of the cable you are pulling and to the box or reel from which the cable is fed

Understand the information on the cable jacket Record the length of each cable run

Pathways

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Equipment rooms and telecommunications rooms in a building act as junctions between the backbone and horizontal pathways Both may house such items as the main distribution

frame, small telephone systems (PBXs), secondary voltage protection, active voice and data telecommunications equipment, termination fields, and cross-current wiring, which connects a circuit from one facility to another in a network

Standard ANSI/EIA/TIA-569-A provides a design guide for telecommunications/equipment rooms

Equipment Rooms and Telecommunications Rooms

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Equipment rooms: The equipment room houses the main distribution frame,

a steel-bar framework that typically holds the phone company’s central office protective devices, serves as the major cross-connect point for the central office lines and the customer’s wiring, and interconnects loop cable pairs and line-equipment terminals on a switching system

This room is often appended to the entrance facility or computer room to allow sharing of air conditioning, security, fire control, and lighting


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Telecommunications rooms: The telecommunications closet on each floor provides

the junction point between the backbone and horizontal pathways; these rooms contain active voice/data telecommunications equipment, termination fields, and cross-connect wiring

More than one telecommunications closet per floor is required if the distance to a work area exceeds 100 m, or if the floor area served exceeds 10,000 sf

Requirements for power, lighting, air conditioning and access are the same as for equipment rooms


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The ANSI/EIA/TIA-569-A standard provides instructions and guidelines for ensuring successful installations: Conduit capacity, the number of cables it can hold,

depends on the size of the cables and the conduit Typically, the conduit size for outlets of data and voice

cables is 21 mm In general, high- and low-signal cables should not be run

in the same conduit; in addition, the NEC forbids the installation of telecommunications cables in the same conduit as power cables

Cable Installation Guidelines

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Instructions and guidelines (cont.): There are maximum recommended pulling tensions for

conductors since copper will begin to permanently stretch under approximately 15,000 pounds per square inch

During installation, the total pulling tension must be equally distributed among all conductors

The following factors determine pull force: cable type, number of pairs and quantity of cable; conduit type, size, and length; number and configuration of conduit bends; use of cable lubricants


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Instructions and guidelines (cont.): Every ceiling distribution system must properly support

cables from the telecommunications room to the work area it serves

Ceiling conduits, raceways, cable trays, and cabling must be suspended from or attached to the structural ceiling or walls, using hardware specifically designed to support their weight

Where building codes permit cables to be placed in suspended ceilings without conduit, ceiling zone distribution pathways may consist of cable trays


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Instructions and guidelines (cont.): Cable bend radius is the amount a cable can bend

before it is damaged or its performance is impaired; maintaining correct bend radius is critical when terminating wire pairs and creating service loops

The minimum bend radius for cable (six or fewer pairs) is four times the cable’s outside diameter

Cable stress is avoided by: supporting suspended cables every four to five feet; fastening cable ties; not exceeding pulling tensions during installation; not allowing cables to snag during installation


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Instructions and guidelines (cont.): Proper cable termination leads to communications

systems that require little or no service Terminate horizontal and backbone cables on appropriate

connecting hardware; since these cables are always terminated on separate connectors, use patch cords or jumpers

To prevent the effects of improper termination practices: remove only as much cable jacket as needed for termination and trimming; follow the manufacturer’s instructions; minimize untwisting


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Cable system performance is degraded by: Connector terminations Cable installation and management Use of cross-connect jumpers and patch cords Multiple connections in close proximity

It is important to follow proper guidelines to manage horizontal and backbone cables, cross-connects, vertical and horizontal pathways, and ceiling and zone distribution

Cable Management Practices

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Horizontal and backbone cable management: Be especially compliant to cable bend radius and pull-

force guidelines during cable installation In both the cable pathways and telecommunications

room, use appropriate cable routing and dressing fixtures to organize and manage the cable types

This type of management can eliminate cable stress caused by: tension in suspended cable; tightly clinched cable bundles, which damage jackets; twisting cable jackets during installation


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Cross-connect management: The two most common cross-connect systems are the

BIX and the 110 systems Keep voice and data fields separate Use color-coding to identify termination areas Avoid patch cord or jumper slack Manage cross-connects by following these precautions:

After each cross-connection is completed, eliminate patch cord and jumper slack; be especially aware of patch cord bend radius for twisted-pair and fiber


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Vertical and horizontal pathway management: Vertical cable management channels made of copper

provide cable and patch cord protection and routing space; those made of fiber contain uniquely designed wire guides to maintain bend radius

Vertical cable management channels can be easily fastened on either side of the racks

Horizontal cable management channels also provide patch cord protection and routing space; they are usually equipped with a front-cover panel fastened with plastic rivets


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Ceiling zone distribution management: Perform these steps: place cables into the zone pathway;

leave sufficient slack to reach work area outlets; run all cables to the center point of their zone and from there, distribute cables to work areas; support all cables with Velcro cable ties; coil cable not in service; label cables and pathways

Cable management and ANSI/EIA/TIA-606 ANSI/EIA/TIA-606 defines administration as a necessary

foundation for effective cable management and reliable infrastructure


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Good network documentation accounts for: A diagram of the physical network The topologies and network architecture in use Protocols and logical addressing schemes Operating systems and directory services Cabling standards and network conventions The documenting of manufacturers and vendors

Documenting Your Network

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Chapter Summary

Cabling pathways provide the means for placing cables between the equipment room, the telecommunications rooms, and the work areas. These pathways can be horizontal or vertical

A common method of horizontal cabling is zone cabling, in which cable bundles are run to a particular area from the telecommunications room along J-hooks suspended above a plenum ceiling. Upon reaching the zone, cables are fanned out and dropped through interior walls, support columns, or raceways, and terminated at the work area outlet

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Chapter Summary

The equipment room and telecommunications rooms in a building act as junctions between the backbone and horizontal pathways. Both rooms may house such items as the main distribution frame, PBXs, secondary voltage protection, active voice and data telecommunications equipment, termination fields, and cross-connect wiring

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Chapter Summary

Cabling installations begin with the placement of all the large backbone and intrabuilding cables, followed by the smaller horizontal cabling, and then the interconnect cables. The ANSI/EIA/TIA-569-A standard provides important instructions for ensuring successful installations, including information on conduit capacity, cable pulling tensions, pathway and cable support, bend radius, cable stress, termination practices, and jackets

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Chapter Summary

Connector and cable components that meet transmission performance requirements are crucial to your installed cabling system, but they do not ensure success. Performance may be degraded by poor or improper cabling practices related to connector terminations, cable installation and management, use of cross-connect jumpers and patch cords, and multiple connections in close proximity

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Chapter Summary

Make your network documentation more effective by including a compete network diagram, along with specific information about hardware, software, topologies, conventions, cabling standards, and configuration. The more you document the network, the better equipped everyone will be to work on it. Remember to keep this documentation up to date; incorrect information can be worse than none at all

1 guide to network cabling fundamentals chapter 4

Documents

horizontal pathway systems

horizontal cabling

network slide

horizontal distribution

cable tray systems

cablerelated work

telecommunications rooms

pathway choices