Telecommunications Cabling Installation Practices for Commercial Buildings

Kray Cabling, Inc.

Telecommunications Cabling Installation Practices
for Commercial Buildings
(TIA-568A Compliant)

Contents of this document:

Benefits of TIA-568A Compliance
Star Topology
Horizontal Cabling Systems
Grounding and Bonding Considerations
100 ohm UTP Telecommunications Cabling Systems

The practices in this section should be followed in order for a horizontal cabling installation in Commercial buildings to comply with TIA-568A.

Scope: This Guide only covers horizontal cabling, not backbone cabling. Backbone cabling for the MDF, IDF, Equipment Room and Telecommunications Closet is beyond the scope of this document. This is due to the fact that backbone cabling in TIA-568A is very application and building specific, and dependent upon the type of communications, type of building, and many other issues. Thus for backbone and crossconnect design and installation the user is cautioned to consult the TIA-568A standard document and if necessary, communications consultants. But in general, the specifications for backbone wiring are: * a maximum of two levels * star topology * limited to 90 meters for Category-rated applications; 800 meters for voice applications.

Horizontal cabling in TIA-568A, on the other hand, is a generic cabling system. If horizontal cabling is installed according to the practices in the standard, the system will be sufficient for the majority of applications for which it will be used.

For the purposes of this section, horizontal cabling is considered the cabling from the work area to the telecommunications closet. It includes the crossconnects in the telecommunications closet; horizontal cable; and the outlet at the work areas.

Note on Scope of TIA-56SA: TIA-568A covers only the building's cabling systems, not the pathways such as conduit or raceways. Commercial building pathways and spaces for telecommunications wiring are covered in a separate standard, TIA-569. Grounding is covered in TIA-607.

3.1. BENEFITS OF TIA-568A COMPLIANCE

Commercial building horizontal cabling that is installed in accordance with the TIA-568A standard is like having one type of foundation that can support any type of structure that is built upon it -- even if the structure keeps changing. The benefits are that you have one system which will:

a) Simplify ongoing maintenance, relocation, and addition;

b) Accommodate future equipment and service changes;

c) Accommodate a diversity of user applications , including voice, data, LAN, switching, and other building services.

3.1.1. STAR TOPOLOGY

TIA-568A specifies a star topology; a hierarchical series of distribution levels. In the backbone are the main distribution frame (MDF) and the optional intermediate distribution frame (IDF). Only one IDF is allowed between the MDF and telecommunications closet.

The first level backbone, the MDF, links to other hubs via the backbone cabling. The MDF may link to the third and final level of backbone, the telecommunications closet (TC) directly, or in large installations it may link to some TCs via an optional second level backbone, the intermediate distribution frame (IDF). The TC terminates the backbone cable and crossconnects to the horizontal cabling. The horizontal cabling terminates in the work area. The TC and work area must be on the same floor.

3.1.1.1 Equipment Locations

Communications equipment (phones, fax machines, computers, etc.) may be located in any space -- work areas, telephone closets, distribution frames, or a separate space called an equipment room.

3.1.1.2 Non-Star Topologies

Bus, tree and ring topologies are implemented in the telecommunications closet or other crossconnects rather than directly between work areas. Application distance limitations must be checked.

3.1.2 Maximum Horizontal Distances

Horizontal closet-to-workstation run: Maximum cable length from the mechanical termination of the media in the TC to the telecommunications outlet is 90 meters (295 feet), independent of media type.

Splices and bridged taps are not allowed as part of the horizontal cabling.

Only one transition point is allowed between flat undercarpet cables and one of the recognized horizontal cables.

Length of work area equipment cable: It is suggested that the maximum equipment cable length from the telecommunications outlet to the work area equipment be limited to 3 meters (10 feet). Work area cords, however, are outside the scope of the standard.

In addition, it is suggested that the maximum cable length for jumpers and patch cords in the telecommunications closets be limited to 7 meters (23 feet), with no single cord exceeding 6 meters; see Figure 3-2. A maximum of 2 patch cords is allowed per horizontal run.

It is suggested that equipment cables meet or exceed patch cable performance requirements.

3.1.3. HORIZONTAL CABLING SYSTEMS

There must be a minimum of two cabling runs from the telecommunications closet to each individual work area. The requirement of having two cabling runs is due to the importance of both voice and data telecommunications in a commercial building, and to allow implementation of bus and ring topologies. TIA-568A realizes that most work areas will require both voice and data telecommunications within the lifetime of the cabling system, and so requires that all work areas be wired with a minimum of two outlets.

The required two horizontal cabling runs to each work area shall be as follows:

1) One shall be a four-pair 100 ohm UTP.

2) The other/second shall be one of:

a) Four-pair 24 AWG 100 ohm UTP, or

b) Two-pair 150 ohm STP, or

c) Two-strand, 62.5/125 micron optical fiber.

Hybrid cables (consisting of more than one of the above recognized cables under a common sheath) may be used in the horizontal cabling provided that they meet the hybrid cable requirements in TIA-568A.

Coaxial cable (allowed, but not part of a compliant system).

3.1.3.1. HORIZONTAL CABLING SYSTEM SELECTION

There are three types of cable recognized for standard-compliant installation: 100 ohm UTP, 150 ohm STP and 62.5/125 micron fiber optic cable.

100 ohm UTP is the most universal cabling system and generally the least expensive. It covers almost all applications up to 100 MHz with a minimum of cost. The user must decide which category of 100 ohm UTP cabling system is needed for the application. For voice cabling systems, Category 3 is sufficient; for data cabling systems, Category 5 is highly recommended.

150 ohm STP is usually installed as a hybrid system, consisting of one 15O ohm STP data cabling system and one 100 ohm UTP Category 3 voice cabling system under one sheath. 150 ohm STP is usually used for token ring applications, but the extended bandwidth 150 ohm STP has application hardware for broadband video up to 300 MHz and 155 Mbps ATM.

Optical fiber is typically the most expensive cabling system to install, but it has the widest bandwidth (in excess of 1 GHz). While optical fiber is not practical for voice and other low bandwidth applications in the horizontal, optical fiber should be the cabling system choice for high bandwidth applications such as FDDI, ATM, broadband video and multiplexed signals.

For specific cabling system requirements, see Sections 3.2 (100 ohm UTP), 3.3 (150 ohm STP) and 3.4 (optical fiber).

3.1.3.2. CABLING SYSTEM COMPONENTS

Each cabling system is composed of four main components:

1) Telecommunications outlet

2) Horizontal cable

3) Crossconnect hardware

4) Patch cables, equipment cables and jumpers

The telecommunications outlet is in the work area and provides access to the building telecommunications cabling system.

Horizontal cables connect the work area outlet to the crossconnect system in the telecommunications closet.

Crossconnect hardware terminates the horizontal cable, backbone cable, and equipment in the telecommunications closet.

Patch cables and jumpers connect crossconnect hardware in the telecommunications closets.

Equipment cables connect telecommunications equipment to the outlet in the work area or to the cross connects in the telecommunications closet .

Per the National Electrical Code, each component must be listed for the purpose. Look for the UL or ETL listing for each component (CSA in Canada).

All components must comply with FCC Part 68 (CS-03 in Canada). Look for the compliance statement on the component or the component packaging. Wire and cable are listed with the FCC.

Each cabling system, along with its components, is described in the sections to follow.

3.1.3.3. OTHER CABLING SYSTEMS

If you need to include other cabling systems but still wish to have a TIA-568A compliant installation, other cabling systems may be included to the work area , as long as they are in addition to the two TIA-568A required cabling systems. Examples of additional cabling systems are IBM 3270 on RG-62U or 100 ohm UTP with baluns; video on RG59, Category 5 100 ohm UTP or 150 ohm STP; and voice on 25 pair 100 ohm UTP.

3.1.4. GROUNDING & BONDING CONSIDERATIONS

Grounding and bonding systems are normally an integral part of the specific application or telecommunications cabling system that they protect. They protect personnel and equipment from hazardous voltages, and reduce the effect of electromagnetic interference (EMI) to and from the telecommunications cabling system. Improper grounding and bonding can induce voltages which disrupt telecommunications circuits.

Grounding and bonding shall meet the National Electrical Code (NEC) requirements and practices, except where other authorities or codes impose a more stringent requirement or practice.

Grounding and bonding instructions and requirements of the equipment manufacturer should also be followed. Grounding and bonding requirements of specific data and telecommunications networks could possibly exceed the grounding and bonding requirements of the national or local requirements or practices.

3.2. 100 ohm UTP CABLING SYSTEMS

100 ohm UTP cabling systems currently are the most versatile and often the most cost effective. They cover:

Category 3: up to 16 MHz (10 Mbps)

Category 4: up to 20 MHz (16 Mbps)

Category 5: up to 100 MHz (100 Mbps)

For category selection for a specific application, refer to Section 1. A general rule of thumb is to use Category 3 for voice cabling systems, and Category 5 for data cabling systems.

As a minimum for any category-rated installation, make sure all components are at least of the minimum category required. Just as a chain is no stronger than its weakest link, the lowest category-rated component in a system reduces the entire cabling system to that category.

3.2.1. 100 ohm UTP WORK AREA OUTLETS

Generally, screw terminations for cable outlets limit an outlet to Category 3 performance.

Category 4 outlets usually terminate on an insulation displacement connector (IDC) such as 110, Krone or BIX, and internal leads are twisted and are often limited to less than 8" in length.

Category 5 outlets always use an IDC for cable terminations, and have internal compensation to meet the transmission requirements.

3.2.1.1. 100 ohm UTP Work Area Outlet Installation

Each four-pair cable shall have all pairs terminated on an eight-position jack.

Pin/pair assignments shall be as per T568A or T568B. T568A is the new pin-out scheme and is generally used for analog voice applications using 2 lines. T568B is the more common pin-out scheme, and is generally used for multi-line electronic key systems and most data applications. Either will comply with most voice and data applications including ISDN, 10BASE-T, 16 Mbps token ring, TP-PMD and ATM.

Maintain the twists of the cable as close to the termination on the outlet as possible, to maintain the transmission characteristics of the category. Category specifications require that pair twisting be maintained to within the following distances from the outlet termination:

Category 3 max. allowed untwisting: 3"

Category 4 max. allowed untwisting: 1"

Category 5 max. allowed untwisting: 1/2"

Note: TIA-568A does not specify the maximum allowable untwisting for Category 3 UTP, but 3" is suggested as the maximum distance for standard practice.

Leave a sufficient service loop of the horizontal cable for future adds, moves and changes. Usually 1/3 to 1 meter (1 to 3 feet).

Each telecommunications outlet must comply with pair color codes or have a conversion chart shipped with each outlet. The bend radius of the cable must be no tighter than four times (4x) the cable's outside diameter, at any point in the horizontal channel (such as pathway corners, and station outlet entrances and service loops). For four-pair UTP plenum cable, this translates to about a 1" bend radius.

For multi-pair cable (>4 pairs; typically 25-pair), the minimum allowed bend radius is 110x the outside diameter.

3.2.1.2. INSTALLING OUTLETS FOR CABLING SYSTEMS

In Addition to the Minimum TIA-568A Cabling System Any 100 ohm UTP modular jack or adapter may be added to the minimum cabling system outlet, as long as the minimum cabling system for TIA-568A is met. Baluns, 6 position USOC, 8 position USOC or MMJ outlets may be added to the work area telecommunications outlet as required by the specific site.

Installation in colder climates may require cables with special jackets. PVC and other jacket materials may require treatment to remain flexible in the colder regions.

3.2.2. 100 ohm UTP CABLING SYSTEMS

The unshielded inside cable used in the horizontal cabling system is 24 AWG thermoplastic insulated conductors formed into four individually twisted pairs and enclosed by a thermoplastic jacket.

Four-pair 22 AWG cables may be used if they meet the physical transmission requirements of the desired Category.

Four-pair screened twisted pair (100 ohm STP) cables may be used if they meet the physical and transmission requirements of the desired Category.

Undercarpet cables may be used for certain applications, but only one transition point from round cable to flat undercarpet cable is permitted on any horizontal run. Undercarpet cables shall meet ANSI/IPC-FC-21 and must be listed for that purpose.

3.2.2.1. 100 ohm UTP CABLE INSTALLATION

For TIA-568A-compliant installations, do not exceed 25 pounds of pulling tension on the cable (4-pair, 24 gauge).

Do not chafe or damage the outer jacket of the cable. Watch out for sharp corners, screws, nails, or excess flashing that may cut or chafe the jacket.

Installation in colder climates may require cables with special jackets. PVC and other jacket materials may require treatment to remain flexible in the colder regions.

3.2.3. 100 ohm UTP CABLING SYSTEM TELECOMMUNICATIONS CLOSET CONNECTING HARDWARE

The telecommunications closet is where connecting hardware for 100 ohm UTP cable is installed as a means of connecting the horizontal cabling to the backbone cabling or equipment.

Two types of crossconnects are common: patch panels and crossconnect blocks.

Patch panels often have the backbone cable, horizontal cable, or electronic equipment cord directly terminated on the cable terminations. Crossconnecting is achieved by patch cords.

Crossconnect blocks are usually IDC connections with the electronic equipment cords, horizontal cables and backbone cables terminated on one side. The crossconnect jumpers terminate to the other side of the block, and between blocks to complete the crossconnect.

It is desirable that hardware used to terminate cables be of the insulation displacement connector IDC type. Screw terminals are not recommended except as required for specific applications.

3.2.3.1. 100 ohm UTP CONNECTIN HARDWARE INSTALLATION

Install connecting hardware in a neat, well organized manner, using wire management and mechanical termination practices in accordance with manufacturer's guidelines.

Connecting hardware must be organized into connecting fields for ease of administration; see Section 3.5, Telecommunications Closet.

Document the installation, and use color coding and labeling; see Section 3.7, Administration.

Preserve wire pair twists as closely as possible to the point of mechanical termination, in order to minimize signal impairment. This will maintain the transmission characteristics of the category. Category specifications require that twisting be maintained to within the following distances from the outlet termination:

Category 3 UTP = 3- max. untwisting Category 4 UTP = 1" max. untwisting Category 5 UTP 1/2" max. untwisting

*NOTE: TIA-568A does not specify allowed untwisting for Category 3, but 3" is suggested as the maximum distance.

3.2.4. 100 ohm UTP CROSSCONNECT JUMPERS PATCH CORDS AND EQUIPMENT CORDS

The summed lengths of the jumpers, patch cords and equipment cords should not exceed 23 feet (7 meters) in length in the telecommunications closet.

It may be preferable to buy pre-manufactured patch and equipment cords made to the required lengths since in-the-field installation of modular plugs on equipment and patch cord cable can be difficult for category compliance.

The twists of the individual pairs must be maintained up to and into the plug. This is especially crucial for Category 5 applications. For Category 5, the twist must be maintained to within .5" of the front of the plug.

Modular plugs for solid wire provide the best connection on TIA compliant patch cord cable.

Use only the modular plug crimping tool recommended by the plug manufacturer.

Patch cord cable must be Category compliant. Tinsel cordage ("silver satin") is not acceptable.

3.2.4.1. 100 ohm UTP CROSSCONNECT JUMPERS

TIA-568A requires that all jumper cables comply with Category transmission requirements. These jumpers may be 1 through 4 pairs.

3.2.4.2. 100 ohm UTP PATCH CORDS

TIA-568A requires all patch cords to comply with category transmission requirements. However, patch cords are allowed additional attenuation so that a more "lossy" (less stringent attenuation characteristics) flexible cable may be used.

It is recommended that stranded, twisted conductor patch cords be used. Ordinary flat, solid, silver satin patch cords are allowed by TIA-568A but do not comply with any Category. Both solid or twisted conductors can be used, but the trade-off is that the twisted conductors provide superior electrical performance, while the flat, solid cords provide a little better flex life.

Patch cords do not reverse the wires with the plugs. Pin 1 of end 1 connects to pin 1 of end 2.

3.2.4.3. 100 ohm UTP EQUIPMENT CORDS

Although equipment cords are supplied by the equipment vendor, TIA-568A does require that they meet the same performance criteria as patch cords, and comply with Category transmission requirements. The one exception is equipment cord for analog telephones, such as "500" sets. Ordinary flat, silver satin equipment cords may be used for analog telephones.

Maximum length for work area equipment cords is 10 feet (3 meters).

In the telecommunications closet, the summed lengths of the equipment and patch cables and jumpers together should not exceed 7 meters (23 feet) total.

Equipment cords for data applications usually do not reverse the wires with the plugs; pin 1 of end 1 connects to pin 1 of end 2.

Equipment cords for analog telephones usually reverse the wires with the plugs.

© Copyright 1995 Leviton Manufacturing Co., Inc.

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