This piece was originally published in the November/December 2019 issue of electroindustry.

Rick Pimpinella, Panduit Fellow

Dr. Pimpinella is a Panduit Fellow, is a member of the IEEE, and is actively pursuing his research interests in multimode and single-mode optical fiber. He has published more than 50 technical papers and articles, and he holds more than 60 U.S. patents.

Whether you’re an engineer, installer, consultant, or network designer, you might have multiple questions regarding
cabling infrastructure and management: “What type of cable should I be using? Can I run power and data cables in the same pathway? Do I run my data cable in a conduit or cable tray? What cable tie should I be using? How do I ensure proper fill ratio for future expansion?” The answer is typically the same: “Well, that all depends …” For the answer to these questions and a host of others, it is necessary to understand why and how a data communications infrastructure is designed and implemented.

Table 1

Structured cabling for data communications is a Standards-based system of cabling, connection methods, and hardware, consisting of distinct and well-defined segments including: entrance facility, equipment room, the work area, a consolidation point, horizontal and backbone cabling, cross-connects, cable management components, and equipment cords. Not all segments must exist to be defined as structured cabling. A single, well-designed structured cabling system can be thought of as a set of well-defined building blocks that reduce moves, adds and changes, installation time, and maintenance costs.

The design and implementation of a structured cabling system is based on industry Standards. In Table 1 the Standards bodies that define methods and best practices are listed. The Standards dictate all aspects of the build: the spaces that house the active and passive equipment, the copper and fiber connectivity, the cables carrying data and power, and delivery system or pathways running overhead or through the floors, ceilings, and walls, as well as cable and patch cord management.

ANSI/TIA 568 and 569 Standards govern the delivery systems for copper and fiber cabling.

The Space

At a minimum, the Standards specify a telecommunications room (TR), sometimes referred to as an equipment room (ER), which is an enclosed architectural space for housing telecommunications equipment, cable terminations, cross-connect cabling, and cable management. There must be a minimum of one TR/ER per floor. Floor space exceeding 10,000 ft² should consider a second TR/ER. Conduit entering the TR must be placed so that terminations are performed from left to right. There may not be any bends 1-2 in. into the room, and they should enter at least 8 ft. above the floor. The minimum ceiling height for each space should be 8 ft. with a recommended height of 10 ft. There must also be clearances of 3.28 ft. of unobstructed space around racks, cabinets, and enclosures within the TR. Note: attention is to be paid in industrial/manufacturing spaces, as accommodations are necessary to comply with controls system architectures and harsh environments.

Bend radius guidelines must always be adhered to when determining placement of cable trays and conduit. It is recommended to feed a single TR with four 4-trade-size conduit or sleeves for horizontal cross-connect and a single 3-trade-size conduit or sleeve for interconnecting multiple TRs on the same floor. Standards specify that the bend radius shall not exceed the limitations of four times the diameter for solid copper cable (10 times for stranded copper), and a 2 in. minimum bend radius for optical fiber. The 2 in. bend radius for fiber was originally defined for legacy fiber to ensure high reliability. Today, however, both multimode and single-mode fibers are “bend insensitive” and can withstand tight bends (0.5 in. radius) with no impact on performance or reliability. Fiber cable management systems are designed to maintain minimum bend radii.

The Delivery System

The horizontal distribution system consists of trunk cabling, the pathways supporting the cables,  and the data communications spaces that support the pathways. A horizontal cabling system may consist of many elements, but cable lengths must comply to application Standards. In Table 2, the maximum cable lengths for common data rates and media types are listed.

The cable types used in a structured cabling system  do not dictate the type of pathways. The pathways used for distributing horizontal and backbone cabling from all associated connected hardware consist of two types: continuous and non-continuous. Examples of continuous pathways would be conduit, cable trays, and ladder racks. Non-continuous pathways would consist of J-hooks and cable clamps.

When designing the pathway, plan for changes over the facility lifecycle. Use Standard components and cabling systems. The pathway must support multiple technologies and accommodate future moves, adds, and changes.

A conduit delivery system may not exceed continuous runs of 100 feet. Runs greater than 100 feet require pull points. Bends greater than 90° are prohibited. Aggregate bends may not exceed 180° between pull points. Conduit shall be grounded/bonded per Standards. Conduit fill shall not exceed 40 percent.

Cable trays are preferred over many systems due to their greater accessibility and their flexibility in accommodating moves, adds, and changes, and overall building structural changes. Cable trays are supported every 5.ft., with supports placed 2 ft. from each side of system fittings. All metal parts shall be grounded/ bonded per Standards. Capacities are based on manufacturer’s guidelines and those of the AHJ. ANSI/ TIA-569-E dictates maximum fill is not to exceed 50 percent. Some cable trays also provide the capability of separating telecommunications and power cables. See ANSI/TIA-569-E, Section 9.3 for specific best practices.

Table 2

^a OM1 cabling contains 62.5/125 micron multimode fiber
^b OM2 cabling contains 50/125 micron multimode fiber
^c OS1 cabling contains single-mode optical fiber

An access floor distribution system is a raised floor within the data center and equipment room. This floor is made up of 18-inch or 24-inch modular panels atop a structural floor via 6-inch-high steel footings. A minimum floor height of 12 in. is recommended if serving an ER or plenum. The access floor should not contain connecting hardware.

A ceiling distribution system is used when space between the structural ceiling and a suspended ceiling grid is accessible. The area must allow for 3 in. of clear vertical space above conduits and cables and  12 in. of vertical space above cable trays and raceway systems. Conduits, raceways, trays, and  cabling must be attached to structural walls and/or ceilings via hardware specifically designed to support all anticipated weight. All pathways must allow for 3 in. of clear vertical space above the ceiling while cable “sag” must be no closer than 4 in. J-hooks for supporting the cabling infrastructure must be spaced no more than 5 ft. apart. The number of existing cables, weight of existing cables, and anticipated growth must be considered when sizing the support mechanism.

Surface-mount raceway serves the work area where telecommunication devices are accessed via walls and partitions. It is mounted directly to the wall and other surfaces, providing a multichannel medium for routing telecommunications and electrical cabling. When run horizontally, these metal, plastic, and wooden raceways are placed at baseboard and chair-rail levels. They are versatile in that outlets and connectors can be placed and mounted anywhere along the length of the run. Cable fill is based on manufacturer’s guidelines, with recommendations typically 20 to 40 percent.

Cable Types and Management Components

The cable type depends on the functionality and environment. In Table 3 the Standards-specified cable types are listed.

Plenum cable is the most common flame type, and CM is commonly used for patch cables.

Cable management is a major component within the cabling infrastructure system. Vertical and horizontal managers organize, manage, and protect network cabling and patch cords. They ensure bend radius compliance while protecting cabling from inadvertent snagging, abrasion, and other damaging forces.

Cable ties, hook and loop, and cable straps are vital to cable management. They are used to harness, bundle, and secure cables. Since they are of a multitude of materials, it is important to follow manufacturer’s guidelines for best practices.

To avoid issues when designing and deploying a telecommunications infrastructure, it is imperative to use Standard-compliant components, follow Standard guidelines, implement manufacturer’s best practices, and adhere to local codes. Doing so will eliminate costly changes in the future, unpredictable downtime, and negative strain placed on a business’s network. ei

References:

1. ANSI/TIA-568
   568. ANSI/TIA-568.0-D “Generic Telecommunications Cabling for Customer Premises”
   569. ANSI/TIA-568.1-D “Commercial Building Telecommunications Cabling”
   570. ANSI/TIA-568.2-D “Balanced Twisted-Pair Telecommunication Cabling and Components”
   571. ANSI/TIA-568.3-D “Optical Fiber Cabling Components”
2. ANSI/TIA-569
   1. ANSI/TIA 569-E “Telecommunications Pathways and Spaces”
   2. ANSI/TIA-569
3. IEEE 802.3at “Power Over Ethernet” (PoE)

Table 3