TIA Adds Structure to BAS Cabling

TIA TR 41.8.1 is trying to do for building automation cabling what it did for building telecommunications cabling—add structure, standards, and guidelines. TIA TR 41.8.1 is the committee that brought open, structured cabling to the building telecommunications industry via the publication of TIA/EIA-568, now in its third revision. Approximately two years ago, this committee started developing an equivalent specification for building automation cabling. It is in its third round of industry ballot and is expected to be approved and published this year. Let us explore why TIA decided to address this market and basically what the proposed specification states.

In the past, buildings merely needed to be functional; today, they must also be “intelligent.” In an intelligent building, the services and facility technologies converge to help business owners, property managers, and occupants realize their goals for cost, comfort, convenience, safety, long-term flexibility, and market appeal. The intelligent buildings concept was introduced in the United States in the early 1980s, but the technology and methods necessary to effectively integrate the various functions and systems were not readily available or accepted. Now, nearly two decades later, there is a re-emerging focus on intelligent building systems. Today, however, the benefits of intelligent buildings are proven and the technology is readily available. A major component of an “intelligent” building is what the TIA calls “Building Automation Systems (BAS)”, which control fire alarm; security and access; energy management systems, both heating ventilation and air conditioning (HVAC) and lighting/power; and other low-voltage systems such as audio/video paging and service/equipment alarms.

Previously, the major obstacles to integrated building automation cabling system development and deployment were that the various systems described above had proprietary, independent communications systems from numerous manufacturers and that typically each system had its own specialized trade for installation. Of course, we are experiencing a convergence in the trade with the electrical and communications contractor now branching out into other areas of business. Additionally, the manufacturers of these systems have started to use ethernet as communications systems, making the systems less proprietary and universal, allowing for the use of a common cabling system to support it.

The TIA document presently out for ballot is Building Automation Cabling Standard for Commercial Buildings, SP-3-4655-B, which will be published as TIA/EIA-862 when approved. This document’s scope is very similar to TIA/EIA-568-B.1 in its intent to provide specifications, requirements, and guidelines for a generic building and campus cabling system in support of BAS requirements, just like TIA/EIA-568-B.1 provides for voice/data/video systems.

First, the specifications for the cabling components (cable and connectors) are the same as those for TIA/EIA-568-B. The document simply references the previously established TIA/EIA-568-B.2 requirements for balanced twisted-pair cabling (Category 3 or 5e) and by TIA/EIA-568-B.3 for optical fiber cabling (62.5- or 50-micron multimode or single-mode). The backbone requirements, both intra- and inter-building, are basically the same as those established within TIA/EIA-568-B.1 with some cautionary notes relative to sheath sharing, because of safety considerations established by local codes and regulations.

The significant difference between TIA/EIA-568-B and the proposed BAS specification is with the topologies recognized for horizontal cabling. Two new terms are required to explain these differences: horizontal connection point (HCP) and coverage area cable. The horizontal connection point is similar to the consolidation point recognized for open office (zone) cabling in TIA/EIA-568-B.1 in that both are connection points located in the office area between the telecommunications room and the user/device. However, unlike the consolidation point, which requires that it be connected to telecommunications outlet and that it not be used as a cross-connect, the HCP can be used either in conjunction with a BAS outlet or can be directly connected to a BAS device without an outlet. When it is directly connected to a BAS device, the HCP can be used in a cross-connect function. “Coverage area cable” is a new term for the cable connecting either the BAS outlet or HCP to the BAS device. The figure shows the basic three options allowed. The distance limitations for horizontal cabling are 90 meters, just as with TIA/EIA-568-B.1.

As with TIA/EIA-568-B, the BAS document requires that the HCP or BAS outlets be installed in a star-topology from the telecommunications room. However, the BAS document allows the coverage area cables to be installed in additional topologies, such as bus or ring, using multipoint connections.

While TIA/EIA-568 had immediate market acceptance with its introduction in 1990, TIA/EIA-570 for residential cabling had limited acceptance with its introduction in 1995; however, it is gaining market acceptance. Whether structured, generic BAS cabling systems become widespread in the United States is yet to be determined. EC

BEAM is director of systems marketing at AMP NETCONNECT Systems. He can be reached at (336) 727-5784 or tebeam@tyco- electronics.com.

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