Residential cabling standards put to the test
Sorting through residential-wiring specifications helps determine what you must test, and how
Sorting through residential-wiring specifications helps determine what you must test, and how.
My first recollection of residential wiring consisted of one hard-wired telephone line in the kitchen and one color television connected through an electrical outlet, using rabbit ears for fine-tuning three local stations. In fact, wiring for telephones was an afterthought; electricians or telephone company employees typically pulled the cable to one or two locations after home occupancy.
Today, I could not fathom life without a complete home office, including a minimum of two, four-pair Category 5 unshielded twisted-pair (UTP) cables for telephone, fax, and modem use in every room, and multiple rooms with RG-6 coaxial cable for television.
At any rate, we are certainly not dealing with plain old telephone service (POTS) wiring anymore. Today, many homeowners expect multiple pre-wired jacks for high-speed data networks, telephone, and cable TV access.
Residential and commercial systems
In the workplace, we have come to expect high-speed commercial wiring for data- and voice-intensive applications. But with the growing use of the Internet and telecommuting, as well as the emergence of high-speed home automation wiring to control voice, audio/video, and security applications, the residential cabling market is demanding efficient, structured cabling systems comparable to those found in commercial environments.
Just as commercial structured cabling manufacturers have jumped on the bandwagon to provide comprehensive product lines, certified commercial cabling systems installers are in demand to specify, install, and test residential cabling systems to assure that they meet today's networking demands and comply with evolving standards.
Although the basics of residential cabling can be derived from standards and practices in commercial cabling systems, residential wiring is its own discipline with its own set of rules. The networking differences between single-home units and larger office complexes can include cable type and networking applications. Whereas commercial networks are data- and voice-intensive, residential systems frequently encompass audio and video applications.
One of the newest tools for the residential installer, the MicroScanner Pro, tests both UTP and coaxial cable without external adapters.
The cable types chosen for use in commercial networks must be capable of handling bandwidth-intensive applications and high-speed backbone traffic, and must also accommodate long runs. For these reasons, many commercial users choose Category 6 UTP or fiber-optic cables. Types of cable typically used in residential systems include Category 3 UTP for voice, Category 5 UTP for data and voice, and coaxial cable for audio and video applications. Often, these mixed-media types are bundled by the manufacturer and pulled together. Another common characteristic of residential systems is shorter, less-dense cable runs.
But whether the system resides in an office, a single-family home, or an apartment, a cabling infrastructure should be efficient and, therefore, well-planned. For any structured cabling system of any size, system designers should consider all possible applications-current and future-and make sure enough media is included to handle those possibilities.
When designing a residential cabling system, you can emulate some of the flexibility found in commercial structures, such as using patch panels rather than punchdown blocks for simple plug-and-play capabilities. In fact, many product manufacturers have entered the residential marketplace with their own line of in-home products, which are scaled-down versions of the high-density equipment used in commercial environments.
To truly emulate a commercial environment, however, importance must be placed not only on products and installation practices, but also on verification and certification standards to assure system reliability. To address the unique cabling found in the residential market, commercial field tester manufacturers, including Microtest (Phoenix, AZ), are producing equipment that can test UTP and coaxial cabling. These testing procedures are crucial to verifying the cables' performance and ability to meet evolving standards. The Micro-Scanner Pro, for example, has been developed to test both UTP and coaxial cable at the same time. It also runs tests that specifically apply to residential systems, but does not have the complex test capabilities or associated costs of field testers necessary for certifying commercial systems.
Since telephone deregulation in the 1980s, the homeowner has become owner of the home's wiring. But to provide some level of assurance that a home's cabling system can carry data, users are best served by following guidelines and regulations currently being developed.
"Before the Internet took off in 1994, telephone analog lines in homes were installed for the sole purpose of voice connection," says FCC chairman Michael Powell. "With the introduction of the Internet, those same phone lines are now expected to carry high-speed digital data. We now need to look at other options, since today's and tomorrow's data transmissions over long distances through analog telephone lines become weak. POTS wires, which have been the standard for builders, will not suffice anymore. Poor-quality telephone wiring can substantially degrade the performance of evolving broadband technologies."
Working on the idea that verifying residential systems does not require the sophistication of commercial-grade cabling testers, Microtest introduced the MicroScanner Pro, which is a far less complex tool.
In late 1999, the Telecommunications Industry Association/ Electronic Industries Alliance (TIA/EIA-Arlington, VA) published the TIA/EIA-570A standard for residential telecommunications cabling. The standard encompasses the products, installation practices, and testing procedures involved in residential cabling. It is patterned after the TIA/EIA-568A standard for commercial building telecommunications cabling systems, the TIA/EIA-569A standard for commercial building pathways and spaces, and the TIA/EIA-758 standard for customer-owned outside plant cabling.
Basically, 570A seeks to standardize the requirements for new construction, additions, and remodeled single- and multi-tenant residential buildings in the realm of telecommunications services. It encompasses more applications than the 568A standard, since it includes guidelines for installing voice, data, video, multimedia, home-automation, security, alarm, and home-automation systems.
Last January, the FCC adopted the 570A standards and the installation practices put forth by BICSI (Tampa, FL), under a filed report and order document. That order concentrates on the connection of residential inside wiring to the telephone network in order to establish minimum inside-wiring quality standards, so that poor-quality inside wiring will not hamper today's services.
"We predict that the inclusion of these inside-wiring quality standards will be built into local building codes and will facilitate enforcement by causing simple inside-wiring installations to be subject to the same inspection and approval process as electrical wiring," Powell says.
Commercial vs. residential standards
Residential cabling standards for voice and data are still not as sophisticated as those of the commercial world. The TIA/EIA-570A standard specifies two acceptable cabling grades, which include Category 3, Category 5, Category 5E, coaxial, and fiber-optic cable. TIA/EIA-568B.1 specifications for commercial infrastructures will include performance levels of Category 5E cabling, as well as recognizing 50/125-micron multimode fiber, and allowing optical-fiber connectors other than the SC throughout a cabling system. The standard, however, will not support Category 5 in the horizontal, instead recommending Category 5E as the minimum-accepted performance level.
An addendum to the 568B standard, which will regulate the performance of Category 6, is currently under review. Many commercial users today are already choosing to install cabling that meets the proposed Category 6 specifications (currently in draft seven).
By contrast, the two grades mentioned in residential standards support telephone, television, data, and multimedia transmission:
- Grade 1 provides a generic cabling system that meets the minimum requirements for telecommunications services; it includes one four-pair UTP cable and associated connectors to meet Category 3 cabling requirements, and one 75-ohm coaxial cable.
- Grade 2 provides a system that meets the requirements for basic, advanced, and multimedia telecommunications services. Systems specified include a minimum of two four-pair UTP cable and associated connectors that meet or exceed Category 5 performance requirements, two 75-ohm coaxial cables, and an optional two-fiber optical cable. Also, the 570A standard recommends, but does not require, the use of Category 5E rather than Category 5 cable in residential systems.
Standards for residential cabling include recommendations for distribution-panel location, wall-space allocation, electrical power, cabling topology and pathways, outlets, and cable protection. Bear in mind, however, that while some standards intended for commercial applications may also apply to multi-dwelling housing, those standards may be overkill for single-unit residential environments. With fewer cables, conduits are smaller and, therefore, cable protection is more lenient in single dwellings.
Maximum span lengths for commercial buildings are 90 meters for a link and 100 meters for a channel, but an average house does not even encompass that distance when the user implements a star configuration. The standard recommends a minimum of one outlet per room, but also recommends additional outlets for every 12 feet of wall space.
Testing is key
Residential system installers must apply the appropriate standards to both installation practices and testing procedures to guarantee cabling reliability. In commercial cabling, standards are solidly in place for testing and certifying structured cabling systems. Business systems are expected to place high demands on installed cabling. While such networks are certified to meet standards, most home-cabling systems are verified.
Verification follows basic cabling procedures and installation practices, such as cable placement, stress, protection, and proper connectorization to ensure cable continuity. Certification is significantly more stringent, as it refers to specified measurements that must be compared and must meet predefined industry standards.
Certification is a crucial element of the total cabling-installation process, and is necessary before a cabling plant is turned over to the user. For example, certifying an installed Category 5E system typically involves thousands of measurements, which are processed in complex formulas to derive pass/fail results. Characteristics measured include near-end and far-end crosstalk, wiremapping, length, delay, delay skew, and return loss. Verification, on the other hand, does not attempt to measure the link's information-carrying capacity because links in home networking are considerably shorter than those in commercial systems. So, for example, residential links do not suffer nearly as much from attenuation losses.
The TIA/EIA-570A standard includes normative field-test requirements of the cable and connecting hardware. Backbone testing includes checking for continuity, shorts, crossed pairs, reversed pairs, split pairs, and any other miswiring. Specific tests for the UTP cable and outlets include wiremapping, length, attenuation, and near-end crosstalk. Additional field tests conducted when Category 5E is installed include power-sum near-end crosstalk, power-sum equal-level far-end crosstalk, and return loss.
In verifying residential cabling, wiremap is the most important measurement or diagnostic function. Wiremap ensures proper pin-to-pin connectivity between both ends of the link. In a home, a cable could be cut or shorted by a nail; it could be stapled, incorrectly terminated, or miswired. A good wiremap tester will find any breaks, shorts, or miswires to help installers identify and fix the problem quickly.
High-end, high-cost, complex testers used on commercial sites are excessive for residential applications. Installers can achieve the necessary results by using a tool that performs fewer tests, but does so efficiently and at a lower cost.
As an example, Microtest's MicroScanner Pro was developed specifically to let residential application installers verify all cable functions. It measures length and wiremapping, and tests both coaxial and UTP cabling without the need for external adapters. It is also a troubleshooting tool that can pinpoint opens, shorts, as well as crossed and split pairs. Its active network identification can determine if a network tap is operating at 10-, 100-, or 10/100-Mbit/sec Ethernet. It can also identify drops and outlets in each room.
To support the versatile products and technology used in the home, the cabling infrastructure installed today must support applications of the future. Cable, termination equipment, and tester manufacturers are charged with ensuring that these systems also address the unique requirements of each residential location and application.
Experienced vendors already involved in commercial cabling will tap into their engineering expertise to provide a list of customized home products that will eventually become standards for tomorrow's smart homes. Those who will emerge in this marketplace are those who can apply the principles of the commercial environment to the uniqueness of the residential market.
Carol Everett Oliver is principal of Everett Communications, a marketing and public relations firm in Ashland, MA. Mark Johnston, RCDD, director of technology development at Microtest (Phoenix, AZ), also contributed to this article.