Understanding residential wiring systems for the digital age

Nov. 1, 2000
A recent FCC ruling, effective in July 2000, now requires that homes as well as businesses be wired with better telephone cabling.The home of the future is not quite here, even though PC companies and telcos are touting technology that can network computers and a host of other gadgets in a home and perform marvelous feats of service.Now that microprocessors have changed the way we work (the home office)

A recent FCC ruling, effective in July 2000, now requires that homes as well as businesses be wired with better telephone cabling.

The home of the future is not quite here, even though PC companies and telcos are touting technology that can network computers and a host of other gadgets in a home and perform marvelous feats of service.

Now that microprocessors have changed the way we work (the home office) and play (the living room and home entertainment center) companies are pressing on to conquer the next frontier - the way we cook, sleep or wash clothes. However, to really make home networking a reality, firms have to make the technology easy to use as well as relatively inexpensive. And electrical contractors have to know how to wire these homes.

A study by the Consumer Electronics Manufacturers Association (CEMA) reveals that 96% of home offices have a computer, and 25% of them have more than one. About 60% of these households have Internet access, of which 93% use e-mail. And 30% of these home offices have more than one telephone line.

Presently, the kitchen is where most pervasive-computing appliances are emerging. Sunbeam, for example, recently announced the creation of a company called Thalia Products (Thalia stands loosely for "thinking and linking intelligent appliances") and is planning to offer items like a coffee maker, mixer and alarm clock this fall.

Most appliances plug into the wall, which means they are already connected to wiring that runs through the whole house. Thalia's HLT[TM] (Home Linking Technology) circuitry uses a home's electrical wires to communicate with other appliances.

It may sound like just so much new-millennium hype, but Net-enabled applications are just around the corner.

In similar fashion, Symbol Technologies announced that its product code scanners are integrating into the line of General Electric Smart Appliance, allowing consumer to easily develop a grocery list. A user simply scans the UPC code printed on any type of packaged food product, whether from the refrigerator or the pantry. At the same time, Voice Signal Technologies is planning to add speech technology to a General Electric oven.

GETTING THE HOME NETWORKED To gain many of these automating and control features, a consumer needs what is called a connected home. With a connected home, users can gain high-speed Internet access from almost any room. They can program the lights to create a "lived-in" look and check the security system via telephone while away, answer the door through the phone or monitor the nursery via video through a PC. The first step in creating a connected home is the installation of a structured wiring system.

What is structured wiring? A structured wiring system is made up of three main components:

The service center - The cabinet, or panel, where all outside service enter the home, including telephone, cable TV and DSS satellite. This center hub then distributes these services throughout the house.

High performance cables - To carry telephone and data, four-pair (Cat. 5 or better) twisted-pair copper cabling is needed. For digital satellite television and digital CATV, a quality coaxial cable is needed. Multimode optical fiber is also included in this list, although presently only high-end homes use this media.

Optical fiber may not be needed for the typical home at this time, but 3Com Corp. and two other companies have jointly developed technology that delivers High Definition Television (HDTV) over the Internet. HDTV is a digital television standard that offers high-resolution, superior video and DVD-quality sound distribution on cable TV lines and satellite TV systems. The consortium has demonstrated video streaming at 20Mbps, so somewhere in the future, optical fiber may be considered.

Wall Outlets - These hardware devices, such as modular jack, connect to a telephone or computer. Using these three main components, a structured wiring system, begins at about $600 and can run as high as $10,000 or more, depending on the size of the new residence and the number of connections and options specified. A rough average is somewhere in the $3,000 to $5,000 range. In addition, a 2-in. PVC pipe, installed as a riser from the basement to the attic, is recommended. This enables new wires to be pulled, if ever necessary, between floors without having to cut into walls or ceilings.

The ANSI/EIA/TIA 570-A Residential Telecommunications Cabling Standard is the best place to start in developing a connected home. Naturally it is telecom-, or telephone-wiring, oriented. The standard bluntly states that the home telephone wiring of the past, often referred to as quad wiring because it has four copper wires, is now obsolete. A Cat. 3 or a Cat. 5 rated telephone cable is needed. These cables have four twisted pairs, or eight wires, and all of them are needed to provide the multiple services discussed here.

In fact, an FCC ruling now requires that when copper wiring is installed for telecommunications applications, at a minimum, it must be solid, 24AWG or thicker, twisted pairs, marked to indicate compliance with specifications for Cat. 3 cabling, as defined by the 570-A standard. The FCC ruling covers both new construction and retrofit projects, and it refers to single or multifamily installations made on, or after, July 8, 2000.

The 570-A standard offers two grades of service: Grade 1 is minimum performance; Grade 2 is better. The difference in the category relates to bandwidth, or the ability to carry lots of information with ease. Cat. 5 cable, with a bandwidth of 100MHz, is the currently referenced in the standard, but, in the future, an even higher bandwidth cable will be required. On the horizon are, for example, Cat. 5e (e for enhanced) and perhaps Cat. 6, which has more than twice the bandwidth of Cat 5 at a small cost premium.

In addition to listing performance categories of cable construction, later versions of the standard will expand its coverage. For example, currently under development, the 570-B standard will include the cabling to serve security, HVAC, audio control, etc.

Contractors and installers involved in residential work should have this document, which is sold by Global Engineering Documents. Orders are taken at (800) 624-3974, by fax at (303) 379-7935 and on the Web at www.global.ihs.com.

The 570-A standard requires a star-wired topology. That is, each outlet (jack) is an individual home run of cabling extending back to the service center, or distribution panel (hub). This topology layout offers three important advantages:

Flexibility. All changes in distribution of services can be easily made at the service center. Each outlet can be treated independently from all others. (In the old loop method - also know as "daisy chain" wiring method - where a number of outlets are tied together in series, outlets cannot be treated independently).

Isolation of problems. When damage occurs (such as when a nail is driven through a wall into a cable or where a cable is severed) only one outlet is affected.

Quality of signal. Star wiring eliminates additional connection points, which are a potential source of interference and other problems, causing a loss of signal quality.

Most industry professionals suggest running "extra wire" to any location where it might be needed later. For example, two 4-pair cables might be run to each outlet, rather than one, to provide expansion and flexibility.

An 8-pin modular RJ-45 jack is used at each outlet. This device provides connection points for all eight conductors in the four twisted pairs and the device must have a rating equal to the cable. That is, if Cat. 5 cable is used, all devices must be at least Cat. 5 rated.

PROPER INSTALLATION A contractor needs to know how to install this communications wiring, and these "hows" include:

- How long a cable run can be (about 300 ft, this part of the standard);

- How much pull can be applied to a cable (usually 25 lbs.);

- How much separation is needed between power and data cables (6 in. at least, crossing, if necessary, at 90 deg.);

- How far back the cable sheathing can be stripped (no further than necessary, typically 1 1/4 in.);

- How much untwisting of the pairs can be done when making connections (1/2 in. is usually the maximum recommended, 3/8 in. is better) and;

- How tight a bend radius can be tolerated (usually about 1 in., although there are exceptions).

For broadband video applications, manufacturers recommend RG-6 quad-shield coaxial cable with an all copper center conductor for maximum performance, not the thinner RG-59 cable. Copper-plated steel center conductors are also available, providing additional stiffness, but they can't handle low-frequency currents used to power some devices.

Any firm getting into home automation wiring has a number of resources available to assist in marketing efforts. An organization called Wiring Americas' Homes recently published a new consumer brochure, "Get Connected for Living," to support dealer/installer marketing efforts. The four-color brochure is available through Home Automation Association (HAA), which can be reached at (202) 712-9050 ([email protected]).

Wiring Americas' Homes also recently unveiled its new connectedhome.org Web site. The site explains how some new technologies work, the "connected home" and provides information about structured wiring and standards.

About the Author

Joseph Knisley

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