Articles and whitepapers

6/5/2003

Wiring Options

By David Webster

Today's homes are more than places in which to just eat and sleep, they are an integral part of our modern lifestyle, and as such are called upon to provide many services. These include heating and lighting of course - but newer services, such as security, communications and entertainment, have become just as important - particularly for the increasing number of people who work from home.

Just as traditional services, such as water and heating, have needed infrastructure, so do the newer services. Today this usually means wiring - lots of it - and many different types of cable for all the various applications.

So when planning the wiring for your home, exactly what cables do you need and where should you run them?

The options

Generally speaking, each service will be expected to be wired separately from the others, and if cost is not a consideration, it is straightforward to wire each room from a central location, with all cable types to allow for current and future needs. In practice, this may not be possible, and the solution will be to run a more limited number of general-purpose cables, and to optimise mains power wiring for lighting control.

Conventional lighting control uses mains wiring local to the room. This is simple to upgrade to wall-box-mounted dimmers, but be aware that many require a mains neutral connection. This is the easiest retrofit, but precludes the possibility of controlling more than one room at a time.

A more sophisticated alternative is whole-house centralised dimmers, where each lighting circuit is mains-wired directly to the dimmer, with a separate low-voltage network for all the in-room control keypads. The control cable will probably be a twin twisted-pair type or maybe CAT5. Once installed however, this kind of wiring is not suitable for any other kind of lighting control.

A third option is to use in-wall dimmers that are controlled through signals carried on the mains wiring itself, such as EIB, X10 etc, thereby eliminating the need for separate control cables. Currently, there are few of these products available, and many have only the most basic of controls, but if suitable for your needs, the cabling is straightforward.

Distributing audio and video signals can be achieved simply with a UHF cable and RF modulators for TV, and speaker cable for audio, but the quality can be greatly enhanced by using baseband systems. These usually use low-level balanced signals to connect the central sources to rooms. Each room must then have a receiver box that converts the signals back to unbalanced form for connection to local audio power amplifiers and video displays. CAT5 cable can often be used for this purpose, but multiple cable runs may be needed if full bi-directional audio and video is required.

If touch panel control systems are to be included to integrate many of these services, then they have their own cable requirements. Often this will be twin twisted-pair cables that deliver low-voltage DC power and bi-directional communications to touch panels and other components.

Many devices and control systems however, are now being fitted with Ethernet ports which will allow them to be attached to a home network. This can permit any existing CAT5 computer network wiring to be used for equipment control, as well as sharing broadband access etc. In the future, higher network bandwidths than the current 10/100baseT types may also permit high-quality audio and video distribution around the house.

Summary

For maximum flexibility at lowest cost, the current trend is to flood-wire houses with as many CAT5 cables as possible to RJ45 sockets in every room, preferably wired in a star configuration back to a central location with a patch panel to permit different services to uses the cables. This is fine for computer networks, telephones, and audio and video line-level distribution, but is not really suitable for in-wall devices such as lighting control keypads or touch panel control systems. To accommodate these, twin twisted-pair cables should be used so that volt drop problems are reduced. Additional speaker-grade wiring may also be needed for built-in wall- and ceiling-mounted loudspeakers.

While more radio based systems will become available that may eliminate the need for many of today's cables, it should be remembered that most sources and displays will still need wires to supply the power.

David Webster is the Technical Director of RGB Communications Ltd.

Telephone 01488 73366
www.rgbcomms.co.uk