A correctly specified and installed cable management system ensures that a structured cabling system performs at its best - so cable management should be considered from the start of a project, says Mita's Steve Davis:
An appropriate cable management system will do much more than simply contain the data cables. It will ensure the best network performance by segregating them from power cables and maintaining minimum bend radii.
Sadly, on many projects, cable management is little more than an afterthought. Some building owners think nothing of spending £100,000 on a structured cabling system with a 25-year warranty, but leave it to others to specify cable management products during fit-out.
Maximising performance:
In the past, this approach has rarely caused problems. Even today, almost half of structured cabling installations are Category 5e, and standard containment systems have proved suitable for many of these data networks.
Category 5e cables consist of four twisted conductor pairs in a cable between 5 and 5.5mm in diameter; and although bending the cable too sharply will compromise the performance of the cable, the demands on the cable management system are not too onerous.
Today, however, Category 6 installations are increasingly popular. Category 6 cables also consist of four twisted pairs, this time separated by a central spine or cross member. There are also more twists per unit length of cable than there are in Category 5e cables, and their overall diameter is between 5.8 and 6.5mm.
Because any copper cable's ability to transmit data at high speeds depends to a large extent on the precision with which the individual pairs of conductors are twisted together, excess bending will disturb the geometry of the twists, reducing network performance.
This means that standard cable management products are unlikely to be suitable for a Category 6 network. To make matters worse, many structured cabling jobs are in speculative office developments, and it may not be clear during fit-out what kind of data network is to be installed. A recent project I worked on in London is a good example. It had been planned that the cable management system would accommodate Category 5e cables throughout. However, when interest was shown by potential tenants, they indicated that they wanted Category 6 networks. Fortunately, we were able to supply more appropriate cable management products at the last minute. Some people have not been so lucky, and have had to rip out entire cable management installations and replace them - an expensive business.
In today's fast changing markets, both specifiers and installers require cable management solutions that not only keep pace with current demands, but are also future proof - allowing for the rapid pace of future changes.
Burgeoning bandwidth:
Looking to the future, the newly emerging Category 7 specifies four individually screened conductor pairs and the cable is about 10mm wide. Its bulk alone demands a greater minimum bend radius.
Then, on the horizon, is the possibility of 10 Gigabit over copper networks. Recent experiments suggest that this will only be possible with shielded cables - either Category 7 or shielded Category 6. Cables will be thicker, and bend radii critical for optimum performance.
However, at a recent TIA meeting, a number of structured cabling manufacturers have launched a new Cat 6 copper solution for 10 Gigabit which meets the current draft set by the standard bodies, making the choice of cable management system even more critical in delivering these protocols to the desktop.
For optical fibre the situation is different, although the result is the same. If a fibre cable is bent excessively, the optical signal escapes through the fibre cladding. Bending, especially during installation, can also permanently damage the fibre by causing micro cracks. Bend radii are as critical for fibre as they are for copper cables.
And then there are the other factors that make the choice of cable management products vital if network performance is to be optimised:
- Copper data cables must be separated from power cables. BS EN 50174-2 sets out separation distances for horizontal lengths of cabling that are over 35m long.
- Over-enthusiastic application of cable ties can have a similar effect to an insufficient bend radius - particularly on the cables on the outside of the bundle - distorting the twisted conductor pairs.
- Pulling the cables too tightly during installation can also untwist the conductors.
Containment's crucial role:
If there is one lesson to take away from all of this, it's that, as bandwidth increases, the choice of cable containment products becomes more important - and it's something that must be considered from the start of a project, not left until the end.
It should be the responsibility of the client or the M&E consultant to consider cable containment. After all, the consultant is in a position to say to themselves: "I want this particular trunking because I know the client plans to install a Category 6 network."
It is also vital to think ahead. Clients and consultants must make every effort to future-proof their installations, including cable management. To do so, they need detailed knowledge, not only of today's structured cabling systems, but of those that will be commonplace in a few years.
So what should consultants be looking for when they are specifying cable management products? Modern trunking, backboxes and floorboxes - and their accessories - reflect the changes taking place in the structured cabling environment. They are designed to accommodate not only conventional Category 5e and 6 cables, but also Category 7 and fibre optic cables.
The latest two-compartment perimeter trunking, for example, is deeper than that in conventional systems, with enough space for an increasing number of network cables.
Also, the data compartment may be larger than the power cable compartment, and to prevent interference, the two will be separated with a divider. Internal and external angles are designed to provide a minimum bend radius of 50mm thereby protecting the integrity of the data cabling.
Trunking backboxes - and floorboxes - are also changing with the times. The latest products are deeper than their predecessors to accommodate larger cable bend radii and Category 6 RJ45 connectors, which are larger than the older Category 5e versions.
So, given that cable management products are crucial to the performance of high-speed data networks, how can we be sure that specifiers are making the best choices?
Setting the standard:
Perhaps the most significant recent developments are in standards. Most people working in the structured cabling industry will be accustomed to seeing specifications that refer to standards from a confusing array of different sources - the Telecommunications Industry Association (TIA) in the US, the International Standards Organisation (ISO) or Europe's Cenelec, for instance.
That is set to change following the publication this year of BS 6701, Telecommunications equipment and telecommunications cabling, specification for installation, operation and maintenance. BS 6701: 2004 is an update to a decade-old code of practice that, unlike its predecessor, is mandatory.
One of the reasons for the standard's new status is the IEE Wiring Regulations, BS 7671, which calls for the segregation of power and data circuits in accordance with BS 6701. As a result, any building that is covered by the Wiring Regulations is covered by parts of BS 6701.
BS 6701, in turn, refers to the BS EN 50174 series of standards, in particular BS EN 50174-2, which covers the separation of UTP and unscreened power cables to prevent electromagnetic interference.
Some of the standard's specific requirements are that power and data cables sharing a compartment of a cable management system must be installed following the installation specification and the cable supplier's instructions. Also, fixtures and fittings that support telecommunications network cabling must be used in accordance with the installation instructions of both the cabling manufacturer and the supplier of the fixtures and fittings. Similarly, installers must observe the minimum bend radii of cables set out by the cable manufacturer or supplier.
Installers must also ensure that they record the locations of all cable pathways and their contents.
Knock-on effect:
But these are just the technical details. The new standard will have a knock-on effect - making people think about cable management at the design stage, and throughout a project. It puts more responsibility on the shoulders of the building owner, or the consultant working for them, and on the installer contracted to fit the cable management system.
It's also good news for consultants, who will no longer have to prepare specs that refer to a plethora of standards from the TIA, the ISO and Cenelec. A simple reference to BS 6701 should do the trick.
While it may take some time for the effects of BS 6701: 2004 to be felt, it should encourage more effective communication between all parties involved in a structured cabling project. In its new incarnation, BS 6701 promises to clear up a lot of confusion surrounding the installation, operation and maintenance of structured cabling.
It's good to talk:
Beyond the standards, there are signs of better communications between the makers of cables and cable management equipment, and between data installers and electrical contractors.
I've been talking to the manufacturers of structured cabling systems, and with the TIA. And in recent years, there have been fruitful discussions, helping to ensure that the latest cable management products are suitable for today's networks, and for those of the future.
For their part, makers of structured cabling systems are taking cable management more seriously as it becomes crucial to the performance of their networks. Many manufacturers guarantee their installations for up to 25 years, and when they arrive on site to inspect an installation, they expect to see good practice.
There are also signs that electrical contractors have been taking more interest in data installations, and talking to the data installers. The exchange of information can only lead to better decision-making.
For too long, cable management has been an afterthought when network cabling is installed in a building.
Fortunately, with the new products coming onto the market, and a greater emphasis on containment at the design stage, we can rest assured that today's - and tomorrow's - structured cabling systems will fulfil their potential.