Wire cable tray is highly regarded as a cost-effective solution for the containment and protection of general wiring and power cables in commercial and industrial installations. However, Paul Courson, managing director at Cablofil UK suggests that its many advantages for modern structured wiring networks are less well understood.
With literally millions of metres of wire cable tray installed in buildings of every type since its European launch more than 30 years ago, this versatile product is now firmly established as a flexible and cost-effective cable management system. Fast and very easy to handle and use, even under the most difficult and restricted site conditions, its flexibility means that curves, bends and changes in mounting levels don’t need to be planned in advance, saving contractors’ time and costs.
It’s also worth noting that because of excellent air circulation, both power and control cables installed in wire cable tray can be classed as ‘clipped in free air’, allowing significant de-rating. The open mesh construction also provides free drainage and prevents the build-up of dust and debris, giving far higher levels of cleanliness and hygiene and eliminating possible fire and safety hazards. Cables can be dropped out safely at any point and are highly visible, allowing cable runs to be easily identified, visually inspected and controlled, while the smooth rounded welded wire construction of the tray reduces the possibility of damage when wire and cable is being installed.
However, although wire cable tray has gained widespread popularity for the containment and protection of both power and control wiring and cabling, some installers still have reservations over its use with high-tech, high-bandwidth data-communications cabling for structured and converged network solutions.
Despite the lack of documented evidence, it is assumed that the large number of cables capable of being carried in deep-sided cable containment would have sufficient total weight to cause mechanical stress or even partial crushing of the lowest layers, impairing their performance. Since its introduction, many millions of metres of Cat5e and Cat6 cables have been installed in wire cable tray without a single reported problem due to installation density. Nevertheless a ‘flat surface’ is still assumed to be the most suitable cable management system, irrespective of either the material used or its properties, frequently forcing installers to use unduly expensive products or containment which is difficult and time consuming to install.
Dispelling any previous misconceptions, independent tests to international TIA/EIA standards show that at a depth of 40 Cat5e or Cat6 cables there is no difference in performance between a wire cable tray and a ‘flat surface’. Temperature cycling tests also indicate that as wire cable tray containment allows air to circulate freely, it can provide a positive advantage, preventing overheating.
While wire cable tray provides ideal containment for power as well as communications cables, the situation is less clear where space is limited or only a small number of communications cables and power cables need to be installed along the same route, especially if costs are under pressure. Current standards call for a minimum separation distance between unscreened power and unscreened UTP cable of 200mm. This is reduced to 50mm for screened data cable and to just 30mm if the power cable is screened, as although electro-magnetic interference from the power cable can reduce data cable performance and speed of data-flow, it is unlikely to corrupt the data.
Having said that, if a steel divider is used in a metallic cable tray it will reduce significantly the necessary separation between power and data cables. If these are unscreened and the divider is both physically and electrically continuous, separation can be as low as 50mm. Independent tests have supported the guidelines given in the data cabling standards, showing that increased separation reduces interference levels. However, tests also show that if both power and data cables are placed in enclosed trunking, interference levels on the data cables are far higher. Installing data and power cables in an open wire cable tray with low impedance couplings and a continuous metallic divider reduces the problem instantly, providing significant savings in space, installation time and costs.
Particularly in large installations, data-communications cables are installed below false flooring, either on cable matting, or occasionally laid directly on the concrete sub-floor after treatment with a suitable sealant. Despite the relatively high cost of matting, neither system can avoid the potentially damaging effects of poor water drainage. Ingress of water into a data cabling system can have serious implications for performance, will usually invalidate any warranty and can be extremely costly, time-consuming and disruptive to put right. To reduce the risk of damage, data communications cable manufacturers recommend consistently that their cables are installed in appropriate containment raised above floor level. The type of containment chosen by the installer should be designed for use with Cat5e Cat6, Cat7 or optical fibre cabling to provide a ‘controlled pathway’ and suitable protection against water ingress or mechanical damage.
With wire cable tray providing free air circulation for efficient cooling and protection from condensation, ‘tray’ containment systems mounted on suitable brackets offer all the necessary protection for underfloor installations. This type of cable containment not only provides a simple, clearly defined pathway, but also allows cable runs to be identified easily, effectively and very inexpensively. No matter where it’s installed, any cable containment system which can meet these requirements while saving the contractor or installer both time and money, must be a pretty good bet in today’s cost-conscious building environment.
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