Electricity distribution is best achieved through trunking that allows for the availability of as many socket outlets as are needed to avoid the use of extension leads, as these can be potentially dangerous. It is significant that reported statistics show that 15 percent of serious injuries caused by electricity are in schools and colleges, and many ‘electricity’ accidents are attributable to people tripping over extension leads.

For the specifier there is a wide choice of different brands of compartmented trunking available on the market. But it is only now that a product has been introduced that is eminently suitable for schools, as well as being of a superior design that overcomes many of the common problems associated with trunking generally.

Three-compartment compact trunking is the result of the conclusions reached by focus groups comprising installers, end users and specifiers, who were asked to identify the criteria by which they chose trunking, and what they saw as any special requirements pertaining to schools. They ranked aesthetics as one of the most important specification criterion, followed by ease of installation, but given that trunking is probably treated more roughly in schools than anywhere else, emphasis on strength and durability was also ranked very highly.

A common problem associated with trunking is that, however aesthetically pleasing it may be as a manufactured item, when installed it can be ungainly and unsightly. This is not necessarily due to poor workmanship by the installer, but more likely due to imperfections in the structure of the building in which the trunking is installed. Uneven walls, for instance can create obvious gaps between the wall and trunking, and non-square corners can have a dramatic effect on the overall neatness of an installation.

The problems that arise from non-square corners are overcome through the provision of hinged and flexible trunking corners. External corners can be especially tricky, particularly when the trunking accommodates data cabling; this must not be bent below a minimum radius to ensure that its transmission capability is not to be compromised. These potential unsightly corners can be avoided through a data sweep component that allows cables to be taken round an external bend without resulting in a bulbous appearance and without reducing capacity or performance. And with or without data cabling, external corners require maximum strength to avoid accidental damage from the everyday wear and tear exerted by pupils and staff.

Where trunking is required to be run from a horizontal to a vertical direction, then moulded flat angles can provide the best solution for maintaining Cat 6 compatibility. Instead of a fabricated angle, as would be the norm, a moulded fitment would allow for greater design flexibility, and a one-piece cover would make it easier to install. No loss of data capacity would be experienced, and the resulting moulding becomes more aesthetically pleasing. Similar benefits accrue from moulded tee and crossover bridges that can be used in place of fabrications.

Of the trunking currently available on the market, the sales growth of three-compartment versions with dimensions of 170 x 50mm is slowing. This is because 140 x 45mm compact two and three-compartment trunking has gained in popularity. Sales of this grew by 150 percent between 2000 and 2003 and are predicted to grow a further 15 percent by 2007. Demand for standard twin compartmented trunking, generally favoured for its greater data cable capacity, is significant, but, in line with predictions, sales have not grown as quickly as for compact. This is partially due to the physical size of the product, 210 x 60mm, making it obtrusive in comparison with other systems. Single compartment trunking is also available.

Compared with conventional two-compartment trunking, three-compartment compact trunking allows for the creation for a more aesthetically pleasing installation, hence its recent sales growth. The central compartment, which is not a wireway, is used only for access to wiring devices. This allows for the preferred aesthetic of centrally placed accessories, unlike the top or bottom mounting on two-compartment trunking. Installation time is also significantly reduced when wiring this configuration, especially when the improved design of the constituent components is also taken into account. Specifiers rank ease of installation as an important specification criterion; trunking that is easy to fit saves the contractor time in its installation and therefore as a consequence reduces the cost to the client.

When a central trunking compartment is full of cable, the lack of space makes the installation and termination of wiring devices fiddly and time consuming. The solution is therefore for this to be a cable-free compartment solely for the purpose of mounting and terminating devices. But, of course, going down that road makes it necessary for power and data cables to be able to pass easily from the cable run into this central compartment for termination. The best way to achieve this is to provide large ‘knock-outs’ in the partitions of the inner compartments. Further assistance in cable routing can be provided by the introduction of innovative new backless, topless and bottomless one and two gang boxes. These, in effect, are frames that use their sides and the base of the trunking to completely segregate the power and data services. The benefit is that there are no holes to drill, rendering the complete 45mm of the depth of the trunking useable and consequently making cable termination to the socket or data outlet dramatically much simpler.

The provision of hinged lids for the upper and lower compartments was highlighted. It was included in the new trunking as another requirement from the focus groups to assist installers with the laying of cables before termination, and allow easy expansion of the system for the future.

Three-compartment compact trunking has been developed to overcome space restrictions, now more problematic as building regulations move contractors away from skirting and toward dado trunking. Part M recommends that sockets be installed at a minimum height of 400mm, thus effectively marginalising the use of skirting trunking. In schools, power and data cable trunking is often needed in any event to be wall mounted at bench level. Where the bench is against a window the space for mounting the trunking is often minimal, hence having trunking of the right dimension to fit into the space available can be of paramount importance. This latest compact version of three-compartment trunking is designed to fit into almost all available spaces between bench and window, even in refurbishments.

In addition to making the installation of trunking easier and speedier, the focus groups discussed other problems that arise with trunking, especially for use in schools and colleges. For instance it emerged that trunking installed in schools is likely to receive rougher treatment than in other locations, and may also be subjected to tampering. And to enable the corners and covers of the trunking to be made as secure as possible, an optional screw fixing is required.

Finally, compact trunking has the advantage of accepting standard electrical accessories with 3-pin operated child resistant shutters, designed to inhibit access to the electricity supply, unless all three pins of a standard 13 Amp plug are in position. Dual earth can also be fitted to provide protection against high circuit protective conductor currents.

Alan Durrant is a Product Manager for MK Electric, responsible for MK cable management, Ackermann, circuit protection and dataworks. He has been with MK for five years and has over 15 years marketing experience. Prior to MK he worked for an electrical distributor. Alan has an engineering degree and an MBA.

Printer friendly version

Email this article to a friend