Before the data explosion the main means of distributing power was via cabling in underfloor trunking. Then came power track, a type of underfloor busbar, which is continually being developed and improved. Data and telecoms services in open-plan offices were, and still are, also mainly carried by cable underfloor. The development of systems that are more cost-effective and efficient continues.
A key factor in the evolution of underfloor cabling was the introduction of raised floors. These consist of floor tiles supported on pedestals above the concrete slab to produce a void beneath the usable floor. Raised floors enabled the use of power track and floor box systems for power and data distribution, with the power track and data cabling being installed onto the concrete slab and the floor boxes being installed into the floor tile. As the routing of the power and data services is not dependent upon trunking or ducting embedded into the floor, changes in layout can be more easily accommodated.
The great advantage of underfloor cabling and power track is that they enable more outlets to be installed than are initially required, so when extra desks are put into an office these can be connected to the power, telecoms and data services via floor boxes without too much fuss. This is also of great benefit when desk positions are changed, which in many offices, especially those in the financial sector, happens frequently.
Changing power connections when rearranging desks is not a problem, but if changes must be made to a telephone exchange or data network connections there will be a need to reconfigure the telephone extension numbers and repatch network panels. These tasks must be undertaken by skilled technicians.
Spider weaves its web
An underfloor power, data and telecom cabling system that removes the need for reconfiguration is now available. It is quick and easy and to install and, furthermore, it provides maximum saturation of power and data services without the cost of flood wiring. Called the Spider power and data distribution system, it can be applied to many situations.
The Spider system from Ackermann comprises an underfloor galvanised steel box to which 50 mm-diameter flexible tubes, known as umbilicals, are connected. These umbilicals are used to carry power and data cabling under the floor to service points for desks and workstations. A hub contains power and data units that feed up to eight desks.
It is not necessary to know the final desk layout when planning a Spider installation, but the expected required density of power and data outlets to be provided in a given area is needed. Planning of an installation is based on the grid formed by the 600x600 mm floor tiles commonly used in raised access floors. The service points are positioned according to the grid plan and required density of desks.
Up to 13 tubes can be connected to the hub, but at any one time only eight of the them will be carrying cabling, leaving five for future churn or expansion. This is the secret to the system: it enables desk locations to be moved without the need for repatching of data networks or reconfiguring of telephone extensions, as would be necessary in a conventional system.
When a desk is to be relocated, the services to it are disconnected at the hub and the cable pulled back through the umbilical. Once the desk has been moved to its new location a ferret and cable feeder are used to pull the cables back from this position to the hub, where the services are reconnected to their original socket outlets.
To facilitate access to the hub it must be located immediately under an easily lifted floor tile. This floor tile should have a hatch to provide access to the circuit-breaker located in the hub. This normally has a 16 A-rating, but alternative mcb ratings and types can be supplied and fitted.
The umbilicals are connected at their free ends to grommets that are fitted into floor tiles. These enable the power and data cabling to pass through the floor from the umbilicals to the workstations. The grommets also close off dormant umbilicals.
In a high density application a grommet would be located in every third floor tile, with a centrally placed hub linked to 12 grommets serving every 38 m2 of area. In a low density application the area served by 12 umbilicals from a centrally placed hub could be as much as 108 m2, with a grommet in every fifth tile. A medium density application would have a grommet in every fourth floor tile, the centrally placed hub serving an area of 70 m2.
Having decided on the density of workstations required and mapped out a grid pattern for one Spider, this pattern is repeated across the rest of the floor to be serviced.
The Spider system enables desks to be moved in an estimated ten minutes, with the minimum of disruption. Office churn costs are indisputably reduced.
Grommets versus floor boxes
Floor boxes are the most commonly used product for providing access to underfloor power, data and telecoms services. For the Spider power and data distribution system, grommets are more appropriate, but there are some specifiers who prefer grommets over floor panels boxes, even with standard power track. Grommets have been extensively used in the recently refurbished head office of a major international firm based in London. To meet the power needs of the eight-storey building, each floor has been flooded with six-pin power sockets fed from the power track and with RJ54 voice and data outlets fed from IT cable. Output from these sources is fed to desks by specially designed grommets. These are 200 mm in diameter and have a built-in power outlet, into which the power supply from the track via tap-off is plugged. In addition, there is space to accommodate a voice/data socket unit. The consultants for this project argue that the use of grommets allows more flexibility than underfloor boxes and causes less disruption when changing the location of a desk connected to the data and power system. Grommet manufacturers point out that new versions of their products offer flexibility, as well as being easy and quick to install and use. At the same time, they affirm that the latest versions of their floor boxes have new features that enhance their suitability for most applications. The principal advantage of a floor box is that it will service more than one desk from one outlet in the power track. The latest versions allow for future expansion. Also, as the boxes are the same size as a floor tile they are easy to remove and replace. The most up-to-date versions will have a cable dump that enables excess cable to be stored.Source
Electrical and Mechanical Contractor
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