Feature Cabling & Cable Management A cabling Q&A
Often there’s more than one option when selecting the right kind of cable management for a job, and getting it wrong could lead to over or under specification or a more complex installation on-site. Here, Legrand’s Nigel Leaver answers your cable management questions
hen considering the core cable management installa- tion on an industrial pro- ject, what are my options? The type of cable management required depends on numerous fac- tors including the type, weight and amount of cables the cable manage- ment system needs to carry, the envi- ronment it will be installed into and the amount of space that’s available for the installation. If using single insulated (non-sheathed) cables, then you will need additional mechanical protection rather than simply sup- port. The most common solution here is a distribution trunking system that completely encases the cables. The wiring regulations have changed recently in relation to this product and you will also need to consider the IP rating of these systems to
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Above: Legrand’s Nigel Leaver provides the answers to some burning cable management questions
such as food preparation or chemical plants may also have specific require- ments which should be discussed with the manufacturer as specialist finishes may be beneficial.
For larger heavy duty loads cable
ladder is usually required and for other applications there is a choice between perforated steel cable tray and steel wire cable tray, both of which can be used for power and data cabling depending on the individual application. Here the main considera- tion is the number of cables and ulti- mately the loading required.
How do I calculate the weight of cables that my chosen system can support? In simple terms, the load bearing capabilities of cable management sys- tems decrease as the systems become more lightweight. However, the real picture is more complicated. The total load should be calculated using the weight of the cables, any ancillary items that are subsequently fitted to the cable management and whether appropriate dynamic loads, such as wind or snow, need to be considered. This weight needs to be worked out as a UDL (uniformly distributed load). Caution should be applied to any point loads as a point load placed at the centre of a span can have the effect of doubling the UDL. From there, the span requirement can be calculated and then the load per sup- port checked.
ensure your installation complies. Distribution trunking is also ideal when tamper-proofing of essential supplies is required.
When using double insulated cables the choice is wider and includes steel wire cable tray, perfo- rated steel cable tray and cable ladder systems. Location will dictate the finish required and typical finishes for metallic systems are pre-gal- vanised or electro-plated for internal applications, and stainless steel or galvanised after manufacture for external applications. Environments
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Above: for large heavy duty loads cable ladder is usually required
The cable management manufac- turer will publish loading data, usu- ally in the form of a simple graph, for their products, so it’s as simple as taking your calculated UDL and the span at which you’re supporting the system and comparing it to the graph. The line on the graph is the manufac- turer’s safe working load (SWL) and if your point is below the line then the product is suitable.
Which is the easiest system to install? Legrand’s Salamandre distribution trunking system comes complete with the couplers pre-fitted and slots in the body - making it an easy system to install. When considering cable trays,
Selecting the right kind of cable management for the job can be a very subjective matter
steel wire cable tray is the easiest to quantify as you don’t need to specify bends or tees as they can all be fabri- cated on-site - and you should expect your supplier to offer training and support for any specific installation challenges on-site. Perforated steel cable tray is simple to install but requires ordering of dedicated bends and tees etc prior to installation. However, Legrand’s Universal Bracket for Swifts medium duty (MRF) and heavy duty (SRF) cable tray ranges can be folded easily into numerous configurations. With nine pre-deter- mined folding
points, it can be
folded, bent, hinged or split to fabri- cate fittings (e.g bends, tees, risers etc) quickly and easily on-site.
How do I know the system I have chosen is robust enough for the installation environment?
The location of the installation and the position of the cable manage- ment within (or outside) the building is an important consideration as this will affect how robust the product needs to be. For marine environ- ments, coastal installations or indus- trial settings where there may be corrosive elements, a deep gal- vanised or stainless steel product may be necessary to maximise the service life of the installation.
What features should I look for to make the installation quicker? Always look for a cable management system that has a full range of acces- sories to choose from so that you can select the brackets, fixings and cou- plers that are easiest for you and most appropriate for the installation. Push fit accessories like the Cablofil Fasloc and Fasclic couplers and flex- ible components like the Swifts Universal Bracket will always help, as will a rounded safety edge that allows you to work at full speed without the risk of any snagging to cables or fingers.
Legrand
www.legrand.co.uk T: 0870 608 9000
Enter 211 FEBRUARY 2014 Electrical Engineering
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