Draka writes exclusively for the Means of Escape on cable safety matters.
Specifiers and installers have never had such an extensive choice of fire rated cables. However, the welter of legislation that has come on stream in recent years, the trend towards more buildings being designed with fire engineered solutions, and in some cases what can be described as, at best, misleading and at worst downright dishonest claims means that extreme care needs to be exercised. For one application, cables are being installed that do not comply with the relevant standard; more attention needs to be paid to installing cables only if they have the correct marking; and great care must be taken to avoid the plague of sub-standard counterfeit cables. Finally, to ensure that the cables perform to the expected standard, correct installation is essential. FTP120 - until recently called Firetuf Powerplus - a third-party approved SWA [Steel Wire Armoured] power cable that achieves BS 8491's highest integrated-testing 120-minute rating.
The new Standard has come about because of the increased size, height and complexity of the active fire protection in many high-rise and complex buildings and the adoption of fire engineered solutions. These solutions demand a high level of reliable performance from building services, including the electrical supplies.
BS 8519:2010 also aims to ensure that the level of circuit integrity is not compromised by other elements of the electrical distribution system, including cable glands, terminations, joints and cable support systems. The Standard also makes reference to the recommendations in BS 9999:2008 [Code of practice for fire safety in the design, management and use of buildings] in relation to the design and installation of electrical distribution systems for life safety and fire-fighting equipment.
As a Code of Practice, the aim of BS 8519:2010 is to encourage best practice and takes the form of guidance and recommendations. However, care should be taken to ensure that claims of compliance are not misleading, as any company claiming compliance with a Code is expected to be able to justify any actions that deviate from the Code's recommendations.
There is another distinct danger when selecting electrical cables, when the cable does not carry the proper markings, without which there is no means of establishing the cable's authenticity. In the absence of such marking there is every probability that the quality and performance of the cable is highly suspect and is from a disreputable supplier. It is a problem that should concern wholesalers and distributors, specifiers, installers and building control officers. Depending upon the particular application, there is a legal obligation to include certain information; the more demanding the specification, the more information is required to be shown on the cable.
Every year millions of metres of electrical cable are installed in the UK and it is essential to know that the cable being used is to the correct specification. With no markings on the cable it is impossible to know its origin and, more important, whether you can trust that it is safe to install. This is not just an issue at the initial installation stage, it also a serious concern when circuits are later modified. Fitting poor quality cable can have lethal implications and leave the installer liable to prosecution.
But what markings should a cable carry? To help installers, Draka has published a freely-available pocket guide and has an explanatory video presentation on its website. Both are available at www.drakauk.com.
Among the markings that should be clearly visible on every cable are the manufacturer's name and the British Standard number to which the cable claims to conform. Providing the cable has been tested by one, the name of the independent third-party approval organisation should also be included. However, merely stamping a BS number on a cable is not evidence that it actually complies. Without third-party approval there is absolutely no guarantee that any of the claims made for the cable are true. Even if a third-party approval organisation's name is marked on the cable, if the installer has any doubts whatsoever - particularly if the cable is imported - the marking's validity should be checked with the approval organisation.
Counterfeit cables are still cropping up far too frequently. Their existence not only undermines the endeavours and investment made by reputable cable manufacturers, they also pose a very real threat to life and property.
Counterfeit cables are invariably substandard, posing a life-threatening risk to installers and end users. Perhaps more worrying though is the chilling realisation that these rogue manufacturers are not at all concerned about anyone's welfare; their sole focus is on making a profit. They are not in the least bit concerned about protecting their reputation, establishing integrity, providing safe products or building a reputable brand.
The very fact that there are standards and regulations that bona-fide cable manufacturers adhere to can, ironically, help the counterfeiter to dupe the unsuspecting wholesaler, distributor, installer or fire engineer. These rogue manufacturers and suppliers are only too happy to lay spurious claim to standards; unwarranted BS, EN or other acknowledged standards are often found displayed on the rogue cable sheathing. So, it is vitally important to always check very carefully that the cable being supplied meets the standards being claimed for it.
Currently, cables can be found where the diameter of the copper wire has been reduced, lowering the current rating and increasing the resistivity of the cable. This could potentially result in overheating, which could lead to fire or reduce the level of safety against electrical shock. There have also been numerous instances where materials other than pure copper, such as steel wire, copper-coated aluminium or badly recycled copper have been used in cables, and instances where the insulation or sheathing is sub-standard are also commonplace.
Although it is difficult to assess the precise impact that this is having, it is a fact that, in the UK there is strong correlation between the increase in cable-related fires and the quantity of unapproved and counterfeit cable entering the country. While the statistics on fires in homes and businesses that were caused by faulty wires and cables are alarming enough - 27 percent of all electrical fires - in many major fires the damage is so extensive that it is impossible to establish the precise cause of the blaze. So the published figures may well grossly understate the number of fires that can be attributed to faulty cable.
So, what can - indeed should - be done?
For starters, everyone in the industry has to be involved and accept their legal and moral responsibility. While the majority of distributors and installers that have used sub-standard cable have done so innocently, there are certainly instances where a 'blind eye' has been turned in the quest to reduce costs.
The first step is always to verify that what you are being told or shown is not misleading, incorrect, or simply downright dishonest. However, relying on the manufacturer's or supplier's assertions that a cable is manufactured to a specific standard simply will no longer do; ask for copies of test or membership certificates. Better still, use only cable that is supported by independent test certification by fully accredited organisations that, in the UK, are themselves accredited through UKAS, the United Kingdom Accreditation Service. The UKAS website can be found at www.ukas.com.
The importance of this third-party accreditation lies in the fact that the specifier, the supplier and the installer can be sure that the cable being supplied today is made to precisely the same standard and specification as the cable that was originally tested and approved. If the cable is from a producer that does not have this third-party accreditation there is, in reality, no guarantee of the claims being made for it. This requirement for third-party accreditation is important even when buying cable from a well known manufacturer. Without it, while earlier cable from that supplier may have been up to the standard claimed for it, re-sourcing materials and accepting a different specification, changing the formulation of the coating or sheathing, or modifying the design may have affected the performance of the cable.
It is important though to remember that rogue cable manufacturers are every bit as willing to fake third-party accreditation as they are BS or EN standards, so always check with the accreditation organisation that the claim is genuine.
More information on rouge cables can be found at www.aci.org.uk/ which is the website of the Approved Cables Initiative, an organisation set up to coordinate the efforts to stamp out unsafe, non-approved and counterfeit cable entering the UK.
Any emergency lighting or fire detection and alarm system is only as good as the installation of the cabling. So, it is critically important for installers to follow the manufacturer's guidelines because, if a cable fails to perform in an emergency, no amount of system sophistication or technology will make up for the loss of power to luminaires, detectors or control panels. The correct fixing method, fixing spacing, bending and jointing of cables is a vital part of any installation, as every part of a cable system's critical signal path must resist the effects of fire.
Cable manufacturer's recommendations must be treated as compulsory, and not merely an indication of best practice. Ignoring the manufacturer's guidelines may well put at risk the level of fire survival. Should the cabling fail in a fire as a result of poor installation, it will certainly put the installer in an extremely uncomfortable position in relation to the Regulatory Reform (Fire Safety) Order.
The correct securing of cables is a vital part of any installation. It may seem obvious, but it is still possible to find cases where installers have decided that plastic ties and plastic trunking are sufficient to be the sole means of cable support. The spacing of cable fixings is another issue where there is no scope for disregarding the manufacturer's guidelines. What the installer has to bear in mind is that the cable system has been tested using the fixing methods and fixing distances laid down by the manufacturer.
Of course, these fixing methods and spaces affect the installation cost, but safety and performance must come first and, with increasingly onerous legislation, they are ignored at the installer's peril.
Then there is the issue of the cable's stated minimum bending radius. The manufacturer's typical recommendation is six-times the cable's diameter, although too many instances have been found where this has been ignored. Again, the issue is that the installer will be responsible for proving that the cable can retain its circuit integrity at a tighter radius than the manufacturer adopted for the fire test.
Jointing of alarm cables is another area that demands constant attention. The British Standard clearly states that joints should be such that they minimise the possibility of early failure in the event of fire. It goes on to state that terminals should be constructed of materials that will withstand a similar temperature and duration to that of the cable. So there is a similar need to follow manufacturer's guidance regarding jointing practices.
The agreed view within the cable industry is that joint boxes for fire systems should be metal with steel fixings, coloured red, marked 'fire alarm', and contain a ceramic terminal block. Such purpose-manufactured boxes are readily available on the market, so there is no excuse for making joints from boxes, glands and terminal blocks.
Footnote: Draka is a leading designer and manufacturer of fire performance cables, zero halogen power cables and building wires, and more information on its cable offering and customer support services can be found at www.draka.com. The company is part of the Prysmian Group, which has 22,000 employees across 50 countries and 98 plants. Further details on Draka cables are available by telephone on +44 (0) 1332 345431, by fax on +44 (0) 1332 331237, and via email at [email protected].
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... and installers have never had such an extensive choice of fire rated cables. ...