[ Spotlight: Circuit protection ] Treat cable cleats as circuit protection devices, says Ellis
Leading cable cleat manufacturer Ellis has been extremely vocal in its attempts to draw greater attention to the importance of properly installed cable cleats in
electrical installations. ‘The problem we’ve faced trying to get our message across has been twofold,’ says managing director Richard Shaw. ‘Firstly, there are deeply ingrained installation short cuts that have happened so frequently and for so long that a lot of installers aren’t even aware they’re taking them. And secondly, because different cleat manufacturers don’t all work from the same hymn sheet the market is very much a mish-mash of products of differing quality.’
The publication of European (EN50368) and
international (IEC61914) standards has seen great strides taken in changing people’s attitudes towards cleats, but the journey is far from over,
thinks Shaw. ‘The standards are only advisory, which means those claiming adherence to them can do so through self-certification. And this is where the problems from the manufacturers’ end begin.’ It is common for manufacturers to claim a
given short circuit withstand at a given cleat spacing and legitimately provide third-party certification to support this. However, the overlooked fact is that the quoted short circuit withstand is only valid for a cable diameter equal or greater than the diameter of the cable used in the test. If the project in question is using smaller cables than those referred to in the test (and the fault level and spacing is the same), then the force between the cables is proportionally greater and the certificate is inappropriate. So, the question is how to resolve a potentially
fatal issue that is being inflamed by bad practice and misunderstanding from manufacturers, specifiers, contractors and installers. Of course, the situation could be resolved through a process of education and agreement involving all these
parties and industry regulators, but this would be a long-term process that fails to take into account the dire need for a quick-fix before the unnecessary threat to life caused by the problem turns into the wholly unnecessary loss of life. Therefore, there is only one sensible and
safe solution, according to Shaw. ‘Cable cleats need to start being treated as circuit protection devices – meaning they are given the same degree of importance as a fuse or a circuit breaker,’ he says. ‘After all, in the event of a fault, the forces between cables reach their peak in the first quarter cycle and this is the point that cleats earn their crust. In contrast, circuit breakers typically interrupt the fault after three or even five cycles, by which time, if the cleats are underspecified, the cables will be long gone. ‘The widespread adoption of this attitude
would ensure the correct use of and installation of cleats and when you consider what this means in terms of delivering safer electrical installation, it’s fair to say that such an approach is absolutely the right course of action.’ n
www.ellispatents.co.uk
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