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Crabtree: How Arc Fault Detection Devices can benefit your next installation


Arc Fault Detection Devices are a new addition to the 18th Edition of the Wiring Regulations. This product information feature from Crabtree discusses why arcing shouldn’t become an after thought.

The Wiring Regulations define danger as: “Risk of injury to persons from: fire, electric shock, burns, arcing and explosion arising from the use of electrical energy.” Not that this should surprise us, electricity is a dangerous commodity.

In England in 2016/17, there were 13,347 fires from an electrical origin. Electrical fires are continuing to occur at virtually the same rate year on year, even though many of these incidents are preventable.

Perhaps this is partly because buildings have more items of electrical equipment in them than ever before? Electrical fires caused by arc faults typically occur at loose connections, poor terminations, in damaged leads and cables, or through old, weak and failing insulation.

Arc Fault Detection Devices (AFDDs), can decrease the likelihood of electrical fires from these conditions by detecting the arcing conditions before the overheating and ignition of flammable materials. In countries like the USA, where use of AFDDs started some years ago, there’s been a reported reduction of 10% for this type of incident.

Dave Enefer, Product Manager at Crabtree, comments: “The wiring regulations (BS7671) sets out requirements for electrical installations in the UK, including requirements for protection of persons, livestock and property against the risk from fires that may be generated and propagated in electrical installations.

“Designers and installers should ensure that the installation is arranged so that the risk of ignition from high temperatures or electric arc is minimised, and that protection from harmful thermal effects is provided. Protection requirements include protecting against fire caused by insulation faults, arcs and sparks and high temperature.”

Clearly the wiring regulations require certain design and installation standards. It is permitted to use RCDs as a measure for protection against insulation faults, it’s also a requirement to install other circuit protection devices such as MCBs to provide protection from overcurrent and other conditions.

However, those devices cannot detect or disconnect arc faults. AFDDs detect arc faults that will not be detected by RCDs or MCBs due to the fact that the magnitude of such arc faults is often insufficient to operate an RCD or MCB.

Crabtree Arc Fault Detection Devices cater for the all of the above requirements because the AFDD technology is combined with MCB and RCD technology in one single device, providing for all of the requirements of BS7671.

In countries that have already adopted this technology AFDDs are often used in buildings with sleeping accommodation, those made from combustible materials, and locations with rare or irreplaceable items. Imagine how many incidents could be prevented if these devices were installed in all such locations?

What’s an AFDD?

AFDDs work by protecting specifically against arc faults, as they automatically trip a circuit when they detect dangerous electric arcs – thus preventing the outbreak of a fire.

An arc fault occurs when the arc current either flows between active conductors in parallel with the load of the circuit or when it is flowing through the load(s).

Arcing is incredibly dangerous because it creates high intensity heating at the point of the arc, resulting in burning particles that may, over time, ignite surrounding materials. Moreover, repeated arcing creates carbon paths which generate temperatures exceeding 6,000 degC.

It can take time to develop, it can occur immediately or over a longer period, meaning that the onset of an electrical fire due to ignition of the cable insulation or nearby flammable materials is unpredictable.

AFDDs constantly monitor and analyse patterns in voltage waveforms and electrical current, looking out for divergence from normal patterns of waveform that denote a potentially dangerous arc.

They are designed and tested to not respond to arcing under normal operation of equipment, for examples vacuum cleaners and drills, whilst simultaneously continuing to respond to arc faults whilst the equipment is being used.

Electrical fires can be decreased in number by the use of this recognised device that installers can now easily access and install.

You can read more about Crabtree’s AFDD solution via www.electrium.co.uk/products/crabtree

And there is more about Arc Fault Detection Devices and the 18th Edition over at the 18th Edition Area of the Electrium website at www.electrium.co.uk/18th-edition

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