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Article Date: 21st September 2018

Crabtree - AFDDs Requirements, Recommendations & Solutions

IET Wiring Regulations - Arc Fault Detection Devices - Consumer Unit

Crabtree Starbreaker consumer unit

To help designers and installers comply with the 18th Edition IET Wiring Regulations Crabtree has launched a range of AFDDs (Arc Fault Detection Devices) that fit into any new or existing installation with a Starbreaker consumer unit. These unique miniature devices can be installed without any need for special assembly or new busbars. When arc fault detection devices are used they should be installed at the origin of each final circuit that is being protected i.e. in the consumer unit or distribution board.

The 18th Edition recognises that risk of injury may result from arcing or burning (131.1) and it includes requirements for installations to be so arranged that the risk of ignition of flammable materials due to high temperature or electric arc is minimized, and requires people, livestock and property to be protected against the risk of burns (Chapter 13).

Additionally, persons, livestock and property should be protected against harmful effects of heat or fire which may be generated or propagated in electrical installations. These may be caused by: failure of electrical equipment, insulation faults or arcs, sparks and high temperature particles (421.1.1).

Electrical fires caused by dangerous arc faults typically occur at loose connections, poor terminations, or in impacted and damaged leads and cables, or through old, weak and failing insulation. AFDDs can decrease the likelihood of electrical fires from these conditions by detecting the arcing conditions before the overheating and ignition of flammable materials. Thereby protecting people livestock and property from risks.

AFDDs detect arc faults that cannot be detected by RCDs or MCBs. These new devices use digital technology to provide additional protection against fires caused by arcs in AC 230V final circuits.

Crabtree AFDDs constantly monitor and analyse electrical values and look for any divergence from normal patterns i.e. divergences 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.

Crabtree AFDDDave Enefer, Devices Product Manager at Crabtree comments: “Arc fault detection devices should be used to provide additional protection, in conjunction with the requirements for overcurrent, short circuit and earth leakage protection. This is achieved by combining Crabtree AFDDs with the new Miniature RCBO to create a single device that can provide protection against all of the fault conditions as necessary to meet the requirements of BS7671.”

Crabtree AFDDs are just two modules wide and the same height as an MCB, so they provide lots of wiring space during the installation and test process. These devices are two pole switching and totally isolate any faulty circuit or appliance by switching off live and neutral under fault conditions providing a much safer environment both while waiting for the emergency electrician, or while the contractor carries out maintenance and repair tasks.

Crabtree AFDDs are designed to fit into all Crabtree Starbreaker consumer units, regardless of age. Crabtree AFDDs are fully backward compatible and can be simply plugged into the fully insulated plug self-connecting busbar system for an easy upgrade with additional protection against electrically ignited fires.

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