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What is an AFDD and how does it work? By Kempston Controls


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rc Fault Detection Devices (AFDDs) are an essential advancement in electrical safety, designed to detect and disconnect dangerous arc faults before they can lead to electrical fires.


Unlike traditional Miniature Circuit Breakers (MCBs) or Residual Current Breakers with Overcurrent Protection (RCBOs), which respond to overcurrent or earth leakage, AFDDs identify high-risk electrical arcs that often go unnoticed, but can have devastating consequences.


Why arc fault protection matters Arc faults occur when electrical current unintentionally jumps between conductors due to a breakdown in insulation or physical damage. These faults can result from a wide range of common issues:


• Damaged, twisted, or kinked cables • Loose connections or worn-out terminations • DIY accidents such as drilling into cables • Rodent or pest damage


• Age-related degradation of insulation


These faults generate intense, localised heat that is often insufficient to trip conventional protective devices. As a result, the heat can build up over time, igniting surrounding materials and leading to fires—particularly within walls or hidden spaces.


Introducing the KCM


Classic AFDD Kempston Controls’ KCM Classic AFDD range has been developed to meet the latest electrical safety standards, combining intelligent arc fault detection with a compact, easy-to-install design. These devices are ideal for domestic, commercial and specialist environments where enhanced safety is a priority.


They detect:


• Series arcs, typically caused by damaged wires or poor connections


• Parallel arcs, between live-to-neutral or live-to-earth conductors


Once an arc is identified, the KCM AFDD disconnects power instantly, preventing escalation and helping to stop a potential fire before it can begin.


Where are AFDDs required? According to Regulation 421.1.7 of BS 7671:2018 Amendment 2, AFDDs are mandatory for all single- phase AC final circuits supplying socket outlets rated at 32A or less in the following building types:


• Higher Risk Residential Buildings (HRRBs) – buildings 18m+ tall or with six or more storeys


• Houses in Multiple Occupation (HMOs) • Purpose-Built Student Accommodation • Care Homes


How do KCM AFDDs work? Our AFDDs feature advanced microprocessor- based technology that continuously monitors the electrical waveform within a circuit. By analysing patterns in the current, they can accurately identify the presence of arc faults and differentiate them from normal electrical activity.


Even where not mandatory, AFDDs are strongly recommended to enhance safety in any environment.


Why choose KCM AFDDs? • High detection accuracy: Compliant with BS EN 62606, using advanced arc detection algorithms.


• Integrated design: Combines AFDD and RCBO in a single, compact unit for space and installation efficiency.


• Trusted performance: Backed by Kempston Controls’ industry expertise and nationwide distribution network.


• Ideal for compliance: Particularly suitable for retrofit projects in HRRBs, HMOs, care facilities, and education buildings.


What makes AFDDs essential? Traditional protection methods only cover: • Overcurrent and short circuits (MCBs)


• Earth leakage faults (RCDs/RCBOs)


But AFDDs add a vital third layer of protection: arc fault detection, which tackles one of the leading causes of hidden electrical fires in modern installations.


Quick definitions • AFDD – Arc Fault Detection Device


• HRRB – Higher Risk Residential Building • HMO – House in Multiple Occupation


Explore the KCM AFDD range Whether you’re working on a new build, upgrade, or retrofit, Kempston Controls provides the stock, support, and technical expertise you need to stay compliant and keep people safe.


8 ELECTRICAL ENGINEERING • JULY/AUGUST 2025


electricalengineeringmagazine.co.uk


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