New to the 18th Edition Wiring Regulations is the recommendation of AFDD’s. At Electrical2Go, we have put together a complete guide to help you better understand what an AFDD is, why and if you need one, how AFDDs work and the different types available for domestic dwellings, so you can buy through our website confident you are purchasing the most suitable AFDD for your project.


Are AFDDs mandatory?

Yes in some circumstances AFFDs are now required by 18th edition wiring regulations, and simply advised in others. Let us explain:

An AFDD is an Arc Fault Detection Device and using sophisticated algorithms it is designed to detect the presence of dangerous electrical arcs and disconnect the circuit affected, to prevent possible fires.

There were some significant changes made in the March 29th 2022 Amendment 2 to BS 7671:2018 (18th edition of the IET Wiring Regulations) and included was the new requirement for Arc Fault Detection Devices in AC final circuits supplying sockets-outlets in some types of higher risk residential buildings including: 

  • Higher Risk Residential Buildings (HRRB)
  • Houses of multiple occupancy (HMO)
  • Purpose-built student accommodation
  • Care homes

For other types of properties, the use of AFDD’s is advised for single phase AC final circuits supplying socket-outlets of 32A or below and placed at the origin of the circuit in need of protection.

Arc Fault - By Achim Grochowski -- Achgro - Own work, CC BY 3.0Arc Fault - By Achim Grochowski -- Achgro - Own work, CC BY 3.0
Arc Fault - By Achim Grochowski -- Achgro - Own work, CC BY 3.0

What do Arc Fault Detection Devices Do?

AFDD’s operate using intelligent algorithms which monitor the electronic signatures of devices energised on a circuit, helping to identify faults quickly and with efficiency.

AFDD’s are protective devices installed in consumer units to provide protection from arc faults. They use microprocessor technology to analyse the waveform of the electricity being used to spot any unfamiliar signatures which would indicate an arc on the circuit. Upon sensing this signature using algorithms, the device will operate. The faults detected are usually caused by loose connections or damaged cables, or sometimes a breakdown in insulation, whichever it might be, it’s an arc that could generate enough heat to ignite a fire.


Why do we need AFDDs now?

Pre-present devices which are compulsory in the Wiring Regulations – circuit breakers, fuses and residual current devices, may not always react to the small arc faults which would activate an AFDD. They provide increased preventative protection against fires. Essentially, AFDD’s detect faults that other protective devices can’t.

In 2016/2017 UK Government Statistics show that more than 13,000 fires occurred in electrical appliances and distribution, the introduction of AFFDs as a requirement is an attempt to lower those figures dramatically, and keep household and business better protected.

AFDD’s will detect an arc fault that arises after an installation has been tested, and by detecting the arc fault the AFDD will prevent the initial cause of a potential fire.


What is an Arc Fault and what caused them?

An electrical arc can occur when the current jumps the gap between two conductive materials. If the current is low in comparison, a spark will then be produced. However, if it is a high enough current a continuous arc may occur where the air then changes from a gas to a plasma. This continuous arc is then capable of supporting the arc, the resulting temperatures of this arc can exceed 6000°C. Put simply, an arc fault can lead to fire. AFDD’s will operate at this stage and automatically disconnect power to neutralise the danger.

The most common cause of arc fault are loose terminations and damage to cable insulation.

When do I need to be using AFDD’s by? 

Amendment 2 came into force on 28th September 2022, requiring the use for higher risk properties, and for other properties it is strongly advised.

What type of AFDD will I need for my project? 

They can be fitted as a standalone device in series with a suitable protective device, i.e. your circuit breakers or RCBO’s to the relevant standards

– They can be installed as one single device that consists of an AFDD combined with a protective device such as a circuit breaker or RCBO

– Some manufacturers also offer add on AFDD modules for their other protective devices, these are however, only compatible with that manufacturers’ protective devices

 


Where can I buy AFDD’s? 

Here, at Electrical2Go, we have a number of options for AFDD’s:

Elucian LogoElucian Logo

Scolmore are one of the first to announce it has added a comprehensive range of AFDD’s to its Elucian by Click consumer unit and protective devices collection.

The new range comprises Type A 1 Pole + Neutral True 6 kA B Curve & C Curve 30 mA Trip AFDDs with integral RCBOs, which are available in 6 A, 10 A, 16 A, 20 A, 32 A & 40 A, complete with 450 mm neutral out tails.

 

AFDD Key Features:

  • Arc fault detection – providing a form of protection that pre-existing devices that are mandatory as part of the 18th edition wiring regulations cannot provide.
  • Fault reporting – reports 5 different types of fault conditions. Each fault condition has its own unique LED flashing sequence pattern that signifies the reason why the AFDD has tripped.
  • Self-Test – inbuilt self-test function to ensure the device is fully operational.
  • Green LED Indication – for a clear, visual representation of the flashing sequence to determine fault condition.
  • BS EN 62606 & BS EN 61009-1 Compliant – to cover the general rules and requirements for Arc Fault Detection Devices & Residual current operated circuit-breakers with integral overcurrent protection.
  • Range Available – 6 A, 10 A, 16 A, 20 A, 32 A & 40 A to completely harmonise with the existing range of Elucian RCBOs.
  • B & C Trip Curves Available – to cover both short circuit trip times.
  • 18 mm Single Width Size – to harmonise with the existing range of Elucian RCBOs and circuit-breakers, only taking up a single din rail space to fit seamlessly into the Elucian range or any existing Elucian installation.
  • Neutral Out Tails – 450 mm length supplied as standard.
     
Lewden LogoLewden Logo

The Lewden P4 series of combined AFDD & RCBO provides the highest degree of protection, safeguarding final circuits against the effects of:

Over Current | Residual Current | Arcing Faults

| Over Voltage | Over Voltage Protection

AFDDs can also mitigate the risk fire caused by faults within the whole electrical Installation, both within the fixed wiring and the cabling of equipment connected to it.



Key Features

• The P4 Combined AFDD RCBO is designed for integration within the Lewden range of distribution boards and is fully interchangeable with the Lewden range of 6kA single module MCBs and RCBOs.

• Available in current ratings of 6-40A, incorporated within a single module width

• The device combines a microprocessor based AFDD with a 1P+ Switched Neutral RCBO

• Incorporating a 30mA class A RCD and a 6kA MCB

• Suitable for use on TN-S, TN-C-S & TT network systems

• The switched Neutral pole makes the device suitable as a means of double pole isolation and is particularly appropriate for installations with TT Earthing Systems where it is necessary to disconnect all live conductors to achieve safe isolation of individual circuits (BS7671:2018 Regulation 462).


hager logohager logo

 

Hager Launches New AFDD Solution


Equipped with built-in advanced diagnostics software, every Hager AFDD device benefits from the technology, ensuring that unwanted or operational trips are quickly detected and easily identified.

Pro Tools
Exclusive to Hager AFDD devices, ProTools is the manufacturer’s pioneering diagnostic software that offers two unique elements to guarantee that the installer has the right tools at their disposal to ensure that AFDD installations perform in all scenarios.

 

Key Features

  • Advanced On-Board Diagnostics
    Equipped with built-in advanced diagnostics software, every Hager AFDD device benefits from the technology, ensuring that unwanted or operational trips are quickly detected and easily identified. Once the Hager RCBO/AFDD or MCB/AFDD device has tripped, installers can quickly identify the cause for the disconnected circuit at the push of a button on the front of the device.
  • The multicoloured LED display will flash in a different sequence of colours to identify the fault. With the ability to identify 8 statuses, the device will instantly detect if a Series Arc, Parallel Arc, Overvoltage, Residual Current Fault, Overload, Short Circuit, AFDD failure or manual trip has occurred, saving time and improving diagnostic ability.
  • In Situ Software Upgrades
    The latest AFDD device from Hager contains a microprocessor which runs a sophisticated algorithm, continuously checking the circuits for any indication of an arc fault. Whilst the extensive testing program provides a stable platform for today, it is possible that an electrical goods manufacturer of tomorrow may create an electrical device with a different waveform signature, thus creating a new signature for the Arc Fault Device and causing the device to trip.
  • With ProTools and the In Situ Software Upgrades, Hager is able to modify the algorithm to accommodate new product signatures. These updates can be sent directly to installers’ mobile devices, via the Hager Pilot app, allowing them to connect to the AFDD through Bluetooth technology and perform a software upgrade. This changes the game, and uniquely eliminates the need to physically remove the device from the board, providing a quick and efficient resolution to any nuisance tripping.
  • RCBO & MCB Configurations
    The single module-wide device will be available in both RCBO/AFDD and MCB/AFDD configurations and will be offered with Hager’s exclusive ProTools diagnostic software.
  • Country Marketing Leader, Ian Smith, explains why Hager has introduced both RCBO and MCB versions of the Single Module AFDD: “It is a key part of our strategy that Hager devices are fully backwards compatible. So in addition to our RCBO/AFDD, we have an MCB/AFDD which enables Hager installers to upgrade existing MCB installations to AFDD on the appropriate circuits, without having to upgrade the whole installation to RCBO configuration.”
  • Extensive Testing
    Benefitting from extensive field trials to guarantee best-in-class performance, Hager’s single module AFDD will provide installers with the ‘fit and forget’ reassurance they have come to expect from Hager products. Utilising existing feedback from over 5,000 two-module-wide units, Hager has further developed its algorithm following an additional field trial with 300 single module devices offering real-life feedback from these installations.

How much do AFDD’s cost? 

Now, the cost can be seen by many as off putting when compared to other protective devices installed in consumer units. It’s likely that this will change over the coming years, as the demand for AFDD’s naturally increases.

As AFDD’s are so new to the UK domestic electrical market it is very tricky to obtain a broad range of prices. The cost is currently sitting between £70 to £200 per AFDD depending on its type and rating.