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AFDDs. What are they? Should you fit one? How will AM2 effect you?

With the second amendment to the Institution of Engineering and Technologies (IET’s)18th Edition expected to be announced on the 28th March 2022, the device everyone is asking about is the AFDD.

An AFDD or Arc Fault Detection Device has been an advisory device within the regulations for some time. Its primary function is to detect any arc on a final circuit, to decrease the risk of domestic fires.

What causes an Arc Fault?

An Arc is created when the electrical current jumps the gap between two conductive materials. The most common causes of an arc in a domestic setting are worn contacts in electrical equipment, damage to insulation, loose connections and breaks in a cable.

What is an AFDD and why should you fit one?

AFDDs are protective devices that are installed in a domestic consumer unit to provide protection from arc faults. They contain microprocessor technology to analyse the waveform of the electrical current being used, detecting any unusual signatures or patterns. Any anomalies in the pattern/signatures signify an arc on the circuit and causing the device to trip and cut the power to the circuit like a conventional protection device.

As with most RCD's such as an RCCB or RCBO, AFDDs will usually incorporate a test button, this can be operated with ease by the end user or occupant to confirm the device is functional.

AFDDs are far more sensitive than a normal protection device and contain extensive technology, far greater, than that of a typical RCBO. As a result, the physical size of the devices vary depending on manufacturer. Many are twice the size of a standard MCB protection device and therefore may require larger consumer units to accommodate the installation due to their physical space requirement.

So do you need to fit one? In the current edition of the IET Wiring Regulations, BS 7671:2018, it is recommended that AFDD’s are installed, however the customer can choose to omit them. However, this decision should be based considering any relevant risk and safety factors against the cost of installation.

AFDDs are worth consideration if there is an increased risk of fire, such as in:

  • Premises with sleeping accommodation, for example, houses, hotels, and hostels.

  • Locations with a risk of fire due to the nature of processed or stored materials, for example, stores which hold combustible materials.

  • Locations with combustible constructional materials, for example, wooden buildings.

  • Fire propagating structures, for example, thatched buildings and timber-framed buildings.

  • Locations with endangering of irreplaceable goods, for example, museums, listed buildings and items with sentimental value.

What will change after AM2?

There are a lot of rumours and suggestions for what may be featured in the second amendment of the 18th Edition. One that continues to gain momentum and support is the requirement for AFDDs to be installed on final ring circuits of 32A with a constant load present such as a kitchen final ring circuit. However, it is uncertain at this stage whether this will be for every type of domestic property, or multi-occupancy for example HMO's etc.

At Verso, we have been informed by the local authorities that we work with and are specified on, that they will be specifying 32A AFDDs on such circuits, as soon as April, 2022.

Does Verso have an AFDD?

We do! We have spent the last 12 months refining its design and specification to support the aforementioned local authorities and our wider customer base like you. The Verso AFDD however, is smaller than most traditional and available AFDDs, presently available on the UK market.

Designed to be the same size as our current tall Type A RCBOs, and fit seamlessly on the din rail and with the existing busbar. Making it as simple to install as a traditional RCBO, which is made easier with a Verso consumer unit, due to its extended height and spacious design. With a clear red indicator and the toggle located slightly higher than our RCBOs, one can clearly distinguish between a Verso AFDD and RCBO for maintenance and performance purposes.

The AFDDs will also be Type A as standard (as every RCBO within the Verso range is), to further ensure an additional layer of protection against pulsating DC current that will be present on any modern day kitchen ring. This will prevent the RCBO becoming saturated and failing to trip, as could be the case with a traditional AC device.

How much will an AFDD cost?

There has been a vast amount of negative reception on the use of AFDDs, most of which has centred around the cost of the units. Having a price range from £110 to £150 per unit currently, this is an obvious concern to not only local authorities and developers, but installers and occupants as well.

Will Verso AFDDs be affordable?

As mentioned earlier, AFDDs contain a vast amount of new and advanced technologies, and ensuring their performance and certification, whilst constructing the device to match the size of a regular RCBO comes at a significant cost. We do not believe that AFDDs should be omitted from projects where they could save lives, due to their cost. As such we have worked tirelessly to ensure that our AFDD will be competitively priced and available from our stockists as early as the end of March to support you moving forward.


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