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Are You and Your Clients Ready for AFDD?

As an electrical designer in the UK, Arc Fault Detection Devices (AFDD) will inevitably become a key concern in your day-to-day workflow. Here’s everything you need to know. 

Arc Fault Detection Devices are designed to identify a break or damage in a cable. In the event of a partial break, cables can emit an arc discharge that can cause a system malfunction, or worse, cause a fire. AFDD helps protect against these issues by alerting of electrical anomalies. This has become standard fire prevention technology.

Beginning 2019, Arc Fault Detection Devices will be required when buildings meet certain structural, procedural, and practical criteria. According to UK regulations, AFDD must be integrated into existing and future electrical systems that meet these regulatory conditions.

As an electrical designer you’re probably wondering: which structures actually need AFDD and when would the technology just be another unnecessary expense? Read ahead to better understand how AFDD impacts the electrical design process, and learn how to educate clients about the importance of this technology.


When do I need to use AFDD?

The 18th Edition of the BS 7671 Wiring Regulations  — known as the “Regs” — outlines the national standard for electrical installation and safety in the UK. As of this edition, the regulatory guide includes guidelines and recommendations for implementing AFDD. 

According to Chapter 42, Arc Fault Detection Devices should be integrated under certain circumstances to mitigate the risk of fire within final circuits of a fixed installation. A few key candidates for AFDD according to the guide include:

  • Premises with sleeping accommodations
  • Locations with a risk of fire due to the nature of processed or stored materials
  • Locations with combustible construction materials
  • Fire propagating structures
  • Locations with endangering of irreplaceable goods


Section 710 of the law has particular requirements for medical facilities. Not every medical facility is required to install AFDD, but rather the mandate is location-specific, so clients should check their local legislation to see if this law applies to them.


How AFDD impacts electrical design

As an electrical designer in the UK, AFDD will inevitably become a key concern in your day-to-day workflow. Whether you’re designing a system from scratch or upgrading an existing one, AFDD requirements will change the way you design electrical systems.

For one, Arc Fault Detection Devices are large in size which means you will have to reconsider your standard design practices. These large components are cumbersome additions that can bog down electrical panels. In fact, the addition of Arc Fault Detection Devices can nearly double the space requirements of most electrical panels. When integrating AFDD, you will likely have to either migrate components to a bigger breaker box or start from scratch.

When it comes to designing a new electrical system, AFDD adds yet another component interaction that can complicate functionality. Designers know that electrical design is not as easy as merely dropping a new component into a system — you have to consider the system holistically any time a component is added or removed. “Rule of thumb” only goes so far. When considering AFDD within the greater scheme of electrical design, you will need to go back to first principles and consider how this addition could enhance, or inhibit, existing functionalities. 


Workflow tip: Add protective device details to the model and pass this to the site team. This allows for improved information management during installation and maintenance in the future. Learn more: 5 Ways to Improve Your Electrical Workflow


How will this impact my clients

Integrating AFDD will be expensive, and you should be upfront with clients about this fact. If your clients’ current, or future, structures meet the legal criteria for AFDD installation they will simply have to take the financial hit. There’s really no way around it. 

However, if they are able to delay AFDD installation then they should. Make it clear that AFDD is an emerging trend, but as the market regulates the price of this component with inevitably go down. If residual-current devices are any indication of the electrical device market, AFDD will almost certainly become more affordable over time.

Truth be told, Arc Fault Detection Devices can be difficult to integrate into any electrical system. For one, it is not something that can easily be dropped into an existing environment. It becomes an integral element of electrical design and therefore requires thorough consideration within the context of the greater electrical network. Plus, with the introduction of these recent regulatory requirements, market demand is through the roof making AFDD an expensive addition.

But, when you look past the design challenges and expenses associated with AFDD, you see the inherent value in integrating this technology: safety. At the end of the day, Arc Fault Detection Devices will make your clients’ buildings safer, and, honestly, you can’t put a price on that.  

Learn everything electrical engineers need to know about to stay compliant with BS 7671:2018 in 18th Edition: 20 Things You Need to Know.

About the Author

Grant Webster is a senior electrical engineer and the Product Manager of Electrical Design Products at Trimble MEP with more than 17 years of experience in the industry. By contributing to Constructible he helps electrical engineers improve and learn the best way to achieve their goals.

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