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The safe solution

SELECT Member Craig McGowan gives his verdict on the benefits of arc fault detection devices

When a client came to Craig McGowan to discuss the specification for rebuilding their house that had previously burnt down because of an electrical fault, he had no hesitation in recommending the installation of arc fault detection devices (AFDDs) as part of the electrical safety system.

Craig, who has been Electrical Manager with housing construction services company Macform Ltd for the past 12 years, is a relatively new convert to AFDDs, but after attending a presentation this year by AFDD manufacturer Electrium he admits he was “blown away” by the technology and the ease by which the units can be retrofitted into existing consumer units and commercial fuse boards.

He first came across AFDDs in 2018 when he attended a SELECT training course about the 18th Edition of the Wiring Regulations. He explained: “Malcolm Duncan, Senior Training Adviser from SELECT, was taking the course on the 18th Edition and he spoke about AFDDs and their use. I remember him saying that once the technology had developed into single module AFDDs then they would be very useful, particularly as the 18th Edition of BS 7671 recommends the use of these devices to provide additional protection against fire.

“At the time, I didn’t know of anyone who was fitting AFDDs and because they were still considerably more expensive than traditional protective devices such as residual current breakers with over-current (RCBOs), there was a bit of reluctance from the UK industry about their adoption.”

Craig admitted he was one of these AFDD sceptics as he’d never installed an AFDD or seen the device in operation.

He added: “It’s obviously interesting technology as a single AFDD unit combines three functions: a miniature circuit breaker (MCB); an RCBO to protect a circuit from short circuits, overload and earth leakage faults; and the AFDD to detect dangerous arcs – but the great thing is it only take up one space in a consumer unit per circuit.

“My main concern was how do you know what actually happens when it trips and how do you know what type of arc fault it is indicating. So, as an electrician, I had all these questions, and I also needed to get up to speed with the technology with Amendment 2 ready to come out soon.”

Craig is Chair of SELECT’s Lanarkshire Branch, whose Members received a presentation by AFDD manufacturer Electrium on the technology at a Branch Update in March, during which they also asked questions about its capabilities. Craig said: “When the Electrium representative showed us the technology I was actually blown away by it. It does the job of both an MCB and RCBO, but is also able to detect and disconnect arc faults which could lead to an electrical fire.

“Fault finding is very simple as the amber fault status indicator on the unit flashes in a series of formats: a single repeated flash indicates an arc fault; a twin repeated flash indicates an overvoltage; and a triple repeated flash indicates an earth leakage fault.

“The new single modules are the same as existing circuit breakers and can be easily retrofitted into existing boards – it’s the same process that is used for installing RCBOs – so you don’t need any extra installation time.

“Now you’ve got a fair choice of AFDDs on the market such as Wylex, Fusebox or Hagar; and a wide range of different ampere units.”

However, despite the impressive capabilities of the AFDDs, Craig said there was still an ‘elephant in the room’ – the price. He said: “Some of the guys complained about the price of the AFDDs: a typical AFDD costing around £125 at the time compared with RCBO of about £25. With the increased adoption of AFDDs we could see the costs come down a bit – I think they are around £85 now – but you really can’t compare the two units on price as the technology between an AFDD and RCBO is night and day.

“At Macform, we undertake a wide range of electrical contracting work, such as CCTV and smart lighting systems installation, so I’m very interested in the technology in our industry.

“I came away from our Branch Update very impressed with the capabilities of AFDDs and their contribution to electrical safety.”

Craig was soon recommending the installation of AFDDs on two high-specification construction projects his company was undertaking: a new build property and a retrofit of an existing house.

The retrofitted property was 10 years old and, as the electrical installation condition report showed that the cabling was in good condition, Craig was planning to upgrade the house’s consumer units. Before he approached this part of the work, he took the time to explain to the client about the safety benefits of AFDDs and they agreed that it would be a good idea to install them on all the socket circuits in the house.

Craig said: “I knew the client from previous work, so he took me at my word about the benefits of AFDDs and was reassured that it would improve the safety of the property for his family.

“I was happy enough to install them but as the kitchen had fridges, freezers and other electrical equipment that was probably 10 years old, I was worried that these relatively old appliances might trip the AFDD units. Switching on and off older appliances will create what we call normal arcs, which are not safety issues but could be a nuisance if they trip the system frequently. However, after testing it showed that the AFDDs were unaffected by the day-to-day use of this equipment.”

However, the AFDDs did trip, much to the annoyance of a carpenter working outside until he realised that it was his faulty equipment that had caused the power cut.

Craig said: “The job also involved replacing the outside soffit board on the house. When the joiner came in to complain that the socket had tripped, we checked the AFDD and it was flashing and indicating an arc fault. On further investigation, we checked his grinder tool and found that a cable inside his equipment had come loose and was sparking, so it showed that the AFDD worked perfectly and highlighted a potentially dangerous situation with one of our colleagues’ tools.

“That’s the only time I’ve actually seen AFDDs work, so it proved to me that the device can tell the difference between a normal arc – such as when you turn a light switch or an appliance off or on – and an arc which is due to a fault, which we experienced with the grinder.”

Craig and his team installed five AFDDs in the new consumer unit in the house and three in the unit for the garage/annexe flat and, as they were single module AFDDs, the new consumer units fitted perfectly into the spaces of the old units that formally housed RCBOs.

Craig has also installed AFDDs in a £1.5 million new build house being constructed to replace a property which had been destroyed by a fire a few years previously.

Obviously, electrical safety was a paramount concern to the client.

He added: “This is another high-specification construction project where the client insisted on the very best safety features, so AFDDs have been fitted on the single-phase consumer unit’s socket circuits and will be retrofitted in the three-phase board in the near future, as these were not available at the time.”

Both the examples where Craig installed AFDDs were on high-budget, high-specification projects, so while he appreciates that some of his fellow electricians and their clients may be put off with the higher costs of installing the AFDDs, he believes the extra protection they provide is worth the premium price in many cases.

He said: “I can appreciate the situation where you might be upgrading an RCBO consumer board where the materials cost around £400-£500, and you might be doubling this cost to incorporate AFDDs, but you have to bear in mind that AFDDs are already mandatory in a number of properties, such as high risk residential buildings, houses in multiple occupation, purpose-built student accommodation and care homes.

“While AFDDs are not mandatory in a number of other properties at the moment, you have to appreciate that they are now ‘recommended’ in Amendment 2:2022 to the 18th Edition of the Wiring Regulations.

“Choosing to ignore a recommendation contained in a national standard is not a decision to be taken lightly, especially when it concerns fire safety.

“From my point of view, as an electrician, the two main things that concern me are a fire or somebody getting a shock, and this device prevents both.

“That’s why I believe it’s important to keep trying to get the message across to people about the safety aspects of installing AFDDs; at Macform we highly recommend that our clients fit them on at least their socket circuits within a property.

“I know that cost is an issue for many, and we will never see AFDDs at the same level of RCBO prices because of the advanced technology they contain, but it is a price worth paying in some situations as AFDDs have taken circuit protection and safety to a new level.”

Established in 1997, Macform is a family business based in Wishaw, North Lanarkshire, which has grown and diversified over the years into a company which delivers multi-trade construction services to the commercial and domestic sectors.



BRANCH: Lanarkshire

PHONE: 01555 752 790


What are AFDDs?

The microprocessor in an AFDD is able to identify arc faults by analysing the arc ‘signature’ or its waveform. This enables it to differentiate between normal arcs – created by switching lights or appliances on or off – and arcs due to a fault created by discharges through parallel and/or series faults that result in arcing in the fixed wiring of the installation and the connected equipment. Once the AFDD detects an arc due to a fault, the device automatically trips the affected circuit and cuts the power.


The SELECT verdict

Following their inclusion in BS 7671:2018 +A2:2022, it’s clear that AFDDs are going to play an increasing part in contractors’ lives.

We know there’s been plenty of hearsay about them but, as this article and the one on pages 38 and 39 shows, a lot of these preconceptions can be dismissed with a little practical application.

It was certainly enlightening to hear Craig’s views and see his conversion from sceptic to enthusiast, and also encouraging to hear him wax lyrical about AFDDs taking safety “to a new level”.

I just hope his enthusiasm encourages more Members to consider using them during design and installation – in line with the updated IET Wiring Regulations, of course!

All our BS 7671 SQA customised award training courses have been updated and now include the required information for the design, installation and inspection and testing of AFDDs.

You can also find a more detailed technical breakdown of the implications of Amendment 2 for AFDDs – including where they should be installed – in our brochure which can be downloaded from the ‘Free training guides’ section at

And finally, if you’re in any doubt about the use of AFDDs, please speak to one of our Technical Advisers on the SELECT Technical Helpline by calling 0131 445 9218.


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