Arc Fault Detection Device (AFDD) - Are you being installed?

Having cut myself on the bleeding edge of technology many times over the last 50 years I am not installing them unless specifically asked. As I am semi retired and most of my, as little as possible, work is domestic and agricultural I doubt that any of my customers have any idea what they are. 


Having read the posts on here and done a little research I am not convinced they are an improvement in safety compared with say metal consumer units ?. Their use in America where there is a different standard of wiring, lower voltages and higher currents may increase safety. But having read about the standard arc waveforms that are used in testing which have to exclude arcing from motors, switches etc I am having problems believing they are the solution to a very small potential issue in UK wiring systems. I also have an aversion to electronics in fixed wiring systems, while electronics can be made very reliable the small but significant number of modern RCDs I replace is indicative, to me, that in practice they are not. Please don't get me started on PIRs and LEDs. but they are not safety critical.


I await the comments from those who know far more than me and am perfectly happy to change my mind if there is a good argument or safety stats in their favour.


I suspect the amount of marketing I have seen for them is indicative of  marketing lead persuasion rather than the product being so good every one wants to have them, or am I being overly cynical in my old age ?

I agree.

Would I be correct in assuming that the initial poster might be someone from the manufacturing side of the industry who is trying to garner some opinion in order to lobby for the compulsory introduction of these unicorn devices because the take-up is not as large as his company might like it to be?

I think the benefits are very marginal in an existing installation, and as such I would not generally recommend retrofitting.

Personally I tend to be involved in the specification of supplies for things that involve radio communication equipment, or other electronics kit for use by military establishments.  Operation needs to be rock solid when run on  'power of opportunity' which may well be less clean, not well earthed, the wrong voltage and frequency  and generally more 'wild'  that a typical UK mains.

As such all our installations would include LC filtering and build in SPD (not the overpriced DIN rail stuff that is just coming into the shops now but components built into the fitlers) at the origin. As far as I know the commercial AFDs all fail if the non 50Hz components are removed , and so are effectively neutered by  such  filters.

I feel the IET recommendation is premature, especially as there are currently no easy ways to verify AFD correct operation, or indeed a proper guarantee of what they will and will not detect.

Consider that it took the RCD concept from the 1920s to the 1980s to make it from prototype to mandated in regs, and during that time a great many refinements were made, and blind alleys explored and rejected, and even now they are still an unreliable part of the installation.  In comparison AFD technology is extremely immature.

 I am not surprised to say I have yet to see any in normal use, and I won't be adding any just yet.

Thanks all three.  What you have said questioining whether the units are effective or not, and whether they should be mandated, is very close to my thoughts.  if not aligned.


This has been (and I hope might continue to be) a good sounding board.  :)


I'm particularly interested in the comment regarding how mains-filters might effect AFD operation.  I guess your comment regards the ability to detect an arc downstream of the filter as the filter has removed the arc signature and just presents a [reasonably] clean sine wave?  It sounds like you have some interesting stuff to work on!