My understanding (which may well be incomplete or wrong) is that the standard's tests for AFDDs work on the assumption that once there is a break in a cable which causes intermittent arcing, the arcing chars some of the insulation over time, and the carbon makes future arcing easier. So the tests are with carbon rods. A lot of the youtube tests try to create arcs with small copper to copper gaps, which tend not to last more than a second or two, and may be seen by the AFDD as a motor-type spark and not trigger a disconnect.

So when a youtuber shows an AFDD failing to disconnect, it may be that the AFDD is actually working correctly. Or it may be being completely useless. Or the standard isn't up to scratch. We can't tell from the video.

well that alone is a good reasoin not to use such a brand - it is a massive exposure of a potential vulnerability.

Mike.

Mr Savoury has posted a update video on his previous AFDD episode.

www.youtube.com/watch

I have watched it and the others he has done on AFDD and I find it quite interesting.  Several AFDD tested in what seems to be real world potential fault situations.  Several things come to mind

1)  No real way to test and verify that the AFDD is functioning correctly.  Test button is for the RCBO side of the unit.  POST (Power on SELF Test) may or may not work as intended

2)  Different propriatory software and hardware across different manufacturers.  Fault or status indicators of differing colours and sequence could lead to confusion for the electrician or the person operating the CU eg Home owner

3)  Differing trip characterists on the AFDD tripping side, some are more sensative than others.  However they all to claim they conform to the same standard. 

I'm sure they all do meet the standard - but as said many times, and also demonstrated with a bit of theatre by DES and others, the acceptance tests as written in the standard are not especially realistic of faults as they occur in the real world.

Very few of us when tracking down a fault find pairs of carbon rods, spacing adjustable by a micrometer, to be the cause of the problem - people just do not fit that sort of thing to a UK installation ! To be fair even if someone wanted to, I've never even seen it as a standard part in the catalogues.

Nor do folk go around applying many KV to twin flex to trigger partial decomposition between cores.

And yet those are the series and parallel arc tests that an AFDD  has to identify to earn its badge of compliance.

In that sense Dave's rat bite or abrsaion plus some saline to represent rat wee is perhaps more realistic of the sort of damage that might start a fire in a real property - and by not connecting the CPC it overlooks that in the UK at least, an RCD trips for that sort of fault anyway.

Mike.

mapj1 said:

the acceptance tests as written in the standard are not especially realistic of faults as they occur in the real world.

Maybe the people who write the UK standard need to revisit the standard?

It is not a UK specific standard, it is a European one, and it in turn it is heavily based on the US one. But yes, I would strongly support a bit more transparency about what AFFDs must detect by design to pass type approval, then what else they may detect as a bonus,  and what they  must not trip on,  to avoid false alarms, as well as how well or badly they reject arc like interference coming from the supply side.

The technology is not especially complex by electronic digital signal processing standards - essentially sampling, then Fourier transforms and some spectral pattern recognition, but it is very, very  different to the one condition-one trip operation we associate with existing protective devices.

And I think it really should be testable in the field.

Mike.

mapj1 said:

It is not a UK specific standard, it is a European one, and it in turn it is heavily based on the US one

My understanding is that a US AFDD is quite different to a UK AFDD

I also think that test instrument manufacturers like CA (Chauvin Arnoux) , TIS(Test Instruments Solutions), Megger should be involved with writing the standard that way they can make test kit for the AFDD device for the UK market. 

https://blog.se.com/energy-management-energy-efficiency/energy-regulations/2013/07/09/iec-62606-a-first-step-towards-international-standards-for-arc-fault-protection/

https://www.export.legrand.com/en/white-paper-detection-electrical-arcs

And the American tests are described here (as with Europe the standard itself is expensive, but other folk have discussed it enough that the main tests are well known - and unlike the Euronorms, there is free digital viewing, although copying is forbidden.

https://code-authorities.ul.com/wp-content/uploads/2014/05/Dini2.pdf

https://www.shopulstandards.com/ProductDetail.aspx?productId=UL1699_3_S_20170503

Mike,

Well, given what we have seen and experienced thus far, i would say that these things are next to useless, immature to market, and try to solve a problem which really isn't out there in the real world to any great extent. Surge protection in domestic consumer units was a hard sell but it was swallowed even though it stuck in the gullet, but these things are a very expensive step too far. The technology is not provable and I am surprised that the IET got suckered into mandating these things at all. I would urge that extreme caution be applied to installing these things. There is no come-back on the manufacturer because the things cannot be proved to work in the field either way, so guess who is left holding the baby when things go pear-shaped.

Me? I'm not going near them.

Well put!

Well put!

It is a bit of a conundrum. Refuse to fit and the worst may be a C3 on any future EICR. Fit one and it doesn't work, and a life or property is lost and it's a trip to the High court,hopefully with deeper pockets than those of the manufacturer, who will swear blind that the thing worked 'But you didn't set it up properly, or you didn't install the latest firmware update' There's no means of testing for satisfactory operation either way, so why put yourself at risk in the first place?

Nope, a C3 will do me..

My understanding is that AFDDs have been used in Germany for several years now.  I wonder if they are the same type as that used in the UK?  It would be interesting to know how the Germany Electrcian/Technician see this product?  Are the UK issues we see due to the AFDD being used on a ring final circuit rather than a radial?  Is th cable used a factor, T&E with exposed Earth/CPC?

Maybe some imput from AFDD manufacturers could help to further the debate. 

If you want the German electricians' discussions on this topic, search for Fehlerlichtbogen-Schutzeinrichtung, (AccidentalArcSafetyDevice)

or in or in more informal debate/documents Brandschutzschalter (FireSafetySwitch). Naturally you will need to speak German, or make much use of google translate to make sense of the search results.

This is a typical rant....

https://www.handwerksblatt.de/themen-specials/hitzige-debatte-um-brandschutzschalter/afdd-norm-brandschutzschalter-notwendig-oder-ueberfluessig

regds/mfg

Mike

It is interesting to read that our German colleagues are unhappy about AFDDs as well.  The cost and the way it was forced onto them by industry rather than sound technical engineering. It would good if anyone can reach out to any German Electrcians/Technicians that speak/write English to join the debate.  Are German AFDDs suffering from the same hit and miss scenario as the UK AFDDs?  Do the Germans have a way to test the AFDD in the feild for trip/no trip verification?  Are some of the AFDD used in Germany over sensitive?

You may find the more recent German changes informative also.

https://www.handwerksblatt.de/themen-specials/hitzige-debatte-um-brandschutzschalter/neue-regelung-fur-brandschutzschalter

To save you some translation effort. I attach the google translation below.

Also on other fora the general fermentation is that it is a victory for common sense, as now German electricians are free to do an RA to see if they need AFDD in a particular situation or not.  Reading between the lines, I think that many will now be deciding 'not' unless it is wiring for a  fuel dump or an art gallery..

regards Mike.

"

Well, judging by that, it seems that good old engineering common sense has prevailed over the marketing hype for once, and about time too.

Since JPLE64 or whatever they call themselves, seem to have cross border involvement, I wonder why back in Jan 2020, if they were aware of this debacle and subsequent DIN reform at the time, they didn't take it into consideration before mandating AFDDs into BS7671?

Maybe Grenfell, to say "We are doing something?"

Even though it seems to be an appliance that caused the initial fire. Anyone who takes an appliance apart knows they are made to a (low) price point. Their moulded plugs are rubbish, the connections inside are tiny and loose. Yet they get away with it.

Same with the plastic consumer units that were catching fire, but, we know,they couldnt catch fire, as the BS stated it should be made of self extinguishing or non-flammable plastic.But some did not meet the Standard, some Makers were making flammable plastic CUs.

But the Electricians got the blame for loose connections (yes, there were some), and the CU makers didnt get taken to Court for supplying Goods that didnt meet the British Standard they were supposedly tested and certified for. And of course, the Makers then got more income, as metal CUs were called for in high risk places, so , what should have been a perfectly good plastic CU was changed due to the Manufacturers bypassing the Rules, and then they made more money because of that. Cynical, me?

Do JPEL64 publish the minutes to their meetings or could we request the minutes to the meeting where AFDD were discussed and then mandated into BS7671.  If JPEL64, BSI and IET  were aware of what was going on in Germany they could have used the word recommend rather than the world shall.  After all the BS7671 has a definitions section that state what they mean when using the word shall.

We've been there before in another thread.

engx.theiet.org/.../afdds---when-do-they-work

I would urge you to have a look at who sits on the wiring regs committee to find your answers.

Mr Savoury has published another rather humorous Hager AFDD update -

www.youtube.com/watch