So let's take stock.

Is anybody persuaded that AFDD would have saved Grenfell?

Is nuisance tripping a significant phenomenon?

It would be lovely to have a show of hands. Has anybody in here installed that at home? (I made further progress with my own installation today, but AFDDs are nowhere to be seen.)

Not me. Although I am intrigued as to exactly where this 'crimp' was actually situated. Was it a manufacturer's joint inside the fridge? Or was it in the appliance flex to enable the lead to reach a socket outlet? The report seems to be at odds with itself in places as to whether or the the crimp was the root cause.

As for AFDDs saving the day? How could it be proved either way? Hager are going down the same route as many motor vehicle makers - 'Sell the service and not the product', is the new mantra. No money to be made in selling the vehicle, rather, why not sell a monthly paid app to enable certain features instead? It is a akin to buying a loaf of bread, yet having got it home you have to pay an app firstly to open the package, then pay another on a slice by slice basis as you consume it.

Personally, I dislike the introduction of smart and other electronics into mains kit just to enable data gathering. Although not mains, the fact that a otherwise mechanically sound motor vehicle can be rendered useless because some sensor or other decides that the levels of certain gases emitted from the exhaust pipe are out of range, or that the thing itself simply fails, is reason enough to simplify and get rid of the weak links in the chain.

My understanding is that the crimp with the voids in the CT scans was a crimp as part of a spade terminal connector to what he refers to as the starter relay - which is actually a thermal thing that releases the start capacitor once up to speed. In any case one of the fridge freezer makers factory crimps.

But as I have said before, given that amount of damage it would be a brave soul who spoke with more than 'perhaps' or 'probably' . This caution leads to the slightly contradictory statements that more than one thing might be true.

I'm with you on the AFDD being useless in this case, and indeed a great many cases.   It may even make things worse if folk decide an AFDD means you can be more careless.

As for Dave Savery's results, while the language is a bit unprofessional, I'd agree the fact the thing does not trip under the conditions shown is scarcely confidence inspiring, and suggests the euronorm to which the things are tested is inadequate as I'm sure it passes that.

Mike

I dodn't think that AFDDs would have averted the tragedy of Grenfell.  A better smoke/fire/heat detection system may have helped saved more people.  So could of regular fire drills and evacuation drills prepare people.  Unfortunately there are many things that I think were done wrong.  I am no expert but asking people to stay put rather than evacuate the builder I think was wrong.  However saying that I have seen a horizontal evacuation work perfectly well in other places.  I also think that wrapping a fire proof building made of rocks and brick and cement in a PetroChemical flammable insulating material was criminal negligence.  

Back to AFDDs.  I have not fitted any but my understanding is that MOST AFDDs but not ALL are dual function.  They are a RCBO module and an AFDD module in one package.  Thus ever could trip on their respective fault. 

However the cost and the fact that they are possibly not able to function for their intended task is worrying.  Maybe the BS EN for AFDDs needs to be looked at with respect to the following.

How are they tested by the manufacturer

How can they be tested by the installer/Electrican

How can they be tested by the end user

Colours of the flags or LED used.  On some Green means good and functional on other Red is used. 

Personally speaking if I was to fit a CU in my house today I would go for a full RCBO board DP (Daul Pole or Single Pole with switched neutral) with type 2&3 SPD I would also force the DNO/DSO/MO to provide and install mains isolation switch for the safety of the installer. 

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.

Indeed - actually the type test for AFDDs is quite odd.  A section of PVC twin cable without CPC is pre-damaged with high voltage, to create a local decomposition.

The standard is too expensive for causual readers, but luckily you can read a pretty good description of the process  on page 16 here.

You are quite right passing the test does not guarantee real world operation  - copper copper arcs tend to either burn clear or weld shut and stop arcing, carbon electrodes or brass can usually be persuaded to maintain an arc for a while.

  Cables with a CPC like we use in the UK are likely to trip an RCD once the PVC carbonises to the point of conducting, if arcing  or not, and LSF type cables do not respond in the same way as the PVC, and tend to produce rather less conductive char.

The doc above is a Swedish chap doing a rather more lab based check on AFDDs with other scenarios, that  may or may not be more realistic.
He too find situations where the varuious makers offerings are not the same.

As I said above, the devices and the standard, appear very immature, and the absence of testgear and diagnostics to allow any kind of fault tracking is a serious obstacle.

Mike.

I have reached out to Kevin at Chauvin Arnoux UK to see if they are working on an AFDD tester or are working on bringing anything to market to test AFDDs with the prospective of an installer/tester. 

Indeed, and another point made in the video but glossed over here, is who is going to pay for the time spent by an installer going round all of the sites where he has installed AFDDs to do a firmware update every time one is issued?

There are some Klien AFDD testers around in the USA but they don't test to the standards here.

Are you thinking of these testers ?

The Klein Patent of 2008 gives away how they do it. I suspect something similar could be done for the 220V equivalent.

It only really does one sort of arc waveform, but it would at least trigger that part of the AFDD.

There is a Siemens patent that achieves the same ends with a differnt circuit and generates a slightly different waveform though that style is not out in the wild in any actual test gear to my knowledge.

Note that apart from the wait 20secs between retests, for the Klein uint, there are no special energy related precautions. The Siemens patent mentions a small fan to cool the resistor bank- which could probably be ommitted with a similar time limitation

It may become more common once the 20 years is up and patents have expired.

Mike.

Personally I say to Hagar if it needs a firmware update then you better send your Hagar electrician to site to get the job done or Hagar can pay me to attend site to do the firmware upgrade.  Unfortunately my time is not free.  Lets say my call out charge and first hour of labour are £75 plus vat.  Additional charges may apply if it is outside my local area of lets says 10 miles. 

On a side note I have upgraded many routers back in the day via telnet and FTP and TFTP.  Every so often a firmware update would fail and render the unit useless.  This meant when I went to site to do the firmware upgrade I would take a spare, do a backup of config and then apply the firmware upgrade.  I wonder what happens if the AFDD firmware upgarde breaks the AFDD what is the electrician espected to do?  Do the Hagar AFDDs have 2 firmware partitions so it can fail safe or allow recovery.  Do Hagar exspect the engineer to carry a spare b16 c16 D16, C16, C20, C32, D6, D16, D20, D32 with them.