AFDD

Albert Law said:

Is it proven on enhancing electrical safety and is it worthwhile on the additional cost involved ?

To the best of my knowledge, the UK does not record fire safety statistics for electrical installations to an appropriately granular level to assess this properly.

gkenyon said:

Happy to let everyone draw their own conclusions ... but at the end of the day, I'm firmly of the opinion that any comments about the performance, operation, relevance or need for the device ought to be aimed at BS EN 62606 and IEC 62606 ... BS 7671 is not, after all, a product standard (and nor is IEC 60364 series).

BS 7671 is stipulating that AFDDs "shall" be used in some situations and generally "recommended" in other situations (421.1.7).

This is a moderately serious regulatory intervention, directly changing wiring practices with direct financial costs being imposed on the end-consumer.

To state the obvious, there must be some evidence base, a safety incident analysis, a cost-benefit calculation to justify the imposition of this requirement. 

Presumably the committee responsible for deciding to add that requirement into the BS 7671 must have that evidence and analysis, does anyone know where that is recorded? 

Apologies for any confusion Graham, that was supposed to be a reply to Albert's main request for supporting evidence, not to you in particular - that is just a mixture of my fumble fingers and a counterintuitive  software feature. My slightly odd turn of phrase is because I had already seen a copy of that article some time ago, as a private communication, but only now realised it was now on the web, and so I felt I could therefore mention it.

But there is a second serious point.

I am reminded that back when RCDs first came into common use and long before they first got snuck into the regs and then only for sockets that might be used to supply equipment outdoors, there were a whole rash of newspaper and tragic That's Life style  reports to encourage us to use them of the form ' boy saved from cut lawnmower lead by new safety device'; 'disaster averted', 'life could have been saved' ' tragedy in the sun' Sun says 'whew what a scorcher'  etc.

Far more recently, prior to the changes about cables remaining supported in fires driving the installation of metal clips and so on, there were several reported cases of folk becoming entangled in fallen wiring during fires and rescue attempts, and nasty injuries or deaths occurring that could have been fewer or maybe even avoided altogether as supporting evidence that the changes were proportionate.

Comparatively any equivalent reporting has been very quiet on the AFDD front, even in North America where the things originated, and the UK regulatory requirements rather appear to have preceded the body of evidence. 

Mike. 

It seems to me that an engineer can demonstrate in the lab that an AFDD does what it is intended to do during product development, but that is very different from demonstrating that they can save lives or property.

Along similar lines, a statin can be shown to reduce harmful lipids in the blood, but evidence of added quality adjusted life years could only emerge after they had been in extensive use for a number of years.

TurboGen said:

This is a moderately serious regulatory intervention, directly changing wiring practices with direct financial costs being imposed on the end-consumer.

It's definitely not a 'regulatory intervention' ... that would require legislation!

TurboGen said:

To state the obvious, there must be some evidence base, a safety incident analysis, a cost-benefit calculation to justify the imposition of this requirement. 

Presumably the committee responsible for deciding to add that requirement into the BS 7671 must have that evidence and analysis, does anyone know where that is recorded? 

All I can say to that, is that it's been through public consultation (multiple times) and rigorous debate ... I've added something to a subsequent reply that might be of interest, that is in the public domain.

mapj1 said:

I am reminded that back when RCDs first came into common use and long before they first got snuck into the regs and then only for sockets that might be used to supply equipment outdoors, there were a whole rash of newspaper and tragic That's Life style  reports to encourage us to use them of the form ' boy saved from cut lawnmower lead by new safety device'; 'disaster averted', 'life could have been saved' ' tragedy in the sun' Sun says 'whew what a scorcher'  etc.

Don't forget that there has also been expert evidence given in court on a few occasions, that in certain cases, presence of an RCD (for additional protection) might have saved a lives.

TurboGen said:

To state the obvious, there must be some evidence base, a safety incident analysis, a cost-benefit calculation to justify the imposition of this requirement. 

It's definitely the case that the expert evidence given in the Grenfell Enquiry pointed to the most likely cause of the fire (on the balance of probabilities) being an arc fault in a fridge-freezer.

gkenyon said:

It's definitely the case that the expert evidence given in the Grenfell Enquiry pointed to the most likely cause of the fire (on the balance of probabilities) being an arc fault in a fridge-freezer.

Did the Enquiry come to the conclusion that an AFDD would (on the balance of probabilities) have prevented the fire please?

The report you need to read is that relating to the expert witness Dr John Glover.
In summary he opined that wiring he has inspected showed that  the FF175BP fridge-freezer in Flat 16 has what appeared to be a "poor crimp connection" - suggesting a weakly compressed wire in the connecter barrel.
https://humanfactors101.com/wp-content/uploads/2023/10/Grenfell-Tower-Inquiry-Phase-1-Report-Volume-4.pdf pages 505 (the first page of actual text, page 4 of the PDF) to about 520.
The MCB and RCD did both trip, and the occupant turned off the power at the CU before they left the flat. Sadly by then the spread of fire was already irreversible.

Mike.

Chris Pearson said:

Did the Enquiry come to the conclusion that an AFDD would (on the balance of probabilities) have prevented the fire please?

Dr GLover's complete report is here: webarchive.nationalarchives.gov.uk/.../dr-j-duncan-glovers-expert-report

TurboGen said:

To state the obvious, there must be some evidence base, a safety incident analysis, a cost-benefit calculation

I tend to disagree with the "MUST" aspect.

We shouldn't need to kill people first, so as to gather evidence to allow our selves to be safer. We do have to match that tendency to being scared of our own shadow, to decide about ALARP (as low as reasonably possible), or other 'value of a life' etc. financial measures of safety.

It is a 'gamble'. We are happy to pump prime commercial industries for gain (the early funding for wind power, solar power, etc), where that investment creates rapid learning with scale benefits, so we should be able to do the same with safety systems.

Chris Pearson said:

Did the Enquiry come to the conclusion that an AFDD would (on the balance of probabilities) have prevented the fire please?

Another thought on this ... if the statistics are not there at present to support such a conclusion, would Dr Glover have been confident making that judgement?

Philip Oakley said:

I tend to disagree with the "MUST" aspect.

We shouldn't need to kill people first, so as to gather evidence to allow our selves to be safer. We do have to match that tendency to being scared of our own shadow, to decide about ALARP (as low as reasonably possible), or other 'value of a life' etc. financial measures of safety.

The difference between making a decision about a provision of a standard, vs coming to a conclusion without sufficient supporting evidence as an expert witness.

Chris Pearson said:

Did the Enquiry come to the conclusion that an AFDD would (on the balance of probabilities) have prevented the fire please?

Another thought on this ... if the statistics are not there at present to support such a conclusion, would Dr Glover have been confident making that judgement?

Philip Oakley said:

I tend to disagree with the "MUST" aspect.

We shouldn't need to kill people first, so as to gather evidence to allow our selves to be safer. We do have to match that tendency to being scared of our own shadow, to decide about ALARP (as low as reasonably possible), or other 'value of a life' etc. financial measures of safety.

The difference between making a decision about a provision of a standard, vs coming to a conclusion without sufficient supporting evidence as an expert witness.