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.

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.

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.

To make something safer, requires that there must be some level of unsafety, some risk, some hazard or danger to begin with, and further it requires that whatever action we propose to take will somehow reduce that risk or danger. 

Evidence does not require us to wait until people are killed or injured, the Accident Triangle principle of identifying near-hits, low level events that point to the risk of more severe events occurring in future, is still good evidence toward justifying action.

If we're then going to make some intervention, then to know it actually improves safety requires some evidence that it is effective, that it does indeed reduce the danger or risk, otherwise we could pursue ineffective and ultimately pointless activities, when our efforts and expenditure would have been better spent on other more effective measures. Again, that does not require us to wait for severe events, deaths injuries, the evidence could come from testing, trials, sampling or other methods.

But to go back to your key point "to allow our selves to be safer" well if we have no evidence of there being a hazard, a risk and we have no evidence that what we propose to do will effectively reduce that hazard or risk, then have we really made anything safer? Arguably we may have been better searching out and focusing on other safety hazards.

Philip Oakley said:

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.

Today, we already have a number of highly effective safety measures which are not universally used, for example smoke alarms, probably one of the most powerful and effective measures to prevent deaths by fires. A quick check, shows Government statistics indicate 20% of all electrical fires occur in houses without a working smoke alarm, greatly increasing the risk of injury and death.

So if our goal is to improve public safety, wouldn't you start by amending the Wiring Regulations to stipulate that in every domestic property at least one hard-wired smoke alarm shall be installed, connected into the fixed wiring, either a lighting circuit, or a dedicated smoke alarm circuit where available to provide protection against electrical fires, and all fires in general.

That is likely to be a far more effective safety measure, and provide a far better cost-benefit outcome than AFDDs.

gkenyon said:

Dr GLover's complete report is here

Mike, Graham, thank you for the links.

I am struggling a bit with the addendum to Dr Glover's report.

Figure 7 shown a L-N fault. 

Figure 5 shows what appear to be two multi-strand conductors which have fused together due to an arc. They could have been at line and neutral potential respectively.

I agree that such an event could have tripped the MCB of circuit 7. However, I am troubled by the explanation for the RCD tripping.

Smoke and smoke particles (soot) are electrically conductive. When smoke and smoke particles attack an electrical socket, the socket receivers can be affected by deposition of soot. After the 32-A MCB for Circuit No.7 tripped and prior to Mr. Kebede turning off the Main Switch at the Consumer Unit, Circuit No.8-Flat Sockets (not including those in the kitchen) as well as the RCCB remained energized. It is probable that smoke and smoke particles, having exited the kitchen before Ms. Kinfu vacated Flat 16 and before Mr. Kebede turned off the Main Switch, attacked an energized socket resulting in a current flow to the grounding socket receiver in excess of thirty milliamperes (30mA), which tripped the RCCB.

How did so much soot enter a socket? How did it get behind the shutters?

Then we have:

Mr. Kebede states, however, that when he left his flat, the smoke had not spread beyond his kitchen [Paragraph 76, IWS00000490].

But he had opened the main switch. So there is an important inconsistency here.

Then we have in (paper) page 516 of the report which Mike linked, In my view it is better to accept that it is not possible within the scope of this Inquiry to identify with confidence the precise nature of the defect in the large fridge-freezer which caused the fire.

The real issue was to do with the cladding.

I have to say, with the assistance of Occam's razor, that there had to be a L-E fault in the fridge-freezer, and it tripped both the MCB and the RCD.

It follows that an AFDD would have added nothing.

gkenyon said:

Dr GLover's complete report is here

Mike, Graham, thank you for the links.

I am struggling a bit with the addendum to Dr Glover's report.

Figure 7 shown a L-N fault. 

Figure 5 shows what appear to be two multi-strand conductors which have fused together due to an arc. They could have been at line and neutral potential respectively.

I agree that such an event could have tripped the MCB of circuit 7. However, I am troubled by the explanation for the RCD tripping.

Smoke and smoke particles (soot) are electrically conductive. When smoke and smoke particles attack an electrical socket, the socket receivers can be affected by deposition of soot. After the 32-A MCB for Circuit No.7 tripped and prior to Mr. Kebede turning off the Main Switch at the Consumer Unit, Circuit No.8-Flat Sockets (not including those in the kitchen) as well as the RCCB remained energized. It is probable that smoke and smoke particles, having exited the kitchen before Ms. Kinfu vacated Flat 16 and before Mr. Kebede turned off the Main Switch, attacked an energized socket resulting in a current flow to the grounding socket receiver in excess of thirty milliamperes (30mA), which tripped the RCCB.

How did so much soot enter a socket? How did it get behind the shutters?

Then we have:

Mr. Kebede states, however, that when he left his flat, the smoke had not spread beyond his kitchen [Paragraph 76, IWS00000490].

But he had opened the main switch. So there is an important inconsistency here.

Then we have in (paper) page 516 of the report which Mike linked, In my view it is better to accept that it is not possible within the scope of this Inquiry to identify with confidence the precise nature of the defect in the large fridge-freezer which caused the fire.

The real issue was to do with the cladding.

I have to say, with the assistance of Occam's razor, that there had to be a L-E fault in the fridge-freezer, and it tripped both the MCB and the RCD.

It follows that an AFDD would have added nothing.