Requirements for AFDD's on new installations following amendment 2?

This what the 'Departures' box is for on the certificate. Unlike RCDs, there is no evidence that these things actually work, nor is there any regime in place to monitor their alleged effectiveness or otherwise. Until any of this changes,I shall refuse to the fit things. They stink of snake oil to me.

You may wish to watch this excellent item on the subject.

www.youtube.com/watch

Your likely correct and I agree with your sentiments, however in court you have to ultimately consider yourself as in precarious position against the underwriting elite 

Your likely correct and I agree with your sentiments, however in court you have to ultimately consider yourself as in precarious position against the underwriting elite 

Well, since there is no regime set up to determine the actual effectiveness or otherwise of these things, then we'll never know what may or may not have been prevented upon the deliberate omission of said item will we?

Where will the burden of proof fall? How can they claim without reasonable doubt that a AFDD would actually have saved the day somewhere when they are not measuring and recording? It's hard enough getting hold of reliable stats for fires of all courses, let alone the absence of a AFDD

whjohnson said:

Well, since there is no regime set up to determine the actual effectiveness or otherwise of these things, then we'll never know what may or may not have been prevented upon the deliberate omission of said item will we?

Hang on !!! A standard for these devices exists (BS EN 62606).

Comments that the product standard did not "determine the actual effectiveness of these things" could have been submitted in response to the drafts for public comment on that standard.

There has been an opportunity to do so at least 4 times in the UK - the standard was published originally (after DPC) in 2013, Amendment 1 was published (after DPC) in 2017, and the latest DPCs were 2019 and 2021.

Now we have products ... to a product standard published for 8 years ... that are rumoured not to be "effective"?

If an incident is believed to have been caused by a fault that could have been prevented (note, that doesn't even mean it would have been prevented), then it would be very difficult to show that not complying with 7671 was reasonable.

A requirement published in a standard (to use a device that is covered by another standard) would be accepted by a court as being "reasonably practicable best-practice". You would need to be able to demonstrate (by the production of documentary evidence) that what was put in place (or not) was at least as good.

Just because something passes a standard, it doesn't mean it does anything useful.  All it shows is that it meets the requirements of that standard.

That's especially true if the tests described in the standard were written by the manufacturers of the things being tested.

That is a common situation - there are loads of BSi documents and Euro-norms and other 'standards' for things that no-one takes a blind bit of notice of, and a few that even get withdrawn as being completely unsatisfactory after release - for a good example of the latter look at the EMC standards for power line comms that conflict with the CISPR emissions limits...

The problem is they are written in a bubble, with large contributions from a few key individuals, who may be sponsored by companies  with an agenda to sell a particular product  or service where  they have intellectual properties , and only once released does the effect become evident to folk who did not even know the document was even being created.

Very few folk look have the resources to review everything being drafted on the off-chance it may affect them at some point in the future.  It might be nice if the BSi was able to interconnect various committees better than it does, and it would also be better if the process was generally more open to scrutiny, more as it is for telecom standards, but that would adversely affect the revenue stream.

Mike.

That's exactly the case with surge protective devices.

Kirsty from an SPD manufacturer helped draft the requirement now activate in BS7671. Yet there is little data to warrant there requirement. 

Simon Barker said:

Just because something passes a standard, it doesn't mean it does anything useful.  All it shows is that it meets the requirements of that standard.

That's especially true if the tests described in the standard were written by the manufacturers of the things being tested.

So who is going to develop a standard for AFDDs? And what would be the driver?

I can see the point you are trying to make, but I think that BSI (and the relevant international standards committees) would be justified in asking why these concerns were not raised many years ago, after all the work has been done on the standard so far.

What is good, is that more people are looking at the properties of arc faults in trying to argue against the device.

The parallel with RCDs is, for me, astounding, though - the argument started with cost, then moved to technical challenges in various different areas, until now the technology is accepted. It's been really interesting to follow the slow acceptance of RCDs over the past 30 years or so.

RCDs were not cost effective when first introduced, either on new installations or retrofit.   And probably still are not in retrofit even today in many cases. I'm sure you know this, but for other readers, let me make it clear what it means to be cost effective in the sense of a safety device.

The value of the number of lives saved, plus the cost of fires and so forth avoided, must exceed the outlay proposed. 

So for a noddy example with big handful numbers if  a blanket campaign of fitting RCDs were to save 50 lives a year at say £ 1million per life,  and maybe ten thousand fires per year at say £10,000 each, that is a benefit to society of 150 million pounds per year we can decide if it is worth it or not.

If on average the RCDs last 25 years and then need replacing, then the predicted saving over the lifetime of the measure is ~ 3700 million pounds.

So if that involves installing one RCD in each one of say 37 million houses, there if it costs more than £100 all up parts and labour per house to do so, the expense will exceed the 3700 million saved, and it is not worth it.

More accurately, the money that would have been thus wasted should be spent on something with more bang per buck in terms of lifesaving potential, like free issue of £10 fire alarms or an inspection of loose stair carpets.Now when RCDs first came in at about £50 each, and the treasury value of life was about 300k, they were certainly not worthwhile, Which is RCD use it was only mandated for high risk situations initially, or where essential for basic ADS..

Now they are less than £50 and in effect free-issue with the consumer unit,  and the cost per life has risen, they clearly are.  There are additional complications with devices that have high CPC currents by design, and a great many industrial  situations where their absence is still quite normal.

There are a number of flaws with the numbers in this example - high rated of inflation favour actions now, that may not look cost effective, but may become so as the cost of a life or damages rise during the duration of the measures. Low rates of inflation work the other way and favour deferral.However apart from some dogy rounding and compound interest,  the principles stand.  Various governments around the world asssign different values of life when compiling their  safety policies - Germany for example values its citizens at about 5 times that of the UK, and is reflected in the money spent on healthcare, road improvements, and AFDDs.

UK value of life calculations study for HSE  

A1.43 of the green book is supposed to steer policy in such cases

And the current values used by the govt when doing a proper cost benefit analysis, for example to see if road safety changes in the UK are worthwhile is set in A4.1.1 of the TAG Data tables. Note that we are expecting an update from the 2010 values soon, so expect a few things currently not worth it to shift to be worth it after all.

Is it so unreasonable  to ask for a similar level of transparency of thinking from the likes of the BSI ?

Mike.

I would say that given the upgrade costs, then more transparency should be de rigour prior to any mandating of the use of such devices. Standards are mainly based upon the theoretical, but what about a regime for recording in-service performance and effectiveness? Does the standard require that too? Or can we just sit back with the confidence that the device is fully capable in all instances? How are the numbers of preventative interventions being recorded?

Another thing, a board full of microprocessors sitting there sucking juice out of the mains 24/7. How much will that cost at a time when energy prices are surging and we are being told to use less energy overall?. How 'green' is that?

And how many of those on prepaid metering will have to choose between starving or supposedly being 'kept safe'?

With RCDs. the physics and science are plain to see and the argument for their use can be justified in the majority of instances. With AFDDs there are too many spurious 'maybes', and may of the problems they are intended to intervene upon would have already been picked up, either by a RCD or the MCB protecting the circuit in question.

I agree, but retrofitting, whether it be RCDs, house insulation, or seatbelts is always problematic.

I might just be able to see the point in new builds where an extra £200 on a total of £200,000 is barely significant, but an extra £200 on a CU change (or even worse, the installation of a new circuit) is unlikely to be welcomed.

I shall not be fitting them when I change my CUs, hopefully this year and definitely before they become mandatory.