Post Brexit - Why are we still permitting CENELEC etc to influence how we govern our own engineering affairs?

At the risk of deviating somewhat, have you tried testing an AFCI for anything other than it's RCD function ?  The real bone of contention is that they are not demonstrated to do any good. The fact that they are used by Americans who use aluminium wiring and lower voltages and higher currents and seem unable to coordinate flex sizes with the breaker that protects them, is not a guarantee that the same device performs any useful function on a 240V circuit wired in copper. 

In fact if you take your arc welder and put a length of copper wire in the welding grip, and try and strike and sustain an arc with it, you will find it is all but impossible, the stuff either sticks, or burns back to self-extinction almost instantly. Not surprising as for years we made fuse wire from the stuff precisely because it does blow open circuit  gracefully.  There is a reason no-one makes aluminium or magnesium alloy fuse elements. But for the instant, the copper flash in the welder is a very pretty colour. (for the opposite of the no-effect try a wire "sparkler" from a kit of fireworks but be ready for it!! )

If you look at the official EN test for an AFDD you will see that it involves something that might as well be voodoo in terms of "preconditioning" the wire with a few kV to induce the deposition of high temperature PVC char before demonstrating detection of what is really a carbon-carbon arc.

Now you may get charring I suppose, in something like a low current flexible extension lead fitted with the wrong fuse that is burnt and then pulled tight to snap a core so that a series arc forms, but really the best place to fix that is with a thermal cut our in the drum of the extension lead.

Certainly here that has been no solid body of evidence presented to suggest that on UK house wiring (mostly solid copper cores and power in rings of  2.5mm)  they will do anything other than provide a false sense of security from spending some more money than a basic RCBO would have been. The reason for the absence of the substantial body of relevant evidence, I suggest, is that there isn't any.

Mike.

Mike, I'm not being drawn on my own opinion of AFDDs, but I fear we are disappearing down a pseudo-science hole (again).

I am happy to repeat the fact that I have experience of, on more than one occasion, sustained flames from cables, caused by, parallel arcs, but granted in some specified circumstances which are, I openly admit, not often found in domestic fixed wiring, but might be found in appliances.

I would also add what should be obvious in all of this.

It is entirely possible to comment on the product standards in exactly the same was as BS 7671. BS 7671 is not concerned with the specification of products (cue discussion on 722.411.4.1), and, further, if there is a deficiency in a product standard, surely there is a duty to bring it to the attention of the relevant BSI Committee?

Graham I suspect you are correct. The problem is that the real evidence-based science is getting thinner and thinner with every revision of BS7671. It used to be the case that a scientific innovator put up his work for peer assessment and critique and to be prepared to have his work shot down with solid scientific counter-evidence.

Now, it is as if there are none who are prepared to tell the Emperor the real truth about his new clothes.

Every time we try to question and examine the scientific rationale behind the mandating of of the likes of afdds for example, the shutters come down. We ask 'Why?' and are informed "we've had a meeting of the committee and we think it's a good idea', When we push further for the evidence and proof of concept we are stonewalled, and that's about the sum of it, or at least that is how it seems to me.

I think Mike pretty much has hit the bullseye with his previous comments.

Graham I suspect you are correct. The problem is that the real evidence-based science is getting thinner and thinner with every revision of BS7671. It used to be the case that a scientific innovator put up his work for peer assessment and critique and to be prepared to have his work shot down with solid scientific counter-evidence.

Now, it is as if there are none who are prepared to tell the Emperor the real truth about his new clothes.

Every time we try to question and examine the scientific rationale behind the mandating of of the likes of afdds for example, the shutters come down. We ask 'Why?' and are informed "we've had a meeting of the committee and we think it's a good idea', When we push further for the evidence and proof of concept we are stonewalled, and that's about the sum of it, or at least that is how it seems to me.

I think Mike pretty much has hit the bullseye with his previous comments.