There seems to be a repeating mantra throughout the youtube presentation which becomes irksome if you listen for long enough. It seems that we just adopt, or rather 'harmonize' without question and then defer the responsibility for decision making back to CENELEC rather than think it through and act for ourselves.
How is it that we allow the tail to wag the dog? Isn't it time that we departed from harmonization and went our own way?
Comments welcome
I don't see the debate being about "harmonization", but the extent of standards. By all means have national standards instead of international ones, but then why not county standards instead of national ones; or why not city standards instead of county ones? So then you end up with no standards at all.
Imagine no standardized wiring colours, or if you like, pre-Whitworth nuts and bolts of whatever dimensions the local blacksmith fancied!
It doesn't have to be that granular - an independent national standard for wiring practices would be fine, but I suspect you know that. It seems impossible to drill down to the exact origin of some of the regulations, who introduced them for discussion and why. The origins seem to be deliberately obscured. If you wish for an example of this, try drilling down to the origin of the idea to introduce and mandate afdds.
Good luck.
The origins seem to be deliberately obscured. If you wish for an example of this, try drilling down to the origin of the idea to introduce and mandate afdds.
How so?
AFCIs have been in use in other nations that use NEC for some time, and had been before they were even suggested for consideration in IEC 60364, HD 60364 and BS 7671.
Surely it would be remiss of both our national committee, and international committees, not to consider quite seriously the question of why we don't recognise them?
Turning this discussion around, we have the situation with cables concealed in walls, where the industry was railing against the supposed "continued pushing of expensive RCDs", and it took a Coroner's Letter to bring about the change. Had the industry more quickly embraced widespread use of RCDs, perhaps lives could have been saved.
Sadly, with AFDDs, the discussion in the UK has now degenerated into a social media minefield ... what is the real story, and who do you believe?
Interesting that arc fault breakers should be at all controversial.
In the aftermath of the in-flight fire and breakup of TWA 800 off Long Island in 1996, there was a serious investigation of wiring in (then-)older aircraft. There is a huge amount of wiring in a typical commercial transport, and almost all of it is inaccessible. Lots of it was found to be at risk. And an in-flight fire is one of the worst scenarios imaginable. A couple of years after TWA 800, and before the report was finished, Swissair 111 suffered an in-flight fire and came down near Halifax, Nova Scotia. Swissair wasn't necessarily an "old-wiring" problem; there had been a post-manufacture installation of an entertainment system, and there is fairly good evidence a fault with that was involved. Because of the physical constraints, it can be hard to see induced damage or inappropriate kinks in wires you are newly installing.
The only reasonable solution to such wiring problems was to post-install AFCI. But at the time they cost real money. Militaries were also interested, in particularly naval aviation, because salty water and sea mist is a harsh environment for aircraft wiring. I remember talking to people at Schneider Electric about the prospects.
Since then, of course, the price of AFCI has come down enormously.
It is not just in-wall wiring installation. Even if you have open wiring, mice and martens like to chew insulation. My house is constructed with bricks and concrete on a wooden frame, and the floors in the older part are pure wooden construction with plasterboard ceilings (in the newer part they are concrete) and of course that's where the wires go and the critturs like to live. Type A RCDs were routinely installed on all circuits when I partially rewired in 2006 (they became German law in 2007) but with the occasional four-footed residents I have been thinking I should really put in Type B.
The state of domicile wiring is not good anywhere in Europe. Installations are supposed to be good for 35 years, in a place such as Germany some 70% are older (data from 2010). Some are of the order of 80-90 years old. About a third of building fires are of electric-fault origin; some 600 people die per annum in building fires, 75% of them in their domicile (also 2010 data). We don't have any idea of course how many of those are down to arc faults; AFCI are not a panacea. But some of them are. I should really put in those Type B.
And an in-flight fire is one of the worst scenarios imaginable.
Possibly worse than a fire in a submarine!
Graham, why would it be remiss of us not to give consideration to bad science? Why should we slavishly adopt something which is of dubious merit? You keep returning to the RCD analogy - it smacks of obfuscation - the science behind RCDs and their ensuing benefits is clear. The 'science', or rather 'pseudo-science' behind the reasoning which has pushed the mandating of the installation of afdds not so much.
Indeed! This is a bad analogy, with a completely different risk profile. Unlike a house fire, the consequences of a fire at 30'000ft means that you cannot just walk out of the front door to escape, Same with any fire at sea, whether it be a submerged vessel or a surface one.
Most is MIL spec and that is quite variable (MIL-C-27500). See e.g. https://www.ryanelectronics.com/products/m27500-wire-specification-breakdown/
The issue is the insulation and its properties. An aromatic polymide known as Kapton was commonly used up to and beyond the 1990's (for a list of aircraft which used it, see https://www.interconnect-wiring.com/blog/aircraft-kaptontm-insulated-wire/ I don't know whether the list is complete). With age,iIt tends to build carbon conductive stripes on the inside, presumably with some release of hydrogen, and then when it gets cracked an arc through the crack explodes the wire. There are some FAA videos from the 1990's showing this (I can't put my finger on one at the moment).
Most is MIL spec and that is quite variable (MIL-C-27500). See e.g. https://www.ryanelectronics.com/products/m27500-wire-specification-breakdown/
The issue is the insulation and its properties. An aromatic polymide known as Kapton was commonly used up to and beyond the 1990's (for a list of aircraft which used it, see https://www.interconnect-wiring.com/blog/aircraft-kaptontm-insulated-wire/ I don't know whether the list is complete). With age,iIt tends to build carbon conductive stripes on the inside, presumably with some release of hydrogen, and then when it gets cracked an arc through the crack explodes the wire. There are some FAA videos from the 1990's showing this (I can't put my finger on one at the moment).
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