I'm certainly surprised that there hasn't been a lot more fuss about this. I don't think one can really blame the manufacturers (other than for their involvement in JPEL/64). One imagines that the main reason they are not making plastic ones is because the wording of BS7671 (and the absence of relevant definitions) means that it is impossible for them to know whether or not it is possible to make plastic ones which would comply, hence it also would be impossible for them to give any guarantees that any plastic product they manufactured was compliant. No-one in their right mind would, next year, install a CU which the manufacturer could only say "might" then comply with BS7671.
You remind me that, somewhere, I presumably must still have my set of (Imperial) Q-Max punches that I once used extensively for making holes for valve holders! I have a vague recollection that the most-used ones were ⅝" (I think for B7G holders), ¾" (B9A) and 1⅛" (octal etc.) - but I'm talking many decades ago, so my memory may well be very faulty!
Indeed, that's essentially the problem. Even more confusing, it says that that CUs should comply with BS EN 61439-3 and shall have enclosures manufactured of non-combustible material. Given that my understanding is that BS EN 61439-3 contains at least some 'combustible' tests(s) (e.g. the 'hot wire' test) it is therefore not clear whether they are saying that they require a degree of non-combustibility (although, as BAS would point out, NON-combustibility can't really have 'degrees'!) over and above that required by the Standard, or whether they are saying that compliance with BS EN 6149-3 is adequate (the "and shall..." words therefore being redundant). All they say is that ferrous metal is "deemed to be an example of a non-combustible material".
Indeed - and I would have imagined that, for example, many thermosetting plastics would probably be satisfactory (sounds like turning the clock back 60+ years!), even if rather brittle and hence difficult to work with.
If one of the manufacturers states that their plastic CU is non-combustible will you believe them?
Conscientious caring attitude.
Ok.
So, you have thought about it and are pontificating.
Agreed.
It's obviously your prerogative not to be concerned about these issues, but I think many people find the situation very unsatisfactory - in that a very poorly worded regulation is currently seriously limiting what manufacturers can produce and claim to be compliant. Unless some official clarification is obtained, I doubt that any manufacturer would be prepared to gamble with producing, or that (come next year) any electrician would be prepared to gamble with installing, an allegedly-compliant CU made out of anything other than ferrous metal.
Exactly - not to mention the possible increase in risk of electrocution (particularly for 'DIYers') if the result of the reg is to cause a widespread change to metal CUs. My understanding is that JPEL/64 probably allowed itself (seemingly had little choice, in view of 'threats') to be bullied by the Fire Service (or, one or two members thereof) into introducing this new regulation - which, as you say, does nothing to address the underlying problem. Indeed, I'm far from convinced that a lot of the fires cited by the Fire Service necessarily originated in (rather than 'came to involve) CUs, anyway.
That's because there is not, and can not be, any meaning.
And, I'm sure, the composition of the atmosphere it's in. Some substances will self ignite in an oxygen-rich one. Some substances contain their own oxidising agent and will burn in a vacuum, or under water.
I'm sure you can make ceramics burn if you try hard enough, therefore they are not non-combustible.
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