Socket Wiring, Horizontally or Under Floor

[bernardgreen]

http://www.eponthenet.net/article/48882/Fired-up-over-consumer-units.aspx

All five plastic consumer unit enclosures were subjected to a needle flame test in accordance with the EN 60695-11-5:2005 standard. The needle flame was introduced into the consumer unit via a small opening to enable access to the main neutral connection at the neutral connection bar.

One of the consumer units with a flame retardant did not ignite and the flame was applied at four additional areas, again without ignition. The second consumer unit with a flame retardant ignited and once the needle flame was removed, the flame self-extinguished within eight seconds.

The remaining three consumer unit ignition tests resulted in fires that spread from the initial needle flame to involve the entire plastic enclosure. The shortest time from needle flame application to the ignition of the plastic was eight seconds. Two of the ignition tests had to be halted after four minutes as the smoke being produced by the fire began to overwhelm the dedicated extraction system of the test facility (figure 3)

Which suggest to me that there safe plastic consumer units are possible. I do wonder what will happen if the incoming Live ( fused 100 Amps ) and 25 mm² comes loose inside the consumer unit and touches the inside of the metal case which is probably earthed by a 10 mm² earth cable to the Neutral at the cut out. Would the 100 Amp fuse open before the 10 mm ² became hot enough to cause a fire outside the consumer unit. ?

 

[EFLImpudence]

It has long been a maxim of mine that one should "never assume those in charge know what they are doing".

Why do they keep proving it? How can they be so poor?

 

[JohnW2]

Which suggest to me that there safe plastic consumer units are possible.

I don't think many of us doubt that. Indeed, as has been discussed, the evidence that there is anything particularly 'unsafe' about tens of millions of plastic CUs out there is unlikely to be at all convincing.

The LFB would surely prevent far more fires by banning chip pans and toasters (and maybe any gas hobs with exposed flames)??

I do wonder what will happen if the incoming Live ( fused 100 Amps ) and 25 mm² comes loose inside the consumer unit and touches the inside of the metal case which is probably earthed by a 10 mm² earth cable to the Neutral at the cut out. Would the 100 Amp fuse open before the 10 mm ² became hot enough to cause a fire outside the consumer unit. ?

In a TN installation, I feel pretty sure that the fuse would blow even before the temperature of the (probably very short) earthing conductor even got particularly hot. With TT, of course, you'd probably be hard pressed to blow a 5A fuse, let alone a 100A one - but, by the same token, the 10mm² cable would not be remotely overloaded (the entire CPC system, including all exposed-c-ps would, of course, be close to 230V above true earth).

Kind Regards, John

 

[JohnW2]

It has long been a maxim of mine that one should "never assume those in charge know what they are doing". Why do they keep proving it? How can they be so poor?

Indeed, but more seriously, and as I often say, I find it very hard to understand how large groups of highly educated, qualified and experienced (and presumably mainly 'intelligent') people can sometimes come up with things which make no sense even to much less educated, qualified and intelligent individual.

Mind you, I have seen the same phenomenon in a whole range of fields over the years/decades, so it's certainly not peculiar to electrical regulations!

Kind Regards, John

 

[ban-all-sheds]

The drafting of the regulation is so poor that there is no way of determining whether a CU constructed of anything other than ferrous metal would be compliant.

Ferrous metal is not compliant.

 

[JohnW2]

Ferrous metal is not compliant.

It may not be "non-combustible" but it is an example (the only example) of a material which the regulation says is deemed to be (i.e. whether it actually is, or not) compliant with the regulation.

Kind Regards, John

 

[ban-all-sheds]

Just like it is not possible for a regulation to make something safe that was previously unsafe, or vice-versa, it is not possible for it to make something combustible non-combustible simply by deeming it so.

Since they do not mandate ferrous metal, but only use that as an example of something they deem to be other than it is, then there is no reason why someone else, an installer, for example, should not deem something else to be non-combustible.

 

[DetlefSchmitz]

I still haven't seen a convincing statement of how to comply with the regs on a TT supply with a metal CU. Some mutterings about double insulation for tails, but I haven't been convinced.

 

[JohnW2]

Since they do not mandate ferrous metal, but only use that as an example of something they deem to be other than it is, then there is no reason why someone else, an installer, for example, should not deem something else to be non-combustible.

We know it is very badly written, in all sorts of ways, but you are (as so often) just 'going on' about it in an unhelpful manner.

In what most of us recognise as the real world, when it comes to attempts to comply with a regulation, people are obviously going to take a lot more notice of what the authors of the regulation deem to be compliant with that regulation than any 'deeming' done by anyone else - and that remains the case even if what those authors are 'deeming' appears to be silly, incorrect or even 'impossible'. I doubt that many people, other than perhaps you, would waste time and effort trying to argue otherwise, for the sake of arguing.

Kind Regards, John

 

[ban-all-sheds]

We know it is very badly written, in all sorts of ways, but you are (as so often) just 'going on' about it in an unhelpful manner.

I'm sorry you regard it as unhelpful, but your opinion in that regard has no bearing on the truth.

In what most of us recognise as the real world, when it comes to attempts to comply with a regulation, people are obviously going to take a lot more notice of what the authors of the regulation deem to be compliant with that regulation than any 'deeming' done by anyone else - and that remains the case even if what those authors are 'deeming' appears to be silly, incorrect or even 'impossible'. I doubt that many people, other than perhaps you, would waste time and effort trying to argue otherwise, for the sake of arguing.

It's not for the sake of arguing - it is because I genuinely believe that it has no place bring in the regs, and that for this kind of sloppy, imprecise and impossible-to-comply-with to go uncriticised, or for the uncaring CBA crowd to shrug and say "so what" is pernicious.