Wiring conventions

[Tim Watts]

BS7671:2008 17th Edition pre Amendment 1:

514.4.2 (Excerpt):

"The bi-colour combination green-and-yellow shall be used exclusively for identification of a protective conductor and this combination shall not be used for any other purpose.

Single-core cables that are coloured green-and-yellow throughout their length shall only be used as a protective conductor and shall not be over- marked at their terminations, except as premitted by Regulation 514.4.3..."

Yes, it makes a big point of single-cores but the overall meaning is pretty clear - it would be a brave man that would argue against that. IMHO the first sentence covers all eventualities and the second is just reinforcement.

Reg 514.4.3 refers to PEN conductors which are G/Y with blue sleeves at the terminations.

Yes - but even qualified electricians don't like being caught out with extreme weirdness ;-> This is why there are colour standards - which are otherwise arguably irrelevent to safety as the electrons don;t really care.

That's their view, but I don't much like it - I think it is argued on the letter rather than the spirit of 514.4.2

[Tim Watts]

Not really - at least not these days. 17th basically states that "neutral" is to be considered a live conductor, as opposed to what we all call live which is now called "line" (rather than "phase" like it used to be).

In other words, neutral is regarded as dangerous and not to be left uninsulated, exposed, connected to random metalwork etc.

In this repsect the CPC has a very special status which is why it's important to avoid mistakes of this nature.

[Mike Tomlinson]

En el artículo , Tim Watts escribió:

Thanks for that.

[Interloper]

"Tim Watts" wrote

This rule is referring specifically and only to the colour identification of a conductor (at the termination point). If the conductor colour is the bi-colour combination of green-and-yellow , then that conductor must be a CPC. The bi-colour combination of green-and-yellow shall not be used for any other purpose. However, this rule has no bearing on the reassignment of a green/yellow conductor by oversleeving with a different colour at the termination points.

This rule specifically precludes the reassignment of a single-core green/yellow conductor for any other purpose. I suggest this rule exists to ensure reassignment of a green/yellow conductor will only occur in a multicore cable. This rule would be superfluous if the reassignment of a green/yellow conductor was not permitted under any circumstances. The rule could have been made much clearer.

The first rule (sentence) is very clear about the use of the bi-colour combination of green-and-yellow only. It refers just to the colour identification, and not to conductor reassignment.

IMO, the colour standards are now a mess that frequently has to be clarified by the use of additional alpha-numerical identifiers.. The latest colours were chosen as the EU standard in such a way that no country could be seen to be at an advantage as a consequence of the colour standard they were already using. At least the UK was instrumental in persuading the other European countries to adopt three different phase colours (brown, black and grey, rather than brown, black, black). It's taken since 1969 to agree and implement these colour changes!

[Tim Watts]

It's a compelling argument - I'm inclined to change my POV about the interpretation. I still maintain that it's a bad idea though.

Yep.

[Interloper]

I agree it's not the perfect solution, but as a last resort when you have run out of cores, it's useful to know that reassignment of the green/yellow conductor in a multicore cable is permitted under the IEE Regulations. Providing, of course, that the integrity of the earthing system is not compromised as a consequence of the reassignment.