Following on from my recent installation of an extractor fan.
The fan I fitted requires 4 connections: neutral, permanent live, and two switched lives. I bought myself a length of 4 core cable of the required rating but I'm confused about which colours to use and whether there might be a different coloured cable that I should have used.
The cable that I bought has inners coloured brown, blue, black and green/yellow. I wired the blue to the neutral and the brown to the permanent live - leaving the black and green/yellow for the two switched lives. I have a 3 pole isolator on all of the live cables, but even so, I'm not comfortable with having a green/yellow for a potentially live cable and I'd like to find a solution to this asap.
What is the normal convention in these situations - is there a 4 core cable with different colours made specifically for this type of installation?
Blue is neutral, while brown, and black are "live" colours (in the harmonised colour scheme). Green/yellow is earth.
Its very bad practice to re-purpose a green/yellow CPC in a cable/flex.
The typical 5 core flex used by central heating installers may be more appropriate. Or I would probably run a length of T&E and one of 3&E to give five cores plus earth.
As both John and Andy have pointed out you should not use the green/yellow for anything other than "earth". It's also bad practice not to run an earth out with all the other cores even for something that will not be earthed. You "park" the earth core in a piece of strip connector inside the fan.
As they both said, 5 core flex is one suitable answer.
If it really doesn't need an earth (double insulated), and he can find four core in blue, brown, grey and black, that should be enough.
While not disagreeing with you, I notice that Googling for "For green and yellow conductors in multicore cables, overmarking in another colour at terminations is permitted. This is prohibited for single core green-and-yellow conductors." has a few hits.
The bi-colour combination green-and-yellow shall be used exclusively for the identification of a protective conductor and this combination shall not be used for any other purpose"
The problem is that there is a silicon grommet at the entrnce to the unit which is designed to seal around a single inlet cable. Using multiple cables would provide a moisture ingress path :-(
You've bought the wrong cable. It is presumable a flex since it has sleeved earth? It is flex designed for three phase stuff by the colours. And yellow/green is for earth *only*.
Any decent wholesaler will have 4 core plus earth flex. Like this:-
formatting link
you don't need the earth, leave it unused, but taped safely out of the way.
I would suggest that this regulation specifically refers to the visible green/yellow colour combination of the conductor. If the visible colours of a conductor are green/yellow, then that 'exclusively identifies that conductor as a protective conductor'.
However, if the exposed green/yellow conductor of a multicore cable is fully oversheathed or sleeved in another colour (e.g. brown) at the terminations, then IMO, the new designation for that conductor would not contravene the regulations.
It's not that different from oversheathing the blue neutral in a switch drop with brown sleeving to redesignate it as a live conductor.
Hang about - whilst I cannot put my finger on the reg this second, I believe that using a green/yellow conductor for any other purpose is absolutely verboten.
Give me a few hours - I think I can back that up...
But common sense wise - what if someone cuts the cable later, determines an apparant CPC and bonds it to something exposed?
There is of course an exemption for this if you are a plumber, then the green/yellow, or even just the bare copper earth lead can be, and is, used for a live return.
You might be right, but I couldn't find a regulation prohibiting the reassignment of the green/yellow conductor in a multicore cable.
I think you'll find that using the combination green/yellow *COLOUR* for anything other than a protective conductor is 'absolutely verboten' (or 'absolutely forbidden', once the UK is out of the EU). However, reassigning the green/yellow conductor of a multicore cable (*NOT* a single core conductor, which is forbidden), does not appear to contravene the regs.
Reassignment of a conductor at the termination using tape, sleeving, or alphanumeric identifiers takes precedence over the original core colour (although it would be good practice to also oversleeve a reassigned green/yellow conductor in a multicore cable when alphanumeric identifiers are being used).
OK, over to you, then ;-)
What, without checking/testing the 'apparent aspect of their CPC observation? I guess the protective device/mcb/rcd will trip on re-energisation :-)
If someone 'cuts the cable later', they should be a qualified electrician and know what they're doing. If they are remaking the termination for some reason, they should at least notice that the green/yellow conductor has been reassigned at the old termination. If they're simply reusing the cable for something else, then any previous reassignments at the terminations would be irrelevant.
This extract is taken from an ECA Guide to the 17th Edition IEE Wiring Regulations:
"D 3.1 Principle of required identification (514.3.1)
It is most important to understand the principle behind the drafting of the
17th Edition in respect of cable identification. Cable cores shall be identifiable at their terminations either by colour or by alphanumeric characters. While this has not changed from the 16th Edition it is worth discussing the principles.
It is noted that cores should preferably be identifiable throughout their length. For many applications coloured cables, either single- or multicore, will be used and these cables are obviously identified throughout their length. However, in many other applications installers will need to make use of this Regulation (514.3.1) for overmarking at terminations. The principles and applications of identification are now discussed with the use of diagrams.
[sorry, can't post the diagrams]
Figure D 3.1 shows the principle of identification where colours are used, i.e. marking by colour at all terminations and preferably throughout the length.
In Figure D 3.1 marking throughout the length is not used and single core cables have been used. It should be noted that the colour of the cables originally used is not important and overmarking by tape or similar takes precedence.
Building on this principle, Figure D 3.2 shows the principle of identification where alphanumeric identification is used.
It is perhaps more obvious now that marking throughout the length is not necessary. It should be noted that the colour of the cables originally used is not important and overmarking takes precedence. This principle holds whatever the colour of cores of the original cable, and applies at terminations by coloured tapes or by characters.
In summary, an important principle is established in that, wherever marking at terminations by either tapes, lettering or numbering is used, the original cable colours must be ignored; this can be against your gut feeling but you must get used to it!
Common examples and applications where identification is only practised at terminations include the following:
- Multicore cables with more than five cores. - MICC cables. - Control applications wired in single-core conductors. - Applications where coloured cable is not available, including connections to large generators or transformers, where often only black cable is available.
It should now be established that installers may wish to use any single cable colour, or combination of colours, and overmark at terminations, and this is not considered a lesser option. For green-and-yellow conductors in multicore cables, overmarking in another colour at terminations is permitted. Overmarking at terminations is prohibited for single-core green-and-yellow conductors."
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