3 core twin and earth cable what colour should you use as the neutral

[Steve1412]

yes steve correct, but we are talking 3c + cpc dommestic cable [no blue] keefy is adament the standard is to use grey but i can find no such official standard,merely that whatever you use is sleeved blue

Right..I get the problem now mate....each to his own I would have thought...cant even go down the 'common practise' route as everyone will have differing practises.....give me RYB anyday!!!!!!

 

[keefy]

keefy. where are you taking this standard from? the only thing i can see is that the blue of a three core is now grey, thats true but nowhere does it say that we must use it as the neutral. it is just because we used to use the blue that you think we must now use the grey. if so that is you own decision and not an official standard. as you say i am probally being dim and would be gratefull if you could give me the publication and page no of this standard

Nick, link to article from NICEIC connections (page 4 of PDF) from 2004 just after the colour change (I think). There is other stuff on this forum under the 'de-neutralising black' header.


http://www.niceic.com/en/account/media/connections/Connections_151.pdf

 

[malcolmsanford]

The yellow and green is puzzling. Where did it come from? Yellow and green can't be used for anything else for earth/CPC or bonding.

They used the green/yellow in a 3 core flex to feed the extract didn't they? V bad...

As long as the yellow/green in a flex is sleeved at the termination the appropiate live colour and is feeding a class II type of equipment that does not require a CPC then IMO there is nothing wrong with this practice.

It is just the colour Yellow /Green that can not be used for any other purpose other than earthing or bonding, and as long as it is not a single core conductor there is nothing prohibiting the use of a sleeved yellow/green conductor in flex as a live conductor.

 

[keefy]

As long as the yellow/green in a flex is sleeved at the termination the appropiate live colour and is feeding a class II type of equipment that does not require a CPC then IMO there is nothing wrong with this practice.

It is just the colour Yellow /Green that can not be used for any other purpose other than earthing or bonding, and as long as it is not a single core conductor there is nothing prohibiting the use of a sleeved yellow/green conductor in flex as a live conductor.

I suppose it is down to the interpretation of the regulation. I have always been told by respected engineers that the green / yellow identification in multicore cables is referred to in the first part of the regulation and sleeving it to re-assign its use makes no difference, thus using it as anything other than CPC is breaking this regulation. The reasoning behind it is that if you connect a green / yellow core to a live terminal you could present a potentially dangerous situation. Someone may assume that the cable possess no danger then gets electrocuted (although the get out to that is isolation procedures but that's a different ball game), even if the core was identified with sleeving or tape, which could come off anyway or be forgotten.

Another approach is the cost / benefit of the situation. It costs about 6p more to use 4 core flex in an average hook up of 1.5m in an extract which is deemed as good practice at least, and complying with the Regs at most. A small price to pay don't you think?

 

[malcolmsanford]

Is this regulation 514.4.2 your refering to. as to me there is not a lot of interpretation involved. It clearly states in paragraph one the the colour yellow/ green can not be used other than earthing or bonding.

The second tells us that if it's a single condutor ie a single cable in say a trunking, then you can not terminate this as a live conductor even if you want to over mark this at the termination, so therefore a green/ yellow in a flex, as that is a multi core cable, can be over marked at a termination and can be uses as a live conductor.

Cost is irrelevant really, as the regulations don't consider this, it may not be a practice I particualry adhere to, but in some cases it maybe called for and as it is not prohibited in the regulations it can be done.

 

[keefy]

Is this regulation 514.4.2 your refering to. as to me there is not a lot of interpretation involved. It clearly states in paragraph one the the colour yellow/ green can not be used other than earthing or bonding.

The second tells us that if it's a single condutor ie a single cable in say a trunking, then you can not terminate this as a live conductor even if you want to over mark this at the termination, so therefore a green/ yellow in a flex, as that is a multi core cable, can be over marked at a termination and can be uses as a live conductor.

Cost is irrelevant really, as the regulations don't consider this, it may not be a practice I particualry adhere to, but in some cases it maybe called for and as it is not prohibited in the regulations it can be done.

Cost is always relevant, although the Regs don't refer to costs in any way, working practices do take it into account, especially when we are dealing with safety critical parts of the installation of which live conductors are.

The interpretation is the first paragraph saying green / yellow cannot be used for anything but bonding or earthing. It means to me that anything carrying them colours as identification on the cores, irrelevant of whether you over sleeve it or not, can only be used for earthing or bonding. it seems to mean to you that you cannot pick up a piece of green / yellow sleeving and mark a switch wire with it? I see it as a total exclusion of green / yellow identified conductors for anything else other that earthing or bonding.

What circumstances may it be called for?

 

[malcolmsanford]

Low voltage fans, some CH wiring systems off the top of my head, could even strectch the point to strappers in 2 way lighting, Cost is of no relevance as far as regulations go, you seem to be confusing one with the other.

 

[keefy]

Low voltage fans, some CH wiring systems off the top of my head, could even strectch the point to strappers in 2 way lighting, Cost is of no relevance as far as regulations go, you seem to be confusing one with the other.

You seemed to misread my post. I never said cost was relevant to the regulations, but GOOD working practices are relevant to cost. If you spend an extra 10 pence on cables to make a good job then surely that is 10p well spent?

As pointed out, the regulation states that you should not use green / yellow cables for anything else but earthing or bonding, period! Too many people I have been involved with in this industry agree with, or sometimes even influenced, my view on this one for me to start saving a few pennies.

If you are happy to install 2way lighting circuits with 3 core flex then carry on. You would not get away with that on one of my sites.

 

[telectrix]

so, when the makers of 4" bathroom fans make them capable of taking the extra diameter of 4 core flex. i will use 4 core flex. and snip off the redundant cpc core.

 

[keefy]

so, when the makers of 4" bathroom fans make them capable of taking the extra diameter of 4 core flex. i will use 4 core flex. and snip off the redundant cpc core.

Never had a problem myself, but you are supposed to terminate, not cut off the cpc in a connector. I know fans don't have one as a cause but that's no excuse.