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

nick611 · Mar 4, 2011

keefy said:
A standard is just that, something drawn out that people stick to. If you don't agree with grey as neutral; tough. It was decided a long time ago that was the case and it has to stick. If you continue to be a rebel and create your own system you are creating problems for everyone who works on your installations after you. Just because you have 3 colours in the neutral bar (colour coded with sleeving of course so not to cause confusion) does not make it difficult, it just makes you dim if you don't understand it.

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

Steve1412 · Mar 4, 2011

Haven't read all the posts in this thread but have caught the jist of it. Doesnt table 51 state AC power single or three phase circuit neutral colour BLUE?????

nick611 · Mar 4, 2011

Steve1412 said:
Haven't read all the posts in this thread but have caught the jist of it. Doesnt table 51 state AC power single or three phase circuit neutral colour BLUE?????

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

Deleted member 26818 · Mar 4, 2011

As this is about 3core T&E, I'm assuming that there is actually going to be 4 conductors. Brown, Black, Grey and a bare earth.
When I use 3core and earth, It is usually for extractor fans or EM lighting, where a permanent and switched live is required.
In those circumstances, I would use the the Brown as permanent, and Black as a switched live.
This appears to me to be logical, as the fittings usually have terminals marked as L1 and L2. Brown in L1 and Black in L2.
Obviously the grey would in such circumstances, be used for neutral.

RogertheBodger · Mar 4, 2011

[ElectriciansForums.net] 3 core twin and earth cable what colour should you use as the neutral

wirepuller said:
I've been in the industry 30 yrs and am not averse to change....However this country has a long and distinguished tradition of implementing daft ideas....and harmonising cable colours has to be up there with the daftest.
Thanks to this piece of genius thinking we now have a situation where blacks and blues could be either phase or neutral...and drab dingy phase colours which are hard to tell apart in low light..and just to let everyone know how silly wev'e been we have to stick silly stickers over every DB pointing out our sillyness.
The UK is an island...there is no overlapping of wiring systems with our european masters...we didnt need to change.

Look what Harmonisation has done for Spain ..............

Steve1412 · Mar 4, 2011

nick611 said:
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 · Mar 4, 2011

nick611 said:
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 · Mar 5, 2011

keefy said:
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 · Mar 5, 2011

malcolmsanford said:
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 · Mar 5, 2011

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 · Mar 5, 2011

malcolmsanford said:
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 · Mar 5, 2011

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 · Mar 5, 2011

malcolmsanford said:
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 · Mar 5, 2011

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 · Mar 5, 2011

telectrix said:
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.

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

nick611

Steve1412

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nick611

Deleted member 26818

RogertheBodger

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Steve1412

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keefy

malcolmsanford

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keefy

malcolmsanford

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keefy

malcolmsanford

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