Colour coding SWA question

[HawkEye244]

Why does SWA cable have grey, black and brown cores compared to normal 2.5mm2 which has brown, blue and yellow/green?

Sorry for the question but this is how we get to know and understand.

 

[pete01]

Brown, black, grey is for 3 phase with 4 core you also get a blue.

You need to sleeve it accordingly.

 

[flameport]

3 core SWA is available with single phase colours, https://www.wickes.co.uk/3-Core-SWA-Armoured-Single-Phase-2-5mm²-6493X-Black-25m/p/214676

 

[pete01]

3 core SWA is available with single phase colours, https://www.wickes.co.uk/3-Core-SWA-Armoured-Single-Phase-2-5mm²-6493X-Black-25m/p/214676

I've not seen that before.

 

[flameport]

The general idea was that the armour would be used as the CPC / earth, and then it's
2 core blue/brown for single phase
3 core brown/black/grey for 3 phase without a neutral
4 core brown/black/grey/blue for 3 phase with a neutral

however there are installations where a core is used as the CPC, hence 3 core with green/yellow, blue, brown for single phase and 5 core green/yellow, blue, brown black, grey for 3 phase.

7 core and above generally has numbered cores with all of the conductors white or black.

 

[plugwash]

In the UK (other countries may vary), re-identifying a green/yellow core for any other use other than an earthing and/or bonding conductor is at best frowned upon. It may be a violation of BS7671 (the wording is not very precise). OTOH re-identifying a phase-colored conductor as a neutral or CPC or re-identifying a blue (formerly black) conductor as a CPC is considered perfectly fine.

So if a supplier is only going to stock one type of three and four core SWA, it makes more sense for them to stock the variety that does not have a green/yellow core.

 

[JohnW2]

In the UK (other countries may vary), re-identifying a green/yellow core for any other use other than an earthing and/or bonding conductor is at best frowned upon. It may be a violation of BS7671 (the wording is not very precise).

I would say that the wording is precise enough. BS7671 generally allows use of any conductor for anything, so long as it is properly identified at its terminations (e.g. by over-sleeving). However, it explicitly forbids the use of G/Y single-core cables for anything other than a protective conductor - so I think the fairly clear implication is that, in a multi-core cable, a G/Y conductor can (if appropriately over-sleeved etc.) be used for anything (otherwise the explicit prohibition in relation to single-core G/Y would be unnecessary).

Kind Regards, John

 

[bernardgreen]

The general idea was that the armour would be used as the CPC / earth, and then it's

possible for a damaged sheath to admit moisture resulting in rusted steel armour and eventual loss of CPC.

Very uncommon but not unknown

Connect the armour to Earth at the supply end and run the CPC on a core

 

[plugwash]

I would say that the wording is precise enough. BS7671 generally allows use of any conductor for anything, so long as it is properly identified at its terminations (e.g. by over-sleeving). However, it explicitly forbids the use of G/Y single-core cables for anything other than a protective conductor

IIRC there is also a reg that says "green and yellow shall be used exclusively for identification of a protective conductor and this combination shall not be used for any other purpose." someone taking a paranoid interepretation could easilly read that as banning any use of a green/yellow conductor for anything other than protective earth, even if the green/yellow is part of a multicore cable and is completely covered by sleeving at terminations.

But it seems it's now moot, because it looks like amendment 2 to the 18th edition has banned such use https://electricaltesting.co.uk/18th-edition-amendment-2/

 

[EFLImpudence]

IIRC there is also a reg that says "green and yellow shall be used exclusively for identification of a protective conductor and this combination shall not be used for any other purpose.

Semantics? - How could it (i.e. green and yellow) be used for any other purpose? Who thinks it means anything else?
Were you to put G&Y sleeving on a brown conductor, how could it be thought that it was anything but a protective conductor.

" someone taking a paranoid interepretation could easilly read that as banning any use of a green/yellow conductor for anything other than protective earth, even if the green/yellow is part of a multicore cable and is completely covered by sleeving at terminations.

Yes - but it is only referring to the colours G&Y being used for anything other than a protective conductor; as above, how could it be?
Were you to sleeve it brown, what would anyone then think it was?

But it seems it's now moot, because it looks like amendment 2 to the 18th edition has banned such use https://electricaltesting.co.uk/18th-edition-amendment-2/

It would indeed, but at least that is clear.

Presumably sleeving other colours with G&Y is still allowed as long as it means protective conductor.

 

[ebee]

i have for some years taken it as any protective coded conductor (irrespective of oversleeving or not) must never be used as anything but a protective conductor. live coded conductors, however, may be oversleeved and used as protective conductors.

some of you might, like me, be old enough to remember proper colour coding Red/Black and Green - Yellow (or plain green for E).
R Y Blue for 3 phase and R Y B with Black if N was required.
often the 3 core was used for single phase and used R for L, Blue for N and Y for E. a bit naughty, especially considering that Brown for L and Blue for N was only for flexes for quite a few years

"Red to Brown and Blew to bits" was a common saying.

ps - what`s wrong with using both armour and a conductor in SWA ?

 

[JohnW2]

i have for some years taken it as any protective coded conductor (irrespective of oversleeving or not) must never be used as anything but a protective conductor. live coded conductors,

If that were the intent, there surely would not be a reg explicitly saying that such is true for single-core cables (implying that it isn't for a G/Y within a multi-core cable)?

live coded conductors, however, may be oversleeved and used as protective conductors.

Indeed - I see nothing in the regs which prohibits that.

ps - what`s wrong with using both armour and a conductor in SWA ?

Nothing. In fact, if one uses a conductor within the SWA as a CPC, at least one end of the armour has to be effectively connected to that CPC.

Kind Regards, John

 

[SUNRAY]

some of you might, like me, be old enough to remember proper colour coding Red/Black and Green - Yellow (or plain green for E).
R Y Blue for 3 phase and R Y B with Black if N was required.

Don't you mean red WHITE and blue?

 

[JohnW2]

Don't you mean red WHITE and blue?

I've seen it with both WHITE and YELLOW (probably most commonly the latter) - I don't know if they relate to 'different eras', or what.

Kind Regards, John

 

[securespark]

Don't you mean red WHITE and blue?

I have come across a few installations with cpc-less PVC three core with RWB.

From the 7th to the 9th Editions (1916 - 1934), you could use white or yellow for L2.

From the 10th to the 13th Editions (1934 - 1966) only white was allowed.

Surprisingly, in the 7th Edition (introduced 1916), neutral was colour coded green.