Why are armoured cable colours different from twin and earth?

[joe90]

Just wiring my garage and although I have wondered this before I never knew the answer. Armoured cable feeds from the house underground. (It’s too hot to be on the roof fitting shingles) @ProDave….?

[Timedout]

I was expecting one of the Brexit freedoms would be a return to black and red. My place would have come back into fashion.

[markc]

@joe90 what colours do you have?

[dnb]

At a guess grey and black.

[joe90]

  On 07/09/2023 at 15:51, markc said:

@joe90 what colours do you have?

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Brown (live) grey (neutral) black (earth)

[joth]

Guess: often earth is not sent down swa (depending if it's a local earth stake or not, or separate earth bonding) and making one core yellow/green kinda limits what you can do with it. I for one feel dirty using yellow/green for anything other than earth. 

And I guess no blue because if you're driving a perfectly balanced 3ph load (motor) you don't need a neutral??? 

It's consistent with 3+E cable at least.

 

I wired my driveway lights up yesterday, to a test 13A lead that was literally inherited from my grandad, so wiring red to brown, black to grey, and green to black gave me a right old chuckle.

 

Edited September 7, 2023 by joth

[joe90]

  On 07/09/2023 at 16:36, joth said:

It's consistent with 3+E cable at least.

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That makes sense (I know nothing about three phase), using it as I have duplicates the earth I guess 🤷‍♂️

Edited September 7, 2023 by joe90

[ProDave]

You can, if you shop hard enough get brown, blue, green/yellow SWA.  but much more common is brown, black, grey, which are the three L colours used for 3 phase.

 

What annoys me more is 3 core and earth is usually sold as brown, black, grey.  I have NEVER come across 3 core and earth used for three phase L.  It is usually used for 2 way lighting where the colours make some sense or for L, switched L and N to a fan where it does not make sense.

[joe90]

It’s too late for me now but should I have sleeved to the correct colours ( as i do with switched live for light switches) or is it acceptable to leave as is (in future).

[FuerteStu]

3 core swa is coloured 3 phase as standard.. 

 

The vast majority of swa cable is used in industrial or commercial situations. Lots of motors and pumps run on 3 phase wiring, often with no neutral as the loads are balanced,and in a star formation. The armour being used as circuit protection (bonding). 

 

You can buy standard coloured swa (blue, brown, yellow/green) but it's not as common. 

 

BS7671 says that line conductors and bonding should be identified.. 

 

Standard is to sleeve with heatshrink, or Wrap with insulating tape. 

 

Usually, brown stays the same, black is the earth, and grey is the blue. But always Double check both ends are the same.

 

 

[FuerteStu]

  On 07/09/2023 at 18:17, joe90 said:

It’s too late for me now but should I have sleeved to the correct colours ( as i do with switched live for light switches) or is it acceptable to leave as is (in future).

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I would Wrap some tape around the cores.. Just to identify them. 

 

It doesn't have to cover the old colour completely, just to identify which core is being used for each conductor. (I usually Wrap a 3" piece of insulating tape every 4" or so to old cores not identified)

[Mattg4321]

Just to add to this, if you buy 2 core armoured cable, then it will be brown and blue cores, with the steel wire armouring used as the cpc/earth. 
 

Most people now prefer to have a separate core for the cpc/earth these days though, even if not actually required. Usually to mitigate the risk of some idiot builder damaging the sheathing, thus exposing the swa and starting the process of it rusting away. I usually try and buy single phase colours (brown, blue and g/y), for when using it in single phase applications, but it usually needs to be ordered in as no wholesalers seem to stock it. 
 

It’s now specifically against the regulations to use a green/yellow core for anything other than a cpc/earth, single 18th A2. This one is going to catch out a lot of plumbers!!!

[FuerteStu]

  On 08/09/2023 at 06:05, Mattg4321 said:

 

Most people now prefer to have a separate core for the cpc/earth these days though, even if not actually required.

 

It’s now specifically against the regulations to use a green/yellow core for anything other than a cpc/earth, single 18th A2. This one is going to catch out a lot of plumbers!!!

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I've seen SWA in a plastic Stuffing gland with a few strands twisted together and terminated into the MET. It tested with effective results, it was still potentially dangerous as any strain on the cable would transfer to the cores, not the armour. 

 

To me the armour is additional protection through bonding, not a reliable cpc. 

 

Plumbers shouldn't be touching anything other than flex.. I've seen them use the cpc in twin as a neutral for smart thermostats and say 'that's alright blue isn't as dangerous as brown'.. Idiots

 

 

 

[Mattg4321]

  On 08/09/2023 at 06:41, FuerteStu said:

 

I've seen SWA in a plastic Stuffing gland with a few strands twisted together and terminated into the MET. It tested with effective results, it was still potentially dangerous as any strain on the cable would transfer to the cores, not the armour. 

 

To me the armour is additional protection through bonding, not a reliable cpc. 

 

Plumbers shouldn't be touching anything other than flex.. I've seen them use the cpc in twin as a neutral for smart thermostats and say 'that's alright blue isn't as dangerous as brown'.. Idiots

 

 

 

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Anybody terminating SWA like that shouldn’t be touching it! If you haven’t got all the strands, then how do you know that all of them are satisfactorily connected so that if something were to pierce the cable and short out the armour to a line conductor you could be sure the circuit would be disconnected? To connect all the strands after using a stuffing gland would be harder work than just using the correct gland in the first place!
 

There’s absolutely nothing wrong with using the armour as the cpc, if done properly, and especially if the cable is mechanically protected in a duct in my opinion. 

Plumbers should stick to pushing pipes together! I’ve seen far too many dodgy boiler wiring centres in my time.  😜 

[FuerteStu]

  On 08/09/2023 at 20:09, Mattg4321 said:

Anybody terminating SWA like that shouldn’t be touching it! If you haven’t got all the strands, then how do you know that all of them are satisfactorily connected so that if something were to pierce the cable and short out the armour to a line conductor you could be sure the circuit would be disconnected? To connect all the strands after using a stuffing gland would be harder work than just using the correct gland in the first place!
 

There’s absolutely nothing wrong with using the armour as the cpc, if done properly, and especially if the cable is mechanically protected in a duct in my opinion. 

Plumbers should stick to pushing pipes together! I’ve seen far too many dodgy boiler wiring centres in my time.  😜 

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I refer to those 'wiring centres' as idiot boxes.. Wiring by numbers. 

[Onoff]

I just tidied the 3-core swa feeding my garage. In reality it's "3-phase" cable.

 

For single phase use, brown stayed brown, sleeved the grey with blue and the black with green and yellow.

 

Tbh it's pretty easy to get cable with "proper" colours. Search "single phase armoured cable".

 

CableColoursLeaflet.pdfFetching info...

[TonyT]

Proper colours are red yellow and blue

[Onoff]

  On 08/09/2023 at 20:53, TonyT said:

Proper colours are red yellow and blue

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Nah, we should get all patriotic & go back to red, white and blue:

 

 

[TonyT]

Yeah I think you are needing a rewire 😜

[FuerteStu]

  On 08/09/2023 at 21:22, Onoff said:

 

Nah, we should get all patriotic & go back to red, white and blue:

 

 

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My only concern about those wires is the grey sheath.. Isn't that the tasty oily stuff that rats love to nibble on? 

[Onoff]

  On 08/09/2023 at 21:44, FuerteStu said:

My only concern about those wires is the grey sheath.. Isn't that the tasty oily stuff that rats love to nibble on? 

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Polythene inslated cable with a pvc sheath to BS1557. So 3-cores, red, white & blue, no earth, Imperial 3/0.29 I think, 3 tinned strands per core equates to about 1.5mm2. It was like new. Found in a time warp, unfinished outbuilding of an elderly neighbour. 

 

BS1557 was withdrawn in 1954!

[Mattg4321]

Loads of that still in service in good condition! 
 

It’s rubber insulated cable you want to be careful of, especially if it’s the lead sheathed stuff! Only ever seen that still in service once in my 20+ years. 

[Onoff]

  On 09/09/2023 at 07:19, Mattg4321 said:

Loads of that still in service in good condition! 
 

It’s rubber insulated cable you want to be careful of, especially if it’s the lead sheathed stuff! Only ever seen that still in service once in my 20+ years. 

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Found some black rubber sheathed in one of the original walls here (<1930s). Not connected to anything but like new. There must have been some sort of preservative used in the bricks and mortar back then! 

 

I remember bundles of lead wiring in my first house (built in 1865). Still had the gas mantles on the wall. Was obviously electrified sometime after 1965. Then pulling the stuff out of the walls from the lime plaster and loads of it falling off!

[joe90]

Ha, my first house (a wreck) still had lead covered cables buried in the plaster. The electric had been disconnected so when the DNO came to re connect it he tested the wiring and nearly had a fit, “I am not connecting that it’s fecking dangerous”, he pulled the main fuse (but left it there). To work on the house I put the main fuse back in, went upstairs and leant on the damp wallpaper and got a right tingle. I quickly rigged a temp power and lighting ring 😱

[HughF]

I tend to use 3 core (in the correct colours), then earth the armour at one end only, for protection and export the earth to where I'm going. If that's not appropriate and I'm making a TT island then I'll still earth the armour.