Outer Sheath Cable Colour - Wiring and the Regulations BS 7671 - IET EngX - IET EngX
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Outer Sheath Cable Colour

Is there any guidance, best practice or standard when selecting cables dependant on the use of the circuit? As for example a Red cable will usually indicate a Fire system cicuit, a Yellow cable would indicate a 110v CTE construction supply.

I'm aware of the Table 2 in the IEC 60309 relating to plug and socket colours, but I'm sure I've seen some guidance in the past relating to cables also.

  • BS 1710 and NJUG Guidelines on the Positioning and Colour Coding of Underground Utilities' Apparatus.

    Having said that, it may be possible to mark containment, conduits etc., or, for BS 1710, apply separate marking to an otherwise coloured sheath of a cable. Clients may have their own preferences in this respect.

  • I'm looking more for a generic colour guidance rather than in a specific application. But I've added this to my list for points of reference.


  • Blue seems to have become established for mains voltage emergency lighting, for example from a generator. Possibly a network rail requirement, that has spread to non railway premises.

    First seen at Waterloo station and now at many larger stations.

    Yellow is the norm for 110 volt flexible cords, but not seen yellow outer sheaths for fixed 110 volt cables.

    I have seen orange PVC singles in conduit for fixed 110 volt circuits.

  • I don't think there's much official for the general case - certainly some prefer to match flex sheath colours to plug colours - but there are lots of other variables/constraints. Some cable types (e.g. HxxRN types) have a limited colour palette available for the sheaths (i.e. matt black only) - others (e.g. T&E) use the sheath colour for other characteristics (e.g. grey = ordinary smoky PVC, white = LS0H). In some cases matching the existing decor is the first consideration.  Yes some specific applications demand something special (e.g. fire) but I think that's the exception rather than the rule.

          - Andy.

  • The origin of my question comes from having black HxxRN type cables at an installation, then being asked by the installer if a different colour cable can be used (in this case green) as it's available and they can get there hands on it quickly. It looks odd and I would call it poor practice, but I'm struggling to find a reason/justification to say it's not permittable.


    Can you post a web link to this readily available HxxRN type cable with a green sheath? 

  • It’s RZ1-K cable 

  • This https://www.elandcables.com/cables/rz1mz1-k-xlpe-swa-halogen-free-cable ?

    Looks more like SWA than HxxRN (rubber) type to me.

       - Andy.


  • https://www.elandcables.com/cables/rz1-k-xlpe-lszh-flexible-cable

    My initial question relates to different cable colours, rather than type given it’s use and location

  • Yes it is an XLPE cable not a rubber one, as you can see from the temperature rating. The sheath colour is very unimportant, it is useful to use bright colours for flexible cables in some environments, garden stuff seems to like orange, and site cables are yellow or blue depending on voltage, but they are all made to BS6500 and the usual 250/400V rating. This green SWA has a higher voltage rating and is obviously aimed at the chemical industry, but I have never seen it as DNO usage in the UK, they are usually black or red sheathed for HV.