Identification of electrical wiring should be clear and accurate so that the risk of injury or damage is minimised. This article looks at requirements relating to the identification of conductors contained in Section 514 of BS 7671.
As required by Regulation 514.1.2, wiring should be arranged and/or marked so that it is readily identified for the purposes of inspection, testing, repair or alteration, and each circuit protective device (circuitbreaker, fuse or RCD) should be arranged and identified so that the circuit protected may be easily recognised (Regulation 514.8.1).
Where it is impracticable to individually label protective devices, the protective devices may be identified by means of a durable chart or schedule fitted inside the cover of, or adjacent to, the consumer unit or distribution board. Regulation 514.9.1 requires that the form of information provided is legible and durable, and indicates:
- the type, and composition of each circuit (number of points served, number and size of conductors, type of wiring) and,
- the method for providing shock protection (which protective measure (such as ADS) has been provided), and
- the information necessary for the identification of each device performing the functions of protection, isolation and switching, and its location, and
- any circuit or equipment vulnerable to a typical test.
For a typical domestic premises and other simple types of installations, a copy of the combined ‘Schedule of Circuit Details and Test Results’, which forms part of an NICEIC Domestic Electrical Installation Certificate, fixed within or adjacent to the consumer unit is likely to achieve compliance with Regulation 514.9.1. For more complex installations, however, more comprehensive information will be required.
Requirements for conductors
Except where identification is not required, the cores of cables should be identified by colour, letters or numbers. Every core of a cable must be identifiable at its terminations and preferably throughout its length (Regulation 514.3.2). Identification of conductors is summarised in Table 51 of BS 7671.
Omissions
Identification is not required for concentric conductors of cables, metal sheath or armour of cables where used as a protective conductor, certain bare conductors where identification is not practicable, extraneous-conductive-parts used as a protective conductor and exposed-conductive-parts used as a protective conductor (Regulation 514.6.1).
Identification of conductors by colour
For a single-phase installation, the line conductors should be identified by the colour brown and for a three-phase installation the line conductors should be identified by the colours of brown, black and grey. In either case, the neutral conductor must be identified by the colour blue (Regulation 514.4.1). A PEN conductor shall be identified in accordance with Regulation 514.4.3.
Where a conductor identified with the colour blue is used as a switch line, as is common for wiring in domestic premises, the correct identification must be applied at the terminations (both the switch and the ceiling rose). This is achieved, as shown in Fig 2, by sleeving the (blue) switch line conductor with brown sleeving. In addition, the protective conductors should be identified using green-and-yellow sleeving only (Regulation 514.4.2).
Identification by lettering and/or numbering
Where lettering and/or numbering is used it should be clear, legible and durable. in order to avoid confusion, unattached numerals 6 and 9 must be underlined (see Regulation 514.5.1). Where identification is by numbers, the number 0 (zero) is reserved for the neutral conductor (Regulation 514.5.4).
Bare conductors
By the application of tape, sleeve or disc (or by painting) a bare conductor should be identified in accordance with Table 51 of BS 7671 (Regulation 514.4.6). Where a bare conductor or busbar is used as a protective conductor it must be identified, where necessary, by equal green-and yellow stripes, each not less than 15 mm and not more than 100 mm wide, close together, either throughout the length of the conductor or in each compartment and unit and at each accessible position.
Colours to previous versions of BS 7671:
Except where there is no possibility of confusion, unambiguous marking must be provided at the interface between conductors identified in accordance with BS 7671 and wiring to previous versions of the Regulations. Where newly installed cables interface with conductors identified to a previous version (older colours), the guidance given in Appendix 7 of BS 7671 should be followed.
As shown in Fig 3, where an addition is made to an existing installation that is wired using the ‘older’ colours a ‘Caution’ notice in accordance with Regulation 514.14.1 must be provided at the appropriate consumer unit or distribution board.
Switchgear and control gear
Labels or other means of identification should be provided, where necessary, to indicate the purpose of switchgear and control gear (Regulation 514.1.1).
Other notices and labelling required
For safety reasons, BS 7671 requires a number of labels and notices to be provided, including the following:
- An RCD test notice should be provided at (or near) the origin of an installation which incorporates one or more residual current devices (Regulation 514.12.2).
- An inspection recommendation label should be fitted on completion of installation work (including additions and alterations) and on each completion of periodic inspection, in a prominent position at or near the origin, giving the recommended date within which the installation should be re-inspected (Regulation 514.12.1).
- A voltage warning should be visible before gaining access to live parts in an enclosure where a nominal voltage exceeding 230 V to earth exists but would not normally be expected (Regulation 514.10.1).
- Where a circuit is likely to have a high protective conductor current, information should be provided at the distribution board or consumer unit indicating the circuit(s) likely to have a high protective conductor current. The information should be positioned so it is visible to a person modifying or extending the circuit (Regulation 543.7.1.205).
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