Places of work - New installations

 

  • Q1. The 17th Edition requires socket-outlets rated at up to 20 A and intended for use by ordinary persons to be provided with additional protection by means of a 30 mA RCD. Many socket-outlets in offices may be considered to be subject to this requirement. However, many offices will have computers producing protective conductor current, individually and/or collectively. This accumulated protective conductor current could cause the circuit RCD to operate. Such disruption will not be acceptable to the office users, particularly in banks etc. How can such unwanted tripping be avoided?

    Where additional protection by RCD is necessary, unwanted tripping can be avoided by appropriate sub-division of circuits.

    Regulation number(s)

    • 314.1
    • 531.2.4

  • Q2. Which 13 A socket-outlets in commercial and industrial premises are required to have additional protection by RCD?

    Socket-outlets in commercial and industrial premises must have additional protection by means of an RCD if they are rated at 20 A or less and are for general use without the supervision of a skilled or instructed person.  An exception is made for a specific labelled/identified socket-outlet for a particular item of equipment.

    The decision as to which socket-outlets are provided with RCD protection in accordance with these criteria should be made in consultation with the client’s duty holder under the Electricity at Work Regulations 1989.

    As a general principle, it may be considered that socket-outlets in commercial and industrial premises needing to have additional protection by means of an RCD include the following: those in common, circulation and public areas; those in self-catering areas; those intended for use by cleaners; and those that may reasonably be used to supply mobile equipment for use outdoors. 

    Regulation number(s)

    • 411.3.3

  • Q3. Which socket-outlets in commercial and industrial premises are NOT required to have additional protection by RCD?

    Socket-outlets in commercial and industrial premises must have additional protection by means of an RCD if they are rated at 20 A or less and are for general use without the supervision of a skilled or instructed person.  An exception is made for a specific labelled/identified socket-outlet for a particular item of equipment.

    The decision as to which socket-outlets are provided with RCD protection in accordance with these criteria should be made in consultation with the client’s duty holder under the Electricity at Work Regulations 1989.

    As a general principle, it may be considered that socket-outlets in commercial and industrial premises NOT needing to have additional protection by means of an RCD include the following: a socket-outlet labelled for the connection of a specific item of equipment; socket-outlets not intended for general use, such as those in floor service boxes intended for the connection of workstations and other IT equipment; socket-outlets for use under the supervision of skilled or instructed persons so as to minimize the possibility of careless use.

    Regulation number(s)

    • 411.3.3

  • Q4. How do I decide what grade and/or type of fire alarm and emergency lighting systems should be provided for a commercial property?

    Reference should be to the applicable Building Regulations, BS 5839-1 and BS 5266 which give specific recommendations.

  • Q5. If an RCD is used to achieve automatic disconnection within the prescribed time, is the supplementary bonding called for in 411.3.2.6 still required?

    No. An RCD is a valid way of complying with automatic disconnection requirements.

    Regulation number(s)

    • 411.3.2.2
    • 411.3.2.3
    • 411.3.2.4
    • 411.4.4
    • 411.4.9

  • Q6. In a milking parlour, is supplementary bonding required only where livestock can make simultaneous contact with extraneous-conductive parts (such as metallic gate posts and gates) and exposed-conductive-parts?

    No. The 17th Edition requires all extraneous- and exposed-conductive-parts that can be touched by livestock to be supplementary bonded, whether or not the parts are simultaneously accessible.

    Regulation number(s)

    • 705.415.2.1

  • Q7. Does a portacabin that is intended to be moved from place to place only infrequently, and which is supplied for example by SWA cable, fall within the scope of Section 717 of the 17th Edition?

    No. Section 717 applies to transportable units that are intended to be moved relatively frequently from place to place and which therefore need to be supplied through flexible cables.

    Regulation number(s)

    • 717.1

  • Q8. Where automatic disconnection to Regulation 411.3.2.1 cannot be achieved in the prescribed time and supplementary bonding is be provided in accordance with Regulation 415.2, where should the supplementary bonding be located?

    At the location of the equipment which cannot be disconnected in the prescribed time. Consideration must be given to disconnection required for reasons other than electric shock, for example, overcurrent protection.

    Regulation number(s)

    • 411.3.2.6
    • 415.2

  • Q9. Where automatic disconnection to Regulation 411.3.2.1 cannot be achieved in the prescribed time and supplementary bonding in accordance with Regulation 415.2 cannot be provided because there are no simultaneously accessible exposed-conductive-parts and extraneous-conductive-parts, (including flooring) is shock compliance achieved?

    Yes.

  • Q10. Does a single 4 mm2 protective conductor in a multicore or flexible cable that does not incorporate additional protection against mechanical damage comply with indent (ii) of Regulation 543.7.1.3 with regard to protection against mechanical damage?

    No. The above cable does not meet indent (ii). To comply with indent (iii), duplicate protective conductors would be required. Alternatively, the solutions offered by indent (iv) or (v) could be adopted.

    Regulation number(s)

    • 543.7.1.3

  • Q11. When the designer of an electrical installation does not intend the steel wire armour of a cable, or a metallic cable management system such as conduit or trunking, to be used as a circuit protective conductor, and a separate protective conductor is employed, does the designer:

    a) need to verify that in the event of a fault, line to armour or line to cable management system, the associated disconnection time is met?

    b) need to verify the suitability of the cross-sectional area of the armour or cable management system for the earth fault current?

    a) Yes, except where the cable management system is not an exposed-conductive-part. (The steel wire armour of a cable is considered to be an exposed-conductive-part.)

    b) No. There is no requirement to calculate or select the cross-sectional area of an exposed-conductive-part unless it intended to be used as a circuit protective conductor.

    Regulation number(s)

    • 411.3.2.1
    • 543.1.1

  • Q12. A circuit is comprised of different cable types and/or conductor sizes due, for example to take allow for volt drop or connection methods. Should the distribution board schedule and schedule of test results record all the types and sizes of cable used in a circuit?

    The information should be recorded somewhere in the installation details, but not necessarily in the distribution board schedule and schedule of test results.

    Regulation number(s)

    • 514.9.1(i)

  • Q13. Does a single 4 mm2 internal core, used as a protective conductor in a steel wired armoured (SWA) multicore cable, comply with indent (ii) of Regulation 543.7.1.3 with regard to protection against mechanical damage?

    Yes. The armour provides suitable protection against mechanical damage.

    Regulation number(s)

    • 543.7.1.3 (ii)

  • Q14. An installation uses Automatic Disconnection of Supply (ADS) as a protective measure against electric shock. One or more items of double insulated equipment are installed, such as luminaires. On the schedule of inspections, should the “double insulation” box for both basic and fault protection as a method of protection against electric shock be ticked?

    No. That item in the Schedule of Inspections is intended for use when that protective measure is used as the sole protective measure, that is, where a whole installation or circuit is intended to consist entirely of equipment with double insulation. In such a case, the installation or circuit would be required to be under effective supervision in normal use.

    Regulation number(s)

    • 412.1.3
    • Appendix 6

  • Q15. An installation uses Automatic Disconnection of Supply (ADS) as a protective measure against electric shock. One or more items of separated extra-low voltage (SELV) equipment are installed. On the schedule of inspections, should the “SELV” box for both basic and fault protection as a method of protection against electric shock be ticked?

    No. That part of the Schedule of Inspections is intended for use when a part of an installation relies specifically on that method of protection.

    Regulation number(s)

    • Appendix 6

  • Q16. An installation uses Automatic Disconnection of Supply (ADS) as a protective measure against electric shock. An electric shaver is supplied using electrical separation through a shaver supply unit. On the schedule of inspections, should the “electrical separation” box for fault protection as a method of protection against electric shock be ticked?

    No. That part of the Schedule of Inspections is intended for use when a part of an installation relies specifically on that method of protection.

    Regulation number(s)

    • Appendix 6

  • Q17. In a mobile or transportable unit, what are the conductive parts that need to be bonded to meet Regulation 717.411.3.1.2?

    Primarily the chassis. Any conductive parts connected electrically to the chassis would be effectively bonded. Any conductive parts not connected electrically to the chassis would be isolated, and would therefore not need to be bonded for reasons of safety.

    Regulation number(s)

    • Part 717
    • 717.411.3.1.2

  • Q18. A new mobile or transportable unit has been supplied as new with a “dead test only” Electrical Installation Certificate stating that a competent person must ensure that the unit is connected to a suitable and reliable supply. Is this compliant or must live tests also be completed by the unit manufacturer?

    In principle, dead testing by the manufacturer prior to despatch is sufficient, followed by live testing by installer will satisfy the inspection and testing requirements of BS 7671.

  • Q19. In a factory, plastic trunking containing socket-outlets is attached to metal tables used to assemble products. Is there a requirement to main bond, supplementary bond or earth these tables?

    No. If the tables are not liable to introduce a potential, generally Earth potential, they will not require main bonding.

    A dry assembly area would not be considered to be a location of increased shock risk, so there is no requirement for supplementary bonding.

    The tables are not items of electrical equipment, so there is no requirement for them to be earthed.

    Regulation number(s)

    • 411.3.1.2
    • 415.2 Note 4
    • 411.3.1.1

  • Q20: Is it permissible to use equipment (such as circuit-breakers, RCDs, main switches etc) made by one manufacturer in a consumer unit or distribution board made by another manufacturer?

    Usually not. Manufacturers’ instructions for consumer units and distribution boards generally advise against this for technical reasons (such as potential overheating). Equipment from different manufacturers should not be mixed unless documentation is obtained from the consumer unit or distribution board manufacturer which confirms that the specific mixed arrangement is suitable for use in an assembly conforming to BS EN 60439-3.  Further guidance can be found at www.beama.org.uk

    Regulation number(s)

    • 510.3
    • 511.1
    • 512.1.5