For 18th Edition Wiring Regulations

Requirements for Additional Protection (30mA RCD)

The 18th Edition Wiring Regulations also has the requirement for additional protection from 30mA RCDs, summarised below.

    Requirements for Additional Protection (30mA RCD)

  1. 421 Protection against fire caused by electrical equipment 421.1.201
    • Within domestic (household) premises, consumer units and similar switchgear assemblies shall comply with BSEN 61439-3 and shall

    • Have their enclosure manufactured from non-combustible material, or
    • Be enclosed in a cabinet or enclosure constructed of non-combustible material complying with Regulation 132.12
    • NOTE: Ferrous metal, e.g. Steel, is deemed to be an example of a non-combustible material

  2. 411 Protective Measure: Automatic disconnection of supply(section 411.3.3)
    • Additional requirements for socket-outlets and for the supply of mobile equipment for use outdoors.In AC systems, additional protection by means of an RCD with a rated residual operating current not exceeding 30mA shall be provided for

    • Socket-outlets with a rated current not exceeding 32A, and
    • Mobile equipment with a rated current not exceeding 32A for use outdoors
    • An exception to (i) is permitted where, other than for an installation in a dwelling, a documented risk assessment determines that RCD protection is not necessary
    • The requirements of Regulation 411.3.3 do not apply to FELV systems according to Regulation 411.7 or reduced low voltage systems according to Regulation 411.8
    • NOTE 1: See also Regulation 314.1(iv) and 531.3.2 concerning the avoidance of unwanted tripping

      NOTE 2: See Appendix 2, item 11 in respect of risk assessment

      NOTE 3: A lighting distribution unit complying with BS5733, luminaire track system, installation coupler, LSC or DCL is not regarded as a socket-outlet for the purposes of this regulation

  3. 522.6 Impact (section 522.6.201)
    • A cable installed under a floor or above a ceiling shall be run in such a position that it is not liable to be damaged by contact with the floor or ceiling or their fixings
    • A cable passing through a joist within a floor or ceiling construction or through a ceiling support (e.g. under floorboards), shall:
    • Be installed at least 50mm measured vertically from the top, bottom as appropriate, of the joist or batten, or
    • Comply with Regulation 522.6. All circuits serving or passing through a room with a fixed bath or shower
  4. Location containing a bath or a shower (section 701.411.3.3)
    • Additional protection by the use of one or more RCDs having the characteristics specifie in Regulation 415.1.1 shall be provided for low voltage circuits
    • Serving the location
    • Passing through zones 1 and/or 2 not serving the location
    • NOTE: see also Regulations 314.1(iv) and 531.3.2 concerning the avoidance of unwanted tripping

  5. Division of installation (section 314.1)
    • Avoid danger and minimize inconvenience in the event of a fault
    • Facilitate safe inspection, testing and maintenance (see also chapter46 and section 537)
    • Take account of hazards that may arise from the failure of a single circuit such as a lighting circuit
    • Reduce the possibility of unwanted tripping of RCDs due to excessive protective conductor (PE) currents not due to a fault
    • Mitigate the effects of electromagnetic disturbances (see also chapter44)
    • Prevent the indirect energizing of a circuit intended to be isolated
  6. Safety Services 560.7.1
    • Except where the recommendations of other safety standards apply, circuits of safety services shall be independent of other circuits

18th Edition BG Consumer Unit Options

Possible consumer unit options to support 18th Edition Wiring Regulations compliance:

Note: The following diagrams use a 12 module consumer unit to demonstrate the available options.

Main Switch

  • Main switch plus the use of RCBOs for every circuit

Split Load

  • Some circuits using MCBs protected by an RCD
  • Other independent circuits using RCBOs
  • Can be created using standard mains switch consumer unit, additional RCD and cable kit CUA5

Dual RCD

  • Some circuits using MCBs protected by an RCD1
  • Some circuits using MCBs protected by an RCD2

High Integrity Dual RCD

  • Some circuits using MCBs protected by an RCD1
  • Some circuits using MCBs protected by an RCD2
  • Other independent circuits using RCBOs
  • Standard Dual RCD consumer unit offers option of High Integrity Dual RCD as standard
  • Note: High Integrity Triple RCD is achieved using only the 22 module Consumer Unit

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