17th Edition Wiring Regulations Amendment 3

The BS 7671 : 2008 17th Edition IET Wiring Regulations Amendment 3 :2015, Regulation 421.1.201 prescribe that within Domestic (household) premises, consumer units and associated switchgear assemblies (enclosures), are manufactured from non combustible material or enclosed in a non combustible cabinet/enclosure and comply with product standard BS EN 61439-3.

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The purpose of the new regulations is to reduce the risk and limit the spread of fire from consumer units due to faulty components or poorly installed components.

The new range of BG ‘all metal’ consumer units and enclosures meet this requirement.

Domestic (household) premises include houses, bungalows, flats, apartments, student lets, sheltered accommodation, static homes, home offices, and attached garages etc. Other types of property that are classed as commercial, and you may wish to consider using all metal consumer units for are :- Nursing Homes, guest Houses, bed and breakfast houses and hostels, etc.

BG ‘all metal’ consumer units, consist of a metal base, cover and visor and are manufactured from steel – a non-combustible material.

Regulation 421.1.201 requires all designs for new installations from July 1st 2015 to be to the new standard, between July 1st and end of December 2105 installation of ‘all metal’ consumer units is optional unless designed after July 1st, from Jan 1st 2016 ‘all metal’ consumer units must be installed in domestic premises unless designed before July 1st 2015, in which case choice of metal or plastic is optional.

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Requirements for Additional Protection (30mA RCD)

The 17th Edition Wiring Regulations also has the requirement for additional protection from 30mA RCDs, summarised below.

  1. All Socket outlets should be protected
  2. Socket outlets (section 411.3.3)
    • All sockets up to 20A
    • All mobile equipment up to 32A, used outdoors
    • Exceptions are socket outlets under supervision of someone skilled/instructing, and labelled socket, e.g. ‘Freezer’
  3. Cables buried in Walls (section 522.6.200)
    • All cables concealed in a wall/partition less than 50mm depth, and without earthed mechanical protection, e.g. earth metal conduit
  4. Location containing a bath or a shower (section 701.411.3.3)
    • All circuits serving or passing through a room with a fixed bath or shower
  5. Circuit Separation (section 314.1)
    • Regulation 314.1, Installation shall be divided into circuits as necessary, to avoid danger and prevents unwanted tripping
    • Regulation 314.2, Separate circuits that need to be separately controlled so that so that these circuits are not affected by the failure of other circuits
  6. Safety Circuits
    • Safety circuits such as smoke alarms should be on independent circuits

17th Edition BG Consumer Unit Options

Possible consumer unit options to support 17th 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

Technical Information


New all metal consumer units comply with 17th Edition Wiring Regulations BS 7671 Amendment 3'

Product Standard
Consumer Unit BS EN 61439-3
Main Switch EN/IEC 60947-3
MCB EN/IEC 60898
RCBO EN/IEC 61009-1
Product Standard
RCD EN/IEC 61008
Enclosure EN/IEC 60439
Contactor EN/IEC 60947, 61095
RCBO EN/IEC 61558-1


Devices - Pole pitch 18mm

Consumer Unit Metal(A)
8 modules 244mm
12 modules 316mm
16 modules 388mm
19 modules 442mm
22 modules 496mm


Device Capacity mm2 Max Torque Nm
Switch 35 2.5
MCB 16(32-50A 25mm2) 2
RCD 35 2.5(80A 3.5Nm)
RCBO 16(32-40A 25mm2) 2

*Note 8 & 12 module ‘Tall’ variant, height is 261mm

Cut Outs and Knockouts

Range Top & Bottom Face Sides Base
Metal 8 Module 6 x ø20mm, 1 x ø32mm 1 x ø32mm 1 x ø50 x 100mm
Metal 12 Module 8 x ø20mm, 1 x ø32mm 1 x ø32mm 1 x ø50 x 100mm
Metal 16 Module 9 x ø20mm, 2 x ø32mm 1 x ø32mm 2 x ø50mm, 1 x ø50 x 100mm
Metal 19 Module 11 x ø20mm, 2 x ø32mm 1 x ø32mm 2 x ø50mm, 1 x ø50 x 100mm
Metal 22 Module 13 x ø20mm, 2 x ø32mm 1 x ø32mm 3 x ø50 x 100mm
Insulated 8 Module 4 off - 40, 25 x 16mm 40, 25 x 16mm 3 off - 50, 30 x 40mm
Insulated 12 Module 6 off - 40, 25 x 16mm 40, 25 x 16mm 4 off - 50, 30 x 50mm
Insulated 12 Module Tall 6 off - 40, 25 x 16mm 40, 25 x 16mm, 1 x Ø25 or Ø20mm 4 off - 50, 30 x 50mm
Insulated 16 Module 8 off - 40, 25 x 16mm 40, 25 x 16mm 2 off 50,30 x 50, 4 off 50,30 x 40mm
Insulated 19 Module 9 off - 40, 25 x 16mm 40, 25 x 16mm 6 off - 50, 30 x 50mm
Insulated 22 Module 10 off - 40, 25 x 16mm 40, 25 x 16mm 2 off 50,30 x 50, 6 off 50,30 x 40mm

• Positive contact status indication on Switch, MCB, RCD & RCBO provided by green indicator to show contacts are open

Consumer Unit

  • Max current rating 100A
  • Operating Voltage 230V
  • Short circuit withstand 16kA rms
  • Metal CU base manufactured from
  • 1.2mm steel


  • IP65
  • 5 Module
  • Dims- W-176mm, H- 241mm, D- 100mm
  • Knockouts- Dia ø20mm can be drilled to 32mm, sides - 2 off, top and bottom - 3 off, base - 1 off

Bell Transformer

  • Output voltage 4, 6, 8, 12, 16, 24V
  • Rated output 8VA
  • Consumption 1, 15W


  • Type AC
  • Tripping Time : 1 x In≤100mS, 5 x In≤40mS


  • Type AC
  • Poles: 1 (1P + N)


  • Breaking Capacity 6000A
  • Type B operating 3-5 x In
  • Type C operating 5-10 x In


  • Poles: 2 (1 +N)
  • NO (Normally Open)

Metal Consumer Units

Consumer units for use in domestic household premises

  • Modern stylish design with a profile that matches Nexus wiring accessories
  • Flexibility for maximum circuit combinations, and easy upgrades
  • Fast and simple installation
  • Taller 8 & 12 module consumer unit, with extra space for RCBO’s
  • Consumer unit and devices tested to all relevant standards
  • 10 Year Guarantee
Find out more about Metal Consumer Units
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