Hager Consumer Units – Features

1. Best in class cabling space top side and back;
2. Rear cutouts optimised for size and position;
3. Top wall removes for easy cable access and reseals to IP4X using two foam strips provided;
4. Quick fit meter tail kit accessory;
5. Quick fit meter tail kit accessory;
6. Integrated spirit level;
7. Top wall removes for easy cable access and reseals to IP4X using two foam strips provided;
8. Terminal bars are top mounted for easy cable dressing, fully rated to 100A;
9. Snap-able busbar;
10. Full metal DIN rail allowing ease of configuration and fitting of control devices;
11. Optional key lock;
12. Door available in both transparent and plain variants opening downwards for easy access.

Benefits of the consumer units from Hager

The Consumer Unit from Hager has been designed to fit into today’s home environment. Whether used to house electrical distribution or smart control devices, the unit’s colour and form have been designed to complement and integrate.

With preconfigured and configurable variants available, choice comes as standard. A full metal DIN rail allows devices to be fixed securely and a snap-able busbar allows contractors to choose the configuration. MCBs feature a new DIN clip allowing devices to be removed without the need to remove the busbar from other devices.

The Consumer Unit range from Hager – it really was inspired by you.

• Easy and fast unit to fit;
• Best cable space – largest amount & in all the right places;
• Easy to remove cable entries safely;
• IP4X seal to top surface;
• Optimised positions for cable entries & terminations;
• Fewer tools required to fit;
• Integrated spirit level allows for simple levelling;
• Easy unit to cable.

The Installation of the Consumer Units(Hager Guide)

1. Preparation of unit for fixing
   Remove cover. Select the cutouts required to bring the cables into the unit.
2. Remove cable entry cutout
   Remove the required cutouts if bringing cables through the bottom of the consumer unit.
3. Bring cables in on surface
   If cables are being brought in on the surface, the top wall can be removed to aid cable entry and can be sealed to IP4X rating using the sealing strips provided.
4. Fix unit to wall
   The units have a large range of fixing points allowing avoidance of obstructions in the wall.
5. Integrated level
   The unit has a built in spirit level which helps with fitting the unit neatly.
6. Snapable busbar
   The units can be wired to the configuration of your choice thanks to the snap-able busbar.
7. Wire the unit
   The unit is easy to wire thanks to the increased space between the devices and terminal bars.
8. Fix front cover
   The unit’s curved design fits in well with the home environment and the cover is secured by quarter turn fixings. The units allow for compliance with Part M of the latest building regulations.

The Consumer Units from Hager – Flush fit

The Hager range of flush fit consumer units are up to 25 percent faster to fit in both solid and partition walls.

• For partition walls, a flange and frame clamps the unit to the wall. There is no need for separate fixings, the unit simply slots into the prepared hole and the integral fixing screws are tightened.
• With solid brick walls, the installer refits the flange to the sides of the back box and uses it as a fixing bracket to secure the base unit to the wall. This allows the base unit to be held well away from the edge of the blocks or bricks and the plastering can be levelled to the edge of the base. The front cover can then be fixed from the front.
• There is a choice of 32mm or 25mm knockouts for the incoming cable. You can also fit the back box either way up, so the incomer cable can enter from the top or bottom from either the left or the right. Similarly for the outgoing cables, two removable plates at the top and bottom of the box allow the choice of slotted, overlap or 20mm knockouts from either the top or the bottom.
• When it comes to cabling, there is plenty of space between the devices and the terminal bars. The neutral and earth bars are aligned with the devices at the top of the board for easy access and there are no restrictions under the DIN rail to obstruct cable runs.
• A full metal DIN rail minimizes distortion and ensures that devices fit square in the unit and are not dislodged. A clip on the device makes them easy to remove and replace, without releasing others from the busbar.
• Finally you can mount a label on either the cover of the unit or on the devices. There is a recessed section on the board for an RCD label to meet wiring regulations.

To purchase Hager consumer units(including 17th Edition Consumer units), please visit the Consumer Units, Domestic Consumer Units, Hager Consumer Units or Industrial and Commercial Consumer Units – Hager. This guide is part of the official guide by Hager: CU Inside Out. Watch the Consumer Unit 17th Edition regulations movie from Hager for more details about the 17th edition consumer units.

RCD – Residual Current Device - is a generic term for all types of residual current operated device which by definition is: A mechanical switching device or association of devices intended to cause the opening of the contacts when the residual current attains a given value under specified conditions. The more common types are:

• Residual Current Operated Circuit Breaker (RCCB)
  A mechanical switching device designed to make, carry and break currents under normal service conditions and to cause the opening of the contacts when the residual current attains a given value under specified conditions. Depending on the age of these devices they will comply with either BS EN 61008 or BS 4293.
  The British Standard BS 4293 was withdrawn on 1st July 2000 and its moratorium period ended in July 2005, which means manufacturers continued to produce residual current devices complying with BS 4293 up to 2005 providing the devices are in production before July 2000. In line with the Company’s forward thinking and innovative approach to product development, Hager has already introduced residual current devices complying with the Harmonised Standards.
• Residual Current Operated Circuit Breaker With Integral Overcurrent Protection (RCBO)
  A residual current operated circuit breaker designed to perform the functions of protection against earth fault currents, overloads and short-circuits. These devices comply with BS EN 61009. ‘Appendix G’ of this Standard also covers RCD add-on blocks for BS EN 60898 circuit breakers.
• Circuit Breaker Incorporating Residual Current Protection (CBR)
  A circuit breaker providing overcurrent protection and incorporating residual current protection either integrally or in combination with a residual current unit, which may be factory fitted or fitted in the field. These devices comply with BS EN 60947-2: Circuit Breakers – Annex B.
• Socket Outlet Incorporating A Residual Current Device (SRCD)
  A socket outlet for fixed installations, which incorporates an integral sensing circuit that will cause the switching contacts in the circuit to open automatically at a predetermined value of residual current. These will comply with BS 7288: 1990.
• Earth Fault Relay
  A device incorporating the means of detection of an earth fault current, comparing its value to the earth fault current operating value and giving a signal to an associated switching device to open the protected circuit when the earth fault current exceeds this value. Relays can be directly connected or fed from a separate torroid. There is currently no specific standard for this type of device. It should therefore comply with IEC 755 general requirements for residual current operated protective devices.

The residual current device – principle of operation

The residual current devices monitor the current flowing in a circuit by means of a torroid, which is a small current transformer specially designed to detect earth fault currents. All live conductors will pass through this coil, the currents flowing in the live conductors of a healthy circuit will balance and therefore no current will be induced in the torroid. Live conductors of a circuit include all phase and neutral conductors. When an earth fault is present on a circuit, current will be flowing to earth through an abnormal or unintended path. This earth fault path could be through a person in contact with live parts as shown in Figure 20 as Ic or where insulation has failed through an exposed conductive part shown as Id.

The Technology behind the RCD’s

There are two types of technology available in residual current devices, electromagnetic & electronic and both offer very reliable performance. Electromagnetic devices use a very sensitive torroid, which operates the trip relay when it detects very small residual currents. These devices generally require no reference earth lead and are unaffected by temporary loss of supply, as the power to trip the device is derived directly from the fault current. Electronic devices do not need such a sensitive torroid as electronic circuits within the device amplify the signal to operate the trip relay. However, these devices often require a safety earth reference lead to ensure that the device will continue to operate in the event of the supply neutral being lost. The power to trip the device is taken from both the fault current and the mains supply, enabling the overall size of the devices to be reduced.
These devices should be disconnected while carrying out insulation resistance tests to prevent damage to the device and to avoid incorrect test results. Hager manufacture a range of devices using both technologies. The RCCB range, CBR CB add-on blocks and two module RCBO range are electromagnetic devices, while the single module RCBO range and Earth Fault Relays use electronic technology. The CBR MCCB add-ons are available in both technologies.

• Current flowing through torroid in healthy circuit: Ires = I1-I2 = 0
• Current flowing through torroid in circuit with earth fault: Ires = I1-I2=Ic + Id

This earth fault current, known as ‘Residual Current’ (Ires), is seen by the torroid as an imbalance. When the magnitude of this residual current reaches the sensitivity setting IΔn of the device, it will operate to open the contacts.

The RCD’s are used in many practical applications, like: the consumer units(Hager Consumer Units, the 17th edition consumer units, MK Metal Clads, etc), RCD sockets, RCD modules, MCB’s and RCCB’s, etc.

18W configurable consumer unit – options

• 18W consumer unit with Plain door – VC818CU;
• 18W flexible consumer unit with Glazed door – VC818CUG;
• Description – 18W Split Load Configurable 100A SW 2x 80A RCCBs;
• Buy online 18 way configurable consumer unit and read the technical specs(pdf file).

18 Way flexible consumer unit – Configuration examples

Purchase online 17th edition compliant consumer units from Hager, for domestic use, by visiting the Hager Consumer Units section on our website and choosing among the following consumer units available:

• 17th Edition Consumer Unit, Hager 14 Way Split Load Configurable 100A SW 2 x 63A RCCB Insulated Enclosure (VC714C1);
• 17th Edition Consumer Unit, Hager 14 Way Split Load Configurable 100A SW 2 x 63A RCCB Metal Enclosure (VH714C1);
• 17th Edition Consumer Unit, 14W (5+6+3) 100A MS 2X63A RCCB 3XMCB WAY (VC7563U);
• 17th Edition Consumer Unit 10W (3+4+3) 100A MS 2X63A RCCB 3XMCB WAY (VC7343U);
• 17th Edition Consumer Unit 12 way configurable 100A MS 2 X RCCB (VC712C1);
• 17th Edition Consumer Unit Hager 12 Ways 1 Switch 2 X 63A RCD 30mA Split Load Insulated Enclosure (VC766H1);
• 17th Edition Consumer Unit, Hager 10 Ways 1 Switch 2 X 63A RCD Split Load Insulated Enclosure (VC755H1);
• 17th Edition Consumer Unit, 16 ways configurable Twin RCCB (VC816C1).

BS 7671:2008 includes changes necessary to maintain technical alignment with CENELEC harmonization documents. A summary of the main changes is given below.

NOTE 1: This is not an exhaustive list.
NOTE 2: Particular attention is drawn to Section 701. This section now allows socket-outlets (other than SELV and shaver supply units to BS EN 61558-2-5) to be installed in locations containing a bath or shower 3m horizontally beyond the boundary of zone 1.

• Regulation 131.6 – adds requirements to protect against voltage disturbances and implement measures against electromagnetic influences. In doing so, the design shall take into consideration the anticipated electromagnetic emissions, generated by the installation or the installed equipment, which shall be suitable for the current-using equipment used with, or connected to, the installation.
• Regulation 132.13 – requires that documentation for the electrical installation, including that required by Chapter 51, Part 6 and Part 7, is provided for every electrical installation.
• Chapter 35 – Safety services, recognizes the need for safety services as they are frequently regulated by statutory authorities whose requirements have to be observed, e.g. emergency escape lighting, fire alarm systems, installations for fire pumps, fire rescue service lifts, smoke and heat extraction equipment.
• Chapter 36 – Continuity of service, requires that an assessment be made for each circuit of any need for continuity of service considered necessary during the intended life of the installation.
• Chapter 41 – Protection against electric shock, now refers to basic protection, which is protection under normal conditions (previously referred to as protection against direct contact), and fault protection, which is protection under fault conditions (previously referred to as protection against indirect contact).
  - Chapter 41 now includes those requirements previously given in Section 471 of BS 7671:2001.
  - Chapter 41 now requires that for the protective measure of automatic disconnection of supply for an a.c. system, additional protection by means of an RCD with a rated residual operating current (IΔn) not exceeding 30 mA and an operating time not exceeding 40 ms at a residual current of 5 IΔn be provided for socket-outlets with a rated current not exceeding 20 A that are for use by ordinary persons and are intended for general use, and for mobile equipment with a current rating not exceeding 32 A for use outdoors. This additional protection is now to be provided in the event of failure of the provision for basic protection and/or the provision for fault protection or carelessness by users of the installation.
  - Note that certain exceptions are permitted – refer to Regulation 411.3.3.
  - Chapter 41 includes Tables: Table 41.2, Table 41.3 and Table 41.4 for earth fault loop impedances (replacing Tables Table 41B1, Table 41B2 and Table 41D). These new tables are based on a nominal voltage of 230 V (not 240 V), hence the values are slightly reduced. It has been clarified that where an RCBO is referred to in these Tables, the overcurrent characteristic of the device is being considered.
  - Chapter 41 includes a new Table 41.5 giving maximum values of earth fault loop impedance for RCDs to BS EN 61008-1 and BS EN 61009-1.
  - FELV is recognised as a protective measure and the new requirements are detailed in Regulation 411.7.
  - Chapter 41 includes the UK reduced low voltage system. Requirements are given in Regulation 411.8.
• Chapter 42 - Protection against thermal effects, includes requirements in Section 422 Precautions where particular risks of fire exist (These requirements were previously stated in Section 482 of BS 7671:2001).
• Chapter 43 - Protection against overcurrent, includes those requirements previously given in Section 473 of BS 7671:2001. Information on the overcurrent protection of conductors in parallel is given in Appendix 10.
• Chapter 44 - Protection against voltage disturbances, includes a new Section 442, Protection of low voltage installations against temporary overvoltages due to earth faults in the high voltage system and due to faults in the low voltage system. This new section provides for the safety of the low voltage system under fault conditions including faults in the high voltage system, loss of the supply neutral in the low voltage system and short-circuit between a line conductor and neutral in the low voltage installation.
• Section 443 - Protection against overvoltages of atmospheric origin or due to switching, retains the existing text from BS 7671 and adds regulations enabling designers to use a risk assessment approach when designing installations which may be susceptible to overvoltages of atmospheric origin.
• Chapter 52 - Selection and erection of wiring systems, now includes busbar trunking systems and powertrack systems.
  - It is now required to protect cables concealed in a wall or partition (at a depth of less than 50 mm) by a 30 mA RCD where the installation is not intended to be under the supervision of a skilled or instructed person, if the normal methods of protection including use of cables with an earthed metallic covering, mechanical protection (including use of cables with an earthed metallic covering, or mechanical protection) cannot be employed. This applies to a cable in a partition where the construction includes metallic parts other than fixings irrespective of the depth of the cable.
  - Table 52.2 Cable surrounded by thermal insulation, gives slightly reduced derating factors, to take account of the availability of material with improved thermal insulation.
• Chapter 53 – Protection, isolation, switching, control and monitoring. Simplification means that requirements previously in Chapter 46, Sections 476 and 537 of BS 7671:2001 are now in this single chapter. Chapter 53 also includes a new Section 532 Devices for protection against the risk of fire, and a new Section 538 Monitoring devices.
• Chapter 54 - Earthing arrangements and protective conductors. The requirement that a metallic pipe of a water utility supply shall not be used as an earth electrode is retained in Regulation 542.2.4 which also states that other metallic water supply pipework shall not be used as an earth electrode unless precautions are taken against its removal and it has been considered for such a use. An example of other metallic water supply pipework could be a privately owned water supply network.
  - A note to Regulation 543.4.1 states that in Great Britain, regulation 8(4) of the Electricity Safety, Quality and Continuity Regulations 2002 prohibits the use of PEN conductors in consumers’ installations. Regulation 543.7 has earthing requirements for the installation of equipment having high protective conductor currents, previously in Section 607 of BS 7671:2001.
• Chapter 55 - Other equipment, includes new additional requirements in Regulation 551.7 to ensure the safe connection of low voltage generating sets including small-scale embedded generators (SSEGs).
• Section 559 - Luminaires and lighting installations, is a new series of Regulations giving requirements for fixed lighting installations, outdoor lighting installations, extra-low voltage lighting installations, lighting for display stands and highway power supplies and street furniture (previously in Section 611 of BS 7671:2001).
• Chapter 56 - Safety services, has been expanded in line with IEC standardization.
• Part 6 - Inspection and testing, was Part 7 of BS 7671:2001. Changes have been made to the requirements for insulation resistance; when testing SELV and PELV circuits at 250 V, the minimum insulation resistance is raised to 0.5 MΩ; for systems up to and including 500 V, including FELV, the minimum insulation resistance is raised to 1.0 MΩ.
• Part 7 - Special installations or locations, was Part 6 of BS 7671:2001. The structure of Part 7 includes the following changes.
  - Section 607 in BS 7671:2001 relating to high protective conductor currents has been incorporated into Chapter 54.
  - Section 608 in BS 7671:2001 relating to caravans, motor caravans and caravan parks has been incorporated into
  - Section 708: Electrical installations in caravan/camping parks and similar locations and Section 721: Electrical installations in caravans and motor caravans.
  - Section 611 in BS 7671:2001 relating to highway power supplies is now incorporated into Section 559.
  - The following major changes are incorporated in Part 7:
  ~~ Section 701 Locations containing a bath tub or shower basin.
  ~~ Zone 3 is no longer defined.
  ~~ Each circuit in the special location must have 30 mA RCD protection.
  ~~ Supplementary bonding is no longer required providing the installation has main bonding in accordance with Chapter 41.
  ~~ This section now allows socket-outlets (other than SELV and shaver supply units to BS EN 61558-2-5) to be installed in locations containing a bath or shower 3m horizontally beyond the boundary of zone 1.
• Section 702 - Swimming pools and other basins. This special location now includes basins of fountains. Zones A, B and C in BS 7671:2001 are replaced by zones 0, 1 and 2.
• Section 703 - Rooms and cabins containing sauna heaters. Zones A, B, C and D in BS 7671:2001 are replaced by zones 1, 2 and 3 (with changed dimensions).
• Section 704 - Construction and demolition site installations. The reduced disconnection times (0.2 s) and the 25 V equation no longer appear.
• Section 705 - Agricultural and horticultural premises. The reduced disconnection times (0.2 s) and the 25 V equation no longer appear. Additional requirements applicable to life support systems are included.
• Section 706 - Conducting locations with restricted movement, was Section 606 in BS 7671:2001.
• Section 708 - Electrical installations in caravan/camping parks and similar locations, now includes the requirement that each socket-outlet must be provided individually with overcurrent and RCD protection.
  The following new sections are now included in Part 7:
• Section 709 - Marinas and similar locations
• Section 711 - Exhibitions, shows and stands
• Section 712 - Solar photovoltaic (pv) power supply systems
• Section 717 - Mobile or transportable units
• Section 721 - Electrical installations in caravans and motor caravans – previously in Section 608 of BS 7671:2001
• Section 740 - Temporary electrical installations for structures, amusement devices and booths at fairgrounds, amusement parks and circuses
• Section 753 - Floor and ceiling heating systems.
  Appropriate changes have been made to Appendices 1 to 7, in particular the methods and tables used in Appendix 4. The following new appendices are now included:
• Appendix 8 – Current-carrying capacity and voltage drop for busbar trunking and powertrack systems
• Appendix 9 - Definitions – multiple source, d.c. and other systems
• Appendix 10 - Protection of conductors in parallel against overcurrent
• Appendix 11 - Effect of harmonic currents on balanced three-phase systems
• Appendix 12 - Voltage drop in consumers’ installations
• Appendix 13 - Methods for measuring the insulation resistance/impedance of floors and walls to Earth or to the protective conductor system
• Appendix 14 - Measurement of earth fault loop impedance: consideration of the increase of the resistance of conductors with increase of temperature
• Appendix 15 - Ring and radial final circuit arrangements, Regulation 433.1

You can download this guide as a PDF from the IET website. Read the 2 parts of the introduction to the 17th Edition of Wiring regulations – part 1 and part 2 (and more here). On our website, you can purchase 17th edition consumer units, 17th edition Multi-tester, and 17th edition junction boxes(17th edition compliant consumer units and junction boxes). Watch the Consumer Unit 17th Edition regulations movie from Hager for more details about the 17th edition consumer units.

The IET (The Institution of Engineering and Technology)

The IEE Wiring Regulations are of interest to all those concerned with the design, installation and maintenance of electric wiring in buildings. The market includes electricians, electrical contractors, consultants, Local Authorities, surveyors and architects. This book will also be of interest to professional engineers, as well as students at university and Further Education colleges.

The 17th Edition brings in significant changes to both the technical content and the structure of the book. Some of the key changes are:

• A change allowing a socket outlet in bathrooms (if 3m from the edge of a bath or shower and rcd protected);
• Extension of the Regulations to cover new ‘special locations’: exhibition shows, photovoltaic (pv) power supply systems, floor and heating systems, marinas and fairgrounds and amusements parks;
• Re-numbering and re-structuring of chapters to align with international standards;
• The Regulations move from being the 16th to the 17th edition – a major shift in name and perception of its contents. The 16th edition has been in place since 1991.

The major sections and an introductory word/explanation for each of the chapters of the book can be downloaded as a pdf file from the website. We would like to place here below some of the contents of these regulations.

Table of contents:

• Introduction to BS 7671:2008
• Notes on the plan of the 17th edition
• Part 1 – Scope, object and fundamental principles
  - Chapter 11: Scope;
  - Chapter 12: Object and effects;
  - Chapter 13: Fundamental principles;
• Part 2 – Definitions
• Part 3 – Assessment of general characteristics
  - Chapter 31: Purpose, supplies and structure;
  - Chapter 32: Classification of external influences;
  - Chapter 33: Compatibility;
  - Chapter 34: Maintainability;
  - Chapter 35: Safety services;
  - Chapter 36: Continuity of service;
• Part 4 – Protection for safety
  - Chapter 41: Protection against electric shock;
  - Chapter 42: Protection against thermal effects;
  - Chapter 43: Protection against overcurrent;
  - Chapter 44: Protection against voltage disturbances and electromagnetic disturbances;
• Part 5 – Selection and erection of equipment
  - Chapter 51: Common rules;
  - Chapter 52: Selection and erection of wiring systems;
  - Chapter 53: Protection, isolation, switching, control and monitoring;
  - Chapter 54: Earthing arrangements and protective conductors;
  - Chapter 55: Other equipment;
  - Chapter 56: Safety services;
• Part 6 – Inspection and testing
  - Chapter 61: Initial verification;
  - Chapter 62: Periodic inspection and testing;
  - Chapter 63: Certification and reporting;
• Part 7 – Special installations or locations
  - Section 700: General;
  - Section 701: Locations containing a bath or shower;
  - Section 702: Swimming pools and other basins;
  - Section 703: Rooms and cabins containing sauna heaters;
  - Section 704: Construction and demolition site installations;
  - Section 705: Agricultural and horticultural premises;
  - Section 706: Conducting locations with restricted movement;
  - Section 708: Electrical installations in caravan / camping parks and similar locations;
  - Section 709: Marinas and similar locations;
  - Section 711: Exhibitions, shows and stands;
  - Section 712: Solar photovoltaic (PV) power supply systems;
  - Section 717: Mobile or transportable units;
  - Section 721: Electrical installations in caravans and motor caravans;
  - Section 740: Temporary electrical installations for structures, amusement devices and booths at fairgrounds, amusement parks and circuses;
  - Section 753: Floor and ceiling heating systems;
• Appendices
  #1. British Standards to which reference is made in the Regulations;
  #2. Statutory regulations and associated memoranda;
  #3. Time/current characteristics of overcurrent protective devices and rcds;
  #4. Current-carrying capacity and voltage drop for cables and flexible cords;
  #5. Classification of external influences;
  #6. Model forms for certification and reporting;
  #7. Harmonized cable core colours;
  #8. Current-carrying capacity and voltage drop for busbar trunking and powertrack systems;
  #9. Definitions – multiple source, d.c. and other systems;
  #10. Protection of conductors in parallel against overcurrent;
  #11. Effect of harmonic currents on balanced three-phase systems;
  #12. Voltage drop in consumers’ installations;
  #13. Methods for measuring the insulation resistance/impedance of floors and walls to Earth or to the protective conductor system;
  #14. Measurement of earth fault loop impedance: consideration of the increase of the resistance of conductors with increase of temperature;
  #15. Ring and radial final circuit arrangements, Regulation 433.1.

This British Standard(the 17th Edition of the Wiring Regulations) is published under the direction of the British Electrotechnical Committee (BEC) and The Institution of Engineering and Technology (IET). Following a full review, this Standard replaced the 16th Edition of the IEE Wiring Regulations BS 7671:2001 as amended. Copyright is held jointly by The IET and BSI. Technical authority for this Standard is vested in the Joint IET/BSI Technical Committee JPEL/64. This Joint Technical Committee, which is responsible for the work previously undertaken by the IEE Wiring Regulations Committee and the BSI Technical Committee PEL/64, meets the constitutional and operational requirements of both parent bodies. JPEL/64 has the responsibility for the content of this British Standard under the joint authority of the IET and the BSI Standards Board. All references in this text to the Wiring Regulations or the Regulation(s), where not otherwise specifically identified, shall be taken to refer to BS 7671:2008 Requirements for Electrical Installations.

Continue to read the second part of this short guide to the 17th edition of the Wiring regulations – main changes to the previous standards(read more here). On our website, you can purchase 17th edition consumer units, 17th edition Multi-tester, and 17th edition junction boxes(17th edition compliant consumer units and junction boxes). Watch the Consumer Unit 17th Edition regulations movie from Hager for more details about the 17th edition consumer units.

• Building Regulations;
• Requirements of the 17th Edition Wiring Regulations;
• Downlighter Junction Box;
• Maintenance Free Connections;
• Traditional Junction Boxes;
• Conclusions;
• Product Selection Guide;
• Selection Chart.

Maintenance Free Connections

Junction boxes are commonly used during alterations and additions to an installation. With certain exceptions regulation 526.3 requires that every connection shall be accessible for inspection, testing and maintenance. The Electrical Safety Council Technical Manual states that “a junction box with screw terminals is an example of where connections must be accessible”. The reason is to allow inspection of joints which could have relaxed or loosened over time, a recognized problem with screwed terminals.

Unless provision is made for access, where boarding, carpet or other similar covering is laid over a junction box with screw terminals, it may not be considered accessible and maintenance free terminals should be used. This is further reinforced in Appendix 15 of the Wiring Regulations which states “Junction boxes with screw terminals must be accessible for inspection, testing & maintenance or, alternatively, use maintenance-free terminals / connection (Regulation 526.3)”

Maintenance free terminals provide a solution where accessibility is an issue.

Tests, including long term vibration, shock test, long term connection test, pull out, voltage drop, temperature rise and exposure to corrosive atmospheres validate the suitability of these terminals.  Equally suitable are solutions such as a ‘joint made by a compression tool’.

Maintenance free terminals have the additional advantages of allowing the direct insertion of solid, stranded or flexible conductors, and allowing the connection of up to four conductors from 0.5mm2 to 4.0mm2(see Hager J501, Hager 803 and Hager J804).

Traditional Junction Boxes

As we have discussed, unless using a solution such as maintenance free terminals, the access to electrical connections should be adequate for their safe and proper inspection, testing and maintenance. In this respect, connections should be in a location where they can reasonably be reached and where there is adequate working space.

Where connections are made in roof spaces and inter-floor spaces the enclosures containing the connections should normally be fixed and provision must be made for their access.

Providing these two constraints are complied with, then the continued use of standard circular junction boxes remains acceptable.

Providing the enclosure is fixed and accessible traditional junction boxes are acceptable.

The requirement for accessibility applies equally to the situation where, because of damage to an existing cable, a repair is effected by the introduction of a joint. The joint must be accessible, alternatively the joint may be made by an appropriate method, a maintenance free terminal for example(see Hager J501, Hager 803 and Hager J804).

Some conclusions regarding the 17th edition compliant Junction Boxes

• Junction boxes are an integral part of virtually every electrical installation. Unfortunately these connections often do not comply with the Wiring Regulations due to incorrect product selection.
• It is clear that careful consideration from designers and installers will be required to meet the requirements of the 17th Edition of the Wiring Regulations.

Product Selection Guide

17th Edition Junction Boxes Selection chart

Download this 17th Edition Junction Boxes guide by Hager online here, or read part 1 and part 2 on our website. To purchase online 17th edition junction boxes, visit the Electrical Items section, Accessories, Junction Boxes. Some of the Hager 17th Edition compliant junction boxes are:  Hager J501, Hager 803 and Hager J804.

• Building Regulations;
• Requirements of the 17th Edition Wiring Regulations;
• Downlighter Junction Box;
• Maintenance Free Connections;
• Traditional Junction Boxes;
• Conclusions;
• Product Selection Guide;
• Selection Chart.

The Building Regulations & the Electrical Equipment

Since 2005 the Building Regulations for England and Wales have made direct reference to Electrical Installations, increasing the influence on how Electrical Equipment is installed in buildings. The part P of the Building Regulations 2000 came into effect on 1st January 2005 and was further amended on 6th April 2006. This document states that the requirements will be met by adherence to the ‘Fundamental Principles’ for achieving safety given in the Wiring Regulations BS 7671 Chapter 13.

For Scotland, the Building (Scotland) Regulations 2004 apply to domestic and non-domestic buildings. Section 4.5 Electrical Safety in the Scottish Building Standards Agency (SBSA) Technical Handbook prescribes that an electrical installation should be designed, constructed, installed and tested such that it is in accordance with the recommendations of the Wiring Regulations BS 7671. The ‘Fundamental Principles’ that are given in chapter 13 are intended to provide for the safety of persons, livestock and the protection of property against dangers and damage which may arise in the reasonable use of electrical installations.

Good workmanship by competent persons using the proper materials will reduce the risk of overheating or fire: It is recognised that good workmanship by competent persons using proper materials will reduce any hazards that may arise and that every item of equipment shall comply with the appropriate British Standard.

The electrical joints are a potential source of overheating and, if not securely made, could ultimately cause a fire. For this reason there are several regulations relating to electrical connections – these are mentioned in chapter 13 in regulation 134.1.4.

‘Every electrical joint and connection shall be of proper construction as regards conductance, insulation, mechanical strength and protection’.

Requirements of 17th Edition Wiring Regulations BS 7671: 2008

In this section we aim at explaining some of the regulations contained within the 17th Edition Wiring Regulations, regarding the connection of conductors both for lighting and power final circuits.

Electrical Connections

The requirements of the 17th Edition Wiring Regulations concerning electrical connections are covered mostly within section 526. This section states that every electrical connection shall have durable electrical continuity, adequate mechanical strength and protection.  The wiring method illustrated here is a common cause of non-compliance particularly with lighting circuits and the connections to downlighters in particular(see Hager J501, Hager 803 and Hager J804).

• It can be seen that the sheath of the flex is not enclosed. This is due to the junction box connection method not facilitating an easy means of enclosing the outer sheath, a non-compliance with regulation 526.9.
• Another problem is that during installation and maintenance, mechanical strain may be placed on the terminations of the conductors within the junction box. This is due to the lack of a clamping method for the cable, a non-compliance with the regulation 522.8.5.

Connections to downlighters are a common cause of non-compliance.

A further potential problem can be found within the junction box (opposite) concerning the type of conductors that are typically terminated. It is often the case in domestic installations that solid twin & cpc cables will be used for the fixed wiring with the conductor to the light fitting (or transformer if the lighting is ELV) being a flexible conductor.

Care must be taken to ensure the strands of the flexible cable are secured adequately in the terminal and have not been damaged to ensure compliance with regulation 526.2.

Also, as can be seen in the illustration on the left, when the conductor was removed for inspection it is clear that some of the strands have been damaged during termination.

Ensure that the connection method selected is fully compliant.

Downlighter Junction Box

When fitting recessed downlighters the following method would overcome all the issues raised previously.

It can be seen here that the sheath of both solid conductors and flexible conductors for the light fitting can be secured as they enter the enclosure. This enables compliance with regulation 522.8.5 in particular where it states that there shall be no undue mechanical strain on the terminations of the conductors. Also regulation 526.9, which requires the cores of sheathed cables from which the sheath has been removed to be enclosed, can be seen to be complied with(see Hager J501, Hager 803 and Hager J804).

Cable clamps prevent strain on terminations for compliance with regulations.

Regulation 526.2 is complied with where the method of connection shall take account of the number and shape of wires forming the conductor. In this junction box solid conductors and flexible conductors can be terminated separately by means of the unique three plate style terminal arrangement(see Hager J501, Hager 803 and Hager J804)..

Continue to read the Hager Junction Box guide to the 17th Edition, part 2.

• Consumer Unit Arrangements – not permitted – A consumer unit with a 30mA RCD main switch;
• Consumer Unit Arrangements Option 1 – Main Switch with RCBO’s On All Circuits;
• Consumer Unit Arrangements Option 2 – Split Load Twin RCCB plus Dedicated RCBO;
• Consumer Unit Arrangements Option 3 – Split Load 3 RCCB Board;
• Consumer Unit Arrangements Option 4 – Split Load Twin RCCB;
• Consumer Unit Arrangements Option 5 – Split Load Twin RCCB plus unprotected circuit.

Consumer Unit Arrangements
Not Permitted

A consumer unit with a 30mA RCD main switch would not be suitable for 3 main reasons:

• The Fire detection circuit and the socket outlet circuits share a common RCD. This could reduce the reliability of the mains supply to the Fire detection circuit as appliances and portable equipment are likely causes of RCD tripping.
• The cumulative effects of electronic equipment in the modern home, is such that some current is likely to flow in the protective conductor. A 30mA RCD will trip between 15-30mA. This could cause unwanted tripping, regulation 314.1 (iv) refers.
• Any fault would result in the loss of all the lighting, this could in itself cause a hazard and the lack of power to the fridge/freezer circuit for example would be very inconvenient. Regulation 314.1 (i) asks the designer to consider this eventuality.

A consumer unit with a 30mA RCD main switch should not be used to protect all the circuits

Consumer Unit Arrangements Option 1
Main Switch with RCBO’s On All Circuits

A standard main switch disconnector controlled consumer unit could be used with every circuit having individual RCD protection at 30mA. This could be achieved by selecting RCBO’s for every outgoing circuit instead of the usual MCB’s. A fault on any circuit would not affect other circuits and hence all relevant regulations would be met by such a design.

Selecting RCBO’s for every outgoing circuit meets all relevant regulations.

Consumer Unit Arrangements Option 2
Split Load Twin RCCB plus Dedicated RCBO

This arrangement provides a dedicated 30mA RCBO for the smoke detector circuit, but combines the rest of the circuits across two further 30mA RCCB’s. Careful arrangements of the circuits can reduce the likelihood of nuisance tripping, thereby limiting the inconvenience or potential hazards that a loss of supply can cause by limiting the number of circuits affected.

This arrangement provides a dedicated RCBO for the smoke detector circuit.

Consumer Unit Arrangements Option 3
Split Load 3 RCCB Board

This arrangement provides a 30mA RCCB for the smoke detector circuit which could also supply other circuits e.g. lighting, and combines the rest of the circuits across two further 30mA RCCB’s. Careful arrangements of the circuits can reduce the likelihood of nuisance tripping, thereby limiting the inconvenience or potential hazards that a loss of supply can cause by reducing the number of circuits affected.

This arrangement provides a RCD for the smoke detector circuit which could also supply other circuits e.g. lighting.

Consumer Unit Arrangements Option 4
Split Load Twin RCCB

This arrangement provides two separate 30mA RCCBs with the circuits spread across both. The design of the circuit arrangements ensure the smoke detector is not fed from the same RCD as socket outlets to improve the reliability of the mains supply to the Fire detection circuit as appliances and portable equipment are likely causes of RCD tripping.
Careful arrangement of the other circuits can reduce the likelihood of nuisance tripping, thereby limiting the inconvenience or potential hazards that a loss of supply can cause. However with all socket outlets being supplied from one RCD certain compromise must be accepted.

One option is for the smoke detector not to be supplied from the same RCD as socket outlets.

Consumer Unit Arrangements Option 5
Split Load Twin RCCB plus unprotected circuit

Under the 17th Edition requirements it is still possible to install some circuits in domestic premises that are not fed via an RCD. Different wiring systems would need to be used. The cost of installation could rise considerably if most circuits were installed using armoured cable or earthed metal conduits.

The smoke alarm circuit could be installed in such a way to negate the need for RCD protection, this may be possible by using one of the other wiring methods described in 522.6.6 for the length of run that the cable is in the wall (use of earthed metal conduit for example). Or depending on the layout of the property there maybe an attached garage for example where surface wiring might be possible. The requirements of that regulation are therefore not applicable. The level of compliance with the Regulations would therefore be the same as option 2 Split Load Twin RCCB plus Dedicated RCBO.

If the smoke alarm circuit is not to be protected by an RCD it must be installed using a method from (i) to (iv) of regulation 522.6.6.

Types of Residual Current Devices normally used in Consumer Units

• RCD – Residual Current Device.
  A generic term for devices providing earth fault protection.
• RCBO - Residual Current Operated Circuit-Breaker with Integral Overcurrent Protection
  A mechanical switching device designed to make, carry and break currents under normal service conditions and to cause the opening of the contacts when the residual current attains a given value under specified conditions. In addition it is designed to give protection against overloads and/or short circuits and can be used independently of any other overcurrent protective device within its rated short circuit capacity.
• RCCB - Residual Current Operated Circuit-Breaker without Integral Overcurrent Protection
  A mechanical switching device designed to make, carry and break currents under normal service conditions and to cause the opening of the contacts when the residual current attains a given value under specified conditions. It is not designed to give protection against overloads and/or short circuits and must always be used in conjunction with an overcurrent protective device such as a fuse or circuit-breaker.

Above, in the pictures, from left to right: Consumer unit, RCCB, RCBO and MCB.

This is the second part of the full Consumer Unit Guide to the 17th edition, by Hager, which can also be found here for download, the first part can be found here. Buy online consumer units, either domestic consumer units(MK or Hager) or industrial consumer units(Hager, ryefield boards, or isolators and switch fuses) by visiting the Electrical Items category at sparksdirect.co.uk.
P.S. View also our small guide to the 17th edition concerning the smoke and fire alarms.

Building Regulations

Part P of the building regulations relates to the electrical safety in dwellings. The approved document prescribes that consumer units should be located so that they are easily reachable where this is necessary to comply with Part M of the building Regulations.

Part M requires that reasonable provision be made for people to gain access to a building and use its facilities. The approved document prescribes that switches, socket outlets and “other equipment” needs to be at appropriate heights, these are defined as between 0.45m and 1.2m from finished floor level.

Other equipment may be taken to include the consumer unit, as it contains devices such as MCB’s and RCD’s that may need operation or resetting by the user of the dwelling. The consumer unit should therefore be accessible, with the devices mounted at a height no greater the 1.2m above the floor. In addition the consumer unit should not be in a location that would make it difficult to access such as an under stairs cupboard. Neither should it be placed in a position where is likely to be damaged by impact. Therefore depending on the layout of the dwelling a flush consumer unit may be considered.

Consumer Units should be easily reachable and be mounted with the switches at a height of between 0.45m & 1.2m above floor level

Requirements of 17th Edition Wiring Regulations BS 7671:2008

This section aims to explain some of the new Regulations contained within the 17th Edition Wiring Regulations, regarding the consumer unit and final circuits. Firstly however, to fully understand what is required, we need to consider some definitions from Part 2 of the Regulations.

• Ordinary Person – Someone who is neither skilled or instructed
  e.g. General public / Home owner
• Skilled Person – A person with technical knowledge or experience to enable him/her to avoid dangers which electricity may create
  e.g. Qualified Electrician
• Instructed Person – A person who has been adequately advised or supervised to enable him/her to avoid dangers which electricity may create
  e.g. Facilities Manager

Typically commercial installations will be under the control of a Skilled or Instructed Person. However domestic and some commercial installations will not. This is particularly important, as certain Regulations only apply to installations not under the supervision of a Skilled or Instructed Person. A significant change is the introduction of Regulations requiring additional protection by RCDs. There are 3 points of consideration,

1. Socket Outlets
2. Cables buried in walls
3. Locations containing a bath or shower

together with some other considerations, like the Division of Installation and about the Fire Detection and Fire Alarm Systems for buildings.

Certain Regulations only apply to installations not under the supervision of a Skilled or Instructed Person i.e. Ordinary persons.

The Regulations have introduced new requirements regarding socket outlets, particularly where used by ordinary persons e.g. Home owners.

Sockets Outlets

The definitions for persons are important to consider when we look at the requirements for protection of circuits supplying socket outlets.  Regulation 411.3.3 requires that an RCD of not exceeding 30mA be provided for:

1. Socket outlets up to 20A that for general use by “ordinary persons”.
2. Mobile equipment up to 32A that is for use outdoors.
   Exceptions to 411.3.3 are permitted where:
3. Use of socket outlets is under the supervision of someone “skilled” or “instructed”.
4. Specifically labelled or otherwise suitably identified socket outlets provided for a particular item of equipment.

This is a change from the 16th Edition that required only socket outlets ‘reasonably expected’ to supply equipment used outside the equipotential zone to have RCD protection e.g. used for an Electric lawn mower. Now under the requirements of the 17th edition it is likely that every socket outlet in a domestic installation will require RCD protection not exceeding 30mA. This may also apply to some commercial installations, like small offices or shops etc where there is no control on the use of those socket outlets. Consideration should also be given to areas where free access to socket outlets is available to the general public e.g. airport lounges.

Socket outlets for general use in a domestic installation require RCD protection not exceeding 30mA

Significant changes affect installations where cables are buried in the wall. This is the normal practice in dwellings.

Cables buried in the wall

Here we need to consider Section 522, Selection and erection of wiring systems in relation to external influences. The particular requirements of this section apply to cables which are concealed in a wall or partition at a depth of less than 50mm, or where metal partitions are used. The definitions for persons are once again important for this section. There are 5 options of installing cables in walls. The cables shall:

1. Incorporate an earthed metal covering which is suitable as a protective conductor. Eg SWA cable.
2. Be enclosed in earthed metal conduit, such that is suitable as a protective conductor.
3. Be enclosed in earthed metal trunking, such that is suitable as a protective conductor.
4. Be protected against damage from penetration by nails or screws.
5. Be installed in a safe zone.

This is much the same as the 16th Edition requirements and the usual option is to install cables in a dedicated safe zone. However, where an installation is not under the supervision of someone skilled or instructed, regulation 522.6.7 applies. In this regulation where (5) only from above is used then the cable must have additional protection by the use of a RCD not exceeding 30mA. This would apply where thermoplastic (PVC) wiring systems are used, this is typical in most domestic installations and some commercial installations.

Where buried cables are not mechanically protected additional protection by an RCD not exceeding 30mA must be provided

Although additional regulations relating to bathrooms etc are not new, there are some important changes to consider.

Section 701, Locations containing a bath or shower

Regulation 701.411.3.3 requires that all circuits within this location shall be additionally protected by an RCD not exceeding 30mA. This would mean 230V lighting, the 230V supply to the source for SELV, a shower circuit and bathroom heater for example will all need RCD protection. A standard 13A socket outlet is now permitted in this location provided however the socket outlet is more than 3m from the boundary of zone 1.

The 16th Edition required local supplementary bonding be provided connecting together all exposed and extraneous conductive parts in the zones. This is no longer required in this location provided the following conditions are met:

• All final circuits of the location comply with the automatic disconnection requirements according to regulation 411.3.2.
• All circuits are RCD protected in accordance with 701.411.3.3.
• All extraneous-conductive parts of the location are effectively connected to the protective equipotential bonding according to regulation 411.3.1.2 (Previously termed main equipotential bonding).

All circuits in locations containing a bath or shower shall be protected by an RCD not exceeding 30mA

Other Considerations

There are additional Regulations and Codes of Practice that need to be considered during the design of an installation. These will affect the choice of consumer unit.

Division of Installation

Section 314 calls for the installation to be so divided to:

1. Avoid hazards and minimize inconvenience in the event of a fault
2. Reduce the possibility of unwanted tripping of the RCD due to excessive protective conductor currents.

To comply with these requirements the circuits of an installation should not be connected to a single RCD, as this could lead to loss of supply to the entire installation in the event of a fault on one circuit, clearly inconvenient for the user of the building.

All circuits of an installation should not be connected to a single RCD

The Wiring Rules & Building regulations are not the only documents that need to be consulted, another important document relates to smoke alarms.

BS 5839-6:2004 Fire detection and Fire alarm systems for buildings

This Code of Practice has particular requirements for dwellings. This document makes reference to the power supply to such systems and mentions RCD’s. The circuit supplying these systems should preferably not be protected by an RCD. This however is going to be difficult to achieve if the circuit supplying these systems is buried in the walls and standard domestic wiring systems are used. Indeed the supply cables would need to be specially protected in earthed metal conduit etc. for RCD protection not to be used.

Options for circuits supplying fire or smoke alarms in dwellings protected by an RCD include:

1. The RCD serves only that circuit. For example with the use of an RCBO
2. The RCD operates independently of any RCD feeding socket outlets or portable equipment

So consideration of these points is necessary during the design stage and particular care is needed to select the appropriate consumer unit and wiring system to ensure compliance. BS 5839-6 should always be studied to ensure that all relevant recommendations are complied with.

Where RCD protection is needed for smoke detector circuits one option is to supply that circuit only

This is the first part of the full Consumer Unit Guide to the 17th edition, by Hager, which can also be found here for download. Buy online consumer units, either domestic consumer units(MK or Hager) or industrial consumer units(Hager, ryefield boards, or isolators and switch fuses) by visiting the Electrical Items category at sparksdirect.co.uk.