BS 7671: 2008 Amendment 3 is now published, and you will have to comply!

Amendment No. 3 to BS 7671:2008 (IET Wiring Regulations 17th Edition) has just been published (January 2015). The potentially life-saving changes included make this a vital update – much more so than Amendment 2.

 

There’s a lot more than just a colour change to the front cover – which is now yellow. Amendment 3 has a significant number of quite major changes that electrical installers and contractors will now have to understand and follow in their working practices.

 

Some of these changes affect manufacturers more than installers, but most are important to the latter. The key alterations include some definition changes, a change to protection, a reduction in earth loop impedance values, the addition of protective devices, wiring in escape routes, consumer unit enclosures to be made non-combustible (to come into effect January 2016) and the inclusion of model inspection, testing certificates and reports.

 

 

In more detail, the most important of these changes – as outlined by the IET - are as follows:

 

 

This has various changes in definitions, plus alterations for socket outlet RCD protection. As an example, ‘Ordinary persons’ in Regulation 411.3.3 has been removed. In addition, RCD protection (Regulation 415.1 for socket outlets up to 20A, and for mobile equipment up to 32A for use outdoors) is now required for all installations. Note, though, that there are exceptions for socket outlets up to 20A for a specific labelled socket outlet, or where a documented risk assessment shows that RCD protection is not necessary.

 

Also, the maximum earth fault loop impedances have been revised to take into account the Cmin factor. This is the minimum voltage factor to take account of voltage variations depending on time and place, changing of transformer taps and other considerations, says the IET. The maximum earth fault loop impedances provided in Tables 41.2 - 41.4 and 41.6 have been revised to take account of the Cmin factor given in CLC/TR50480: 2011. Furthermore, the notes to the Tables have been changed in terms of the maximum permitted operating temperature.

 

 

Included is a new requirement for switchgear and consumer unit enclosures to be made more fire safe than they currently are (a number of building blazes have been caused by plastic enclosures catching fire). Regulation 421.1.200 has been added, and it requires switchgear assemblies - including consumer units - to have their enclosures made from non-combustible or not readily combustible material - or be enclosed within a cabinet or enclosure made of non-combustible or not readily combustible material (in effect, this means steel in most cases).

 

 

Within this, Section 442 (dealing with protection of low voltage installations against temporary over-voltages because of earth faults in the high voltage system and because of faults in the low voltage system) has been modified. Regulation 442.2.1 has been redrafted and Table 44.2 has been removed.

 

 

It is the case that compliance with standards requires all electrical equipment to be suitable for the nominal voltage. It also requires that certain information  be noted on the electrical installation certificate. Section 512 now refers to the EMC Directive and includes requirements for the designer of the fixed installation. Note that minor modifications have been made to Sections 513 and 514.

 

 

There is a new Regulation (521.200) here. It provides the requirements for the methods of support of wiring systems in escape routes. The regulations concerning the selection and erection of wiring systems (impact) have been redrafted. Reference to ‘under the supervision of skilled and instructed persons’ has been removed. 

 

The new requirements (see 521.11.201) outline the need for cabling to be supported by fire-resistant fastenings and fixings that cannot prematurely collapse under conditions of extreme heat. For this reason, plastic cable clips, non-metallic cable ties and plastic trunking to support wiring systems would likely not comply with the new requirements (the word the IET uses in this context is 'precludes' the use of non-metallic supports etc), which apply to all wiring systems in a building, including those of distribution circuits and final circuits, safety services, and data and communications services.

 

In essence, therefore, wiring systems should be supported in such a way that they will not collapse when affected by fire, especially around escape routes. The sole use of plastic fixings and non-metallic cable ties will no longer comply with the new regulations and rightly so as exposure to fire could result in the melting of trunking and the risk of loose cabling.

 

Installers should, therefore, look for products – cable ties, cable mounts and other supporting components - that meet high standards of fire resistance, as these will be able to withstand high temperatures and provide durability and strength. 

 

Stainless steel products are ideal where high strength, reliability and fire resistance are needed. Though many installers will see such stainless steel products as being expensive, they do provide the required support, as well as peace of mind. 

 

Also under Chapter 52, cables concealed in a wall or partition (at a depth of less than 50mm) must be protected by a 30mA RCD for all installations - if other methods of protection, including the use of cables with an earthed metallic covering or mechanical protection, are not used. This applies to a cable in a partition where the construction includes metallic parts other than fixings irrespective of the depth of the cable. However, there is still an exception for cables forming part of a SELV or PELV circuit.

 

 

 

Small changes have been made to Regulation 551.7.1 concerning low voltage generating sets.

 

However, a new Section 557 has been added. This covers auxiliary circuits for low voltage electrical installations. Auxiliary circuits are defined as 'circuits for the transmission of signals intended for the detection, supervision or control of the functional status of a main circuit such as circuits for control, signalling and measurement'.

 

Covered are AC or DC auxiliary circuits, power supplies for auxiliary circuits dependent on the main circuit, auxiliary circuits supplied by an independent source, protection against overcurrent, and wiring systems. Special requirements for auxiliary circuits used for measurement are provided. Note, however, that where specific standards already exist, auxiliary circuits are excluded. 

 

Section 559 Luminaires and Lighting Installations - Requirements for outdoor lighting and extra low voltage lighting installations have been moved to new Sections 714 and 715 respectively. A number of changes have been made to the requirements of Sections 559, 714 (Outdoor Lighting installations) and 715 (Extra Low Voltage Lighting Installations). 

 

 

Section 701 - Locations Containing a Bath or a Shower - Regulation 701.411.3.3 now requires all low voltage circuits (including circuits passing through the location) to be RCD protected.

 

Section 704 - Construction and Demolition Site Installations - The earlier exclusion of mining applications in Regulation 704.1.1 is now deleted.

 

Section 711 - Exhibitions, Shows and Stands – Reference to a skilled/competent person has been removed in Regulation 711.55.6.

 

Section 712 - Solar Photovoltaic (PV) Power Supply Systems – This includes minor changes, including to the general schematic.

 

Section 714 - Outdoor Lighting and Section 715 Extra Low Voltage Lighting Installations - A number of changes have been made to the requirements in Sections 714 and 715 – e.g. additional requirements for isolation, switching and control.

 

Section 717 - Mobile or Transportable Units - Regulation 717.551.6 has been added. This does not allow units having different power supply systems and differing earthing systems to be interconnected. Also, changes have been made to the figures showing examples of connections associated with the mobile or transportable unit. Again, more RCDs will need to be tested, as will the necessarily more complex earthing systems.

 

 

In Appendix 3 - Concerning the time/current characteristics of overcurrent protective devices and RCDs - this includes changes in terms of the maximum earth fault loop impedance to take account of the Cmin factor. There are also changes to the Tables in terms of the maximum operating time and current characteristics. In addition, there is a new Table for fuses to BS 88- 2 - fuse system E has been added.

 

In Appendix 4 – The current-carrying capacity and voltage drop for cables includes changes including modifications to Tables 4A3, 4C3, and 4F4A. Reference is made to PD CLC/TR 50480 for calculating circuit impedances, fault currents and other variables. The national annex to PD CLC/TR 50480 is also referred to – this gives calculation methods for cable resistance and reactance – among others.

 

In Appendix 6 - Model forms for certification and reporting – the schedule of inspections for new work only has been replaced by examples of items requiring inspection during initial verifications (which must be appended to the electrical installation certificate). 

 

Moreover, some small changes have been made to the electrical installation condition report and associated notes including a requirement to carry out an inspection within an accessible roof space where electrical equipment is present. 

 

In Appendix 14 - Measurement of earth fault loop impedance - The equation for earth fault loop impedance has been changed to take account of the Cmin factor.

 

Note that Chapter 43 - Protection against Overcurrent, Chapter 53 - Protection, Isolation, Switching, Control and Monitoring, Part 6 - Inspectionand Testing, and Appendix 1 - British Standards - these have all receieved only minor modifications, according to the IET.

 

To see more about the Wiring Regulations in general, go to: http://electrical.theiet.org/wiring-regulations/updates/index.cfm

 

 

All expert IET guidance is being updated at the same time, offering the following: 

 

 

Spread the cost of getting up to date with the new books: subscriptions to  digital versions start from just £60 (+VAT) per year for the Bronze package.  Find out more about all the packages available >

 

The digital versions are also accepted by scheme providers during their inspections. All of the printed versions of the books are individually available for pre-order now.

 

To learn more on specific topics related to Amendment 3 of BS 7671: 2008, please read the other articles in this VoltiTECH.