Changing standards for electrical installations

Published:  09 March, 2008

cables

Giuliano Digilio, provides background to the recently published 17th Edition of the Wiring Regulations and highlights some of the key changes that specifiers should be aware of when engaging electrical contractors.

The introduction of the 17th Edition of the IEE Wiring Regulations (BS 7671) in January this year means that the standards that electrical installations adhere to have changed. By July 2008 all new electrical installation work within the scope of BS 7671 will have to comply with the revised regulations, meaning designers must ensure they are aware of the changes and how they will be affected by them in order to fulfil the needs of their future contracts.

Although there have been many amendments to the 16th Edition, this new edition has been the most significant overhaul of the regulations since 1992, when the British Standards Institution (BSI) made it a national standard.

Whilst the basic principles remain, the revised standard includes the changes necessary to maintain technical alignment with European harmonisation documents, as well as changes in design, specification, terminology and inspection and testing requirements.

About the regulations

The changes to the regulations have been made by the European Committee for Electrotechnical Standardisation (CENELEC) and the International Electrotechnical Commission (IEC) to ensure commonality of electrical installation standards throughout Europe and the rest of the world, respectively.

Such standards are known as harmonised documents (HDs), where BS 7671 is the UK collection incorporated in a single publication with many other regulations that accommodate specific situations and practices applicable in the UK. A number of countries adopt BS 7671 as their national standard and others base their national standard around it.

The 17th Edition is the result of a complete review of the 16th Edition and adopts all HDs that are published to date.

The changes

A grace period is in place, meaning that any existing projects, where the design was completed or started before 1 July 2008, may still be completed and certified in accordance with BS 7671: 2001 16th Edition of the IEE Wiring Regulations. However, there are a number of changes that designers and specifiers should familiarise themselves with, when employing the services of contractors, in preparation for compliance in July, many of which are outlined below.

Preface: A new informative note in the preface advises that publication of the 2008 edition of BS 7671 does not automatically mean that installations complying with previous editions are unsafe for continued use or need to be upgraded.

Numbering: The regulation numbers are changed so as to be in line with IEC Numbers, enabling users to readily relate UK regulations with European HDs and IEC regulations.

Fundamental principles: Requirements have been added for protection for persons and livestock against injury, and property against damage caused by voltage disturbances and electromagnetic influences.

Chapter 41, protection against electric shock: Although this chapter has been rewritten, despite many of the regulations having been reworded, the requirements have not significantly changed.

The terms ‘direct contact’ and ‘indirect contact’ are no longer used and have been replaced with ‘basic protection’ (protection against touching live parts) and ‘fault protection’ (protection against receiving a shock from conductive parts that have become live due to a breakdown of insulation or damage to equipment).

Chapter 41 states that additional protection is required, by means of residual current devices (RCDs) for any socket outlet with a rating not exceeding 20 A for use by ‘ordinary persons’ (i.e. a person who is not a ‘skilled’ or ‘instructed person’).

Socket outlets rated at a maximum of 20 A and intended for general domestic or similar use must be protected with 30 mA RCDs. External sockets rated up to 32 A must also have 30 mA RCD protection.

To meet these requirements, specifiers need to consider areas accessible to non-instructed persons, such as public lobbies.

Chapter 52, selection and erection of wiring systems, includes an important new requirement that particularly affects domestic and similar installations.

Cables buried less than 50 mm into a wall or partition and not enclosed in earthed metallic covering or with mechanical protection capable of resisting nails, screws or drills, are to be protected by a 30 mA RCD, as well as being installed in the ‘safe zones’ created by the position of accessories etc., as previously permitted.

Similarly, cables that are installed in metal-framed walls require 30 mA RCD protection if not otherwise protected by earthed metallic covering.

The above requirements do not, however, apply to installations that are under the control of skilled or instructed persons, such as office buildings, large retail outlets and industrial premises.

Chapter 55, ‘other equipment’, Section 551.2, ’generator sets’: This section contains requirements that are applicable to low-voltage electricity generating sets, including small-scale electricity generators such as wind turbines, solar powered generators, PV systems (see also section 712, ‘PV systems’), water turbines and combined heat and power boilers, for use in domestic and commercial installations.

The use of this equipment is expected to escalate in the next few years, meaning that an understanding of this section will be important.

The following sections have been modified or introduced to accommodate the regulations contained in the European HDs.

Section 559, ‘luminaires and lighting’ is a new section that is applicable to all general lighting installations, as appropriate to particular locations and structures. It includes requirements for fixed outdoor lighting, including highway power supplies and street furniture (previously in Part 6) and extra-low-voltage lighting systems (less than 50 V a.c. and 120 V d.c.). This chapter applies to both individual luminaires and multi-luminaire track lighting and similar systems and incorporates special considerations for protection against fire.

Part 7, ‘special locations’, addresses the particular risks that occur in various special locations. There are several new and modified sections that designers should be aware of.

Section 701, ‘Locations containing a bath or a shower’ contains substantial modifications to the previous edition.

Zones 0, 1 & 2, as defined in the 16th Edition, are retained, and Zone 3 has been removed. The new regulations require all circuits supplying equipment in the bathrooms to be protected by 30 mA RCDs.

All cables buried in walls surrounding bathrooms, regardless of the points they are serving, must now be protected by 30 mA RCDs.

Supplementary bonding between metallic service and waste pipes and the earth connections of equipment is no longer required, provided the main bonding of services within the property is in place and the metallic pipework can be proved by testing to be continuous. This means that the need for green and yellow cables in bathrooms is unlikely to be necessary.

In addition, SELV (separated extra low voltage) socket outlets and shaver socket outlets are permitted outside Zone 1. 230 V socket outlets are permitted provided they are more than 3 m from Zone 1.

Other modified sections are as follows.

• Section 702, ‘swimming pools’.
• Section 703, ‘rooms and cabins containing sauna heaters’.
• Section 704, ‘construction sites’.
• Section 705, ‘agricultural and horticultural premises’.
• Section 706, ‘conductive locations with restricted movement’.
• Section 707, previously 607 in the 16th Edition, is not used. The particular requirements are embodied in the ‘general earthing requirements’ of chapter 54.
• Section 708, ‘caravan and camping parks’ (formerly ‘caravans, motor caravans and caravan parks’) is now divided into section 708 and section 721, ‘caravans and motor caravans’. Of particular note is that each pitch socket outlet is to have separate 30 mA RCD protection.

New sections are as follows.

• 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, ‘caravans and motor caravans’.

• Section 740, ‘temporary electrical installations for structures, amusement devices and booths at fairgrounds, amusement parks and circuses’.

Finding out more

The ECA’s ‘Guide to the IEE Wiring Regulations BS 7671:2008’ explains these changes in greater detail, providing practical applications to demonstrate where the modifications and additions apply and how they should be put into practice. For further information or to order a copy, please contact the ECA on 020 7313 4800 or visit the ECA website.

Giuliano Digilio is head of technical services with the Electrical Contractors’ Association.



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