The aim of this section is to give you an understanding of the numbering system which is used in the 17th Edition Wiring Regulations. Understanding of the numbering system enables you to quickly locate the relevant regulations and gives guidance on how to work your way through the exam and the 17th Edition Wiring Regulations

Numbering

The numbering of the 17th Edition Wiring Regulations follows the pattern of the technical intent of Standards developed at the European CENELEC level. The system is based on the harmonisation documents HD60364 series of standards. Or, in language the rest of us understand, the numbering system has designed to be consistent, easy to follow and easy to update.

For the old timers amongst us who wired our first socket under the 16th Edition Regulations, the most obvious change is that the 17th Edition Wiring Regulations has dropped the dashes and now uses a point/dot numbering system, based on the IEC numbering system.

The structure of the numbering is straightforward

1st digit signifies a Part (Part 5 of BS 7671 in the example below),

2nd digit is a Chapter (the second chapter of Part 5),

3rd digit is a Section (the fourth section of 52)

The final number (or numbers) are the Regulation

Using the example of Regulation 524.1

Regulation 524.1 Refers to:

PART 5 – SELECTION AND ERECTION OF EQUIPMENT

CHAPTER 2 – SELECTION AND ERECTION OF WIRING SYSTEMS

SECTION 4 – CROSS-SECTIONAL AREAS OF CONDUCTORS

REGULATION 1

Now refer to your copy of BS7671 Wiring Regulations and look up this regulation.

This is the regulation: The cross-sectional area of each conductor in a circuit shall be not less than the values given in Table 52.3, except as provided for extra-low voltage lighting installations according to Regulation 715.524.201.

Regulation Groups

Some regulations are organized into Regulation Groups, by example:Regulation 521.9.3 refers to:

PART 5 – SELECTION AND ERECTION OF EQUIPMENT

CHAPTER 2 – SELECTION AND ERECTION OF WIRING SYSTEMS

SECTION 1 – TYPES OF WIRING SYSTEM

REGULATION– GROUP 9 Use of flexible cables

REGULATION 3

Now refer to your copy of BS7671 Wiring Regulations and look up this regulation.

This is the regulation: Stationary equipment which is moved temporarily for the purposes of connecting, cleaning etc., e.g. cookers or flush mounting units for installations in false floors, shall be connected with flexible cable. If the equipment is not subject to vibration then non-flexible cables may be used.

Numbering of Part 7

Part 7 does not have any chapters. For Part 7, the second and third numbers describe the Section. For instance Regulation 703.1 describes the regulation in Part 7, Section 3, Regulation 1 Scope – which relates to saunas.

UK Only Numbering

The 17th edition introduced a new IEC decimal point numbering system to make it easier to embody future changes and additions resulting from ongoing international standards work within IEC and CENELEC. In order to accommodate future IEC changes it was decided to have a 100 numbering system for UK only regulations.

For the third amendment, the 100 numbers now represent CENELEC Harmonization Document reference numbers and 200 numbers represent UK-only regulations. Existing regulations have not been “updated” to indicate 100 and 200 numbers; that will only be done when those regulations require a significant rewrite

In the example of Regulation 715.524.201 ‘The minimum cross-sectional area of the extra-low voltage conductors……..’. That the Regulation number is 524.201 shows that it is a regulation for the UK only and has been substantially rewritten (and in this example: 15 is the Section, which is in Part 7).