17th Edition Amendment 3 BS 7671:2008

Ok so the 1st of July is fast approaching meaning if you haven’t yet got upto speed with the new 17th Edition Amendment 3 now’s probably a good time to. As of the 30th June all electrical installations designs will have to meet BS7671:2008 Amendment 3:2015.

So what’s going to change?

Here’s a run down of some on the changes, for full details please obtain a copy of the IET wiring regulations as amended (Yellow Book) and checkout page 5.

New numbering system

The 17th Edition introduced a new IEC decimal point numbering system. For the third amendment where 100 and 200 numbers have been used, the 100 numbers represent CENELEC harmonisation document reference numbers and 200 numbers represent UK only regulations.

Part 2

Definitions have been expanded and modified, including some new symbols. A list of abbreviations used in the regulations has been added. 

The definition of competent person has been removed and replaced with ‘instructed person’ and ‘skilled person’ electrically of course.

Part 3

Assessment of general characteristics (Chapter 33 – Compatibility) Regulation 332.1 has been modified; it no longer refers to installations but only to equipment.

Chapter 41 – Protection against electric shock

Regulation 411.3.3 has seen a reference to ‘ordinary person’ deleted. There is now a requirement for RCD protection for socket outlets up to 20A for all installations, however exceptions are permitted for:

  • A specific labelled or otherwise suitably identified socket-outlet provided for connection of a particular item of equipment,
  • Or where other than for an installation in at the dwelling, A documented risk assessment determines that the RCD protection is not necessary.

Maximum earth loop impedances given in table is 41.2, 41.3 41.4 and 41.6 have been revised to take account of the Cmin factor.

Cmin is the minimum voltage factor to take account of voltage variations depending on a number of considerations.

Chapter 42 – Protection against thermal effects

Due to the number of consumer unit fires reported within domestic premises, regulation 421.1.201 (UK only) has been added and requires consumer units and similar switchgear to have their enclosure manufactured from noncombustible material or be enclosed in a cabinet or enclosure constructed of noncombustible material and complying with regulation 132.12.

Please note that the above regulation does not come into effect until 1st January 2016 to ensure a suitable supply of cabinets or enclosures are available.

Chapter 43 – Protection against overcurrent

Contains some minor corrections.

Chapter 44 – Protection against voltage disturbances and electromagnetic disturbances

Section 442, which deals with protection of low voltage installations against temporary overvoltages due to earth faults in the high-voltage system and due to faults in a low voltage system, has been modified. Regulation 442.2.1 has been redrafted and table 44.2 removed.

Chapter 51 – Common Rules

Section 551 concerning compliance with standards requires all equipment to be suitable for the nominal voltage and also requires certain information to be noted on the electrical installation certificate.

Chapter 52 – Selection and election of wiring systems

A new regulation 521.11.201 (UK only) has been included giving requirements for the methods of support of wiring systems in escape routes.

The regulations concerning selection and erection of wiring systems have been re-drafted. Reference to “under the supervision of a skilled or instructed person” has been removed.

Chapter 53 – Protection, isolation, switching, control and monitoring

Only some minor changes.

Chapter 55 – Other Equipment

A new section 557 auxiliary circuits is included. All auxiliary circuits are defined in Part 2.

Section 559 – Luminaires and lighting installation

Requirements for outdoor lighting installations and extra low voltage lighting installations have been moved to new sections 714 and 715 respectively.

Part 7 – Special Locations

Section 701 locations containing a bath or a shower. There is now a requirement for RCD protection to be provided for:

  • Low voltage circuits serving the location
  • Low voltage circuits passing through zones 1 and 2 not serving the location.

There are also a number of additional changes in this section.

Appendix 1 – British Standards

Some minor changes

Appendix 3 – Time / current characteristics of overcurrent protective devices and RCDs

The main changes are in connection with earth fault loop impedance to take account of the Cmin factor given in PD CLC / TR50480.

Appendix 4 – Current carrying capacity and voltage drop for cables

Similar changes as above.

Appendix 6 – Model forms for certification and reporting

The schedule of inspections for new work only has been replaced with examples of items requiring inspection during initial verifications which must be appended to the electrical installation certificate.

There are also some changes to the electrical condition report and associated notes have been made, including a requirement to carry out and inspection within a roof space where electrical equipment is present.

Please be sure to check the yellow book IET Wiring Regulations for the complete list of changes.

About The Author