Appendices – BS7671

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Appendix 1: British Standards Referenced by the Regulations

Appendix 1 is described as normative, all other appendices are informative.

Normative means that this Appendix provides reference to documents which are the standards, for all the other appendices, they are informative, which means they provide additional information

Appendix 2: Statutory Regulations and Associated Memoranda

Electrical installations are to comply with not only BS 7671 2008 but to specific Statutory Regulations. Refer to Appendix 2 for the up to date list of Statutory Regulations

Appendix 3: Time / Current Characteristics of Overcurrent Protective Devices and Residual Current Devices

Appendix 3 provides the Time/current characteristics of overcurrent protective devices and RCDs.

The characteristics are provided in the form of graphs and by plotting time in seconds against prospective current in amperes. By referencing the graphs the disconnection time of the selected device can be ascertained when the current passing through the device is known, conversely the current required to disconnect the device in a given time can also be known.

These graphs use a logarithmic scale and this must be kept in mind or mistakes or miscalculations may be made. For this reason a table has been introduced for quick reference.

The information within these graphs, are interrelated onto various other tables throughout BS7671 2008 i.e. tables 41.2 to 41.6 and also in the Onsite Guide.

Appendix 4: Current-Carrying Capacity and Voltage Drop for Cables and Flexible Cords

This section had significant changes in the 17th Edition which have carried through to the 18th Edition. Expect at least one question in the exam from this Appendix.

Appendix 5: Classification of External Influences

The Classification of External Influences is noticeably mentioned throughout BS7671 2008 and are intended to give the classification and codification of the external influences of the installation

The First letter relates to the general category of the external influence.

The Second letter relates to the nature of the external influence.

The number relates to the class within the external influence, i.e. AD4

‘A’  represents the Environment:

  • Ambient temperature
  • Temperature and Humidity
  • Water
  • Foreign bodies
  • Corrosion
  • Impact
  • Vibration
  • Flora fauna
  • Electromagnetic
  • Solar
  • Seismic
  • Lighting
  • Lightning
  • Movement of air
  • Wind

‘B’ represents the Utilization of the building:

  • Capability of the occupants
  • Contact of the occupants with Earth potential
  • Conditions of evacuation in an emergency
  • Nature of stored materials

‘C’ represents the construction of the building:

  • Construction — combustible or non-combustible
  • Building design

It is recommended that installers and designers become familiar with these classifications. There is also a high probability of several exam questions occurring concerning external influence codes.

Appendix 6: Model Forms for Certification and Reporting.

The forms required for the Certification of Electrical Installations are:

  • The Electrical Installation Certificate
  • The Minor Electrical Installation Works Certificate
  • Electrical Installation Condition Report
    (This replaces the Periodic Inspection Report in Amendment 1)

Further information on inspection and testing and periodic inspection, testing and reporting can be found in IET Guidance Note 3.

The documentation above also requires:

  • The Schedule of Inspections
  • The Schedule of Results

As mentioned in Part 6 Testing and Reporting of Electrical Installations is covered more thoroughly in qualifications such as the 2391.

Appendix 7

Deleted  by BS7671:2018 A2+2022

Appendix 8: Current-Carrying Capacity and Voltage-Drop for Busbar Trunking and Powertrack Systems

The rating factors which apply to current-carrying capacity have been changed. The use of Greek character for the subscript of k (a 17th Edition rating factor could be indicated by kα) is replaced by letter/number combinations, for instance k1A

Appendix 9: Definitions — Multiple Source, D.C. and Other Systems

Covers specialized supply systems.

Appendix 10: Protection of Conductors in Parallel Against Overcurrent

Provides information and guidance in relation to overcurrent protection (for overload and short-circuit currents) where conductors are connected in parallel (normally larger current designs).

Appendix 11: Warning and user instruction labels

Regulation 514.9.2 specifies harmonized standards to be used for user instructions and warning signs. The approach permits more flexibility in the sizing of appropriate labels for particular circumstances than previous editions of BS 7671, whilst accounting for an inclusive range of visual clarity and legibility. This appendix provides particular guidance for the types of safety signs, warning signs and instructions required to be applied to electrical installations.

An easy to read sans serif font should be used. Examples include, but are not limited to, Arial, Calibri, Helvetica, and Verdana.

Graphical symbols should comply with appropriate standards, which include BS EN ISO 7010, IEC 60417, IEC 60617, and BS ISO 7001.

Sizes of text and graphical symbols should comply with BS EN IEC/IEEE 82079-1. Table 11A provides minimum sizes for labels relevant to electrical installations.

TABLE 11A – Minimum label text and symbol sizes to BS EN IEC/IEEE 82079-1 relevant to electrical installations

Label use Recommended minimum height of graphical representations Recommended minimum text size
Graphical symbols Graphical safety signs Dark on light background
(e.g. black on white or black on yellow)
Low contrast (e.g. white on blue, white on red, white on black)
General labels 15 mm 15 mm 14 pt (4.9 mm) 16 pt (5.6 mm)
Labels for surfaces less than 10 cm2 5 mm 10 mm 7 pt (2.5 mm)  12 pt (4.2 mm

Appendix 12

Not used

Appendix 13: Escape routes and fire protection

Means of escape in a building is the provisions (i.e. the ‘means’) by which safe escape to a place of safety is provided. Often, particularly in smaller and simple buildings, this can be achieved simply by limiting the distance which has to be travelled to an exit from any place in the building. However, in larger and more complex buildings this is generally not possible and longer distances have to be travelled. It is then necessary to protect escapees during this longer period of travel.

This is achieved by providing protected escape routes (as defined) in which people escaping from the building are protected from the effects of fire by a specific fire and smoke-resisting structure. Such protected escape routes are composed of one or more of the following:

  • Protected lobby
  • Protected corridor
  • Protected stairway.

These protected routes afford a safe passage through the building to an exit leading to a place of safety, usually the open air.


Regulation 434.1 requires the prospective fault current to be determined at every relevant point of an installation. Relevant points are switchgear and protective devices that may have to operate and possibly disconnect a fault current. The devices have to be able to withstand the fault currents safely and protect downstream equipment from damage in the event of a fault.

Appendix 15: Ring and Radial Final Circuit Arrangements

Sets out options for the design of ring and radial final circuits for household and similar premises

Appendix 16: Devices for protection against overvoltage

Refer to Appendix 16 for information on the installation of surge protective devices (SPD)

Appendix 17 : Energy efficiency

This appendix provides additional recommendations for the design and erection of electrical installations, including installations having local production and storage of energy, for optimizing the overall efficient use of electricity.

NOTE: On-site renewable energy sources and other local production sources do not of themselves increase the efficiency of an electrical installation. However, they do reduce the overall public electricity network losses as the consumption of the installation from the public supply is reduced. This may be considered an indirect energy efficiency measure. For installation of solar photovoltaic (PV) power supply systems, see Section 712 of BS 7671.

The recommendations within the scope of this appendix apply for new electrical installations and modification of existing installations. Much of this appendix will not apply to dwellings and similar installations. In dwellings and similar installations it is recommended that use is made of LED lighting. Reference should also be made to the Building Regulations – Part L in England and Wales, the Technical Handbook in Scotland and Technical Booklets F in Northern Ireland.

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