The following list provides an overview of the main changes within the
18th Edition IET Wiring Regulations (publishing 2nd July 2018). This list is not
exhaustive as there are many smaller changes throughout the book not included
Requirements for Electrical Installations will be issued on 2nd July 2018 and
is intended to come into effect on 1st January 2019.
Installations designed after 31st December 2018 will have to comply with BS
The Regulations apply to the design, erection and verification of electrical
installations, also additions and alterations to existing installations.
Existing installations that have been installed in accordance with earlier
editions of the Regulations may not comply with this edition in every respect.
This does not necessarily mean that they are unsafe for continued use or
A summary of the main changes is given below. (This is not an exhaustive list).
Part 1 Scope, object and fundamental principles
133.1.3 (Selection of equipment) has been modified and now requires a statement
on the Electrical Installation Certificate.
Part 2 Definitions
have been expanded and modified.
Chapter 41 Protection against electric shock
contains a number of significant changes. Some of the main ones are mentioned
entering the building having an insulating section at their point of entry need
not be connected to the protective equipotential bonding (Regulation
disconnection times stated in Table 41.1 now apply for final circuits up to 63
A with one or more socket-outlets and 32 A for final circuits supplying only
fixed connected current-using equipment (Regulation 422.214.171.124).
411.3.3 has been revised and now applies to socket-outlets with a rated current
not exceeding 32A. There is an exception to omit RCD protection where, other
than a dwelling, a documented risk assessment determines that RCD protection is
Regulation 411.3.4 requires that, within domestic (household) premises,
additional protection by an RCD with a rated residual operating current not
exceeding 30 mA shall be provided for AC final circuits supplying luminaires.
411.4.3 has been modified to include that no switching or isolating device
shall be inserted in a PEN conductor.
411.4.4 and 411.4.5 have been redrafted.
concerning IT systems (411.6) have been reorganized. Regulations 4126.96.36.199 and
4188.8.131.52 have been deleted and 411.6.4 redrafted and a new Regulation 411.6.5
Regulation group (419) has been inserted where automatic disconnection
according to Regulation 411.3.2 is not feasible, such as electronic equipment
with limited short-circuit current.
42 Protection against thermal effects
Regulation 421.1.7 has been introduced recommending the installation of arc
fault detection devices (AFDDs) to mitigate the risk of fire in AC final
circuits of a fixed installation due to the effects of arc fault currents.
422.2.1 has been redrafted. Reference to conditions BD2, BD3 and BD4 has been
deleted. A note has been added stating that cables need to satisfy the
requirements of the CPR in respect of their reaction to fire and making reference
to Appendix 2, item 17. Requirements have also been included for cables that
are supplying safety circuits.
44 Protection against voltage disturbances and electromagnetic disturbances
which deals with protection against overvoltages of atmospheric origin or due
to switching, has been redrafted.
The AQ criteria (conditions of external influence for lightning) for
determining if protection against transient overvoltages is needed are no
longer included in BS 7671. Instead, protection against transient overvoltages
has to be provided where the consequence caused by overvoltage (see Regulation
(a) results in
serious injury to, or loss of, human life, or
(b) results in interruption of public services/or damage to and cultural
(c) results in interruption of commercial or industrial activity, or
(d) affects a large number of co-located individuals.
For all other
cases, a risk assessment has to be performed in order to determine if
protection against transient overvoltage is required.
There is an exception not to provide protection for single dwelling units in
Chapter 46 Devices for isolation and switching. A new Chapter 46 has
This deals with
non-automatic local and remote isolation and switching measures for the
prevention or removal of dangers associated with electrical installations or
electrically powered equipment. Also, switching for the control of circuits or
equipment. Where electrically powered equipment is within the scope of BS EN
60204, only the requirements of that standard apply.
Chapter 52 Selection and erection of wiring systems. Regulation
521.11.201 which give requirements for the methods of support of wiring systems
in escape routes, has been replaced by a new Regulation 521.10.202. This is a
521.10.202 requires cables to be adequately supported against their premature
collapse in the event of a fire. This applies throughout the installation and
not just in escape routes.
522.8.10 concerning buried cables has been modified to include an exception for
527.1.3 has also been modified, and a note added stating that cables also need
to satisfy the requirements of the CPR in respect of their reaction to fire.
53 Protection, isolation, switching, control and monitoring. This chapter
has been completely revised and deals with general requirements for protection,
isolation, switching, control and monitoring and with the requirements for
selection and erection of the devices provided to fulfil such functions.
Section 534 Devices for protection against overvoltage
focuses mainly on the requirements for the selection and erection of SPDs for
protection against transient overvoltages where required by Section 443, the BS
EN 62305 series, or as otherwise stated.
Section 534 has
been completely revised and the most significant technical change refers to the
selection requirements for the voltage protection level.
Chapter 54 Earthing arrangements and protective conductors. Two new
regulations (542.2.3 and 542.2.8) have been introduced concerning earth
Two further new
regulations (5184.108.40.206 and 5220.127.116.11) have been introduced. These give
requirements for the insertion of a switching device in a protective conductor,
the latter regulation relating to situations where an installation is supplied
from more than one source of energy.
55 Other equipment. Regulation
550.1 introduces a new scope.
559.10 refers to ground-recessed luminaires, the selection and erection of
which shall take account of the guidance given in Table A.1 of BS EN
Inspection and testing
Part 6 has been
completely restructured, including the regulation numbering to align with the
Chapters 61, 62
and 63 have been deleted and the content of these chapters now form two new
Chapters 64 and 65. Section
704 Construction and demolition site installations. This section
contains a number of small changes, including requirements for external
influences (Regulation 704.512.2), and a modification to Regulation 704.410.3.6
concerning the protective measure of electrical separation.
Section 708 Electrical installations in caravan/camping parks and similar
locations. This section
contains a number of changes including requirements for socket-outlets, RCD
protection, and operational conditions and external influences.
Section 710 Medical locations. This section
contains a number of small changes including the removal of Table 710.
Regulations 710.415.2.1 and 710.415.2.3 concerning equipotential bonding.
Regulation 710.421.1.201 which states for all final circuits supplied by
medical IT system in medical locations of group 2, AFDD shall not be used.
715 Extra-low voltage lighting installations. This section
contains only minor changes including modifications to Regulation 715.524.201.
Section 721 Electrical installations in caravans and motor caravans. This section
contains a number of changes including requirements electrical separation,
RCDs, proximity to non-electrical services and protective bonding conductors.
Section 722 Electric vehicle charging installations. This section
contains significant changes to Regulation 722.411.4.1 concerning the use of a
concerning reasonably practicable has been deleted.
also been made to requirements for external influences, RCDs, socket-outlets
730 Onshore units of electrical shore connections for inland navigation vessels.
This is an
entirely new section and applies to onshore installations dedicated to the
supply of inland navigation vessels for commercial and administrative purposes,
berthed in ports and berths.
Most, if not all, of the measures used to reduce the risks in marinas apply
equally to electrical shore connections for inland navigation vessels. One of
the major differences between supplies to vessels in a typical marina and
electrical shore connections for inland navigation vessels is the size of the
Section 753 Floor and ceiling heating systems. This section
has been completely revised.
The scope of
Section 753 has been extended to apply to embedded electric heating systems for
requirements also apply to electric heating systems for de-icing or frost
prevention or similar applications, and cover both indoor and outdoor systems.
for industrial and commercial applications complying with IEC 60519, IEC 62395
and IEC 60079 are not covered. Appendices
main changes have been made within the appendices Appendix
Standards to which reference is made in the Regulations includes minor changes,
characteristics of overcurrent protective devices and RCDs
contents of Appendix 14 concerning earth fault loop impedance have been moved
6 Model forms
for certification and reporting
includes minor changes to the certificates, changes to the inspections (for new
installation work only) for domestic and similar premises with up to 100 A
supply, and examples of items requiring inspection for an electrical
installation condition report.
7 (informative) Harmonized cable core colours
includes only minor changes. Appendix
8 Current-carrying capacity and voltage drop
includes changes regarding rating factors for current-carrying capacity. Appendix
of prospective fault current
The contents of
Appendix 14 concerning earth fault loop impedance have been moved into
Appendix 3. Appendix 14 now contains information on determination of
prospective fault current.
This is a new
appendix that provides 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.
recommendations within the scope of this appendix apply for new electrical
installations and modification of existing electrical installations.
Much of appendix 17 will not apply to domestic and similar installations.
It is intended
that this appendix is read in conjunction with BS IEC 60364-8-1, when published