Ask the experts/Technical
Fully charged Premature collapse of wiring systems Objective To remind contractors that the requirements of Regulation 521.11.201, introduced under the third amendment of BS 7671 for the purpose of preventing premature collapse of wiring systems1 in the conditions of fire, are applicable for all wiring systems within the scope of BS 7671.
I
n addition to general low voltage lighting and power, electrical installation work, particularly in commercial and industrial premises, can often consist of a range of installation systems, including, among others, fire detection, emergency lighting, security, energy management, data and communications. However, irrespective of the type of system(s) being installed, electrical contractors should be aware that the extent of Regulation 521.11.201 is not restricted to any particular cable type or voltage but applies to all wiring systems within the scope of the Wiring Regulations.
BRITISH STANDARD
BS 7671: 2008
Incorporating Amendment 1: 2011 Corrigendum 2013 Amendment 2: 2013 Amendment 3: 2015
Requirements for Electrical Installations
IET Wiring Regulations Seventeenth Edition
© The Institution of Engineering and Technology and BSI NO COPYING IN ANY FORM WITHOUT WRITTEN PERMISSION
The scope of BS 7671 BS 7671 is applicable to the design, erection and verification of most electrical installations, such as domestic, commercial, industrial and the range of others listed in Regulation 110.1.1 being supplied at a voltage up to and including 1 000 V a.c. or 1 500 V d.c. (Regulation 110.1.2 refers). The requirements of BS 7671 apply to all new work and alterations or additions to existing installations. Although for a.c. installations the requirements apply for the preferred operating frequencies of 50 Hz, 60 Hz and 400 Hz, other frequencies are not precluded. Whilst a range of installations are specifically excluded from the scope of BS 7671, such as lightning protection systems and electric fences, it is worth noting what is included in the scope of BS 7671. For example, the fixed wiring for information and communication technology, signalling, control and similar Band I installations are all covered by the general requirements of BS 7671, in addition to any specific technology standards that may apply. British or Harmonised Standards Where necessary, the requirements of BS 7671 should be supplemented by the requirements or
recommendations of other British or Harmonised Standards, or by the requirements of the person ordering the work (Regulation 110.1.3 refers). For example, Regulation 560.8.1 requires the selection of a wiring system for a safety service that is required to operate in conditions of fire, such as a fire detection and fire alarm system, or an emergency lighting system to be compliant with the relevant code of practice for the application and be installed in a manner that minimises the risk of circuit integrity being impaired during a fire. Therefore, for example, on completion of the installation of such a system, in addition to an appropriate certificate to confirm compliance with the relevant parts of the particular standard, such as the BS 5839 series for a fire detection and fire alarm system (Regulation 560.10 refers), an Electrical Installation Certificate or, where appropriate, a Minor Electrical Installation Works Certificate, should also be issued to certify the fixed wiring of the fire detection and fire alarm system for compliance with BS 7671. Due to their function, systems to BS 5839-12 and BS 52663 are generally installed using fire-resistant supports, but for many other types of wiring system this has not generally been the case. Nevertheless, in accordance with Regulation 521.11.201, any installation that encroaches on an escape route, unless excluded from the scope of BS 7671 by Regulation 110.2, should be protected from premature collapse in the event of fire. The definition of what constitutes an escape route was the subject of a previous article in Connections 196, and includes not only defined routes such as corridors, stairways and hallways, but also open areas. Periodic inspection
1 BS 7671 defines a wiring system as an: Assembly made up of cable or busbars and parts which secure and, if necessary, enclose the cable or busbars.
Periodic inspection should identify any damage, deterioration, defects, dangerous conditions and non-compliance with the current requirements of BS 7671, which may give rise to danger (Regulation 634.2 refers). Irrespective of the age of an installation, where non-compliances are observed they should be assigned a Classification code (C1, C2 or C3) according to the risk presented to the user of the installation. This provides the client with an indication of the degree of danger present within the installation. Where the inspector observes cables for any installation that falls within the scope of BS 7671 in escape routes that are not adequately supported to prevent premature collapse, Best Practice Guide 4 (BPG 4): Electrical installation condition reporting, issued by Electrical Safety First and supported by all Connections Summer 2016
58_77_Technical.cc.indd 65
65
29/06/2016 09:44
