Premature collapse of wiring systems

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.

In addition to general low voltage lighting and power, electrical installation work, particularly in commercial and industrial premises, can oft en consist of a range of installation systems, including, among others, fi re 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.

The scope of BS 7671

BS 7671 is applicable to the design, erection and verifi cation 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 specifi cally 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 fi xed 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 specifi c technology standards that may apply.

British or Harmonised Standards 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 fi re, such as a fi re detection and fi re 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 fi re.

Therefore, for example, on completion of the installation of such a system, in addition to an appropriate certifi cate to confi rm compliance with the relevant parts of the particular standard, such as the BS 5839 series for a fi re detection and fi re alarm system (Regulation 560.10 refers), an Electrical Installation Certifi cate or, where appropriate, a Minor Electrical Installation Works Certifi cate, should also be issued to certify the fi xed wiring of the fi re detection and fi re alarm system for compliance with BS 7671.

Due to their function, systems to BS 5839-12 and BS 52663 are generally installed using fi re-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 fi re.

The defi nition of what constitutes an escape route was the subject of a previous article in Connections 196, and includes not only defi ned routes such as corridors, stairways and hallways, but also open areas.

BRITISH STANDARD

Requirements for Electrical Installations

BS 7671: 2008

Incorporating Amendment 1: 2011 Corrigendum 2013 Amendment 2: 2013 Amendment 3: 2015

IET Wiring Regulations Seventeenth Edition

© The Institution of Engineering and Technology and BSI NO COPYING IN ANY FORM WITHOUT WRITTEN PERMISSION

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

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 Classifi cation 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

Fully charged

Fig 1 Premature collapse of

cables in escape routes

sectors of the electrical industry, recommends that a code C3 is recorded for domestic and similar electrical installations. The code refl ects the level of safety risk for persons escaping from the premises in the conditions of fi re.

For a location other than an individual dwelling, such as a communal area forming part of an escape route, BPG 4 recommends that a code C2 potentially dangerous would be more appropriate due to the increased risk. This requires immediate remedial action to be undertaken to address the danger identifi ed.

For wiring systems installed in non-domestic premises the same coding for wiring systems installed in escape routes should be applied. The inspector should note that whilst wiring systems for network/data/telecommunication cabling and the like may not be included on the ‘circuit details’ of the Electrical Installation Condition Report, they should still record any noncompliance and code accordingly.

NOTE: The requirements of Regulation 521.11.201 are not applicable for wiring systems installed above the escape route within the fabric of the building, such as those routed above a ceiling or behind a wall.

2 Fire detection and fire alarm systems for buildings – Part 1:

Code of practice for the design, installation, commissioning and maintenance of systems in non-domestic premises.

3 Emergency lighting –

Part 1: Code of practice for the emergency escape lighting of premises. Summary

Those responsible for the installation of wiring systems or the periodic inspection of electrical installations, including those installations containing data cabling and the like, should be aware that wiring systems not supported in accordance with Regulation 521.11.201 may, as shown in Fig 1, collapse prematurely during the conditions of fi re and drop into the escape route.