screwed steel conduit). However, BS 5266-1: 2011 adds to each of these groups a new type of wiring system, referred to as ‘Enhanced’, which has an increased duration of survival in a fire. A further change is that, unlike BS 5266-1: 2005, BS 5266-1: 2011 does not refer to ‘Cables and cable systems requiring additional fire protection’. Table 1 of this article summarises the above changes. The old classification of ‘Cables and cable systems requiring additional fire protection’, which is not included in BS 5266-1: 2011, consisted of non-fire-resisting cables in conduit, or non-fire-resisting steel wire
armoured cables, with additional fire protection by means such as burying in the structure of the building. The reason this classification is not included in BS 5266-1: 2011 is the practical difficulties of verifying the fire performances of conduits and building structures, and because cables buried in the structure have to leave it at some point. Table 2 summarises the recommendations of BS 5266-1: 2011 for the selection of wiring systems for the connection of emergency escape lighting luminaires to a central power supply, which are given in clause 8.2.2.
Table 2 Cables and cable systems in BS 5266-1: 2011 for the connection of emergency escape lighting luminaires to a central power supply (Notes 1 and 2)
Cables with an inherently high resistance to attack by fire (Note 3).
Enhanced cables with an inherently high resistance to attack by fire (Note 4).
• Mineral insulated cable to BS EN 60702-1: 2002 with terminations conforming to BS EN 60702-2: 2002, or • Multi-core fire-resistant screened cables having low emission of smoke and corrosive gases when affected by fire, conforming to BS 7629-1, or • Thermosetting insulated, armoured, fire-resistant cables having low emission of smoke and corrosive gases when affected by fire, to BS 7846.
All with 60 minutes duration of survival when tested in accordance with BS EN 50200: 2006, Annex D, and 30 minutes when tested in accordance with BS EN 50200: 2006, Annex E.
• Mineral insulated cable to BS EN 60702-1: 2002 with to terminations to BS EN 60702 2: 2002, or • Multi-core fire-resistant screened cables having low emission of smoke and corrosive gases when affected by fire, conforming to BS 7629-1, or • Thermosetting insulated, armoured, fire-resistant cables having low emission of smoke and corrosive gases when affected by fire, to BS 7846.
All with 120 minutes duration of survival when tested in accordance with BS EN 50200: 2006, Annex D, and 120 minutes when tested in accordance with BS 8434-2.
Cable systems with an inherently high resistance to attack by fire (Note 3).
Fire-resistant single-core or multicore cables enclosed in screwed steel conduit, such that 60 minutes’ duration of survival is given by the cable system. The cable should meet the requirements of IEC 60331-3 for a flame application time of 60 minutes.
Enhanced cable systems with an inherently high resistance to attack by fire (Note 4) .
Fire-resistant single-core or multicore cables enclosed in screwed steel conduit, such that 120 minutes’ duration of survival is given by the cable system. The cable should meet the requirements of IEC 60331-3 for a flame application time of 120 minutes.
Notes. 1) Cables and cable systems should be routed through areas of low risk wherever practicable. 2) Methods of cable support and fixings should meet the recommendations of clause 8.2.3 of BS 5266-1: 2011, relating to (amongst other things) non-combustibility and distances between supports. All other recommendations of clause 8 (Wiring systems and circuits) should also be followed. 3) The recommendations of BS 5266-1: 2008 for selection of these non-enhanced cables and cable systems are similar to those of BS 5266-1: 2005. 4) Enhanced cables or cable systems would be recommended where the designer, specifier or regulatory authority judge these to be necessary based on a fire risk assessment. Examples include: • unsprinklered buildings (or parts of) in which the evacuation is phased over four or more stages • unsprinklered buildings greater than 30 m high • unsprinklered premises or sites where a fire in one could affect cables associated with areas remote from the fire, and it is envisaged that people will remain in occupation during the fire.
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