Published: 17 June 2011
Category: Technical articles
In addition to providing adequate support, the method of support for fire alarm cables should be non-combustible
Fire alarm cables supported only by means such as plastic tie clips or plastic trunking can create a serious hazard to fire fighters, who may become entangled in the cables in the event of a fire.
Additionally, BS 5839-1 Fire detection and fire alarm systems in buildings (clause 26.2(f)) requires that methods for cable support should be non-combustible such that circuit integrity will not be reduced below that afforded by the cable used. The support should be able to withstand a similar temperature to that of the cable and maintain adequate support for the duration at least equal to the fire resisting properties of the cable (that is, 30 minutes or 120 minutes, as applicable). This is additional to the requirement for maintaining adequate support for the cable found in BS 7671.
Consequently, if a periodic inspection of a fire alarm system reveals that the cables are not adequately supported to meet the above requirements, a Recommendation Code 2 should be recorded on the Periodic Inspection Report, and an 'unsatisfactory' (or X) inserted in the 'Erection methods' box on the Schedule of Inspections.
Solution
All cables used for fixed wiring, including those for fire detection and fire alarm systems, are required to be properly supported to avoid damage to the sheath, insulation or terminations of the cables during installation, use or maintenance (Regulation 522.8.1 refers)Additionally, BS 5839-1 Fire detection and fire alarm systems in buildings (clause 26.2(f)) requires that methods for cable support should be non-combustible such that circuit integrity will not be reduced below that afforded by the cable used. The support should be able to withstand a similar temperature to that of the cable and maintain adequate support for the duration at least equal to the fire resisting properties of the cable (that is, 30 minutes or 120 minutes, as applicable). This is additional to the requirement for maintaining adequate support for the cable found in BS 7671.
Consequently, if a periodic inspection of a fire alarm system reveals that the cables are not adequately supported to meet the above requirements, a Recommendation Code 2 should be recorded on the Periodic Inspection Report, and an 'unsatisfactory' (or X) inserted in the 'Erection methods' box on the Schedule of Inspections.
Regulation 522.8.1
A wiring system shall be selected and erected to avoid during installation, use or maintenance, damage to the sheath or insulation of cables and their terminationsBS 5839-1: clause 26.2(f)
Methods of cable support should be non-combustible and such that the circuit integrity will not be reduced below that afforded by the cable used, and should withstand a similar temperature and duration to that of the cable, while maintaining adequate supportNote 8 - In effect, this recommendation precludes the use of plastic clips ties or trunking, where these products are the sole means of cable support
Note 9 - Experience has shown that collapse of cables, supported only by plastic trunking, can create a serious hazard to fire fighters, who become entangled in the cables.