Ask the experts/Technical
Fully charged Fig 2 Example of Regulation 522.6.202
Wall
Conditions applying to cables embedded in a wall or partition at a depth of less than 50 mm from surfaces
Wall
Wall
Point or accessory etc Zone within 150 mm of the top of the wall - Regulation 522.6.202 (i) Zone within 150 mm of an angle formed by adjoining walls or partitions - Regulation 522.6.202 (i) Zone either horizontally or vertically, to the point, accessory or switchgear on the surface of the wall or partition, to which the cable is connected - Regulation 522.6.202 (i)
50 mm from the surface of walls and partitions having internal metallic construction. It should be noted that additional protection by an RCD may be required where cables are installed in walls or partitions; however, an RCD is not recognised as providing mechanical protection against impact and is therefore not discussed in this article (see Regulations 522.6.202 and 522.6.203). Fixed equipment and accessories As with wiring systems, fixed equipment and accessories (equipment for short) for a planned installation should be selected and erected for the impact risks (and other external influences), identified during assessment. Where practicable, equipment should be located so as to minimise the risk of impact, for example, in a location having moving vehicles mounting accessories at a suitable height to avoid impact from vehicles whilst still providing accessibility. Equipment that has to be installed where a risk of impact exists should be of such construction to provide sufficient mechanical strength to resist damage should impact occur. The type of fixings used to secure equipment to the structure should also have sufficient mechanical strength. 54
Alternatively, and as permitted by Regulation 512.2.2, additional mechanical protection suitable to withstand the foreseen impact may be provided. For example, where equipment may be subject to vandalism the equipment should be of robust construction to resist such attacks or be given additional protection, such as a metallic enclosure or metallic guard. Where additional protection, such as an enclosure, is applied, it is important that it has no adverse effects on the enclosed equipment through, for example, reduced heat dissipation. Summary In order to minimise impact and subsequent danger, electrical installations must be designed and installed in accordance with the applicable requirements of BS 7671, so they are suitable for the local environment. In particular, cables buried in the ground or installed in walls, floors and ceilings pose an increased risk of impact; they are typically not instantly visible to, for example, persons carrying out building works, and consequently BS 7671 requires robust measures. Further information on impact and other snags may be found in Snags and Solutions Part 2 available from niceicdirect.com.
Spring 2016 Connections
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05/04/2016 11:55