Handbook of Electrical Installation Practice - BeKnowledge

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Special Installations or Locations 253
Proximity of earthed metal
Arduous conditions (possible corrosive effects of chemicals).
The protective measures
Three volumetric zones, A, B and C, are defined by BS 7671 in order to provide
an analytical basis for the design and erection of the electrical installation. It also
recognises the need in a swimming pool environment for portable cleaning equipment
and the desirability of fittings such as special pool luminaires. The zones are
shown in Figs 10.2 and 10.3. As with rooms containing a bath or shower tray, the
2.5m inaccessibility limitation applies.
General requirements in all zones extend to the local supplementary bonding of
all extraneous and exposed-conductive-parts. Requirements for an equipotential
grid changed with the first Amendments to BS 7671: 1992. Where a grid is installed
within the solid floor, in order to ensure that the equipotential principle is maintained
over what could be a substantial area of the building, it is to be supplementary
bonded as any other extraneous-conductive-part. The connections (at remote
ends of the grid) should be accessible for inspection and testing.
Requirements within the zones
Zone A
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Socket-outlets are not permitted
SELV system may be employed, but subject to 12V maximum nominal voltage
and the provision of additional protection against direct contact, comprising:
� Barriers or enclosures to IP2X or IPXXB; or
Fig. 10.2 Zone of dimensions for basin above ground level. The dimensions are measured
taking account of walls and fixed partitions (from BS 7671: 2001).