Code of Practice for the Electricity (Wiring) Regulations - 2009 Edition

(b) Subject to subparagraph (a) above, the cross-sectional area of a
protective conductor, other than an equipotential or supplementary
bonding conductor and not forming part of a twin or multicore
cable, that are selected in accordance with the appropriate Tables
11(2), 11(3), 11(4), 11(5), 11(6) and 11(7) are considered acceptable.
Alternatively, the cross-sectional area of the protective conductor
can be calculated using the formula given in regulation 543.1.3 of
BS 7671.
(c) For an earthing conductor, requirements as stipulated in Code 11H
also apply.
(d ) Requirements for the cross-sectional areas of equipotential bonding
conductors and supplementary bonding conductors are described in
Codes 11E and 11F respectively.
(e) Where metallic enclosures for cables, busbar trunking and
switchgear and controlgear assemblies are used as protective
conductors, they should have cross-sectional area equivalent to that
of copper, not less than that resulting from application of the
formula given in regulation 543.1.3 of BS 7671, or in accordance
with Table 11(2).
11D Earthing of Exposed Conductive Parts
(1) General
Unless other effective precautions are taken to prevent danger, such as
the use of double insulated equipment or the use of isolating transformer
to BSEN 61558 or equivalent, all exposed conductive parts of equipment
(other than live parts) should be connected by means of circuit protective
conductors (CPC) to the main earthing terminal of the installation and
the terminal should be connected to earth electrode(s) via earthing
conductor(s).
(2) Types of exposed conductive parts
(a) Exposed conductive parts include:
(i) metallic enclosure of current using equipment, other than
double insulated equipment;
(ii) metallic conduit, trunking and ducting for enclosure of cable(s);
(iii) metallic enclosures of current distribution equipment such as
switchgear and controlgear assemblies.
(b) Exposed conductive parts do not include:
(i) wall brackets and metal parts connected to overhead line
insulators if such parts are not readily accessible;
(ii) inaccessible steel reinforcement in steel reinforced concrete
poles;
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