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

(Note: 1. An extraneous conductive part means a conductive part liable
to introduce a potential, generally an earth potential, that
does not form part of an electrical installation.
(Note: 2. Connection of a lightning protection system to the main
equipotential bonding should be made in accordance with
relevant standard as specified in Code 26I.)
(b) In a large installation, where there are a number of equipotential zones,
these zones should be bonded together to form one equipotential zone.
(c) Aluminium or copperclad aluminium conductors should not be used for
bonding connections to water pipes likely to be subjected to
condensation in normal use.
(d ) Main equipotential bonding conductors should have cross-sectional areas
not less than half the cross-sectional area of the earthing conductor of
the installation, subject to a minimum of 6 mm2 copper equivalent, and
need not exceed 25 mm2 copper equivalent.
(e) (i) Main equipotential bonding connections to any gas or water services
should be made as near as practicable to the point of entry of those
services into the premises; provided that where there is an insulating
section or insert at that point, the connection should be made to the
metalwork on the consumer’s side of that section or insert.
(ii) In particular, for gas services, the bonding connection should be
made on the consumer’s side of the meter (i.e. between the meter
outlet union and any branch pipework). This connection is
recommended to be made within 600 mm of the gas meter.
(f ) For application of equipotential bonding and earthing in buildings with
information technology equipment, reference can be made to BS EN
50310.
11F Supplementary Bonding
(a) Within the zone formed by the main equipotential bonding, local
supplementary bonding connections should be made to metal parts, to
maintain the equipotential zone, where those parts are:
(i) extraneous conductive parts, and
(ii) simultaneously accessible with exposed conductive parts or other
extraneous conductive parts, and
(Note: a separation of not more than 2 m is generally considered
to be simultaneously accessible.)
(iii) not electrically connected to the main equipotential bonding by
permanent and reliable metal-to-metal joints of negligible
impedance.
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