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

(c) Where cables are to be connected to bare conductors or busbars, it
should be verified that their type of insulation and/or sheath is
suitable for the maximum operating temperature of the bare
conductors or busbars.
(4) Enclosures of wiring installations
(a) The enclosures of wiring installations for conductors and cables
should be selected and installed so that they are suitable for the
extremes of ambient temperature to which they are likely to be
exposed in normal service.
(b) In every vertical channel, duct, ducting or trunking installations
containing conductors or cables, internal barriers should be provided
between floors or at intervals of 5 m whichever is the less so as to
prevent the air at the top of the channel, duct, ducting or trunking
from attaining an excessively high temperature.
(5) External heat sources
(a) To avoid the effects of heat from external sources including solar
gain, one or more of the following methods, or an equally effective
method, should be used to protect the wiring system:
(i) shielding;
(ii) placing sufficiently far from the source of heat;
(iii) selecting a system with due regard for the additional
temperature rise which may occur;
(iv) local reinforcement or substitution of insulating material.
(b) Parts of a cable or flexible cord within an accessory, appliance or
luminaire should be suitable for the temperatures likely to be
encountered, as determined in accordance with Code 15B(1)(a), or
should be provided with additional insulation suitable for those
temperatures.
15C Presence of Corrosive or Polluting Substance (AF)
(a) Where the presence of corrosive or polluting substances is likely to
give rise to corrosion or deterioration, parts of the wiring system
likely to be affected should be suitably protected or manufactured
from materials resistant to such substances.
(b) Metals liable to initiate electrolytic action should not be placed in
contact with each other.
(c) Suitable precautions against corrosion should be taken for metalwork
and metallic parts of wiring systems that are liable to chemical or
electrolytic attack by materials of a structure with which they may
come in contact. Materials likely to cause such attack include:
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