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

(h) In damp situations, enclosures for cores of sheathed cables from
which the sheath has been removed and for non-sheathed cables at
terminations of conduit, duct, ducting or trunking systems, should
be damp proof and corrosion resistant.
(i) Metallic sheaths, conduits etc. in installations underwater or likely to
be underwater should not be relied upon as the only protective
conductor and a separate copper protective conductor should be
used.
(3) Switches and socket outlets
(a) Switches having watertight enclosures with minimum IP54 or
equivalent are acceptable for an installation exposed to weather.
(b) Socket outlets complying with IEC 60309-2 or equivalent and
provided with a push-on cap and cap retaining ring or a screw-on
cap with rubber gasket are acceptable for an installation exposed to
weather. The socket outlets should also have a degree of protection
of at least IPX4 or equivalent.
15B Ambient Temperature (AA)
(1) General
(a) A wiring system should be selected and erected so as to be suitable
for the highest and lowest local ambient temperature likely to be
encountered.
(b) The components of a wiring system, including cables and wiring
enclosures should be installed or handled only at temperatures
within the limits stated in the relevant product specification or as
recommended by the manufacturer.
(2) Electrical insulations
The maximum permissible operating temperature for various classes of
insulation complying with IEC 60085 are given in Table 15(1).
(3) Conductors and cables
(a) The type and current carrying capacity of every conductor, cable and
flexible cord, termination and joint should be selected so as to be
suitable for the highest operating temperature likely to occur in
normal service, account being taken of any transfer of heat from any
accessory, appliance or luminaire to which the conductor, cable or
flexible cord is connected.
(b) The maximum operating and ambient temperatures, in general, for
various types of cable insulations are given in Table 15(2).
106