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

(5) Screws and connections
(a) Screwed connections, electrical and otherwise should withstand the
mechanical stresses occurring in normal use. Screws transmitting
electrical contact pressure should screw into metal.
(b) Screws should not be of insulating material if their replacement by a
metal screw would affect the safety or performance requirements of the
accessory.
(c) Where current carrying parts are screwed together, the current path
should not rely on the screw threads.
(d ) Screws and nuts for clamping the conductors should not serve to fix any
other component.
(6) Creepage distances, clearances and distances through
insulation
(a) When the socket outlet is correctly assembled and wired with the
appropriate cable, the minimum clearance through air and the minimum
creepage distance should be 4 mm:
(i) between live parts of opposite polarity;
(ii) between live parts and any other metal parts; and
(iii) between live parts and the accessible external surface of the
accessory.
(b) The socket outlet should have a minimum distance of 2 mm between
insulated live parts and the accessible external surface.
(7) Accessibility of live parts
Socket outlets should be so designed that when mounted and wired as in
normal use, live parts are not accessible as tested by a test finger shown in
Figure A3(6).
(8) Provision for earthing
(a) The socket outlet should be so constructed with earthing contacts which
should be directly connected to an internal earthing terminal.
(b) Metalclad socket outlets should be provided with an earthing terminal
intended for connection of an external earthing conductor, except for
flush type socket outlets, this earthing terminal should be so arranged
that the protective conductor of the cable, if any, is visible at least when
the plug or appliance inlet is removed from the corresponding socket
outlet.
(c) All accessible metal parts of the socket outlet should be in effective
electrical contact with the earthing contact except that metal parts on, or
screws in or through, non-conducting material, and separated by such
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