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

(ii) between live parts and any other metal parts; and
(iii) between live parts and the accessible external surface of the
accessory.
(b) The minimum clearance between switch contacts in the open position for
socket outlet should be 1.2 mm.
(c) 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 pin shown in Figure
A2(4).
(8) Provision of earthing
(a) The socket outlet should be so constructed that, when inserting the plug,
the earth connection is made before the current carrying pins of the plug
become live. When withdrawing the plug, the current carrying parts
should separate before the earth contact is broken.
(b) All accessible metal parts of accessories should be in effective electrical
contact with the earthing socket contact except the metal parts on, or
screws in or through, non-conducting material, and separated by such
material from current carrying parts in such a way that in normal use they
cannot become live, need not be in effective electrical contact with the
earthing socket contact.
(9) Marking
(a) The socket outlet should be legibly and durably marked with the
following information, which should not be placed on screws, removable
washers or other easily removable parts, or upon parts intended for
separate sale:
(i) rated current;
(ii) rated voltage;
(iii) nature of supply.
(b) If symbols are used they should be as follows—
amperes A
volts V
alternating current a.c.
earth or E
220