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

(2) Isolating devices
(a) An isolating device should be capable of:
(i) opening and closing all live conductors (i.e. phase and neutral
conductors) of the circuit under no-load condition provided
that, for a 3-phase 4-wire a.c. supply, a linked isolator may be
arranged to disconnect the phase conductors only and in such
case, a link should be inserted in the neutral conductor and
securely fixed by bolts or screws;
(ii) carrying the normal circuit current;
(iii) carrying for a specified time abnormal currents which may occur
during an overcurrent condition (i.e. overload or short-circuit).
(b) The position of the contacts or other means of isolation should be
either externally visible or clearly and reliably indicated. An indication
of the isolated position should occur only when the specified
isolation has been obtained in each pole.
(c) An isolating device should be designed and/or installed so as to
prevent unintentional or inadvertent closure.
(d ) The following devices satisfying subparagraphs (a), (b) and (c) are
acceptable as means of isolation:
(i) isolators (disconnectors),
(ii) fuse switches and switch-fuses,
(iii) links, including fuse-links and fuse cut-outs,
(iv) plugs and socket outlets,
(v) cable couplers,
(vi) circuit breakers, including miniature circuit breakers (MCB),
moulded case circuit breakers (MCCB) and residual current
circuit breakers (RCCB).
(e) Emergency stop push button and semiconductor devices, such as a
‘touch control switch’ or ‘photo-electric switch’, must not be used
for isolation.
(f ) Where an isolating device for a particular circuit is placed remotely
from the equipment to be isolated, provision should be made so that
the means of isolation can be secured in the open position. Where
this provision takes the form of a lock or removable handle, the key
or handle should be non-interchangeable with any other used for a
similar purpose within the premises.
(g) Each device used for isolation should be clearly identified by position
or durable marking to indicate the installation or circuit it isolates.
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