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

Code 6 CIRCUIT ARRANGEMENT
6A Division of Installation into Circuits
(a) An electrical installation should be divided into circuits where necessary
or practicable and each circuit should be separately protected and
controlled.
(b) A schematic wiring diagram showing the main distribution system should
be displayed near the main switch with rating 100A or above.
6B Basic Requirements of Circuits
(1) Protection
(a) Each circuit should be protected by an overcurrent protective device
with its operating current value closely related to the current
demand of the current using equipment connected or intended to
be connected to it and to the current carrying capacity of the
conductor connected. This arrangement will avoid danger in the
event of a fault by ensuring prompt operation of the protective
device at the appropriate current value which will otherwise cause
damage to the cable or the current using equipment.
(b) A fault on one circuit should not result in the shutting down of any
unrelated parts of the installation as far as reasonably practicable.
For this, it is recommended that—
(i) fixed lighting fittings of an installation should be arranged to be
fed by two or more final circuits;
(ii) lighting final circuits should be electrically separated from power
circuits except that it may be connected to bell transformers or
electric clocks;
(iii) power circuits for kitchens should be electrically separated from
other power circuits.
(c) Where the supply is designed to be taken from more than one
transformer, interconnection facilities between the main incoming
circuit breakers should be provided if requested by the electricity
supplier. All incoming and interconnection circuit breakers should be
of 4-pole type interrupting all live conductors (i.e. phase and neutral
conductors) and electrically and mechanically interlocked to prevent
the electricity supplier’s transformers from operating in parallel.
(Note: Castell key interlock is one of the acceptable means of
mechanical interlock. When an installation utilizes more than
one set of castell key interlocks, each set of keys should be
different from others so that the key can only be inserted to
the switchgear intended to be controlled. No redundant
castell keys should be readily available.)
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