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

(b) Facilities should be incorporated in the busbar casing to provide
access to the busbars at regular intervals throughout the entire
length. Removal of the cover for access facility should necessitate the
use of tools.
(3) Busbar
(a) For busbar installation having a rated capacity not exceeding 400
amperes in each phase of a 3-phase 4-wire system, the associated
neutral busbars should have a cross-sectional area not less than the
cross-sectional area of the phase busbar.
(b) For busbar installation having a rated capacity exceeding 400A in
each phase of a 3-phase 4-wire system, the associated neutral
busbar may have a cross-sectional area smaller than the cross
sectional area of the phase busbar if overcurrent detection is
provided for the neutral conductor, which is appropriate to the
cross-sectional area of the conductor. This detection shall cause the
disconnection of the phase conductors but not necessarily the
neutral conductor.
(c) The joint part of the busbar, or contact part of the busbars in the
case of plug-in busbar trunking systems, should be electroplated
with tin or other equivalent materials.
(d ) Drilling of all-insulated busbars for connection of cables are not
acceptable.
(4) Expansion unit
Proper expansion unit should be provided where:
(a) both ends of the busbar trunking system are fixed, or
(b) the busbar trunking system is installed across a building expansion
joint, or
(c) the run of busbar exceeds 30 metres or as recommended by the
busbar manufacturer.
(5) Feeder unit
A proper feeder unit should be provided for each busbar trunking system
for connection of incoming supply.
(6) Tap-off unit
(a) Proper tap-off unit should be used where a branch circuit is taken
off from the busbars.
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