60-61 / 319
klik.system | Specification guide to prefabricated wiring systems
10
Design current
The design current for discharge lighting must take into
account control gear losses and harmonic current.
Overcurrent protective devices
The characteristics of the overcurrent protective device must
take into account inrush and starting currents e.g. those
associated with transformers and discharge lighting.
Cross-sectional area of live conductors
BS 8488 prescribes that the rated current shall be assigned
according to a reference method defined by the manufacturer
from BS 7671:2008, Table 4A2. Also, the rated current and
cross-sectional area of the wiring section conductors shall be
determined on the following basis:
• The number of loaded cores defined by the manufacturer.
A loaded core is where the conductor carries more than 30%
of its rating, after applying the rating factor for the total
number of current carrying cores
• Not being grouped with other wiring systems or cables
• Not being in contact with thermal insulation
• The ambient temperature not exceeding 30 °C
• The frequency of operating being not greater than 61 Hz
Fundamentals in the BS 7671 design process
(this list is not exhaustive)
“ BS 8488 requires the rated current to
be marked on each section ”.