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klik.system | Specification guide to prefabricated wiring systems
14
“ Account should be taken of voltage
drop in each part of the circuit, reduced
conductor temperature and connector
contact resistance ”.
Voltage drop
To avoid an over engineered and unreliable system, key
aspects to be accounted for include:
• The voltage drop is determined for individual loads,
including any line conductors passing through a switch /
control device. The total voltage drop being calculated for
each part of the circuit respectively.
• Suitable adjustment for reduced conductor temperature,
where the design current of a circuit is less than the
effective current-carrying capacity of the cable.
• Suitable adjustment for load power factor.
• Suitable adjustment for influence of connector contact
resistance.
Voltage drop and flexible cables
BS 8488 identifies that prefabricated wiring systems may
employ flexible cables, however because the nominal
resistance of flexible conductors is higher than that for solid
or stranded conductors a suitable factor must be applied
when basing the flexible cables on the reference methods in
appendix 4.
BS 7671 appendix 4 identifies that to obtain the correct
voltage drop for cable types similar to those covered by
tables 4D1 etc but with Class 5, flexible conductors, the
tabulated values are multiplied by the relevant factor. The
factor for cables up to and including 16mm
2
is shown in table
2.
Cable size
Voltage drop factor
≤16.0mm
2
1.10
Table 2