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

14E Cable Capacity of Enclosures
(1) General requirements
The numbers of cables drawn into, or laid in, an enclosure of a wiring
installation should be such that no damage is caused to the cables or to
the enclosure.
(2) Determination of cable capacities
Cable capacities of conduit and trunking enclosing single-core PVC
insulated cables can be determined by the ‘unit system’ method
described below:
(a) Straight runs of conduit not exceeding 3 m in length:
(i) For each cable to used, obtain the appropriate cable factor from
Table 14(2)(a).
(ii) Add all the cable factors so obtained and compare with the
conduit factors given in Table 14(2)(b).
(iii) The conduit size is considered satisfactory if the conduit factor is
equal to or exceeds the sum of the cable factors.
(b) Straight runs of conduit exceeding 3 m in length or in runs of any
length incorporating bends or sets:
(i) For each cable to be used, obtain the appropriate cable factor
from Table 14(3)(a).
(ii) Add all the cable factors so obtained and compare with the
conduit factors given in Table 14(3)(b), taking into account of
the length of run and number of bends in that run.
(iii) The conduit size is considered satisfactory if the conduit factor is
equal to or exceeds the sum of the cable factors.
(iv) The term ‘bend’ signifies a 90° bend and one double set is
equivalent to one bend.
(c) Trunking of any length of run:
(i) For each cables to be used, obtain the appropriate cable factor
from Table 14(4)(a).
(ii) Add all the cable factors so obtain and compare with the
trunking factors given in Table 14(4)(b).
(iii) The trunking size is considered satisfactory if the trunking factor
is equal to or exceeds the sum of the cable factors.
(d ) For sizes and types of cable and sizes of trunking other than those
given in Tables 14(4)(a) and 14(4)(b), the number of cables drawn
into a trunking should be such that the resulting space factor should
not exceed 45%.
(Note: Space factor is defined as the ratio (expressed as a
percentage) of the sum of the overall cross-sectional area of
cables (including insulation and any sheath) to the internal
cross-sectional area of the trunking in which they are
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