Segregation circuits
Where installation comprises mixture low-voltage and very low-
voltage circuits such mains lighting and power, fire alarm and tele-
communication circuits, they must separated segregated prevent
electrical contact (IEE Regulation 528.9
for 4.6
for 6.
Band mains voltage circuits.
● Consider the factors for trunking and shown Table 14.
For the purpose these regulations various circuits are identified one
of two bands follows:
Band telephone, radio, bell, call and intruder alarm circuits, emergency
circuits for fire alarm and emergency lighting.5mm solid cable 8. The tables take this factor into account.9.0mm stranded cable 21.8, the cable factors are:
for 1.0mm stranded conductors
16 6.8.Basic Electrical Installation Work
314
tables the Site Guide space factor 45% must not exceeded.0mm stranded conductors
From Table 14.2
The sum the cable terms is:
(20 8.
. The cor-
rect size trunking accommodate the cables that trunking
which has factor equal greater than the sum the cable
factors.
To calculate the size trunking required enclose number cables:
● Identify the cable factor for the particular size conductor, see
Table 14.
● Multiply the cable factor the number conductors give the
sum the cable factors.0) (20 11.0mm stranded cable 16.0
for 2.9, 38mm
trunking has factor 1146 and, therefore, the minimum size trunking accommodate
these cables 38mm, although larger size, say 50mm would equally
acceptable this was more readily available standard stock item.5mm solid conductors
20 2.9) (21 16.5mm solid cable 11. From table 14.
Example
Calculate the minimum size trunking required accommodate the following single-core
PVC cables:
20 1.5mm solid conductors
21 4.8.1).6) (16 21.
This means that the cables must not fill more than 45% the space
enclosed the trunking.2) 1085
