Handbook of Electrical Installation Practice - BeKnowledge

A wider tray would be desirable because the depth of the group would be less, and
smaller conductor sizes would be needed. On the other hand the supporting steelwork
would be more expensive and space available might be limited. A smaller
width would require very much larger conductors and would not be practicable
except for installations where space is extremely limited.
Depth coefficient Cd = 0.9098, Cs = 1.0.
Selection of Wiring Systems 551
Table 20.8 Armoured cable data for use with groups of cables
on trays.
† Note: Values apply to one-core of a multicore cable, at 70°C.
Conductor size adjustment
Conductors Nos 1, 2, 3, 4 and 9 are too small and should be increased in size. While
some conductors, No. 1 for example, need increasing by one size step, others, such
as No. 3, will clearly need more than one size increment. It is useful to have a simple
guide relating the value of Wc/Wa to the likely number of size increments.
Two features must be taken into account at this stage: