Table 4.5 - Derating factors (Ci) for cables up to 10mm˛ in cross-sectional area buried in thermal insulation.
Length in insulation (mm)
Derating factor (Ci)
50
0.89
100
0.81
200
0.68
400
0.55
500 or more
0.50

Extracted from The Electricians Guide Fifth Edition
by John Whitfield

Published by EPA Press
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