Chapter A General rules of electrical installation design

G - Sizing and protection of conductors
2 Practical method for determining
the smallest allowable crosssectional
area of circuit conductors
b Ambient temperature
The current-carrying capacities of cables in the air are based on an average air
temperature equal to 30 °C. For other temperatures, the correction factor is given in
Figure G12 for PVC, EPR and XLPE insulation material.
The related correction factor is here noted k 1.
Ambient temperature °C Insulation
PVC XLPE and EPR
10 1.22 1.15
15 1.17 1.12
20 1.12 1.08
25 1.06 1.04
35 0.94 0.96
40 0.87 0.91
45 0.79 0.87
50 0.71 0.82
55 0.61 0.76
60 0.50 0.71
65 - 0.65
70 - 0.58
75 - 0.50
80 - 0.41
Fig. G12 : Correction factors for ambient air temperatures other than 30 °C to be applied to the
current-carrying capacities for cables in the air (from table A.52-14 of IEC 60364-5-52)
The current-carrying capacities of cables in the ground are based on an average
ground temperature equal to 20 °C. For other temperatures, the correction factor is
given in Figure G13 for PVC, EPR and XLPE insulation material.
The related correction factor is here noted k 2.
Ground temperature °C Insulation
PVC XLPE and EPR
10 1.10 1.07
15 1.05 1.04
25 0.95 0.96
30 0.89 0.93
35 0.84 0.89
40 0.77 0.85
45 0.71 0.80
50 0.63 0.76
55 0.55 0.71
60 0.45 0.65
65 - 0.60
70 - 0.53
75 - 0.46
80 - 0.38
Fig. G13 : Correction factors for ambient ground temperatures other than 20 °C to be applied to
the current-carrying capacities for cables in ducts in the ground (from table A.52-15 of
IEC 60364-5-52)
Schneider Electric - Electrical installation guide 2008
G11
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