Although the load is only 75 Amps, the installer must use a 25 mm² cable. A 16 mm² cable would overheat under these specific installation conditions, despite being rated for currents higher than 75A in isolation.
Where:
| Ambient Temp (°C) | Derating Factor (PVC, 30°C base) | |------------------|----------------------------------| | 30 | 1.00 | | 35 | 0.94 | | 40 | 0.87 | | 45 | 0.79 | | 50 | 0.71 | cable derating factor table
A 10 mm² copper cable has a base ampacity of 60 A in free air at 30°C. If installed in a 45°C ambient (factor 0.79) with three other circuits (factor 0.70), the final ampacity is: 60 A × 0.79 × 0.70 = 33.18 A . Thus, the load current must not exceed 33 A, not the nominal 60 A. Although the load is only 75 Amps, the
Derating factor tables are organized around three main environmental and installation parameters: If installed in a 45°C ambient (factor 0
Note: Factors apply to adjacent cables. If spacing between cables is greater than the cable diameter, factors may be improved.