Cable Derating Factor Table |work| Online

| Ambient Temperature (°C) | PVC Insulation (Max 70°C) | XLPE/EPR Insulation (Max 90°C) | | :--- | :--- | :--- | | | 1.12 | 1.08 | | 25 | 1.06 | 1.04 | | 30 | 1.00 | 1.00 | | 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 |

Derating factors are multipliers applied to the base ampacity to adjust for conditions that impede heat dissipation or increase ambient heat. The governing equation for determining the maximum safe current is: cable derating factor table

As the surrounding temperature rises, the cable’s internal heat adds to the ambient heat, accelerating insulation aging. Derating tables provide multipliers for different temperature ranges. For example, a standard PVC-insulated cable rated for 30°C might have a derating factor of 0.88 at 40°C, and 0.75 at 50°C. Conversely, at very low temperatures, the factor can exceed 1.0, allowing higher currents. | Ambient Temperature (°C) | PVC Insulation (Max

$$I_adjusted = I_base \times F_total$$

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. For example, a standard PVC-insulated cable rated for

What are you following (NEC, IEC, British Standards)? What is the ambient temperature of your installation? How many wires are you running in a single conduit or tray?