Derating Factor For Cables !!better!! Access

| | Reference Temp. | Derating at 50°C | Derating at 60°C | |----------------------|--------------------|----------------------|----------------------| | PVC | 30°C | 0.71 | 0.58 | | XLPE / EPR | 40°C | 0.89 | 0.77 |

A derating factor is a multiplier (less than 1) applied to a cable’s rated current-carrying capacity to reduce its maximum allowable load. This ensures the cable operates within safe temperature limits under real-world conditions. derating factor for cables

For cables in conduit/trunking, use similar or stricter factors. NEC Table 310.15(C)(1) provides detailed adjustments. Soil’s ability to dissipate heat varies. Standard assumes ( R_th = 2.5 , K·m/W ) (damp soil). Dry or sandy soil reduces ampacity. | | Reference Temp

| | Arrangement | Derating factor | |----------------------|--------------------------------|---------------------| | 1 | Single circuit, free air | 1.00 | | 2–3 | Touching, in air | 0.80–0.85 | | 4–5 | Touching, in air | 0.70–0.75 | | 6–8 | Touching, in air | 0.60–0.65 | | >9 | Touching, in air | 0.50–0.55 | For cables in conduit/trunking, use similar or stricter

[ 0.85 \times 0.70 \times 0.75 = 0.446 ]