Derating Factor For Cables ~repack~ -

| | 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 |

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. derating factor for cables

| | 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 | | | Reference Temp

Note: Always check manufacturer tables for exact values. When multiple cables run together, each heats its neighbors. The closer and more cables, the higher the derating. Soil’s ability to dissipate heat varies

[ 0.85 \times 0.70 \times 0.75 = 0.446 ]

[ 200 , A \times 0.446 = 89.2 , A ]

| | Thermal Resistivity | Derating factor | |------------------------|-------------------------|---------------------| | Damp clay/loam | 1.0 – 1.5 | 1.05 – 1.10 | | Standard (IEC assumed) | 2.5 | 1.00 | | Dry sand/gravel | 3.0 – 4.0 | 0.70 – 0.85 | 4. Depth of Burial (for buried cables) Deeper burial reduces heat dissipation (soil is cooler but more insulating).