Soil Thermal Resistivity Derating Factors
From Open Electrical
Following values are valid for the standards IEC 60364-5-52 and BS 7671. Derating factors for installing cables in soil with thermal resistivity other than 2.5 K·m/W.
| Soil Thermal Resistivity (K·m/W) | Soil Thermal Resistivity Derating Factor | |
|---|---|---|
| Buried Direct | Buried in Conduit | |
| 0.5 | 1.88 | 1.28 |
| 0.7 | 1.62 | 1.2 |
| 1 | 1.5 | 1.18 |
| 1.5 | 1.28 | 1.1 |
| 2 | 1.12 | 1.05 |
| 2.5 | 1 | 1 |
| 3 | 0.9 | 0.96 |
Tableau 52M - Facteurs de correction pour les câbles enterrés en fonction de la résistivité thermique du sol
Following values are only for the NF C 15-100. Derating factors for installing cables in soil with thermal resistivity other than 1 K·m/W.
| Soil Thermal Resistivity K.m/W | Derating factors |
|---|---|
| 0.40 | 1.22 |
| 0.50 | 1.17 |
| 0.70 | 1.12 |
| 0.85 | 1.06 |
| 1.00 | 1 |
| 1.20 | 0.94 |
| 1.50 | 0.87 |
| 2.00 | 0.79 |
| 2.50 | 0.71 |
| 3.00 | 0.61 |
