Note: The current carrying capacity for cables laid in direct contact with soil having a thermal resistivity of 2.5K.m/W and at a depth of 0.7m is approximately 10% higher than the values tabulated for Reference Method D. If the specific installation parameters are known (thermal resistance of the ground, ground ambient temperature, cable depth), reference can be made to the cable manufacturer or the ERA 69-30 series of publications, which may result in a smaller cable size being selected. The values given for this method are those stated in Appendix 4 of BS 7671 and are based on conservative installation parameters. standard circuit tables have assumed flat twin and earth cable to BS 6400 with reduced. The cable is drawn into a 100mm diameter plastic, earthenware or metallic duct laid in direct contact with soil having thermal resistivity of 2.5K.m/W and at a depth of 0.7m. 17th Edition IEE Wiring Regulations (BS 7671:2008) Darrell Locke. Flat, twin and earth cables installed in thermal insulation are. For example - Installation method 70 of Table 4A2 (multicore armoured cable in conduit or in cable ducting in the ground). Rating factors for soil thermal resistivities other than 2.5 K.m/W are given in Table 4B3.
0 Comments
Leave a Reply. |