BICC or BS7671 comply for design

Thank you for your response OMS. By "correction", do you mean applying de-rating factors for different conditions or do you mean something else not included in BS7671? 


If the values match up exactly then its not an issue but I have had situations where BS7671 gives a higher required cable size compared to BICC, according to Amtech as I do not have a copy of BICC data. For example, for the following conditions, I was getting minimum 95mm^2 (BS7671 installation method 70) vs 70mm^2 (BICC in Underground single way ducts) for a 4 core cable with SWA and XLPE insulation (ie 90C). In this case, would you say there is any reasonable justification to go with the lower BICC cable size if calculations based on the standard suggest a larger cable size?


1 - Depth of lay - 0.8m

2 - Spacing,

3 - In ducts or buried direct - ducts

4 - Ground Temperature - 15degC

5 - Soil Thermal Resistivity - 1.2K.m/W

6 - Air temperature - 30degC

Thank you for your response OMS. By "correction", do you mean applying de-rating factors for different conditions or do you mean something else not included in BS7671? 


If the values match up exactly then its not an issue but I have had situations where BS7671 gives a higher required cable size compared to BICC, according to Amtech as I do not have a copy of BICC data. For example, for the following conditions, I was getting minimum 95mm^2 (BS7671 installation method 70) vs 70mm^2 (BICC in Underground single way ducts) for a 4 core cable with SWA and XLPE insulation (ie 90C). In this case, would you say there is any reasonable justification to go with the lower BICC cable size if calculations based on the standard suggest a larger cable size?


1 - Depth of lay - 0.8m

2 - Spacing,

3 - In ducts or buried direct - ducts

4 - Ground Temperature - 15degC

5 - Soil Thermal Resistivity - 1.2K.m/W

6 - Air temperature - 30degC