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Table B1: the expected value from the bookWhat should a 45 metre radial read?
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The other way to an expected result is Guidance Note 3 · Appendix B · Table B1, which gives conductor resistance in milliohms per metre at 20 °C, and the formula below turns it into a resistance.
For a line-and-cpc pair you add the two conductors' figures together. That is why 2.5 mm² with a 1.5 mm² cpc comes to 19.51 mΩ/m: 7.41 for the line plus 12.10 for the cpc.
A 45 m radial in 6/2.5 mm², at 20 °C
6 mm² = 3.08 mΩ/m
2.5 mm² = 7.41 mΩ/m
Combined = 3.08 + 7.41 = 10.49 mΩ/m
R1 + R2 = (10.49 × 45) ÷ 1000
= 0.47 Ω
A 30 m cooker circuit in 6/2.5 mm²
R1 + R2 = (10.49 × 30) ÷ 1000
= 0.31 Ω
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