Interactive tool
Ring Final Circuit R1+R2 Predictor
Step 1: r1 = rn (line, neutral)
0.26 Ω
Step 1: r2 (cpc)
0.42 Ω
Step 2 expected at every socket
0.13 Ω
Step 3 / recorded R1+R2
0.17 Ω
Computed Zs (Ze + R1+R2)
0.52 Ω
Table 41.3 maximum Zs
1.37 Ω
Verdict
PASS
Resistance values are taken from IET Guidance Note 3 Table B1 at 20 °C and corrected by F = 1 + 0.004 x (T - 20). Maximum Zs values are from BS 7671:2018+A2:2022 Table 41.3 (0.4 s disconnection at 230 V, Cmin = 0.95). The recorded R1+R2 is the worst-case Step 3 reading at the midpoint of an unbroken ring.