BS 7671:2018+A4:2026 Tables 41.2, 41.3, 41.4 & Appendix 14
Max Zs Calculator (BS 7671)
Calculate maximum earth fault loop impedance (Zs) for Type B, C, D MCBs and fuses with 80% temperature correction rule.
BS 7671 Tabulated Max Zs (100%): 1.37 Ω
80% Temperature Corrected Max Zs (0.8 Rule): 1.10 Ω
Enter measured Zs to compare against BS 7671 limits