Zs Calculator (Ze + R1+R2)
Calculate Zs at the furthest point of a circuit from external loop impedance (Ze) and continuity (R1+R2). Compare against BS 7671 Table 41.3 maximum permitted values.
Enter Ze and R1+R2 to calculate Zs.
The PDF is a calculation record, not a certificate — it carries no declaration and no signature.
Method and standard
Formula
Zs = Ze + (R1 + R2). Pick a protective device and rating to compare your calculated Zs against the BS 7671 Table 41.3 maximum.
Used in
- EICR — recorded per circuit.
- Minor works certificate — required before issue.
Method
Zs = Ze + (R1 + R2)
Reference
BS 7671:2018+A2:2022, Section 411 and Table 41.3
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