What is the maximum earth loop Impedance Zs value for the NG125 miniature circuit breakers?

The maximum earth loop impedance figures can be found in the attached PDF file.

To comply with the 18th Edition Wiring Regulations (BS 7671:2018+A2:2022), these figures must be multiplied by the Cmin factor of 0.95.

The Cmin factor accounts for the lowest expected supply voltage, ensuring that protective devices will still disconnect within the required time under worst-case voltage conditions.

To calculate the Zs value, use the formula shown below. (Zs = Uo x Cmin / Ia)