Fault Loop Impedance Calculator -

Where:

These are Zs max at 20°C before applying 0.8 factor. fault loop impedance calculator

Cut to pocket size (~A6 or half A5). On site: Where: These are Zs max at 20°C before applying 0

Fault Loop Impedance (often denoted as $Z_s$) is the total impedance (resistance + reactance) of the path an electrical current takes during a fault condition, specifically an earth fault or short circuit. For a 32A Type B MCB, the standard

For a 32A Type B MCB, the standard max $Z_s$ is approximately 1.44Ω (at 230V).

If the circuit is protected by an RCD (Residual Current Device), the fault loop impedance becomes less critical for disconnection (as the RCD trips on small leakage currents), but it is still measured to ensure the fault current is sufficient to operate the breaker and limit voltage on the casing.

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