Fault Loop Impedance Calculator -

(Add conversion for higher temps: multiply by 1.2 for operating temp) Draw this table (at rated tripping time, typically 0.4s for final circuits up to 32A):

| Supply type | Typical Ze (Ω) | |-------------|----------------| | TN-S | 0.2 – 0.8 | | TN-C-S (PME) | 0.35 max | | TT | 10 – 20 | Make a second table: fault loop impedance calculator

Zs ≤ 0.8 × Zs(max) (for UK BS 7671 rule of thumb) Draw a table like this: (Add conversion for higher temps: multiply by 1