Fault Loop Impedance Calculator Free Page

| 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:

(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): fault loop impedance calculator

| MCB type | 6A | 10A | 16A | 20A | 32A | 40A | |----------|------|------|------|------|------|------| | B | 7.7 | 4.6 | 2.9 | 2.3 | 1.44 | 1.15 | | C | 3.8 | 2.3 | 1.45 | 1.15 | 0.72 | 0.58 | | D | 1.9 | 1.15 | 0.72 | 0.58 | 0.36 | 0.29 | | Supply type | Typical Ze (Ω) |

| Cable size (mm²) | R1+R2 (mΩ/m) at 20°C | |------------------|----------------------| | 1.0 / 1.0 | 36.2 | | 1.5 / 1.0 | 24.2 | | 1.5 / 1.5 | 30.2 | | 2.5 / 1.5 | 19.5 | | 2.5 / 2.5 | 18.1 | | 4.0 / 1.5 | 13.9 | | 4.0 / 2.5 | 12.9 | | 6.0 / 2.5 | 9.5 | | 6.0 / 4.0 | 8.4 | | 10.0 / 4.0 | 5.8 | | 10.0 / 6.0 | 5.2 | fault loop impedance calculator

Zs ≤ 0.8 × Zs(max) (for UK BS 7671 rule of thumb) Draw a table like this: