Where:

Looking up 250 kcmil Copper in PVC, assume $C \approx 30,000$ (approximate for this example).

Finally, we apply the multiplier to find the fault current at the end of that specific wire run.

As electricity travels away from the transformer through conductors (wires), the resistance of those wires decreases the available fault current. To find the AFC at a specific panelboard or piece of equipment, we use the . Step 1: Calculate the "f" Factor

Iavailable=Istart×Mcap I sub a v a i l a b l e end-sub equals cap I sub s t a r t end-sub cross cap M Why These Formulas Matter