He flipped open the regs to Section 433 – Protection against overcurrent . Then to Appendix 4, the cable rating tables. He grabbed his notepad, the one with coffee stains and a torn spine.
At 9 a.m., he knocked on Ashworth’s door. “What’s the damage?” the client asked. “More than Dave’s quote,” Tom said, showing the scribbled page of calculations. “But Dave’s house hasn’t burned down yet. That’s just luck, not engineering.” cable calculations bs7671
Vd = (Ib * L * (R + jX)) / 1000
