BDTU L7b Finding the EOL in the Field

Most technicians assume the EOL resistor is at the end of the circuit. In the real world: • It gets left in the panel • It gets installed mid-circuit • It gets hidden in the wrong device And when that happens: The panel may look NORMAL while part of the circuit is actually dead. This lesson shows how to electrically prove where the End-of-Line resistor really is using a meter and a simple field process. Topics covered: • Safe resistance testing • Circuit isolation • Proving supervision • NAC circuit behavior • Hidden supervision failures • Real-world troubleshooting methods • Common EOL mistakes in the field Tagline: “Don’t guess where it is — prove where it is.” BDT University (BDTU) Real-world training for real technicians. ⚠️ Always verify procedures against current NEC, NFPA 72, manufacturer instructions, and local AHJ requirements.