Article 725 of the National Electrical Code (NEC) provides the requirements for “Class 1, Class 2, and Class 3 remote-control, signaling, and power-limited circuits.” The title of Art. 725 includes that phrase, so the title is a mouthful. However, a more succinct title would leave much room for misinterpretation. Even with that long title, some explanation is needed. From the Scope [725.1] and the Informational Note that accompanies it, we can see these circuits:
- Are not integrated into a device or utilization equipment.
- Have usage and power limitations that differentiate them from electric light and power circuits.
Because these circuits are different from other circuits, they have their own requirements (instead of Chapter 1 through 4 requirements) for:
- Minimum wire size
- Ampacity adjustments and correction factors.
- Overcurrent protection.
- Insulation requirements.
- Wiring methods and materials.
Furthermore, these requirements differ for Class 1 [Part II] and Class 2 and Class 3 [Part 3] circuits. These circuits all, however, must be identified at terminal and junction locations in a manner that prevents unintentional interference with other circuits during testing and servicing [725.30].
