National Electrical Code Tips: Article 725, Class 1, Class 2, and Class 3 Circuits. Part 2.
- Part II of Article 725 provides the requirements for Class 1 circuits. However, Part III provides the requirements for both Class 2 and Class 3 circuits. Why is Class 1 by itself, and the other two are together? It has to do with the power limitations. These make the requirements for Class 2 and Class 3 very similar to each other, but they make the requirements for Class 1 enough different from the other two that it Class 1 needs to be addressed separately.
- A Class 1 power-limited circuit is one supplied by a source with a rated output of not more than 30V and 1kVA [725.41(A)].
- A Class 1 remote-control or signaling circuit is a circuit that's used for remote-control or signaling and operates at 600V or less [725.41(B)].
- The requirements for Class 1 power sources are in 725.41(A).
- If the conductors are 14AWG or larger, provide overcurrent protection the normal way; except you don't apply the ampacity adjustment and correction factors of 310.15 to the ampacity calculation [725.43].
- Overcurrent protection can't exceed 7A for 18AWG conductors or 10A for 16AWG conductors [725.43]. Except as permitted by other Articles.
- Install OCPDs at the point where the conductors receive their supply [725.45(A)]. This is generally true of all circuits and because of that the OCPD defines the circuit.
- You can use branch and feeder taps, if you follow specific rules pertaining to them [725.45(B) and (C)].
- Install Class 1 circuits using the appropriate Articles from Chapter 3 [725.46].
- You can install Class 1 conductors with other circuits, if you meet the applicable requirements specified in 725.48.