Article 100 Class 1, 2 and 3 Circuits.
Code Change Summary: The existing definitions of a Class 1, 2 and 3 circuit were relocated to Article 100.
Class 1, 2 and 3 circuits were discussed in many articles throughout previous editions of the NEC® but only defined in Article 725. Now the below definitions are found in Article 100.
Class 1 circuits can be either of the following:
- Class 1 Power-Limited Circuits. Supplied from a source that has a rated output of not more than 30 volts and 1000 volt-amperes.
- Class 1 Remote-Control and Signaling Circuits. These circuits shall not exceed 600 volts. The power output of the source shall not be required to be limited.
Class 2 circuits are considered safe from a fire and shock initiation standpoint due to the power limitations of the Class 2 transformer or power supply.
Class 3 circuits can operate at higher voltages than a Class 2 circuit which is why a Class 3 circuit is only considered safe from a fire initiation standpoint, not shock.
See Article 725 for more on Class 1, Class 2, and Class 3 remote control, signaling, and power-limited circuits
Below is a preview of the NEC®. See the actual NEC® text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the 2020 NEC® edition of NFPA 70.
2017 Code Language:
Class 1, 2 and 3 circuits were defined only in Article 725.
2020 Code Language:
Article 100.
N Class 1 Circuit. The portion of the wiring system between the load side of the overcurrent device or power-limited supply and the connected equipment.
Informational Note: See 725.41 for voltage and power limitations of Class 1 circuits.
N Class 2 Circuit. The portion of the wiring system between the load side of a Class 2 power source and the connected equipment. Due to its power limitations, a Class 2 circuit considers safety from a fire initiation standpoint and provides acceptable protection from electric shock.
N Class 3 Circuit. The portion of the wiring system between the load side of a Class 3 power source and the connected equipment. Due to its power limitations, a Class 3 circuit considers safety from a fire initiation standpoint. Since higher levels of voltage and current than for Class 2 are permitted, additional safeguards are specified to provide protection from an electric shock hazard that could be encountered.