I. General
725.3 Other Articles. Circuits and equipment shall com- ply with the articles or sections listed in 725.3(A) through (G). Only those sections of Article 300 referenced in this article shall apply to Class 1, Class 2, and Class 3 circuits.
(A) Number and Size of Conductors in Raceway. Sec- tion 300.17.
(B) Spread of Fire or Products of Combustion. Installa- tion of Class 1, Class 2, and Class 3 circuits shall comply with 300.21.
(C) Ducts, Plenums, and Other Air-Handling Spaces.
725.1 Scope. This article covers remote-control, signaling, and power-limited circuits that are not an integral part of a device or appliance.
FPN: The circuits described herein are characterized by usage and electrical power limitations that differentiate them from electric light and power circuits; therefore, alternative requirements to those of Chapters 1 through 4 are given with regard to minimum wire sizes, derating factors, overcurrent protection, insulation requirements, and wiring methods and materials.
725.2 Definitions.
Abandoned Class 2, Class 3, and PLTC Cable. Installed Class 2, Class 3, and PLTC cable that is not terminated at equipment and not identified for future use with a tag.
Circuit Integrity (CI) Cable. Cable(s) used for remote- control, signaling, or power-limited systems that supply critical circuits to ensure survivability for continued circuit operation for a specified time under fire conditions.
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.
FPN: See 725.41 for voltage and power limitations of Class 1 circuits.
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.
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.
Class 1, Class 2, and Class 3 circuits installed in ducts, plenums, or other space used for environmental air shall comply with 300.22.
Exception: Type CLIP or CL3P cables and plenum signal- ing raceways shall be permitted for Class 2 and Class 3 circuits installed in other spaces used for environmental air in accordance with 725.154(A).