zmVault/nfpa-70_725_control-circuits.md

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nec-725	authorship/other destiny/uncertain exclude-from-word-count topic/construction/electrical type/media/reference	Article 725 Class 1, Class 2, and Class 3 Remote-Control, Signaling, and Power-Limited Circuits

Article 725 Class 1, Class 2, and Class 3 Remote-Control, Signaling, and Power-Limited Circuits

Part I. General

725.1 Scope.

This article covers remote-control, signaling, and power-limited circuits that are not an integral part of a device or of utilization equipment.

Informational Note: 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, ampacity adjustment and correction factors, overcurrent protection, insulation requirements, and wiring methods and materials.

725.2 Definitions.

The definitions in this section shall apply only within this article.

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Part III. Class 2 and Class 3 Circuits

725.136 Separation from Electric Light, Power, Class 1, Non--Power-Limited Fire Alarm Circuit

Conductors, and Medium-Power Network-Powered Broadband Communications Cables.

725.136(A) General.

Cables and conductors of Class 2 and Class 3 circuits shall not be placed in any cable, cable tray, compartment, enclosure, manhole, outlet box, device box, raceway, or similar fitting with conductors of electric light, power, Class 1, non--power-limited fire alarm circuits, and medium-power network-powered broadband communications circuits unless permitted by 725.136(B) through (I).

725.136(B) Separated by Barriers.

Class 2 and Class 3 circuits shall be permitted to be installed together with the conductors of electric light, power, Class 1, non--power-limited fire alarm and medium power network-powered broadband communications circuits where they are separated by a barrier.

725.136(C) Raceways Within Enclosures.

In enclosures, Class 2 and Class 3 circuits shall be permitted to be installed in a raceway to separate them from Class 1, non--power-limited fire alarm and medium-power network-powered broadband communications circuits.

725.136(D) Associated Systems Within Enclosures.

Class 2 and Class 3 circuit conductors in compartments, enclosures, device boxes, outlet boxes, or similar fittings shall be permitted to be instal led with electric light, power, Class 1, non--power-limited fire alarm, and medium-power network-powered broadband communications circuits where they are introduced solely to connect the equipment connected to Class 2 and Class 3 circuits, and where (1) or (2) applies:

1. The electric light, power, Class 1, non--power-limited fire alarm, and medium-power network-powered broadband communications circuit conductors are routed to maintain a minimum of 6 mm (0.25 in.) separation from the conductors and cables of Class 2 and Class 3 circuits.

2. The circuit conductors operate at 150 volts or less to ground and also comply with one of the following:

   • a. The Class 2 and Class 3 circuits are installed using Type CL3, CL3R, or CL3P or permitted substitute cables, provided these Class 3 cable conductors extending beyond the jacket are separated by a minimum of 6 mm (0.25 in.) or by a nonconductive sleeve or nonconductive barrier from all other conductors.

   • b. The Class 2 and Class 3 circuit conductors are installed as a Class 1 circuit in accordance with 725.41.

725.136(E) Enclosures with Single Opening.

Class 2 and Class 3 circuit conductors entering compartments, enclosures, device boxes, outlet boxes, or similar fittings shall be permitted to be instal led with Class 1, non--power-limited fire alarm and medium-power network-powered broadband communications circuits where they are introduced solely to connect the equipment connected to Class 2 and Class 3 circuits. Where Class 2 and Class 3 circuit conductors must enter an enclosure that is provided with a single opening, they shall be permitted to enter through a single fitting (such as a tee), provided the conductors are separated from the conductors of the other circuits by a continuous and firmly fixed nonconductor, such as flexible tubing.

725.136(F) Manholes.

Underground Class 2 and Class 3 circuit conductors in a manhole shall be permitted to be installed with Class 1, non--power-limited fire alarm and medium-power network-powered broadband communications circuits where one of the following conditions is met:

1. The electric light, power, Class 1, non--power-limited fire alarm and medium-power network-powered broadband communications circuit conductors are in a metal-enclosed cable or Type UF cable.

2. The Class 2 and Class 3 circuit conductors are permanently and effectively separated from the conductors of other circuits by a continuous and firmly fixed nonconductor, such as flexible tubing, in addition to the insulation or covering on the wire.

3. The Class 2 and Class 3 circuit conductors are permanently and effectively separated from conductors of the other circuits and securely fastened to racks, insulators, or other approved supports.

725.136(G) Cable Trays.

Class 2 and Class 3 circuit conductors shall be permitted to be installed in cable trays, where the conductors of the electric light, Class 1, and non--power-limited fire alarm circuits are separated by a solid fixed barrier of a material compatible with the cable tray or where the Class 2 or Class 3 circuits are installed in Type MC cable.

725.136(H) In Hoistways.

In hoistways, Class 2 or Class 3 circuit conductors shall be installed in rigid metal conduit, rigid nonmetallic conduit, intermediate metal conduit, liquidtight flexible nonmetallic conduit, or electrical metallic tubing. For elevators or similar equipment, these conductors shall be permitted to be installed as provided in 620.21.

725.136(I) Other Applications.

For other applications, conductors of Class 2 and Class 3 circuits shall be separated by at least 50 mm (2 in.) from conductors of any electric light, power, Class 1 non--power-limited fire alarm or medium power network-powered broadband communications circuits unless one of the following conditions is met:

1. Either all of the electric light, power, Class 1, non--power-limited fire alarm and medium-power network-powered broadband communications circuit conductors or all of the Class 2 and Class 3 circuit conductors are in a raceway or in metal-sheathed, metal-clad, non--metallic-sheathed, Type TC, or Type UF cables

2. All of the electric light, power, Class 1 non--power-limited fire alarm, and medium-power network-powered broadband communications circuit conductors are permanently separated from all of the Class 2 and Class 3 circuit conductors by a continuous and firmly fixed nonconductor, such as porcelain tubes or flexible tubing, in addition to the insulation on the conductors

725.139 Installation of Conductors of Different Circuits in the Same Cable, Enclosure, Cable Tray,

Raceway, or Cable Routing Assembly.

725.139(A) Two or More Class 2 Circuits.

Conductors of two or more Class 2 circuits shall be permitted within the same cable, enclosure, raceway, or cable routing assembly.

725.139(B) Two or More Class 3 Circuits.

Conductors of two or more Class 3 circuits shall be permitted within the same cable, enclosure, raceway, or cable routing assembly.

725.139(C) Class 2 Circuits with Class 3 Circuits.

Conductors of one or more Class 2 circuits shall be permitted within the same cable, enclosure, raceway, or cable routing assembly with conductors of Class 3 circuits, provided that the insulation of the Class 2 circuit conductors in the cable, enclosure, raceway, or cable routing assembly is at least that required for Class 3 circuits.

725.139(D) Class 2 and Class 3 Circuits with Communications Circuits.

725.139(D)(1) Communications Cables.

Conductors of one or more Class 2 or Class 3 circuits shall be permitted in the same cable with conductors of communications circuits provided the cable is a listed communications cable that shall be installed in accordance with the requirements of Part V of Article 805.

The cables shall be listed as communications cables.

725.139(D)(2) Composite Cables.

Cables constructed of individually listed Class 2, Class 3, and communications cables under a common jacket shall be permitted to be classified as communications cables. The fire resistance rating of the composite cable shall be determined by the performance of the composite cable.

725.139(E) Class 2 or Class 3 Cables with Other Circuit Cables.

Jacketed cables of Class 2 or Class 3 circuits shall be permitted in the same enclosure, cable tray, raceway, or cable routing assembly with jacketed cables of any of the following:

1. Power-limited fire alarm systems in compliance with Parts I and III of Article 760

2. Nonconductive and conductive optical fiber cables in compliance with Parts I and IV of Article 770

3. Communications circuits in compliance with Parts I and IV of Article 805

4. Community antenna television and radio distribution systems in compliance with Parts I and IV of Article 820

5. Low-power, network-powered broadband communications in compliance with Parts I and IV of Article 830

725.139(F) Class 2 or Class 3 Conductors or Cables and Audio System Circuits.

Audio system circuits described in 640.9(C), and installed using Class 2 or Class 3 wiring methods in compliance with 725.133 and 725.154, shall not be permitted to be installed in the same cable, raceway, or cable routing assembly with Class 2 or Class 3 conductors or cables.

725.141 Installation of Circuit Conductors Extending Beyond One Building.

Where Class 2 or Class 3 circuit conductors extend beyond one building and are run so as to be subject to accidental contact with electric light or power conductors operating over 300 volts to ground, or are exposed to lightning on interbuilding circuits on the same premises, the requirements of the following shall also apply:

1. Sections 800.44, 800.53, 800.100, 805.50, 805.93, 805.170(A), and 805.170(B) for other than coaxial conductors

2. Sections 820.44, 820.93, and 820.100 for coaxial conductors

725.143 Support of Conductors.

Class 2 or Class 3 circuit conductors shall not be strapped, taped, or attached by any means to the exterior of any conduit or other raceway as a means of support. These conductors shall be permitted to be installed as permitted by 300.11(C)(2).