REMOTE-CONTROL SIGNALING CIRCUITS

70-757 (2) To the power-supply conductors only, where the Class 1 circuit conductors do not carry continuous loads in excess of 10 percent of the ampacity of each conductor and where the number of power-supply conductors is more than three. (c) Class 1 Circuit Conductors in Cable Trays. Where Class 1 circuit conductors are installed in cable trays, they shall comply with the provisions of Sections 318-9 through 318-11. 725-18. Physical Protection. Where damage to remote-control circuits of safety control equipment would introduce a hazard, as covered in Section 725-4, all conductors of such remote-control circuits shall be installed in rigid metal conduit, intermediate metal conduit, rigid nonmetallic conduit, electrical metallic tubing, Type MI cable, Type MC cable, or be otherwise suitably protected from physical damage. 725-19. Circuits Extending Beyond One Building. Class 1 circuits that extend aerially beyond one building shall also meet the requirements of Article 225. 725-20. Grounding. Class 1 circuits and equipment shall be grounded in accordance with Article 250. C. Class 2 and Class 3 Circuits 725-31. Power Limitations of Class 2 and Class 3 Circuits. As specified in Table 725-31(a) for ac circuits and Table 725-31(b) for dc circuits, the power for Class 2 and Class 3 circuits shall be either inherently limited requiring no overcurrent protection or limited by a combination of a power source and overcurrent protection. Notes for Tables 725-31(a) and (b) Note 1. Vₘₐₓ: Maximum output voltage regardless of load with rated input applied. Iₘₐₓ: Maximum output current under any noncapacitive load, including short circuit, and with overcurrent protection bypassed, if used. When a transformer limits the output current, Iₘₐₓ limits apply after one minute of operation. Where a currentlimiting impedance, listed for the purpose, or as part of a listed product, is used in combination with a nonpower-limited transformer or a stored energy source, e.g., storage battery, to limit the output current, Iₘₐₓ limits apply after 5 seconds. VAₘₐₓ: Maximum volt-ampere output after one minute of operation regardless of load and overcurrent protection bypassed, if used. Current-limiting impedance shall not be bypassed when determining 1ₘₐₓ and VAₘₐₓ· Note 2. For nonsinusoidal ac, Vₘₐₓ shall be not greater than 42.4 volts peak. Where wet contact (immersion not included) is likely to occur, Class 3 wiring methods shall be used, or Vₘₐₓ shall be not greater than: 15 volts for sinusoidal ac: 21.2 volts peak for nonsinusoidal ac. Note 3. If the power source is a transformer, (VA)ₘₐₓ is 350 or less where Vₘₐₓ is 15 or less. Note 4. A dry cell battery shall be considered an inherently limited power source, provided the voltage is 30 volts or less and the capacity is equal to or less than that available from series connected No. 6 carbon zinc cells. Note 5: For dc interrupted at a rate of 10 to 200 Hz, Vₘₐₓ shall not be greater than 24.8 volts. Where wet contact (immersion not included) is likely to occur, Class 3 wiring methods shall be used, or Vₘₐₓ shall not be greater than: 30 volts for continuous dc; 12.4 volts for dc that is interrupted at a rate of 10 to 200 Hz. Table 725-31(a). Power Source Limitations for Alternating Current Class 2 and Class 3 Circuits 70-758 Inherently Limited Power Source Not Inherently Limited Power Source (Overcurrent protection not required) (Overcurrent protection required) Circuit Class 2 Class 3 Class 2 Class 3 Over Over Over Circuit Voltage 0 through Over 20 and 30 and Over 30 and 0 through Over 20 and 30 and 100 and Vₘₐₓ (Volts) (Note 1) 20+ through 30+ through 150 through 100 20+ through 30+ through 100 through 150 Power Limitations (VA) max (Volt-Amps) 250 - - - - 250 250 N.A. (Note 1) (Note 3) Current Limitations max (Amps) 8.0 8.0 0.005 150/V max 1000/V max 1000/V, max 1000/V 1.0 max (Note 1) Maximum Over- - - - - 5.0 100/V max 100/V max 1.0 current Protection (Amps) VA Power Source Maximum Nameplate Ratings (Volt-Amps) 5.0 X Vₘₐₓ 100 0.005 X V. max 100 5.0 X Vₘₐₓ 100 NATIONAL ELECTRICAL CODE 100 100 Current 5.0 (Amps) 100/V max 0.005 100/V max 5.0 100/V. max 100/V max 100/V max Supply Conductors and Cables See Section 725-37 Circuit Conductors and Cables See Sections 725-49 through 725-53 t Voltage ranges shown are for sinusoidal ac in indoor locations or where wet contact is not likely to occur. For nonsinusoidal or wet contact conditions, see Note 2. Table 725-31(b). Power Source Limitations for Direct Current Class 2 and Class 3 Circuits Inherently Limited Power Source (Note 4) Not Inherently Limited Power Source (Overcurrent protection not required) (Overcurrent protection required) Circuit Class 2 Class 3 Class 2 Class 3 Over 20 Over 30, Over 60 Over 60 Over 20 Over 60 Over 100 Circuit Voltage 0 through and through and through and through and through 0 through and through and through and through Vₘₐₓ (Volts) (Note 1) 20++ 30++ 60++ 150 100 20++ 60++ 100 150 Power Limitations (VA) 250 max - - 250 250 N.A. - - - (Volts-Amps) (Note 3) (Note 1) Current Limitations max (Amps) 8.0 8.0 150/V max 0.005 150/V max 1000/V max 1000/V max 1000/V max 1.0 (Note 1) Maximum Overcurrent Protection - - 5.0 - - - 100/V max 100/V max 1.0 (Amps) VA 5.0 X Vₘₐₓ 100 100 0.005 X Vₘₐₓ 100 5.0 X Vₘₐₓ 100 100 100 Power Source Maximum Nameplate Ratings (Volt-Amps) ARTICLE 725 REMOTE-CONTROL, SIGNALING CIRCUITS Current 5.0 100/V max 100/v max 0.005 100/V max 5.0 100/V max 100/v max 100/V max (Amps) Supply Conductors See Section 725-37 and Cables Circuit Conductors See Sections 725-49 through 725-53 and Cables tt Voltage ranges shown are for continuous dc in indoor locations or where wet contact is not likely to occur. For interrupted dc or wet contact 70-759 conditions, see Note 5. 70-760 NATIONAL ELECTRICAL CODE 725-32. Interconnection of Power Supplies. Class 2 or Class 3 power supplies shall not be paralleled or otherwise interconnected unless listed for such interconnection. 725-34. Marking. A Class 2 or Class 3 power supply unit shall be durably marked where plainly visible to indicate the class of supply and its electrical rating. 725-35. Overcurrent Protection. Where overcurrent protection is required, the overcurrent-protective devices shall not be interchangeable with devices of higher ratings. The overcurrent device shall be permitted as an integral part of the power supply. 725-36. Location of Overcurrent Devices. Overcurrent devices, where required, shall be located at the point where the conductor to be protected receives its supply. 725-37. Wiring Methods on Supply Side. Conductors and equipment on the supply side of overcurrent protection, transformers, or current-limiting devices shall be installed in accordance with the appropriate requirements of Chapter 3. Transformers or other devices supplied from electric light or power circuits shall be protected by an overcurrent device rated not over 20 amperes. Exception: The input leads of a transformer or other power source supplying Class 2 and Class 3 circuits shall be permitted to be smaller than No. 14, but not smaller than No. 18 if they are not over 12 inches (305 mm) long and if they have insulation that complies with Section 725-16(b). 725-38. Wiring Methods and Materials on Load Side. Conductors on the load side of overcurrent protection, transformers, and current-limiting devices shall be insulated at not less than the requirements of Section 725-50 and shall be installed in accordance with Section 725-52. 725-42. Circuit Conductors Extending Beyond One Building. Where Class 2 or Class 3 circuit conductors that extend beyond one building and are so run as to be subject to accidental contact with electric light or power conductors operating at 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 800-10, 800-12, 800-13, 800-30, 800-31, 800-32, 800-33, and 800-40 for other than coaxial conductors, and (2) Sections 820-10, 820-33, and 820-40 for coaxial conductors. 725-43. Grounding. Class 2 and Class 3 circuits and equipment shall be grounded in accordance with Article 250. ARTICLE 725 - REMOTE-CONTROL, SIGNALING CIRCUITS 70-761 725-49. Fire Resistance of Cables Within Buildings. Single- and multiconductor cables of Class 2 and Class 3 circuits, including PLTC cables, installed as wiring within buildings shall be listed as resistant to the spread of fire in accordance with Sections 725-50 and 725-51. 725-50. Listing, Marking, and Installation of Class 2, Class 3, and PLTC Cables. (a) Class 2 and Class 3 Cables. Class 2 and Class 3 cables installed as wiring within buildings shall be listed as being suitable for the purpose, marked in accordance with Table 725-50, and installed in accordance with Section 725-38. The cable voltage ratings shall not be marked on the cable. (FPN): Voltage markings on cables may be misinterpreted to suggest that the cables may be suitable for Class 1, electric light and power applications. Exception No. 1: Voltage markings shall be permitted where the cable has multiple listings and voltage marking is required for one or more of the listings. Exception No. 2: Cable substitutions as provided for in Section 725-53(g) shall be considered as suitable for the purpose and shall be permitted. (b) PLTC. PLTC shall be marked in accordance with Section 310-11 and Table 725-50 and shall be listed as being suitable for use in cable trays. Table 725-50. Cable Markings Cable Marking Type Reference CL3P Class 3 Plenum Cable 725-51(a) and 725-53(a) CL2P Class 2 Plenum Cable 725-51(a) and 725-53(a) CL3R Class 3 Riser Cable 725-51(b) and 725-53(b) CL2R Class 2 Riser Cable 725-51(b) and 725-53(b) PLTC Power-Limited Tray Cable 725-51(e) and 725-53(c) and (d) CL3 Class 3 Cable 725-51(c), 725-53(b), Exception No. 2, and 725-53(e) CL2 Class 2 Cable 725-51(c), 725-53(b), Exception No. 2, and 725-53(e) CL3X Class 3 Cable, Limited Use 725-51(d), 725-53(b), Exception No. 2, and 725-53(e), Exception Nos. 1, 2, and 3 CL2X Class 2 Cable, Limited Use 725-51(d), 725-53(b), Exception No. 2, and 725-53(e), Exception Nos. 1, 2, and 3 70-762 NATIONAL ELECTRICAL CODE (FPN No. 1): Class 2 and Class 3 Cable types are listed in descending order of fire resistance rating, and Class 3 cables are listed above Class 2 cables, since Class 3 cables may substitute for Class 2 cables. (FPN No. 2): See the referenced sections for permitted uses. 725-51. Additional Listing Requirements. Class 2 and Class 3 cables shall be listed in accordance with (a) through (f) below, and, where single conductors are used for Class 3 circuits, with (g) below: (a) Types CL2P and CL3P. Types CL2P and CL3P plenum cables shall be listed as being suitable for use in ducts, plenums, and other space used for environmental air and shall also be listed as having adequate fireresistant and low-smoke-producing characteristics. (FPN): One method of defining low-smoke-producing cable is by establishing an acceptable value of the smoke produced when tested in accordance with Test for Fire and Smoke Characteristics of Wires and Cables, NFPA 262-1990 (ANSI) to a maximum peak optical density of 0.5 and a maxiumum average optical density of 0.15. Similarly, one method of defining fire-resistant cables is by establishing maximum allowable flame travel distance of 5 feet (1.52 m) when tested in accordance with the same test. (b) Types CL2R and CL3R. Types CL2R and CL3R riser cables shall be listed as being suitable for use in a vertical run in a shaft or from floor to floor and shall also be listed as having fire-resistant characteristics capable of preventing the carrying of fire from floor to floor. (FPN): One method of defining fire-resistant characteristics capable of preventing the carrying of fire from floor to floor is that the cables pass the requirements of Test for Flame Propagation Height of Electrical and Optical-Fiber Cable Installed Vertically in Shafts, ANSI/UL 1666-1986. (c) Types CL2 and CL3. Types CL2 and CL3 cables shall be listed as being suitable for general-purpose use, with the exception of risers, ducts, plenums, and other space used for environmental air, and shall also be listed as being resistant to the spread of fire. (FPN): One method of defining resistant to spread of fire is that the cables do not spread fire to the top of the tray in the "Vertical Tray Flame Test" in Reference Standard for Electrical Wires, Cables and Flexible Cords, ANSI/UL 1581-1985. Another method of defining resistant to the spread of fire is for the damage (char length) not to exceed 4 feet 11 inches (1.5 m) when performing the CSA "Vertical Flame Test - Cables in Cable Trays," as described in Test Methods for Electrical Wires and Cables, CSA C22.2 No. 0.3-M-1985. (d) Types CL2X and CL3X. Types CL2X and CL3X limited use cables shall be listed as being suitable for use in dwellings and for use in raceway and shall also be listed as being flame-retardant. (FPN): One method of determining that cable is flame-retardant is by testing the cable to the "VW-1 (Vertical-Wire) Flame Test" in the Reference Standard for Electrical Wires, Cables and Flexible Cords, ANSI/UL 1581-1985. (e) Type PLTC. Type PLTC nonmetallic-sheathed, power-limited tray cable shall be a factory assembly of two or more insulated conductors under a nonmetallic jacket. The insulated conductors shall be Nos. 22 through 12. The conductor material shall be copper (solid or stranded). ARTICLE 725 - REMOTE-CONTROL, SIGNALING CIRCUITS 70-763 Insulation on conductors shall be suitable for 300 volts. The cable core shall be either (1) two or more parallel conductors; (2) one or more group assemblies of twisted or parallel conductors; or (3) a combination thereof. A metallic shield or a metallized foil shield with drain wire(s) shall be permitted to be applied either over the cable core, over groups of conductors, or both. The cable shall be listed as being resistant to the spread of fire. The outer jacket shall be a sunlight- and moisture-resistant nonmetallic material. Exception: Where a smooth metallic sheath, welded and corrugated metallic sheath, or interlocking tape armor is applied over the nonmetallic jacket, an overall nonmetallic jacket shall not be required. On metallicsheathed cable without an overall nonmetallic jacket, the information required in Section 310-11 shall be located on the nonmetallic jacket under the sheath. (FPN): One method of defining resistant to spread of fire is that the cables do not spread fire to the top of the tray in the "Vertical Tray Flame Test" in the Reference Standard for Electrical Wires, Cables and Flexible Cords, ANSI/UL 1581-1985. Another method of defining resistant to the spread of fire is for the damage (char length) not to exceed 4 feet, 11 inches (1.5 m) when performing the CSA "Vertical Flame Test - Cables in Cable Trays," as described in Test Methods for Electrical Wires and Cables, CSA C22.2 No. 0.3-M-1985. (f) Voltage Rating. Class 3 cables shall have a voltage rating of not less than 300 volts. (g) Single Conductors. Class 3 single conductors shall not be smaller than No. 18 and shall be insulated in accordance with Section 725-16(b). 725-52. Installation of Conductors and Equipment. Conductors and equipment on the load side of overcurrent protection, transformers, and current-limiting devices shall comply with (a) and (b) below. (a) Separation from Electric Light, Power, Class 1, and Nonpower- Limited Fire Protective Signaling Circuit Conductors. (1) Open Conductors. Conductors of Class 2 and Class 3 circuits shall be separated by at least 2 inches (50.8 mm) from conductors of any electric light, power, Class 1, or nonpower-limited fire protective signaling circuits. Exception No. 1: Where either (1) all of the electric light, power, Class 1, and nonpower-limited fire protective signaling circuit conductors, or (2) all of the Class 2 and Class 3 circuit conductors are in raceway or in metal-sheathed, metal-clad, nonmetallic-sheathed, or Type UF cables. Exception No. 2: Where the conductors are permanently separated from the conductors of the other circuits by a continuous and firmly fixed nonconductor, such as porcelain tubes or flexible tubing, in addition to the insulation on the wire. (2) In Cable, Cable Trays, Enclosures, and Raceways. Conductors of Class 2 and Class 3 circuits shall not be placed in any cable, cable tray, compartment, enclosure, outlet box, raceway, or similar fitting with conductors of electric light, power, Class 1, and nonpower-limited fire protective signaling circuits. 70-764 NATIONAL ELECTRICAL CODE Exception No. 1: Where the conductors of the different circuits are separated by a barrier. In enclosures, Class 2 or Class 3 circuits shall be permitted to be installed in a raceway within the enclosure to separate them from Class 1, electric light and power circuits. Exception No. 2: Conductors in compartments, enclosures, outlet boxes, or similar fittings, where electric light, power, Class 1, or nonpower-limited fire protective signaling circuit conductors are introduced solely to connect to the equipment connected to Class 2 or Class 3 circuits to which the other conductors in the enclosure are connected. The electric light, power, Class 1, and nonpower-limited fire protective signaling circuit conductors shall be routed within the enclosure to maintain a minimum 0.25-inch (6.35-mm) separation from the conductors of Class 2 and Class 3 circuits. Exception No. 3: Underground conductors in a manhole where one of the following conditions is met: a. The electric light, power, Class 1, and nonpower-limited fire protective signaling circuit conductors are in a metal-enclosed cable or Type UF cable; b. The conductors are permanently and effectively separated from the conductors of the other circuits by a continuous and firmly fixed nonconductor, such as flexible tubing, in addition to the insulation or covering on the wire; c. The conductors are permanently and effectively separated from conductors of the other circuits and securely fastened to racks, insulators, or other approved supports. Exception No. 4: As permitted by Section 780-6(a) and installed in accordance with Article 780. (3) In Hoistways. Class 2 or Class 3 circuit conductors shall be installed in rigid metal conduit, rigid nonmetallic conduit, intermediate metal conduit, or electrical metallic tubing in hoistways. Exception: As provided for in Section 620-21, Exception Nos. 1 and 2 for elevators and similar equipment. (4) In Shafts. Class 2 or Class 3 circuit conductors shall be separated by not less than 2 inches (50.8 mm) from electric light, power, Class 1, or nonpower-limited fire protective signaling circuit conductors run in the same shaft. Raceway. (b) Conductors of Different Circuits in Same Cable, Enclosure, or (1) Two or More Class 2 Circuits. Conductors of two or more Class 2 circuits shall be permitted within the same cable, enclosure, or raceway, provided all conductors in the cable, enclosure, or raceway are insulated for the maximum voltage of any conductor. (2) Two or More Class 3 Circuits. Conductors of two or more Class 3 circuits shall be permitted within the same cable, enclosure, or raceway. (3) Class 2 Circuits with Class 3 Circuits. Conductors of one or more Class 2 circuits shall be permitted within the same cable, enclosure, or ARTICLE 725 - REMOTE-CONTROL, SIGNALING CIRCUITS 70-765 raceway with conductors of Class 3 circuits, provided that the insulation of the Class 2 circuit conductors in the cable, enclosure, or raceway is at least that required for Class 3 circuits. (4) Class 2 or Class 3 Circuits with Other Circuits. Jacketed cables of Class 2 or Class 3 circuits shall be permitted in the same enclosure or raceway with jacketed cables of any of the following: a. Power-limited fire protective signaling systems in compliance with Article 760. b. Nonconductive and conductive optical fiber cables in compliance with Article 770. c. Communications circuits in compliance with Article 800. d. Community antenna television and radio distribution systems in compliance with Article 820. (c) Support of Conductors. Raceways shall not be used as a means of support for Class 2 or Class 3 circuit conductors. Exception: Except as permitted by Section 300-11(b), Exception No. 2. 725-53. Applications of Listed Class 2, Class 3, and PLTC Cables. Class 2, Class 3, and PLTC cables shall comply with (a) through (g) below. (a) Plenum. Cables installed in ducts, plenums, and other spaces used for environmental air shall be Type CL2P or CL3P. Exception: Listed wires and cables installed in compliance with Section 300-22. (b) Riser. Cables installed in vertical runs and penetrating more than one floor, or cables installed in vertical runs in a shaft, shall be Type CL2R or CL3R. Floor penetrations requiring Type CL2R or CL3R shall contain only cables suitable for riser or plenum use. Exception No. 1: Other cables as covered in Table 725-53 and other listed wiring methods as covered in Chapter 3, where these are installed in metal raceways or located in a fireproof shaft having firestops at each floor. Exception No. 2: Types CL2, CL3, CL2X, and CL3X cable in one- and two-family dwellings. (FPN): See Section 300-21 for firestop requirements for floor penetrations. (c) Cable Trays. Cables installed in cable trays shall be Type PLTC. Exception: Conductors in PLTC cables used for Class 2 thermocouple circuits shall be permitted to be any of the materials used for thermocouple extension wire. (d) Hazardous (Classified) Locations. Cables installed in hazardous (classified) locations shall be Type PLTC. Where the use of PLTC cable is permitted in Section 501-4(b), the cable shall be installed in cable trays, in raceways, supported by messenger wire, or directly buried where the cable is listed for this use. 70-766 NATIONAL ELECTRICAL CODE Exception. Exception No. 1: For Class 2 circuits as permitted by Section 501-4(b), Exception No. 2: Conductors in PLTC cables used for Class 2 thermocouple circuits shall be permitted to be any of the materials used for thermocouple extension wire. (e) Other Wiring Within Buildings. Cables installed in building locations other than the locations covered in (a) through (d) above shall be Type CL2 or CL3. Exception No. 1: Type CL2X or CL3X where installed in a raceway, or other wiring methods as covered in Chapter 3. Exception No. 2: In nonconcealed spaces where the exposed length of cable does not exceed 10 feet (3.05 m). Exception No. 3: Listed Type CL2X, Class 2 cables less than 0.25 inch (6.4 mm) in diameter and listed Type CL3X, Class 3 cables less than 0.25 inch (6.4 mm) in diameter installed in one- or two-family or multifamily dwellings. (f) Cross-Connect Arrays. Type CL2 or CL3 wire or cable shall be used. (g) Cable Substitutions. The substitutions for Class 2 and Class 3 permitted. cables listed in Table 725-53 and illustrated in Figure 725-53 shall be Table 725-53. Cable Substitutions Cable Type Permitted Substitutions CL3P MPP, CMP, FPLP CL2P MPP, CMP, FPLP, CL3P CL3R MPP, CMP, FPLP, CL3P, MPR, CMR, FPLR CL2R MPP, CMP, FPLP, CL3P, CL2P, MPR, CMR, FPLR, CL3R CL3 MPP, CMP, FPLP, CL3P, MPR, CMR, FPLR, CL3R, MPG, MP, CMG, CM, FPL, PLTC CL2 MPP, CMP, FPLP, CL3P, CL2P, MPR, CMR, FPLR, CL3R, CL2R MPG, MP, CMG, CM, FPL, PLTC, CL3 CL3X MPP, CMP, FPLP, CL3P, MPR, CMR, FPLR, CL3R, MPG, MP, CMG, CM, FPL, PLTC, CL3, CMX CL2X MPP, CMP, FPLP, CL3P, CL2P, MPR, CMR, FPLR, CL3R, CL2R, MPG, MP, CMG, CM, FPL, PLTC, CL3, CL2, CMX, CL3X (FPN): For information on FPLP, FPLR, and FPL cables, see Section 760-50. For information on MPP, MPR, MPG, MP, CMP, CMR, CMG, and CM cables, see Section 800-50.