REMOTE-CONTROL SIGNALING CIRCUITS

70-755 (2) Other Power Sources. To comply with the 1000 volt-ampere limitation of Section 725-11(a), the maximum output of power sources other than transformers shall be limited to 2500 volt-amperes, and the product of the maximum current and maximum voltage shall not exceed 10,000 voltamperes. These ratings shall be determined with any overcurrentprotective device bypassed. (FPN): For definitions of Vₘₐₓ, Iₘₐₓ, and VAₘₐₓ, see Note 1, Tables 725-31(a) and (b). (b) Class 1 Remote-Control and Signaling Circuits. Class 1 remotecontrol and signaling circuits shall not exceed 600 volts; however, the power output of the source shall not be required to be limited. 725-12. Overcurrent Protection. Conductors No. 14 and larger shall be protected against overcurrent in accordance with Section 310-15. Derating factors shall not be applied. Overcurrent protection shall not exceed 7 amperes for No. 18 conductors and 10 amperes for No. 16. Exception No. 1: Where other articles of this Code permit or require other overcurrent protection. (FPN): For example, see Section 430-72 for motors, Section 610-53 for cranes and hoists, and Sections 517-74(b) and 660-9 for X-ray equipment. Exception No. 2: Transformer Secondary Conductors. Class 1 circuit conductors supplied by the secondary of a single-phase transformer having only a 2-wire (single-voltage) secondary shall be permitted to be protected by overcurrent protection provided on the primary (supply) side of the transformer, provided this protection is in accordance with Section 450-3 and does not exceed the value determined by multiplying the secondary conductor ampacity by the secondary-to-primary transformer voltage ratio. Transformer secondary conductors other than 2-wire shall not be considered to be protected by the primary overcurrent protection. Exception No. 3: Class 1 circuit conductors No. 14 and larger that are tapped from the load side of the overcurrent-protective device(s) of a controlled light and power circuit shall require only short-circuit and groundfault protection and shall be permitted to be protected by the branchcircuit overcurrent-protective device(s) where the rating of the protective device(s) is not more than 300 percent of the ampacity of the Class 1 circuit conductor. 725-13. Location of Overcurrent Devices. Overcurrent devices shall be located at the point where the conductor to be protected receives its supply. Exception No. 1: Where the overcurrent device protecting the larger conductor also protects the smaller conductor. Exception No. 2: Where overcurrent protection is provided in accordance with Section 725-12, Exception No. 2. 725-14. Wiring Method. Installations of Class 1 circuits shall be in accordance with the appropriate articles in Chapter 3. Exception No. 1: As provided in Sections 725-15 through 725-17. Exception No. 2: Where other articles of this Code permit or require other methods. 70-756 NATIONAL ELECTRICAL CODE 725-15. Conductors of Different Circuits in Same Cable, Enclosure, or Raceway. Class 1 circuits shall be permitted to occupy the same cable, enclosure, or raceway without regard to whether the individual circuits are alternating current or direct current, provided all conductors are insulated for the maximum voltage of any conductor in the cable, enclosure, or raceway. Power supply and Class 1 circuit conductors shall be permitted in the same cable, enclosure, or raceway only where the equipment powered is functionally associated. Exception No. 1: Where installed in factory- or field-assembled control centers. Exception No. 2: Underground conductors in a manhole where one of the following conditions is met: a. The power supply or Class 1 circuit conductors are in a metalenclosed cable, or Type UF cable; b. The conductors are permanently separated from the power-supply conductors by a continuous firmly fixed nonconductor, such as flexible tubing, in addition to the insulation on the wire; c. The conductors are permanently and effectively separated from the power supply conductors and securely fastened to racks, insulators, or other approved supports. 725-16. Conductors. (a) Sizes and Use. Conductors of sizes No. 18 and 16 shall be permitted to be used, provided they supply loads that do not exceed the ampacities given in Section 402-5 and are installed in a raceway, an approved enclosure, or a listed cable. Conductors larger than No. 16 shall not supply loads greater than the ampacities given in Section 310-15. Flexible cords shall comply with Article 400. (b) Insulation. Insulation on conductors shall be suitable for 600 volts. Conductors larger than No. 16 shall comply with Article 310. Conductors in sizes No. 18 and 16 shall be Type FFH-2, KF-2, KFF-2, PAF, PAFF, PF, PFF, PGF, PGFF, PTF, PTFF, RFH-2, RFHH-2, RFHH-3, SF-2, SFF-2, TF, TFF, TFFN, TFN, ZF, or ZFF. Conductors with other types and thicknesses of insulation shall be permitted if listed for Class 1 circuit use. 725-17. Number of Conductors in Cable Trays and Raceway, and Derating. (a) Class 1 Circuit Conductors. Where only Class 1 circuit conductors are in a raceway, the number of conductors shall be determined in accordance with Section 300-17. The derating factors given in Article 310, Note 8(a) of Notes to Ampacity Tables of 0 to 2000 Volts shall apply only if such conductors carry continuous loads in excess of 10 percent of the ampacity of each conductor. (b) Power-Supply Conductors and Class 1 Circuit Conductors. Where power-supply conductors and Class 1 circuit conductors are permitted in a raceway in accordance with Section 725-15, the number of conductors shall be determined in accordance with Section 300-17. The derating factors given in Article 310, Note 8(a) of Notes to Ampacity Tables of 0 to 2000 Volts shall apply as follows: (1) To all conductors where the Class 1 circuit conductors carry continuous loads in excess of 10 percent of the ampacity of each conductor and where the total number of conductors is more than three.