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 fire protective signaling 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. (2) To the power-supply conductors only, where the fire protective signaling 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) Cable Trays. Where fire protective signaling circuit conductors are installed in cable trays, they shall comply with Sections 318-9 through 318-11. C. Power-Limited Fire Protective Signaling Circuits 760-21. Power Limitations. As specified in Table 760-21(a) for ac circuits and Table 760-21(b) for dc circuits, the power for power-limited fire protective signaling circuits shall be either inherently limited requiring no overcurrent protection or limited by a combination of a power source and overcurrent protection. 760-22. Circuit Marking. The equipment shall be durably marked where plainly visible to indicate each circuit that is a power-limited fire protective signaling circuit. (FPN): See Section 760-28(a), Exception No. 3 where a power-limited circuit is to be reclassified as a nonpower-limited circuit. 760-23. 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. 760-24. Location of Overcurrent Device. Overcurrent device, where required, shall be located at the point where the conductor to be protected receives its supply. Table 760-21(a). Power Source Limitations for Alternating-Current Fire Protective Signaling Circuits 70-774 Inherently Limited Power Source Not Inherently Limited Power Source (Overcurrent protection not required) (Overcurrent protection required) Circuit Voltage Over 20 and Over 30 and Over 20 and Over 100 and Vₘₐₓ (Volts) (Note 1) 0 through 20 through 30 through 100 0 through 20 through 100 through 150 Power Limitations 250 (VA) max (Volt-Amps) - - - 250 N.A. (Note 1) (Note 2) Current Limitations max (Amps) 8.0 8.0 150/V max 1000/V 1000/V 1.0 max max (Note 1) Maximum Overcurrent Protection - - - 5.0 100/V max 1.0 (Amps) VA 5.0 X V. 100 100 5.0 X V 100 100 Power Source Maximum Namemax plate Ratings (Volt-Amps) max NATIONAL ELECTRICAL CODE Current 5.0 (Amps) 100/V max 100/V max 5.0 100/V max 100/V max Supply Conductors and Cables See Section 760-25 Circuit Conductors and Cables See Sections 760-49 through 760-53 Table 760-21(b). Power Source Limitations for Direct-Current Fire Protective Signaling Circuits Inherently Limited Power Source Not Inherently Limited Power Source (Overcurrent protection not required) (Overcurrent protection required) Circuit Voltage Over 20 and Over 30 and Over 100 and Over 20 and Over 100 and Vₘₐₓ (Volts) (Note 1) 0 through 20 through 30 through 100 through 250 0 through 20 through 100 through 150 Power Limitations 250 (VA) max (Volt-Amps) - - - - 250 N.A. (Note 2) (Note 1) Current Limitations max (Amps) 8.0 8.0 150/V max 0.030 1000/V. 1000/V 1.0 max max (Note 1) Maximum Overcurrent Protection - - - 5.0 100/V max 1.0 (Amps) VA 5.0 X Vₘₐₓ 100 100 0.030 X V. max 5.0 X max 100 100 Power Source Maximum Nameplate Ratings (Volt-Amps) Current 5.0 100/V max 100/V max 0.030 5.0 100/V max 100/V. max (Amps) Supply Conductors See Section 760-25 and Cables ARTICLE 760 - FIRE PROTECTIVE SIGNALING SYSTEMS Circuit Conductors and Cables See Sections 760-49 through 760-53 Notes for Tables 760-21(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 current-limiting impedance, listed for the purpose, 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- 70-775 limiting impedance shall not be bypassed when determining Iₘₐₓ and VAₘₐₓ· Note 2. If the power source is a transformer, (VA)ₘₐ is 350 or less when Vₘₐₓ is 15 or less. 70-776 NATIONAL ELECTRICAL CODE 760-25. 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 Part B and Chapter 3. Transformers or other devices supplied from power-supply conductors shall be protected by an overcurrent device rated not over 20 amperes. Exception: The input leads of a transformer or other power source supplying power-limited fire protective signaling 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