Signal Cable Company is the leading manufacturer of fire alarm system cables for the fire protection industry. Our innovative line of cable products includes all power limited cables for use under National Electric Code (NEC) Article 760.


National Electric Code (NEC) Article 760

NEC Article 760 covers "the installation of wiring and equipment of fire alarm systems including all circuits controlled and powered by the fire alarm system." These systems are defined in the NEC as, "The portion of the wiring system between the load side of the overcurrent device or the power-limited supply and the connected equipment of all circuits powered and controlled by the fire alarm system."


Power-Limited Fire Alarm System Cables

Three types of power-limited fire alarm cables are currently in use. These are: FPL, FPLR and FPLP.

  1. Type FPL power-limited fire alarm cable is listed by the NEC as being suitable for general purpose fire alarm use. This listing excludes installation in risers, ducts, plenums and other space used for environmental air unless the cable is installed in conduit. All FPL cables are listed as being resistant to the spread of fire and must pass both UL test 1424 and vertical flame test UL 1581.
  2. Type FPLR power-limited fire alarm riser cable is listed as being suitable for use in a vertical run in a shaft or from floor to floor. All FPLR cables are listed as having fire-resistant characteristics capable of preventing fire from traveling floor to floor. Riser cables must pass both UL test 1424 and the vertical riser flame test UL 1666.
  3. Type FPLP power-limited fire alarm plenum cable is listed by the NEC as being suitable for use in ducts, plenums and other space used for environmental air. All FPLP cables are listed as having adequate fire-resistant and low smoke-producing characteristics and must pass both UL test 1424 and UL tunnel test 910.


Power-Limited Wiring Methods and Materials

Power-limited circuit conductors and cables described in section 760-71 of the NEC must be installed in the following ways:

  1. Installed in raceways or exposed surfaces.
  2. Protected against physical damage.
  3. In metal raceways or rigid nonmetallic conduit where passing through a floor or wall to a height of 7 feet above the floor, unless adequate protection can be afforded by the building construction.
  4. In rigid metal conduit, rigid nonmetallic conduit, intermediate metal conduit or electrical metallic tubing where installed in hoistways.


Listing Requirements

Conductor and cables for power-limited fire alarm circuits shall be listed for the purpose and meet the following requirements:

  1. Conductors are solid or stranded copper. 
  2. Conductors in a multiconductor cable shall not be smaller than 26 AWG. Single conductors shall not be smaller than 18 AWG.
  1. The voltage rating shall not be marked on the cable. Voltage ratings marked on the cables may be misinterpreted to suggest that they can be used for Class 1, electric light and power applications. There are exceptions for cables with multiple listings or in cable substitutions.





Cable Substitutions
Cable Type Cable Substitutions



Conductors of Different PLFA Circuits
  1. Cable and conductors of two or more PLFA circuits, communications circuits or Class 3 circuits are permitted in the same cable, enclosure or raceway.
  2. Conductors of one or more Class 2 circuits are permitted with conductors of PLFA circuits, provided that the insulation of the Class 2 circuit conductors is at least that required by PLFA circuits.


Special Cable Constructions

The increased demand for addressable fire alarm systems and the need to conform to the Americans with Disabilities Act (ADA), have created many changes in fire cable constructions. In response to this new demand, Signal Cable Company now supplies a wide variety of low and mid-capacitance cables.


Low and Mid-Capacitance Cables

Capacitance refers to a cable’s unique ability to store an electric charge and to resist sudden changes in the magnitude of that charge (voltage). It is found not only between the two wires of a twisted pair, but also between adjacent conductors in the same cable. The capacitance between two adjacent conductors is called the mutual capacitance and is expressed in picofarads per foot (pf/ft). In high frequency digital transmissions, mutual capacitance distorts the square wave shape of the signal, causing errors in data transmission. The larger the capacitance, the higher the distortion and error rate.

Addressable fire alarm systems using advanced electronics allow the fire alarm panel to communicate with each base individually using a sophisticated polling process. In some instances, more than 100 devices can be located on a single pair of wires. Due to this need for faster and clearer signal transfer, the capacitance of the cable has become a concern.


New Changes in 2008 NEC Code Article 760
  1. Added the requirements for fire alarm system conductors to comply with 300.8 [see NC 760.24]
  2. Added cable ties as a means of support [see NEC 760.24]
  3. Relocated equipment on removing accessible portions of abandoned cables and added requirements on the durability of tags used to identify cable(s) intended for future use [see NEC 760.25]
  4. Revision to specify the intended objective of identifying fire alarm circuits at terminal and junction locations [see NEC 760.30]
  5. Added requirements for NPLFA and PLFA power sources to be supplied by an individual branch circuit [see NEC 760.41, 760.121]
  6. Added 300.7 to compliance requirements for installation for PFLA cables and conductors [see NEC 760.130(B)]
  7. Revised to include mixed circuit classes in a cable tray [see NEC 760.139]
  8. Added requirements that NPLFA cables used in wet locations must be listed for use in wet locations or have a moisture-impervious metal sheath [see NEC 760.176]
  9. Added requirements for PLFA cables used in wet locations must be listed for use in wet locations or have a moisture-impervious metal sheath [see NEC 760.179]
Review of Cable Requirements

All installations must follow guidelines established by the National Electric Code. Below are some basic practices to remember when installing power-limited fire alarm systems. For a more in-depth review of requirements and installation guidelines, refer to the NEC.

  1. All cables must be UL listed. Check all cables for the proper markings.  Refer to NEC Article 760.
  2. Comply with local wiring requirements.
  3. Only use conductors made of copper.
  4. Test wiring for grounds, short circuits and open faults before the system is placed in operation.
  5. Always use the proper gauge of wire to avoid line loss.
  6. Avoid interference when routing wiring.
  7. Installation shall be made to prevent the spread of fire from floor to floor.
  8. A minimum of 6 inches of free conductor is required in each electrical box to facilitate termination.
  9. All wiring must be terminated with UL listed devices.


Local Codes

Most states and cities adopt the NEC. A few states and cities amend the NEC recommendations regarding cable requirements. Any variances in code are easy to obtain through local officials. Check the local codes to determine if the NEC has been adopted in your area.