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.
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."
Three types of power-limited fire alarm cables are currently in use. These are: FPL, FPLR and FPLP.
Power-limited circuit conductors and cables described in section 760-71 of the NEC must be installed in the following ways:
Conductor and cables for power-limited fire alarm circuits shall be listed for the purpose and meet the following requirements:
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.
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.
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.
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.