Circuit Types for Fire Alarm Cable

There are two different types of fire alarm system circuits, NPLFA and PLFA. NPLFA can operate at up to 600V with unlimited power output. A PLFA has limited voltage and power which is dictated by the listed power source. Basically this means that there are easier installation requirements for the PLFA circuit, however listed below is an overview for both NPLFA and PLFA.



Overcurrent protection: For conductors 14 AWG and larger, this must be limited to the conductor ampacity. Overcurrent protection cannot exceed 7A for 18 AWG conductors or 10A for 16 AWG conductors.

Wiring methods: NPLFA wiring methods apply conditionally. If you are trying to install fire alarm cables in ducts or plenums, which is necessary for a smoke detector inside of an air duct, those cables must be installed in electrical metallic tubing, intermediate metal conduit, or rigid metal conduit.

Plenum-rated fire alarm cables can be installed above a suspended ceiling or below a raised floor used for environmental air movement. You can also install nonplenum-rated fire alarm cables above a suspended ceiling or below a raised floor used for environmental air, but the installation of the cable must be within electrical metallic tubing or one of the previously mentioned raceways. Nonplenum-rated fire alarm cables are allowed above a suspended ceiling that is not used for environmental air. Fire alarm cables installed beneath a raised floor in an information technology equipment room aren’t required to be plenum rated.

Splices must be in enclosures, except for splices and terminations in fire alarm devices and utilization equipment (e.g., detectors). This rule does not apply to multi-conductor NPLFA cables for circuits operating at 150V or less.

Conductor size: Only copper conductors can be used for fire alarm systems. You can use conductors of sizes 18 AWG and 16 AWG (installed in a raceway, enclosure, or listed cable). Conductors larger than 16 AWG must not supply loads greater than the ampacity.

Conductor insulation: Use conductors with a 600V insulation rating. For conductors 18 AWG and 16 AWG, comply with application provisions.



Wiring methods: NPLFA wiring methods and materials can be used, instead of PLFA. PLFA wiring requirements are minimal and can easily be summed up. Put cable splices or terminations in listed fittings, boxes, etc., and ensure exposed cables are adequately supported.

Separation from power conductors: Provide a minimum of 2 inches of separation between PLFA conductors and conductors of electric light, power, Class 1, or NPLFA circuits. Do not put PLFA conductors in any enclosure, raceway, or cable with conductors of electric light, power, Class 1, or NPLFA circuit conductors. The only exception is when barriers are provides and conductors are present solely for connection to the same equipment.