Fire Alarm design, installation, monitoring and testing.

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Fire Alarm wire

Larry Love

What type of wire should I install for fire alarm systems?

  1. Use the wire that the manufacturer recommends. Most of the time the following wire will work for most fire alarm systems: 18 gauge 4 conductor FPL, FPLR or FPLP solid copper non shielded for the SLC and 14 gauge 2 conductor FPL, FPLR or FPLP solid copper non shielded for NAC horn strobes and strobe circuits.

  2. Can I use THHN for the horn strobes? THHN exceeds the voltage requirements and yes it will work although often the fire marshal will want the red fire rated wire.

  3. FPL is for one story only

  4. FPLR is for more than one story (more than one floor) the R is for Riser and it means it will hold it’s own weight in a shaft.

  5. FPLP is PLENUM rated and meets the requirements for more than one floor and it lets off less toxic fumes while burning and is to be used when you have PLENUM areas. l

  6. Shielded wire would be appropriate for voice evac speakers. 14g2c FPLP shielded /twisted although it is best to install what the data sheet says for the individual appliances.

Some systems require so many twists per foot for data transfer and other brands will work with or without the twists so make sure you follow the data sheet recommendations from the fire alarm system you purchase.



How many devices can I put on a circuit?

  1. Each system may be a bit different so it all depends on the distance of the wire runs and the mA current draw of your appliances

  2. The old rule of thumb said no more than 8 per circuit although it depends on he mA draw of each appliances added up so if you have a 1.5 amp circuit save 20% for future or 300mA and just use the 1200mA so 1200 divided by 176mA wall mount horn strobe would let you put 6 appliances on one circuit so you have 300mA extra.

  3. If you install 2.5amp circuits then obviously you can install more per circuit depending on the distance of the horn strobes.

  4. Old mini horns had a mA draw of around 17mA so you could put 70 on a circuit but the new low frequency mini horns draw just over 107mA so you could only put 11 on a circuit.


Call Larry Love 801 898 6003 with fire alarm wire questions or when you need a quote for a fire alarm system.