Which statement correctly describes the required power source for a PLFA circuit?

Which statement correctly describes the required power source for a PLFA circuit?

• A. Listed PLFA or Class 3 transformer
• B. Class 2 transformer only
• C. Standard 120V supply
• D. Only battery backup

Answer: (A)

Power-limited fire alarm (PLFA) circuits must be fed from a source that is specifically approved for PLFA use and energy-limited. The only sources that meet this requirement are a listed PLFA power supply or a Class 3 transformer. A listed PLFA power supply is built and tested for fire alarm circuits with the appropriate output limits and protective features. A Class 3 transformer provides a safe, energy-limited source suitable for these circuits. A standard 120V supply isn’t appropriate because it isn’t energy-limited for PLFA use, and a bare battery backup by itself isn’t a complete, listed PLFA power source.

Power-limited fire alarm (PLFA) circuits must be fed from a source that is specifically approved for PLFA use and energy-limited. The only sources that meet this requirement are a listed PLFA power supply or a Class 3 transformer. A listed PLFA power supply is built and tested for fire alarm circuits with the appropriate output limits and protective features. A Class 3 transformer provides a safe, energy-limited source suitable for these circuits. A standard 120V supply isn’t appropriate because it isn’t energy-limited for PLFA use, and a bare battery backup by itself isn’t a complete, listed PLFA power source.