National Electrical Code Tips: Article 760, Fire Alarm Systems, Part 2
- What if your fire alarm system extends beyone one building? If the extension runs outdoors, the circuits must meet the requirements of Parts II, III, and IV of Article 800. Also, they must meet the installation requirements of Article 300 [760.32].
- Fire alarm circuits are one of two types: Non-power limited (NPLFA) (must comply with Article 760, Parts I and II) and Power-limited (PFLA) (must comply with Article 760, Parts I and III) [760.35]. All fire alarm circuits must comply with Article 760, Part I. The difference between NPLFA and PFLA is the former must comply with Part II and the latter with Part III. In this Part 2, we will be discussing only NPFLA circuits.
- The power source of NPLFA circuits must comply with Chapters 1 - 4, and its output voltage cannot exceed 600V nominal [760.41(A)].
- The fire alarm circuit disconnect of an NPLFA circuit can be secured in the "ON" position [760.41(A)].
- The branch circuit supplying the NPLFA fire alarm equipment must be dedicated to that purpose. It can't supply other loads [760.41(B)]. And the circuit disconnecting means must be marked to indicate it's for a fire alarm circuit.
- Overcurrent protection for NPLFA conductors that are 14AWG or larger must be sized per the conductor ampacity, without applying the ampacity adjustment and correction factors of 310.15 to the ampacity calcuation [760.43].
- Overcurrent protection must not exceed 7A for 18AWG conductors or 10A for 16AWG conductors [760.43].
- Locate the OCPDs at the point where the protected conductor receives its supply [760.45]. There are three exceptions to this rule.
- One exception is allowed if the OCPD protecting the larger conductor also protects the smaller conductor. The second exception is for transformer secondary conductors. This is highly detailed in 760.45 Exception No. 2, so read that carefully.
- The third exception is for electronic power source output conductors. As with the second exception, the rule is highly detailed and must be read carefully; 760.45 Exception No. 3. Further, an Information Note follownig Exception No. 3 helps explain what's meant in the wording of that Exception; read it carefully, too!