Special Systems (Fire Alarm, Security, Communications, Data)
This domain covers the systems with their own articles and their own standards: fire alarm under Article 760 and NFPA 72, communications under Article 800, coaxial under 820, network-powered broadband under 830, and optical fiber under 770, plus security and access control interfaces.
Core rules
- Power-limited fire alarm cable is marked FPL, FPLR (riser), or FPLP (plenum); non-power-limited circuits use NPLF types. Separation from power, Class 1, and non-power-limited circuits follows the same barrier or spacing approach used for Class 2/3.
- NFPA 72 circuit classes: Class B uses a single path, so one open disables everything beyond the break while the panel shows trouble; Class A returns the path to the panel so a single open does not disable devices. Styles map across: Style B and D for initiating device circuits, Style Y and Z for notification circuits, Style 4, 6, and 7 for signaling line circuits, with Style 7 adding fault isolation.
- Communications cable maintains 2 in. of separation from power conductors or a permanently installed barrier.
- Access control: fail-safe locks release on power loss (life safety egress) and fail-secure locks stay locked, which requires listed exit hardware and request-to-exit devices.
- Fire alarm interfaces include elevator recall, HVAC shutdown, door hold-open release, and sprinkler flow/tamper monitoring.
Worked example
A notification appliance circuit is rated 2.0 A at 24 V. Thirty horns at 60 mA draw 1.8 A, and ten strobes at 110 mA draw 1.1 A, for 2.9 A total, which exceeds the circuit rating. Split the devices across two circuits or add a listed booster supply, then recheck voltage drop at the end of the run and battery standby for the added load.
Traps that cost marks
Assuming one NAC can carry every appliance; confusing Style letters with Class letters; and installing fail-secure locks without the required egress release.