What does NAC capacity limit in a fire alarm system?

• A. The number of devices that can be simultaneously energized.
• B. The voltage rating of the NAC circuits.
• C. The maximum length of a fire alarm circuit.
• D. The number of zones allowed in the system.

Answer: (A)

NAC capacity is about how many devices the notification appliance circuit can energize at the same time. Each device on a NAC draws current when it activates, and the total current drawn must stay within the NAC’s rated supply. If you add more devices or use high‑current devices on the same NAC, you can exceed that limit, causing some devices not to energize reliably or to behave unpredictably. The voltage of NAC circuits is fixed by design, but capacity isn’t about voltage; it’s about the number of devices that can be energized simultaneously without overloading the circuit. The length of the circuit or the number of zones aren’t what this capacity refers to.