Takeoff & Estimating — Electrical & Low-Voltage

NAC (Notification Appliance Circuit)

The fire-alarm output circuit that powers horns, strobes and speakers.

Quick Answer

A notification appliance circuit (NAC) is the fire-alarm output circuit that carries power and signals from the control panel or a booster power supply to audible and visible devices such as horns, strobes and speakers. Plans show the devices and circuit counts, and estimators count the devices in EA and the cable in LF.

The Full Picture

A fire alarm system has input circuits, which bring information from smoke detectors, pull stations and waterflow switches back to the panel, and output circuits, which tell people to leave. A notification appliance circuit is the output side. When the panel goes into alarm, each NAC energizes the horns, strobes, speaker/strobes or chimes connected to it. The governing document for how those circuits must be arranged and supervised is NFPA 72, the National Fire Alarm and Signaling Code, which the authority having jurisdiction adopts together with the local building code.

On the drawings, the NAC is rarely drawn as a single labeled line. The device layout on the fire alarm floor plans shows each appliance with a symbol and often a candela rating, and the circuits are shown by home-run notation or by a circuit tag at each device. The fire alarm riser diagram shows the control panel, any remote power supplies or NAC extender panels, and how many NACs leave each one. A panel schedule or a sequence-of-operations sheet may give the number of NACs per panel, which is what an estimator uses to confirm that the quantity of panels and power supplies is enough.

The takeoff unit has two parts. The appliances are counted EA by type and rating, because a wall-mounted horn/strobe, a ceiling strobe and a speaker/strobe are priced differently. The cable is measured in LF, usually as the length of each circuit run plus risers, with the conductor count and the cable type read from the specifications, which for fire alarm sit with the electrical and electronic safety divisions (Division 26 and Division 28). Booster power supplies, NAC extenders and the matching end-of-line devices are counted EA from the riser.

The usual pricing mistake is to count the devices on the floor plan and forget the equipment that feeds them. A panel with a fixed number of NAC outputs can run out as the device count grows during design, and the added power supply, its dedicated branch circuit and its battery cabinet all land in the estimate late. A second mistake is measuring cable by straight lines between devices when the spec requires conduit or a particular cable type, or when circuits home-run to a panel instead of daisy-chaining through the floor.

Real Examples

→Worked takeoff: appliances and cable on a three-story office: Each floor plan shows 12 horn/strobes, so the device count is 12 x 3 = 36 EA. Measured circuit runs are 240 LF per floor, so floors total 240 x 3 = 720 LF, and the riser run from the panel is 40 LF. Measured cable is 720 + 40 = 760 LF. An assumed 10% for drops and slack gives 760 x 1.10 = 836 LF, which the estimator carries as 840 LF.

→Counting circuits from the riser: The riser shows one control panel with two NAC outputs and a remote power supply with two more. The estimator confirms the four NACs cover the 36 appliances with the spare capacity the spec asks for. If the device count were to grow, the riser would show whether another power supply is needed.

→Catching a mixed-device scope: The legend lists ceiling strobes in corridors and speaker/strobes in the assembly room. The estimator creates two device lines instead of one, since the speakers need different cable and a different appliance price.

Common Misconceptions

People assume: Counting the horns and strobes on the plans prices the notification system.

Actually: The devices are only the load side. Panels, booster power supplies, battery capacity, end-of-line devices and the cable and conduit between them are separate scope, and they are read from the riser diagram and the specifications.

People assume: A NAC is a type of device.

Actually: It is a circuit that serves many devices. Appliances are counted EA, while the circuit itself shows up as cable in LF and as an output on a panel or power supply.

Does MeltPlan Solve This?

Partially — adjacent

Counting fire alarm appliances by type from the floor plans and measuring circuit runs is takeoff work, and MeltPlan's takeoff service uses AI to pull quantities from PDF plans, with US-based experienced estimators reviewing and adjusting them. Choosing the NAC arrangement, power supply sizing and which devices the code requires stays with the fire alarm engineer and your estimating team.

Get fire alarm device counts and cable runs from your plans →

Frequently Asked Questions

What does NAC stand for in fire alarm systems?

NAC stands for notification appliance circuit. It is the circuit that carries power and control from a fire alarm panel or booster power supply to horns, strobes, speakers and similar devices.

How is a NAC different from an initiating device circuit?

An initiating device circuit brings alarm signals from detectors and pull stations to the panel. A NAC sends power out from the panel to the devices that warn occupants.

What unit is a NAC takeoff in?

Devices on the circuit are counted EA by type, cable is measured in LF, and panels, power supplies and extenders are counted EA from the riser diagram.

Which standard covers notification appliance circuits?

NFPA 72, the National Fire Alarm and Signaling Code, covers how fire alarm circuits are installed and supervised. Which edition applies depends on the code your jurisdiction has adopted.