NAC

Definition

A Notification Appliance Circuit (NAC) is an electrical circuit specifically used to connect fire alarm system output devices, such as bells, horns, strobes, and speakers, to the fire alarm control panel. These circuits are designed to alert building occupants of a fire or other emergencies.

Purpose

The primary purpose of a NAC is to ensure the proper operation of fire alarm notification devices, which are critical for alerting occupants to evacuate a building in the event of a fire or other emergency. NACs ensure that these devices receive the necessary power and signal to activate correctly. They are configured in either a Class "A" or Class "B" configuration to provide redundancy and reliability in emergency communication.

Examples of Use

• Class "A" Configuration: In a Class "A" NAC configuration, the circuit forms a loop, returning to the control panel. This setup provides a path for current to flow in both directions, ensuring that if a single break occurs in the circuit, the devices will still function.
• Class "B" Configuration: In a Class "B" NAC configuration, the circuit does not loop back to the control panel. If a break occurs, devices beyond the break will not operate, but it is simpler and more cost-effective for smaller installations.
• Fire Alarm Systems: NACs are used in fire alarm systems to connect various notification devices. When the fire alarm control panel detects an alarm condition, it sends a signal through the NAC to activate the bells, horns, and strobes.

Related Terms

• Fire Alarm Control Panel (FACP): The central unit that monitors inputs and controls outputs through NACs.
• Initiating Device Circuit (IDC): A circuit used to connect fire detection devices like smoke detectors to the FACP.
• Supervision: The monitoring of the NAC for integrity, ensuring that the circuit can effectively transmit signals to the notification devices.
• Emergency Communication Systems (ECS): Systems that use NACs to broadcast voice messages and instructions during emergencies.

Notes

• Installation Standards: NAC installations must comply with specific codes and standards, such as those outlined by the National Fire Protection Association (NFPA).
• Power Requirements: Notification devices on a NAC must be properly powered, and calculations must ensure that the circuit can supply adequate current to all devices.
• Testing and Maintenance: Regular testing and maintenance of NACs are essential to ensure their functionality in an emergency. This includes checking for proper operation and ensuring that wiring and connections are intact.