Gwen Pots's blog : How to design fire alarm NAC circuits digitally

Notification Appliance Circuits or NAC circuits are a critical part of any fire alarm system. They are responsible for powering and controlling alarms, strobes, bells, and other notification devices that alert occupants during a fire emergency. Designing NAC circuits correctly is essential to ensure proper operation, avoid overloads, and comply with fire codes. Traditionally, NAC circuit design involved manual calculations, hand drawn schematics, and iterative adjustments. This process was time consuming, error prone, and difficult to revise. Modern Fire Alarm Design Software allows engineers and consultants to design NAC circuits digitally, improving accuracy, efficiency, and code compliance.

In this blog, we will explain how to design fire alarm NAC circuits digitally, outline best practices, and highlight why XTEN-AV is a leading choice for fire alarm system design.

Understanding NAC circuits
NAC circuits connect fire alarm control panels to notification devices. Each circuit typically has a voltage limit, current capacity, and a maximum number of devices it can support. Important considerations when designing NAC circuits include:

Device load: Each notification device draws a specific current. The total current on a NAC circuit must not exceed the panel output rating.
Circuit length: Cable resistance affects voltage drop, which can reduce device performance if not calculated correctly.
Zoning: Circuits should be logically grouped to ensure proper alarm coverage and isolation during faults.
Power supplies: Backup power and battery capacity must support all devices on the NAC circuit during emergencies.

Benefits of designing NAC circuits digitally
Designing NAC circuits using Fire Alarm Design Software offers multiple advantages:

Accuracy: Automatic calculations of current, voltage drop, and device limits reduce human error.
Efficiency: Design time is significantly reduced with automated tools for device placement and circuit routing.
Compliance: Built in code checks ensure NAC circuits meet NFPA and local fire codes.
Documentation: Generate professional, submission ready NAC schematics and panel load reports.
Easy modifications: Changes to devices, zones, or circuits can be updated instantly without redrawing diagrams.

Step by step process for designing NAC circuits digitally

Step 1. Import building and floor plans
Begin by importing architectural or structural plans into the software. XTEN-AV supports DWG, DXF, PDF, and BIM models, allowing designers to reference the building layout while planning NAC circuits. Accurate plans are essential to determine cable lengths and device placement.

Step 2. Define zones and panels
Identify all fire alarm control panels in the building and define zones. Each NAC circuit will be assigned to a specific panel and zone to ensure logical grouping of notification devices. Proper zoning is critical for efficient alarm response and fault isolation.

Step 3. Place notification devices
Add all notification devices including horns, strobes, bells, or combination devices. Fire Alarm Design Software can suggest optimal placement based on code requirements, coverage needs, and line of sight for visual or audible alerts.

Step 4. Connect devices to NAC circuits
Digitally draw connections from each panel output to the notification devices. XTEN-AV calculates the total load on each circuit in real time, helping ensure panel outputs are not exceeded.

Step 5. Calculate cable lengths and voltage drop
Accurate cable length estimation is crucial to maintain voltage at the device terminals. The software calculates voltage drop for each device based on cable type, length, and current draw, ensuring proper operation of all notification devices.

Step 6. Validate NAC circuit design
Use built in validation tools to check:

Maximum current for each NAC circuit
Total number of devices per circuit
Voltage drop limits
Proper zoning and circuit distribution

Validation ensures the NAC circuits are safe, reliable, and code compliant.

Step 7. Generate professional schematics and reports
Once the NAC circuits are designed and validated, generate submission ready diagrams and reports. Documentation should include:

NAC circuit diagrams showing panel connections and device placement
Device count and type per circuit
Total current and voltage drop calculations
Panel load summaries
Zone assignments for each circuit

These reports are essential for approvals, installation, and maintenance.

Best practices for digital NAC circuit design

Follow manufacturer specifications
Always check device current ratings, voltage requirements, and panel output limits.
Group devices logically
Distribute devices by zone and floor to ensure alarms are effective and circuits are not overloaded.
Account for backup power
Ensure NAC circuits are designed to operate on battery power during mains failure. Software can calculate total current draw on backup batteries.
Minimize voltage drop
Keep cable runs as short as practical or increase wire gauge to reduce voltage drop and maintain device performance.
Use code compliant spacing
Ensure devices are spaced according to NFPA or local fire code requirements for audibility and visibility.
Review and iterate
Design software allows multiple iterations to optimize circuits, improve coverage, and maintain panel balance.

Why XTEN AV is ideal for NAC circuit design
XTEN-AV provides an advanced Fire Alarm Design Software solution specifically designed for modern fire alarm projects. Its key features include:

Automated NAC circuit creation with device load and voltage drop calculation
Real time validation of panel outputs and circuit limits
Integration with floor plans and BIM models for accurate device placement
Professional schematic and panel load report generation
Multi floor and multi zone support for complex buildings
Cloud based collaboration for multiple team members

Using XTEN-AV ensures NAC circuits are designed efficiently, accurately, and in full compliance with code requirements, reducing installation errors and improving system reliability.

Conclusion
NAC circuits are a vital component of fire alarm systems, providing the connection and power for notification devices that alert occupants during emergencies. Designing them manually can be time consuming and prone to errors. Fire Alarm Design Software like XTEN-AV allows engineers to design NAC circuits digitally, ensuring accurate device placement, proper zoning, correct current calculations, voltage drop management, and professional documentation. By following a structured digital design process, fire alarm professionals can create safe, reliable, and code compliant NAC circuits for any building type, simplifying installation and improving overall fire safety.

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