NICET-Fire-Alarm: Voltage Drop Calculations for Notification Appliance Circuits — Flashcards

Voltage drop on NACs is critical because horns/strobes require a minimum operating voltage at the last device under worst-case load. You calculate voltage drop using circuit current, conductor resistance (wire gauge, length, temperature), and circuit topology. If voltage at the end is too low, devices may be dim, quiet, or fail to operate.

Worked example(s)
Worked example (conceptual): A NAC draws 2.0 A total and uses a long run of smaller gauge wire. Higher resistance increases voltage drop (Vdrop = I × R). To fix: increase wire size, shorten run, split circuit, or reduce device load per NAC.