Step-by-step guide to calculating voltage drop on fire alarm notification appliance circuits (NAC) and initiating device circuits (IDC) — with formulas, examples, and NFPA 72 compliance tips.
Fire alarm notification appliances — horns, strobes, and horn/strobes — are rated to operate within a specific voltage range, typically 16–33V DC for 24V systems. If the voltage delivered to the last device on a circuit drops below the minimum rating, that device may not operate at full intensity or at all during an alarm. This is a life-safety failure.
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