Fire Alarm Voltage Drop & NAC Load

Preliminary sizing aid only. This tool applies the standard NFPA 72 §18.3.7 end-of-line (EOL) voltage drop method with NEC Chapter 9 Table 8 conductor resistance values. It does not include a manufacturer device database — enter each device's worst-case current from the actual UL-listed datasheet. Final voltage drop and NAC loading calculations must be documented and submitted per the AHJ's requirements and reviewed by a qualified fire alarm professional against the specific control panel/power supply manufacturer's own worksheet.

Circuit & WireTag, wire gauge, length, circuit class

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Circuit tag

Wire gauge (AWG, copper) One-way run length (ft)

Circuit class

Devices on CircuitNAC appliance current — worst-case from datasheet

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Label Qty

Current, each (A)

Source & LimitsPanel output, minimum device voltage, NAC rating

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Source voltage, CUSTV (V) Minimum device voltage (V)

Module voltage adjustment (V, optional) NAC circuit rated capacity (A)

Result — Voltage Drop & NAC Load

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End-of-line voltage (V)

Voltage drop

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NAC utilization

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Total circuit current

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Max length at this load

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Wire resistance

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Circuit class

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Include Calculation Ledger in report Include OhmZone brand mark in report

Report template (.docx, optional)

Calculation Ledger

clause-by-clause

Device Load Summary

Label	Qty	Current (A ea.)	Total (A)