⚡ NFPA 72 §10.18 Calculator

Voltage Drop & NAC Circuit Analysis

Calculate end-of-line voltage for notification appliance circuits per NFPA 72 §10.18. Verify all devices receive adequate voltage at full alarm load.

Circuit Parameters

Wire resistance: 7.95 Ω/1000 ft · Total circuit current: 630 mA

NAC Device Schedule

DevicemA eachQtyDistance (ft)V at DeviceStatus
22.5V✓ OK
21.2V✓ OK
20.2V✓ OK
✅
Circuit PASS
All devices receive adequate voltage
Total Circuit Current630 mA
Max Device Distance380 ft
Wire Resistance (EOL)6.042 Ω
Voltage Drop (EOL)3.81 V (15.9%)
Voltage at EOL Device20.19 V
Min Required Voltage16 V
Formula
R = (Ω/kft ÷ 1000) × L × 2
V_drop = I_total × R
V_EOL = V_supply − V_drop
L = one-way wire length (ft)