Edwards Signaling FireShield 10 Zone - Manual (Page 46)

Calculations
A.4 FireShield Technical Reference Manual
Notification appliance circuit maximum
wire length calculation
Use this worksheet to determine the maximum wire length of
a notification appliance circuit. Fill in one worksheet for each
NAC connected to the panel.
Wire length matrix
Wire lengths in the following table are based on a voltage drop
of 1.9 volts or 10% and total load at the end of the line.
Maximum wire length
Current
required 18 AWG 16 AWG 14 AWG 12 AWG
0.25 584 950 1460 2170
0.50 292 474 730 1084
0.75 194 316 486 722
1.00 146 236 364 542
1.25 116 190 292 434
1.50 92 158 242 362
Maximum signal loss allowed [1] V
× 1000
Wire resistance per 1000 ft/pair [2] ÷ Ω
Total operating current required [3] ÷ A
Maximum circuit length ft
Notes
[1] 1.6 V for 230 V at 50 Hz
1.8 V for 230 V at 60 Hz
1.9 V for 120 V at 60 Hz
[2] Use 3.5 Ω for 12 AWG and 2.5 sq mm wire, 5.2 Ω for 14
AWG and 1.5 sq mm wire, 8.0 Ω for 16 AWG and 1.0 sq
mm wire, and 13.0 Ω for 18 AWG and 0.75 sq mm wire.
[3] Use the filtered 20 Vdc Average Operating Current ratings
found on the installation or catalog sheet of each device.