6-3
Power supply wiring distances, continued
Class B NAC
wiring table
Table 6-2 lists the maximum distances from the NAC terminal block to the last appliance in a
Class B configuration, depending on wire gauge and current. Use Table 6-2 to calculate wire
distances for your application if you are using Class B wiring.
Note:
• Max distance = distance from MSS to last appliance.
• This table is calculated at 49
o
C (120
o
F). If you are installing in locations that could be exposed to
higher temperatures, refer to NEC Table 8.
• Distances are based on a 3V drop, and take into account the worst-case panel output voltage.
• If circuit integrity wire is used instead of housing cable in a fire rated enclosure, reduce wiring distances
by 38 ft (12 m) for every 10 ft (3 m) of potential exposure.
Table 6-2. Class B wiring distances
Alarm current
@ 24 VDC
Max distance
w/ 18 AWG
(0.8231 mm
2
)
Max distance
w/ 16 AWG
(1.309 mm
2
)
Max distance
w/ 14 AWG
(2.081 mm
2
)
Max distance
w/ 12 AWG
(3.309 mm
2
)
DC resistance
0.25 A 840 ft (256 m) 1,335 ft (407 m) 2,126 ft (648 m) 3,382 ft (1,031 m) 12 Ohms
0.50 A 420 ft (128 m) 667 ft (203 m) 1,063 ft (324 m) 1,691 ft (515 m) 6 Ohms
0.75 A 280 ft (85 m) 445 ft (136 m) 709 ft (216 m) 1,127 ft (344 m) 4 Ohms
1.00 A 210 ft (64 m) 334 ft (102 m) 532 ft (162 m) 845 ft (258 m) 3 Ohms
1.25 A 168 ft (51 m) 267 ft (81 m) 425 ft (130 m) 676 ft (206 m) 2.4 Ohms
1.50 A 140 ft (43 m) 222 ft (68 m) 354 ft (108 m) 564 ft (172 m) 2 Ohms
1.75 A 120 ft (37 m) 191 ft (58 m) 304 ft (93 m) 483 ft (147 m) 1.71 Ohms
2.00 A 105 ft (32 m) 167 ft (51 m) 266 ft (81 m) 423 ft (129 m) 1.5 Ohms
2.25 A 93 ft (28 m) 148 ft (45 m) 236 ft (72 m) 376 ft (115 m) 1.33 Ohms
2.50 A 84 ft (26 m) 133 ft (41 m) 213 ft (65 m) 338 ft (103 m) 1.2 Ohms
2.75 A 76 ft (23 m) 121 ft (37 m) 193 ft (59 m) 307 ft (94 m) 1.09 Ohms
3.00 A 70 ft (21 m) 111 ft (34 m) 177 ft (54 m) 282 ft (86 m) 1 Ohm
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