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7-6
Table 7-1 lists the maximum distances from the NAC terminal block to the last appliance
in a Class A configuration, depending on wire gauge and current. Use Table 7-1 to
calculate wire distances for your application if you are using Class A wiring.
Table 7-1. Class A Wiring Distances
Alarm
Current @
24 V
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 420 ft. (128 m) 667 ft. (203
m)
1,063 ft. (324
m)
1,691 ft. (515
m)
6 Ohms
0.50 A 210 ft. (64 m) 334 ft. (102
m)
532 ft. (162 m) 845 ft. (258 m) 3 Ohms
0.75 A 140 ft. (43 m) 222 ft. (68 m) 354 ft. (108 m) 564 ft. (172 m) 2 Ohms
1 A 105 ft. (32 m) 167 ft. (51 m) 266 ft. (81 m) 423 ft. (129 m) 1.5 Ohms
1.25 A 84 ft. (26 m) 133 ft. (41 m) 213 ft. (65 m) 338 ft. (103 m) 1.2 Ohms
1.50 A 70 ft. (21 m) 111 ft. (34 m) 177 ft. (54 m) 282 ft. (86 m) 1 Ohm
1.75 A 60 ft. (18 m) 95 ft. (29 m) 152 ft. (46 m) 242 ft. (74 m) 0.86 Ohm
2 A 53 ft. (16 m) 83 ft. (25 m) 133 ft. (41 m) 211 ft. (64 m) 0.75 Ohm
2.25 A 47 ft. (14 m) 74 ft. (23 m) 118 ft. (36 m) 188 ft. (57 m) 0.67 Ohm
2.50 A 42 ft. (13 m) 67 ft. (20 m) 106 ft. (32 m) 169 ft. (51 m) 0.60 Ohm
2.75 A 38 ft. (12 m) 61 ft. (19 m) 97 ft. (30 m) 154 ft. (47 m) 0.55 Ohm
3 A 35 ft. (11 m) 56 ft. (17 m) 89 ft. (27 m) 141 ft. (43 m) 0.50 Ohm
Notes:
• Max Distance = distance from SPS/RPS to last appliance.
• This table is calculated at 49 degrees Centigrade (120 degrees
Fahrenheit). If you are installing in locations that could be exposed to
higher temperatures, refer to NEC Tables 7 and 8 in NFPA code, or
applicable local standard.
• Distances are based on a 3 V drop, and take into account the worst-case
panel output voltage. These distances are worst case to allow for one
single load at the furthest point.
• If circuit integrity wire is used instead of housing cable in a fire-rated
enclosure, reduce wiring distances by 38 feet (12 m) for every 10 feet (3
m) of potential exposure.
• For other wire gauges (e.g. 4 mm
2
) multiply the distance specified for the
nearest wire size by the ratio of the wire area, e.g. for 3A on 4 mm
2
look
up 3A on 12AWG (3.3 mm
2
) and multiply the resulting 43m x 4.0/3.3 =
52m.
Continued on next page
Class A NAC
Wiring Table