4. Do not T-Tap the wiring.
6.2.1.4 NAC wiring distance
This section describes the wiring distances for the Class A and Class B NACs. The wiring distances for the Class A and Class B NACs are
calculated at 49°C (120°F). If you are installing in locations that are exposed to higher temperatures, refer to NEC. The wiring distance is
based on a 3 V drop and takes into account the control unit's worst case output voltage.
Table 5: NAC Class A wiring distances
Maximum wiring distance in feet
Alarm current A 18 AWG 16 AWG 14 AWG 12 AWG Line resistance,
Ohms
.25 420 667 1063 1691 6
.50 210 334 532 845 3
.75 140 222 354 564 2
1.0 105 167 266 423 1.5
1.25 84 133 213 338 1.2
1.50 70 111 177 282 1
The wiring distance for the Class A NACs is from the control unit's terminals to the last appliance and back to the control unit's terminals.
Table 6: NAC Class B wiring distances
Maximum wiring distance in feet
Alarm current A 18 AWG 16 AWG 14 AWG 12 AWG Line resistance,
Ohms
.25 840 1335 2126 3382 12
.50 420 667 1063 1691 6
.75 280 445 709 1127 4
1.0 210 334 532 845 3
1.25 168 267 425 676 2.4
1.50 140 222 354 564 2
The wiring distance for the Class B NACs is from the control unit's terminals to the last appliance.
6.2.1.5 NAC wiring specifications
The NAC ratings for specific voltage specifications are listed in Notification appliances circuits.
• The maximum ripple is 1/2 V peak-to-peak.
• The current rating for the circuit is 1.5 A maximum. The total current rating for the unit's power consumption including the panel
board, NAC circuit and Aux circuits must be less than 2.2 A.
• The maximum wiring capacitance, when using two-wire audible or visible appliances is 0.22 μF.
• See Table 5 and Table 6 for the wiring distances for 0.25 A to 1.5 A loads.
• For all other UL listed notification appliances, the rating for NAC is 24 VDC regulated at a maximum of 1.5 A.
page 24 579-1402 Rev B
2004 Foundation Series Fire Alarm Control Unit Installation Guide
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