Fire-Lite MS-10UD Series FACP - Manual (Page 42)

42 MS-5UD & MS-10UD Series Manual — P/N 52626:C4 3/7/2014
Installation ANN-BUS Devices
To calculate the wire gauge that must be used to connect ANN-BUS modules to the FACP, it is nec-
essary to calculate the total worst case current draw for all modules on a single 4-conductor bus.
The total worst case current draw is calculated by adding the individual worst case currents for each
module. The individual worst case values are shown in the following table:
After calculating the total worst case current draw, Table 2.1 specifies the maximum distance the
modules can be located from the FACP on a single wire run. The table ensures 6.0 volts of line
drop maximum. In general, the wire length is limited by resistance, but for heavier wire gauges,
capacitance is the limiting factor.
These cases are marked in the chart with an asterisk (*). Maximum length can never be more than
6,000 feet (1,800 m), regardless of gauge used. The formula used to generate this chart is shown in
the note below.
The following formulas were used to generate the wire distance chart:
Model Number Worst Case Current Draw 1
1 Total worst case current draw on a single ANN-BUS cannot exceed 0.5 amp .
ANN-80(C) LCD Annunciator/Indicator 0.040 amps
ANN-S/PG Serial/Parallel Printer Interface Module 0.040 amps
ANN-I/O LED Driver Module 0.200 amps
ANN-LED Annunciator Module 0.068 amps
ANN-RLY Relay Module 0.075 amps
24 VDC Power Wiring Distance: ANN-BUS Modules to FACP
Total Worst Case Current
Draw (amps)
22 Gauge 18 Gauge 16 Gauge 14 Gauge
0.100 1,852 ft. 4,688 ft. * 6,000 ft. * 6,000 ft.
0.200 926 ft. 2,344 ft. 3,731 ft. 5,906 ft.
0.300 617 ft. 1,563 ft. 2,488 ft. 3,937 ft.
0.400 463 ft. 1,172 ft. 1,866 ft. 2,953 ft.
0.500 370 ft. 938 ft. 1,493 ft. 2,362 ft.
Table 2.1 Wiring Distances
Maximum Resistance (Ohms) =
6.0 Volts
Total Worst Case Current Draw (amps)
Maximum Wire Length (feet)
(6,000 feet maximum)
=
Maximum Resistance (Ohms)
*500
Rpu
where: Rpu = Ohms per 1,000 feet for various Wire Gauges (see table below)