4 sbus wiring, 1 calculating wiring distance for sbus modules, Sbus wiring -7 – Fire-Lite MS-25E Addressable Fire Control Panel User Manual
Page 37: 1 calculating wiring distance for sbus modules -7
Control Panel Installation
53688
4-7
4.4
SBUS Wiring
This section contains information on calculating SBUS wire distances and the types of wiring
configurations (Class B).
4.4.1
Calculating Wiring distance for SBUS modules
The following instructions will guide you in determining the type of wire and the maximum
wiring distance that can be used with control panel SBUS accessory modules.
To calculate the wire gauge that must be used to connect SBUS modules to the control panel,
it is necessary 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 table below.
Note: Total worst case current draw on a single SBUS cannot exceed 500 mA.
After calculating the total worst case current draw, Table 4-1 specifies the maximum distance
the modules can be located from the panel on a single wire run. The table insures 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, regardless of gauge used. (The formula used to generate this chart is shown in
the note below).
Model Number
Worst Case Current Draw
MS-25 Remote Fire Annunciator
.04 amps
Table 4-1: Wire Distance Per Wire Gauge Using Copper Wire
Wiring Distance: SBUS Modules to Panel
Total Worst Case
Current Draw (amps)
22 Gauge
18 Gauge
16 Gauge
14 Gauge
0.100
1852 ft.
4688 ft.
* 6000 ft.
* 6000 ft.
0.200
926 ft.
2344 ft.
3731 ft.
5906 ft.
0.300
617 ft.
1563 ft.
2488 ft.
3937 ft.
0.400
463 ft.
1172 ft.
1866 ft.
2953 ft.
0.500
370 ft.
938 ft.
1493 ft.
2362 ft.
0.600
309 ft.
781 ft.
1244 ft.
1969 ft.
0.700
265 ft.
670 ft.
1066 ft.
1687 ft.
0.800
231 ft.
586 ft.
933 ft.
1476 ft.
0.900
206 ft.
521 ft.
829 ft.
1312 ft.
1.000 (Max)
185 ft.
469 ft.
746 ft.
1181 ft.