Model 6820 / 6820-EVS Installation Manual
LS10144-001SK-E
4-7
Wiring Distance calculation example:
Suppose a system is configured with the following SBUS modules:
2 - Module 5860 Fire Annunciator
1 - 5895XL Intelligent Power Expander
1 - 5865 LED Annunciator
1 - 5824 Serial/Parallel Interface Module
The total worst case current is calculated as follows:
Note: For assistance with SBUS calculation, please refer to www.silentknight.com.
Using this value, and referring to the Wiring Distance table, it can be found that the available options are:
370 feet maximum using 22 Gauge wire
938 feet maximum using 18 Gauge wire
1493 feet maximum using 16 Gauge wire
2362 feet maximum using 14 Gauge wire
where: Rpu = Ohms per 1000 feet for various wire gauges (see table below)
Table 4-3: Typical Wire Resistance Per 1000 ft. Using Copper Wire
Wire Gauge
Ohms per 1000 feet (Rpu)
22
16.2
18
6.4
16
4.02
14
2.54
5860 Current Draw
= 2 x .100 amps
= .200 amps
5895XL Current Draw
= 1 x .010 amps
= .010 amps
5865 Current Draw
= 1 x .200 amps
= .200 amps
5824 Current Draw
= 1 x .040 amps
= .040 amps
Total Worst Case Current Draw
= .450 amps
