2: Wiring Configurations - Honeywell 6820 Manual

SBUS Wiring
Maximum Resistance (Ohms) =
Maximum Wire Length (Feet) =
(6000 feet maximum)
where: Rpu = Ohms per 1000 feet for various wire gauges (see table below)

Wiring Distance calculation example:
Suppose a system is configured with the following SBUS modules:
2 - Module 6860 Fire Annunciators
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 calculations, 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
2,362 feet maximum using 14 Gauge wire
4.6.2 Wiring Configurations
Figure 4.11 illustrates SBUS Class A wiring configuration and Figure 4.12 illustrates SBUS Class B configuration.
FACP
6820/EVS Manual — P/N LS10144-001SK-E:E 4/6/2022
Wire Gauge
Table 4.3 Typical Wire Resistance Per 1000 ft. Using Copper Wire
6860 Current Draw
5895XL Current Draw
5865 Current Draw
5824 Current Draw
Total Worst Case Current Draw
Table 4.4 Worst Case Current Draw
EXT. COMM
Figure 4.11 SBUS Class A Wiring
6.0 Volts
Total Worst Case Current Draw (amps)
Maximum Resistance (Ohms)
Rpu
Ohms per 1000 feet (Rpu)
22 16.2
18 6.4
16 4.02
14 2.54
= 2 x 0.120 amps
= 1 x 0.010 amps
= 1 x 0.200 amps
= 1 x 0.040 amps
supervised,
power-limited
Control Panel Installation
* 500
= 0.240 amps
= 0.010 amps
= 0.200 amps
= 0.040 amps
= 0.490 amps
SBUS device
For proper system supervision do not use looped
wire under terminals marked A, B, +, and - of the
SBUS device connectors. Break wire runs to
provide supervision of connections.
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