Honeywell Silent Knight SK318PT Installation And Operation Manual page 37

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NOTE: The following formulas were used to generate the wire distance chart.
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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:
5860 Current Draw
5895XL Current Draw
5865 Current Draw
5824 Current Draw
Total Worst Case Current Draw
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
6820 / 6820EVS Manual P/N LS10144-001SK-E:C 09/28/2017
Maximum Resistance (Ohms) =
Maximum Wire Length (Feet) =
(6000 feet maximum)
where: Rpu = Ohms per 1000 feet for various wire gauges (see table below)
Wire Gauge
22
18
16
14
Table 4.3 Typical Wire Resistance Per 1000 ft. Using Copper Wire
6.0 Volts
Total Worst Case Current Draw (amps)
Maximum Resistance (Ohms)
Rpu
Ohms per 1000 feet (Rpu)
16.2
6.4
4.02
2.54
= 2 x .100 amps
= 1 x .010 amps
= 1 x .200 amps
= 1 x .040 amps
* 500
= .200 amps
= .010 amps
= .200 amps
= .040 amps
= .450 amps
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