Honeywell Silent Knight SK318PT Installation And Operation Manual page 36

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 1 amp. If a large number of accessory modules are required, and the
worst case current draw will exceed the 1 amp limit, then the current draw must be distributed using 5895XL Power Expanders. Each 5895XL
Power Expander provides an additional SBUS, with an additional 1 amp of SBUS current. Wiring distance calculations are done separately for
each 5895XL, and separately for the control panel itself.
NOTE: Refer to Table 3.2 is using SK Devices and Table 3.3 if using SD SLC devices for maximum number of each type of device that can be
used per system.
* All devices must use the same SBUS and VBUS.
** When doing wire calculations, use .080 amps per device with .105 amps for the last device.
After calculating the total worst case current draw, Table 4.2 specifies the maximum distance the modules can be located from the panel
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, regardless of gauge used.
The formula used to generate this chart is shown in the note below.
Total Worst Case
Current Draw (amps)
0.100
0.200
0.300
0.400
0.500
0.600
0.700
0.800
0.900
1.000 (Max)
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Model Number
6860, 5860, 6855 Fire Annunciator
5815XL SLC Loop Expander
6815 SLC Loop Expander
5824 Serial/Parallel Printer Interface Module
5880 LED I/O Module
5865 LED Annunciator
5895XL Intelligent Power Supply
5496 Intelligent Power Supply
EVS-50W
EVS-125W
EVS-100W
EVS-100W with EVS-100WBU
EVS-VCM / EVS-VCM with EVS-SW24* **
EVS-LOC / EVS-LOC with EVS-SW24*
SK-NIC Network Interface Card
CELL-MOD/CELL-CAB-SK
SK-F485C Fiber Converter
Table 4.1 SBUS Device Current Draw
Wiring Distance: SBUS Modules to Panel
22 Gauge
1852 ft.
926 ft.
617 ft.
463 ft.
370 ft.
309 ft.
265 ft.
231 ft.
206 ft.
185 ft.
Table 4.2 Wire Distances Per Wire Gauge Using Copper Wire
Worst Case Current Draw
.120 amps
.150 amps
.078 amps
.040 amps
.250 amps
.200 amps
.010 amps
.010 amps
.010 amps
.010 amps
.010 amps
.010 amps
.080 amps / .105 amps
** .080 amps / .105 amps
.021 amps
.145 amps
.125 amps
18 Gauge 16 Gauge
4688 ft. * 6000 ft.
2344 ft. 3731 ft.
1563 ft. 2488 ft.
1172 ft. 1866 ft.
938 ft. 1493 ft.
781 ft. 1244 ft.
670 ft. 1066 ft.
586 ft.
521 ft.
469 ft.
6820 / 6820EVS Manual P/N LS10144-001SK-E:C 09/28/2017
14 Gauge
* 6000 ft.
5906 ft.
3937 ft.
2953 ft.
2362 ft.
1969 ft.
1687 ft.
933 ft. 1476 ft.
829 ft. 1312 ft.
746 ft. 1181 ft.