2: Calculating Wiring Distance For Sbus Modules - Honeywell Farenhyt IFP-75HV Manual

Wiring Specifications
4.6.2 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 SBUS
accessory modules.
To calculate the wire gauge that must be used to connect SBUS modules to the 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 RPS-1000 Power Expanders. Each RPS-
1000 Power Expander provides an additional SBUS, with an additional 1 amp of SBUS current. Wiring distance calculations are done separately
for each RPS-1000, and separately for the panel itself.
RA-2000, RA-1000, RA-100 Fire Annunciators
5824 Serial/Parallel Printer Interface Module
5880 LED I/O Module
5865 LED Annunciator
RPS-1000 Intelligent Power Supply
5496 NAC Expander
SK-NIC Network Interface Card
CELL-MOD/CELL-CAB-SK
SK-F485C Fiber Converter
After calculating the total worst case current draw, Table 4.8 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 chart 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)
The following formulas were used to generate the wire distance chart.
IFP-75 Series Manual — P/N LS10147-001SK-E:E 4/6/2022
Model Number
Table 4.7 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 4.8 Wire Distances Per Wire Gauge
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
Table 4.9 Typical Wire Resistance Per 1,000 ft.
18 Gauge
4688 ft.
2344 ft.
1563 ft.
1172 ft.
938 ft.
781 ft.
670 ft.
586 ft.
521 ft.
469 ft.
6.0 Volts
Total Worst Case Current Draw (amps)
Maximum Resistance (Ohms)
Rpu
Ohms per 1000 feet (Rpu)
22
18
Control Panel Installation
Worst Case Current Draw
0.120 amps
0.045 amps
0.250 amps
0.200 amps
0.010 amps
0.010 amps
0.021 amps
0.145 amps
0.125 amps
16 Gauge
* 6000 ft.
3731 ft.
2488 ft.
1866 ft.
1493 ft.
1244 ft.
1066 ft.
933 ft.
829 ft.
746 ft.
* 500
16.2
6.4
14 Gauge
* 6000 ft.
5906 ft.
3937 ft.
2953 ft.
2362 ft.
1969 ft.
1687 ft.
1476 ft.
1312 ft.
1181 ft.
33