36 MRP-2002 Series Instruction Manual — P/N 53049:E5 7/28/2016Installation ANN-BUS Devices2.7.1 ANN-BUS WiringThis section contains information on calculating ANN-BUS wire distances and the types of wiringconfigurations (Class B).Calculating Wiring Distance for ANN-BUS ModulesThe following instructions will guide the installer in determining the type of wire and the maximumwiring distance that can be used with FACP ANN-BUS accessory modules.To calculate the wire gauge that must be used to connect ANN-BUS modules to the FACP, it is nec-essary 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 eachmodule. The individual worst case values are shown in the following table:After calculating the total worst case current draw, Table 2.1 specifies the maximum distance themodules can be located from the FACP on a single wire run. The table ensures 6.0 volts of line dropmaximum. In general, the wire length is limited by resistance, but for heavier wire gauges, capaci-tance is the limiting factor.These cases are marked in the chart with an asterisk (*). Maximum length can never be more than6,000 feet (1,800 m), regardless of gauge used. The formula used to generate this chart is shown inthe note below.The following formulas were used to generate the wire distance chart:Model Number Worst Case Current Draw11 Total worst case current draw on a single ANN-BUS cannot exceed 0.5 amp.ANN-80(C) LCD Annunciator/Indicator 0.040 ampsANN-S/PG Serial/Parallel Printer Interface Module 0.040 ampsANN-I/O LED Driver Module 0.200 ampsANN-LED Annunciator Module 0.068 ampsANN-RLY Relay Module 0.075 ampsWiring Distance: ANN-BUS Modules to FACPTotal Worst Case CurrentDraw (amps)22 Gauge 18 Gauge 16 Gauge 14 Gauge0.100 1,852 ft. 4,688 ft. * 6,000 ft. *6,000 ft.0.200 926 ft. 2,344 ft. 3,731 ft. 5,906 ft.0.300 617 ft. 1,563 ft. 2,488 ft. 3,937 ft.0.400 463 ft. 1,172 ft. 1,866 ft. 2,953 ft.0.500 370 ft. 938 ft. 1,493 ft. 2,362 ft.Table 2.1 Wiring DistancesMaximum Resistance (Ohms) = 6.0 VoltsTotal Worst Case Current Draw (amps)Maximum Wire Length (feet) = Maximum Resistance (Ohms) *500(6,000 feet maximum) Rpuwhere: Rpu = Ohms per 1,000 feet for various Wire Gauges (see table below)
