Fire-Lite MS-25E Addressable Fire Control Panel User Manual
Page 38
Model MS-25 Installation and Operation Manual
4-8
53688
Note: The following formulas were used to generate the wire distance chart:
Wiring Distance calculation example:
Suppose a system is configured with the following SBUS modules:
1 - Module MS-25 Fire Annunciator
The total worst case current is calculated as follows:
Using this value, and referring to the Wiring Distance table, it can be found that the available
options are:
1852 feet maximum using 22 Gauge wire
4688 feet maximum using 18 Gauge wire
6000 feet maximum using 16 Gauge wire
6000 feet maximum using 14 Gauge wire
Maximum Resistance (Ohms) =
6.0 Volts
Total Worst Case Current Draw (amps)
Maximum Wire Length (Feet) =
(6000 feet maximum)
Maximum Resistance (Ohms)
* 500
Rpu
where: Rpu = Ohms per 1000 feet for various wire gauges (see table below)
Table 4-2:
Typical Wire Resistance per 1000 ft. using Copper Wire
Wire Gauge
Ohms per 1000 feet (Rpu)
22
16.2
18
6.4
16
4.02
14
2.54
MS-25 Current Draw
= 1 x .04 amps
= .04 amps
Total Worst Case Current Draw
= .04 amps