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Add together the alarm existing current draw by all the devices on the wiring run to determine
the maximum allowed distance between the option bus terminals on the control panel and the
last device on the wire run (the device farthest from the control panel).
To determine the maximum allowed length for the run, add up the total alarm load for option
bus devices on the wire run. For example, if the total load of option bus devices on a
particular run is 400 mA, the maximum length of the run can be up to 500 ft (152 m). No more
than 4 000 ft (1 219 m) of wire can be connected to the option bus terminals, even if the
individual lengths of the runs are all within limit.
For the allowed lengths for18 AWG (1.2 mm) wire, see the following figure:
Figure 5.9: 18 AWG cable length for existing current draw
i
Notice!
The graph is for 18 AWG cable!
For16 AWG (1.5 mm) wire, cable lengths can be 1.5 times longer. For14 AWG (1.8 mm) wire,
cable lengths can be 2.5 times longer. The 4 000 ft (1 219 m) maximum length of connected
wire still applies.
Fire Alarm Control Panels Connection | en 35
Bosch Security System, Inc. Installation and Operation Manual 2012.08 | 04 | F01U008458