Addressable fire alarm control panels provide a circuit called a Signaling Line Circuit (SLC) that wires to the addressable input and output devices. Panels may support a single SLC or provide expansion for multiple SLCs. One of the characteristics of an SLC is the distance of wire it supports. SLCs on Silent Knight panels run a specific distance according to the wire gauge being used, regardless of the wire type or how many devices are on the loop.
For example, 14 AWG wire can run up to 7,900 feet on a Silent Knight addressable panel. A benefit of the SLCs on our panels is that they do not require specific wire types, such as twisted or shielded, which make them ideal for retrofit applications.
In certain installations, consideration should be given to using multiple SLCs. An obvious reason for using multiple wire runs is that the point capacity of the SLC is exceeded. However, another consideration for using multiple SLCs is shorter wire runs. Shorter runs can provide the benefit of using less wire, which saves time and money, while making any issues easier to troubleshoot.
The 5820XL/5820XL-EVS is Silent Knight’s expandable panel that supports up to 4 SLCs. A built-in SLC is provided with support for up to 3 of the 5815XL point expander cards. An advantage of using the 5815XL expander cards is the distributed mounting capability.
For example, a multi story building may use the internal SLC to cover specific areas. A common practice is to use the 5815XL with the 5895XL addressable power supply in different areas of floors of a facility (see diagram included here). The point expander and power supply are used to control both the notification outputs and the addressable devices for these different areas of floors. The 5815XL mounts in the 5895XL cabinet, making the wire run a simple 4 conductor SBUS from the panel to the 5895XL. All other wire runs originate from the 5815XL and 5895XL to the designated floors, again saving labor and wiring.
Using multiple SLCs will still allow for individual point reporting. The ID of the SLC is reported along with the point ID so that you are able to distinguish points on each SLC run. Although a single, longer SLC run may work for many installations, please consider the flexibility of multiple SLCs for specific applications.
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About the Author
Jack Grones is an Application Engineer with Silent Knight and holds a NICET Level III certification. Jack joined Silent Knight in 1978 and is responsible for applications and technical support.