Slc Loop Cabling; Example Voltage Drop Condition; Voltage-Drop Of The Twin Conductor Cable - VES Compas Fire Alarm Control Panel Installation Manual

SLC Loop Cabling

The Compas Fire Alarm Control Panel requires that SLC Loops include wire gauge and lengths specified in
tables of this section.
The maximum allowable voltage drop of 6.4 V is necessary on the SLC loop to maintain the minimum device
operating voltage of 17 V. The worst case voltage drop occurs when the load is located at the farthest point from
the terminals of the fire control panel.

Example Voltage Drop Condition

The following example demonstrates the impact of cable size and length on output circuits. A twin-wire of 16
AWG cabling is connected to SLC loop 1. The length of the 16 AWG cable is 1000 ft (305 m) and the device-load
on the loop is 400 mA. The device-load of 400 mA is determined from manufacturer data sheets. The following
figure illustrates the example SLC voltage drop condition of 16 AWG cable:
A voltage-drop of 1.6064V DC is determined from the table of 16 AWG cable for a single wire length of 1000 ft
(305 m) and a load of 400 mA. The resistance of one wire of the 16 AWG cable is 4.016 Ω at 1000 ft.

Voltage-drop of the twin Conductor Cable

(V + V
conductor 1 conductor 2
VES Fire Detection Systems
Compas Fire Alarm Control Panel Installation Manual
) = (1.6064V DC + 1.6064V DC) = 3.2128V DC
Appendix C: Calculations
Version 4.00 | January 2024 | MAN-1431COM
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