Kidde VM-1 - Page 184

Appendix A: System calculations
176 P/N 3101890-EN • REV 006 • ISS 21JUN18
Determining the total loop length
The total loop length is the sum of the lengths of all the wire segments installed in the data circuit.
(1) Loop controller
The total length of all the cable installed in the signaling line circuit cannot exceed the values listed below:
Table 71: Maximum signaling signal circuit cable length
Wire Size
Wire type
14 AWG 16 AWG 18 AWG
Twisted pair
13,157 ft
(4,010 m)
13,888 ft
(4,233 m)
20,000 ft
(6,096 m)
Twisted
-shielded pair 5,952 ft
(1,814 m)
6,098 ft
(1,859 m)
8,621 ft
(2,628 m)
Non
-twisted,
non
-shielded pair
20,000 ft
(6,096 m)
20,000 ft
(6,096 m)
20,000 ft
(6,096 m)
If the cable manufacturer’s data indicates the capacitance per foot of the cable, the following method may be used
to determine the maximum total loop length.
Note: In no case may the total loop length of a signaling line circuit exceed 20,000 feet (6,098 meters).
Lmax = 500,000 / Cpf
Where,
• Lmax = maximum total cable length in feet
• Cpf = Cable capacitance in picofarads per foot
Note: A short circuit on a signaling line circuit can disable the entire circuit. In order to limit the effect of a single
short circuit, GSA-IB Isolator Bases or GSA-IM Isolator modules can be installed at strategic points in the circuit.
10
12
5
1
6
(1)