Edwards Signaling eFSA250 - Manual (Page 234)

Appendix B: Worksheets
222 E-FSA64 and E-FSA250 Technical Reference Manual
Notes
[1] Use the manufacturer’s published wire resistance expressed in ohms per foot. For typical
values, see Table 46 on page 218.
[2] Use the Maximum operating current at worst-case VFWR from the installation or catalog
sheet of each device.
[3] For UL regulated notification appliances, this voltage must not drop below 16 VFWR. For
other devices, get the minimum operating VFWR from the installation or catalog sheet.
Device loop maximum wire length worksheet
Use the instructions provided below to calculate the maximum wire length for a
device loop. The maximum wire length is made up of two components: the total
amount of wire and the longest circuit path.
Step 1: Total wire
Use the worksheet below to calculate the total amount of wire that you can use to
construct a device loop. The total amount of wire is based on the cable
manufacturer’s capacitance per foot rating. In no case shall the total amount of
wire exceed the values listed in Table 49.
700,000 pF
Cable capacitance ÷ pF/ft.
Total wire ft.
Table 49: Maximum wire length for the loop
Wire type
18 AWG or
0.75 mm²
16 AWG or
1.0 mm²
14 AWG or
1.5 mm²
Twisted pair, nonshielded
25, 36, 38 pF
20,000 ft.
(6096 m)
13,888 ft.
(4233 m)
13,157 ft.
(4010 m)
Twisted pair, shielded
58, 82, 84 pF
8,621 ft.
(2628 m)
6,098 ft.
(1859 m)
5,952 ft.
(1814 m)
Untwisted pair, unshielded
20, 20, 20 pF
20,000 ft.
(6096 m)
20,000 ft.
(6096 m)
20,000 ft.
(6096 m)