a) If the loop and spurs are wired with 1.0mm2cable and allowing for maximum permissible
voltage drop with reference to table 1;
Rspur = [ 10 - [ 3.62 x 250 x 0.0012 ] ] (6)
10 x 25 x 0.0012
This corresponds to a maximum spur cable length of 0.820 km
Hence, the total system cable length is 8.3km compared to 0.9 km for a loop system
(see example 2)
b) Similarly, if the system is wired using 1.5mm2cable and following the above rules;
Rspur = 30.9Ω, This corresponds to a maximum spur cable length of 1.27km
Hence, the total system cable length is 12.8 km compared to 1.38 km for a loop system
(see example 2)
13
EASICHECK™
= 29.7Ω
Panel
Loop
of
100m
Number of spurs (ns) Fitting
nfs
RI = Cable resistance of main loop
Fig. 1