Bosch FCS-320-TP2 - Page 77

Aspirating Smoke Detector Planning | en 77
Bosch Sicherheitssysteme GmbH Operation Guide 2018.04 | 2.0 | F.01U.130.926
Line calculation
The maximum line length is derived from the permissible voltage drop on the supply line. The
permissible voltage drop is the difference between the end-point voltage of the backup
battery (21.5V) and the lower operating voltage limits of the aspirating smoke detectors.
I
g
max
=
. .
γ
L
∆
U
.
A
2
where
Lmax = Maximum line length in [m]
A = Strand cross-section in [mm²]
Ig = Total current of all connected aspirating smoke detectors in [A]
γ = Conductivity: Cu=57m/Ωmm²
ΔU = Charging current of the rechargeable batteries (80% of the nominal
capacity within 24hours) in [A]
To guarantee the impermeability of the housing, the corresponding cable bushing must be
selected for the existing cable:
– M25 cable bushing: ∅9-14mm
– M20 cable bushing: ∅8-12mm
The "Fire Alarm System Planning Software" enables case-specific calculations to be carried out
for planning the FPA-5000 Modular Fire Panel.