Bosch FAS-420-TM - Page 56

56 en | Planning FAS-420-TM Aspirating Smoke Detector
F.01U.088.878 | 4.1 | 2010.11 Operation Guide Bosch Sicherheitssysteme GmbH
where
Please refer to Section 2.8 Technical Specifications, page 30 for the current consumption of the
FAS-420-TM.
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.
where
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
I
g
= Total current of all connected aspirating smoke detectors in [A]
I
A
= Alarm current of an aspirating smoke detector in [A]
I
Q
= Standby current of an aspirating smoke detector in [A]
I
PSmax
= Max. power supply of the network power supply in [A]
I
L
= Charging current of the rechargeable batteries (80% of the nominal
capacity within 24 hours) in [A]
K
n
= Rated capacity of the rechargeable battery in [Ah]
n = Total number of connected aspirating smoke detectors
n
max
= The highest number of aspirating smoke detectors in one detection zone
II I
g
QPS
=
n
+
max
.
I
L
NOTICE!
The power supply units are laid out using the calculated total current I
g
with the highest value.
L
max
= Maximum line length in [m]
A = Strand cross-section in [mm²]
I
g
= 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]
I
g
max
=
..
γ
L
Δ
U
.
A
2