74 en | Planning Aspiration smoke detector LSN improved
2020.04 | 6.1 | F.01U.029.275 Operation guide Bosch Sicherheitssysteme GmbH
4.15 Power supply
To measure the power supply, the detector-ready state of the security system and the alarm
case are regarded. When the system is ready to detect, the power supply must provide the
standby current for the aspirating smoke detectors and ensure the emergency power
rechargeable battery is charged in accordance with DINVDE0833, part1 (80% charged in
24hrs).
The current in the event of an alarm is calculated according to the following formula:
Calculation of current for space protection
I I II
g
A
n
max
Q PS
=
.
n
max
+
.
(n
_
)
max
Equipment protection
I I II
g A
n
Q
PS
=
.
+
.
(n
_
)
max
n
Charging current
The power for charging the rechargeable battery is calculated with the following formula:
where
Ig = Total current of all connected aspirating smoke detectors in [A]
IA = Alarm current of an aspirating smoke detector in [A]
IQ = Standby current of an aspirating smoke detector in [A]
IPSmax = Max. power supply of the network power supply in [A]
IL = Charging current of the rechargeable batteries (80% of the nominal
capacity within 24hours) in [A]
Kn = Rated capacity of the rechargeable battery in [Ah]
n = Total number of connected aspirating smoke detectors
nmax = The highest number of aspirating smoke detectors in one detection zone
The power supply can service detectors from several detection ranges, e.g.:
– 1 x FAS-420 in detection zone 1
– 2 x FAS-420 in detection zone 2
– 4 x FAS-420 in detection zone 3
– 1 x FAS-420 in detection zone 4 etc.
In the example, the zone with the highest energy requirement is zone 3 and hence n
max
=4. For
equipment protection, it is assumed that max. √n detectors can trigger an alarm at the same
time.
Notice!
The power supply units are laid out using the calculated total current Ig with the highest
value.
Please refer to
Technical specifications, page 27
for the current consumption of the FAS-420.
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