Airflow Monitoring - Bosch FAS-420-TT Series Operation Manual

36 en | Planning
Testing
For critical applications, test the secure detection with activation attempts. Check also
whether there is airflow at the individual air sampling openings.
Notice!
In order to increase transport speed in critical application areas, the fan voltage can be
increased from 6.9 V to 9 V.
Dual-detector dependency
One aspiration line must be assigned per detector module. Both detector modules of a device
must be evaluated independently of one another. Only one extinguishing area per smoke
aspiration system may be monitored.
Pipe configurations for dual detector dependency
Two alarm stages
To implement two alarm stages, a pipe adapter for the aspiration pipe system is required. The
two detector modules in the aspirating smoke detector require different response
sensitivities.
Pipe configurations for two alarm stages using the example of a U-pipe system
4.3

Airflow monitoring

EN 54‑20 or ISO 7240-20 requires the detection of a 20-percent change in the airflow volume
by the detector module's airflow sensor. In order to achieve this, the activation threshold of
the airflow sensor must be set to level II. Alternatively, level I can also be used. It is
recommended that airflow calibration is carried out dependent on air pressure for both of
these settings. In systems that do not need to comply with EN 54‑20 or ISO 7240-20, any
threshold can be set. The smoke aspiration pipes are planned taking into account the
applicable national regulations for the country concerned.
Adapting the airflow sensitivity
The sensitivity of the airflow sensor must be adapted to the application. For example, a long
pipe system requires a sensitive setting of the airflow sensor. The activation threshold and
thus the sensitivity of the airflow sensor can be set on 4 levels. Breakages and obstructions
must be accurately detected in the event of a malfunction.
2020.04 | 6.1 | F.01U.029.275 Operation guide
Aspiration smoke detector LSN improved
Bosch Sicherheitssysteme GmbH