Function
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ASD 531, Technical description, T 140 416 en
2.2.10
Airflow monitoring
Airflow monitoring is based on the calorimetric measuring method (mass flow rate measuring method).
An air flow sensor is installed in the detector housing in such a way that any change in the sampling pipe (pipe breakage, pipe
blockage) can be evaluated.
If there is an initial reset of the device and the sampling pipe is intact, the data of the airflow measurement is registered and
saved as reference values (100%). The system sets the values in the middle of an electronically formed monitoring window. In
the event of a shift in the values (actual values) out of the monitoring window (±xx%) owing to pipe blockage or pipe breakage
in the sampling pipe, the ASD 531 triggers an “airflow fault”. The monitoring window can be set to different sizes on the
ASD 531.
A variable delay time ensures that disturbance variables, e.g. air turbulence, are ignored. To handle fluctuations in the ambient
temperature, the ASD 531 is equipped with a temperature compensation circuit.
Notice
A requirement for the correct operation of the airflow monitoring is that the airflow is logged when the ASD 531 is
commissioned. With the triggering of an initial reset, the data is acquired and saved in the ASD 531 as reference
values (see also Sec. 2.2.16, “Reset types”).
According to
EN 54-20
a change in the airflow that is greater than
±20%
must be reported as a fault. After the initial reset the
airflow is displayed as 100% in the ASD 531 aspirating smoke detector when the sampling pipe is correct and clean. When all
switches of the
Airflow
DIP switch are on
OFF
, any change in this value greater than ±20% – i.e. below 80% (dirt / pipe block-
age) or above 120% (pipe breakage) – triggers an “airflow fault” after the
LS-Ü
delay time of
300 s
has expired.
Warning
For normative systems the setting
±20%
/
300 s
is required. Other values are
not
EN tested and may be used
only after consulting with the manufacturer.
2.2.11
Smoke sensor monitoring
The smoke sensor used on the ASD 531 is monitored on the AMB 31 Main Board. A failure of the sensor electronics, a dusty
or dirty smoke sensor is registered as an event code and displayed as a state or fault. Likewise, the connection line between
the smoke sensor and the AMB 31 is monitored and a fault is signalled if there is a failure.
To avoid false alarms, the SSD 531 smoke sensors used in the ASD 531 have a technical measure (TM) for comparing fire pa-
rameter pattern matching (measure for verifying the alarm state according to DIN VDE 0833-2).
2.2.12
Alarm release
The smoke sensor cyclically transmits its state as well as the signal amplitude / smoke level to the AMB 31 Main Board. The
state of the smoke sensor is processed further on the AMB 31. If the set limits (alarm, pre-signal 1–3) are exceeded, the corre-
sponding state “
Alarm
”, “
Pre-signal 1–3
” is triggered on the ASD 531.
2.2.12.1 Isolating the smoke sensor
This function is used to place the ASD 531 in an isolated state using the “
Mode
” rotary switch. This means that test alarms can
then be triggered on the ASD 531 without activating superordinate systems (FACP) (relays, OC outputs, XLM do not trigger).
When the “Isolate” function is switched on, a fault is triggered on the ASD and forwarded to the superordinate centre. On the
ASD the “
Fault
” LED is then continuously lit.
