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7
Line disconnector function
8
Response behaviour of the detectors
9
Environmental influences
9.1
Influence of the ambient temperature
9.2
Other influencing variables
10
Fire & Security Products
Siemens Building Technologies Group
If a short circuit occurs on the detector bus, total bus failure is prevented by discon-
nector detectors which inhibit the defective sections of a line. The DOTE1152 is
equipped with such an isolation function. The DOTE1152 is equipped with an «elec-
tronic switch» (FET) in the bus before and after the detector. These switches open
automatically in the event of a short circuit and disconnect the defective section of
the line.
Detectors with disconnector switches are normally installed in unit separations, fire
compartments and T–branches.
Optimum security is provided by a loop line installation.
The DOTE1152 is equipped with efficient algorithms for discriminating between real
fires and deceptive phenomena. To signal a danger level the detector does not sim-
ply respond to a value above a «response threshold», but rather tracks the smoke
density pattern over a longer period of time and evaluates it with appropriate algo-
rithms.
The software parameters determine the response behaviour of the detectors. They
are dependent on the risk prevailing on the installation site (on the selected parame-
ter set) and on the activated operating mode (day, night, special [renovation], test
and switched off).
The current operating mode is signalled to the detectors by the control unit in inter-
vals of approximately 3 seconds.
The algorithms contain, for example, filters for suppressing transient disturbance va-
riables. Slow signal changes caused by contamination are compensated by the au-
tomatic digital compensation circuit. This extremely slow compensation ensures that
also slowly developing fires are reliably detected.
Just as the PolyRex detectors DOT1151/1152, the DOTE1152 evaluates several cri-
teria. The temperature and CO signals are used for the recognition of events, toge-
ther with the scattered light signal. However, no danger level is signalled solely on
the base of the CO signal. (This also applies for the test mode.)
The smoke sensitivity of the PolyRex detectors DOTE1152 typically change by
±10% across the entire operating temperature range, provided that the temperature
and CO signals remain stable. (In the event of a temperature and/or CO value
change, the smoke sensitivity is determined by the selected parameter set).
The PolyRex detectors DOTE1152 are resistant to ambient light and other changes
within the specified data.
The influence of air drafts with fast and large temperature fluctuations depends on
the selected parameter set.
Temperature and relative humidity values outside the specified range reduce the
service life of the CO sensor.
If the detector is exposed to an atmosphere containing solvents for longer periods,
the CO sensor may be damaged.
e4070e
10.2002
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