Bosch FAP-420 Quick Manual page 2

2 | FAP-420/FAH-420 Automatic Fire Detectors LSN improved version
Thermal x
differentia
l
Chemical x
(+ optical)
Functions
Sensor technology and signal processing
The individual sensors can be configured manually or
timer-based via the LSN network.
All sensor signals are analyzed continually by the
internal evaluation electronics (Intelligent Signal
Processing – ISP) and are linked with each other via
an inbuilt microprocessor. The link between the
sensors means that the combined detectors can also
be used where light smoke, steam or dust must be
expected during the course of normal operation.
Only if the signal combination corresponds to that for
the programming of the selected usage site field code
will the alarm be triggered automatically. This results
in a higher level of security against false alarms.
In addition, the time of the sensor signals on fire and
fault detection is analyzed, resulting in an increased
detection reliability for each individual sensor.
In the case of the optical and chemical sensor, the
response threshold (drift compensation) is actively
adjusted. Manual or time-controlled switch-off of
individual sensors is required for adjustment to
extreme interference factors.
Optical sensor (smoke sensor)
The optical sensor uses the scattered-light method.
An LED transmits light to the measuring chamber,
where it is absorbed by the labyrinth structure. In the
event of a fire, smoke enters the measuring chamber
and the smoke particles scatter the light from the LED.
The amount of light hitting the photo diode is
converted into a proportional electrical signal.
The DO detectors use two optical sensors with
different wavelength. The Dual Ray Technology works
with an infrared and a blue LED, so that light smoke
can be detected reliably (TF1 and TF9 detection).
Thermal sensor (temperature sensor)
A thermistor in a resistance network is used as a
thermal sensor, from which an analog-digital converter
measures the temperature-dependent voltage at
regular intervals.
Depending on the specified detector class, the
temperature sensor triggers the alarm status when the
maximum temperature of 54 °C or 69 °C is exceeded
(thermal maximum), or if the temperature rises by a
defined amount within a specified time (thermal
differential).
Chemical sensor (CO gas sensor)
The main function of the gas sensor is to detect
carbon monoxide (CO) generated as a result of a fire,
but it will also detect hydrogen (H) and nitrous
monoxide (NO). The sensor signal value is proportional
x - x
- - -
to the concentration of gas. The gas sensor delivers
additional information to effectively suppress
deceptive values.
Since the service life of the gas sensor is limited, the C
sensor of the FAP‑DOTC420 detector shuts down
automatically after 6 years of operation, and the C
sensor of the FAP‑OTC 420 detector after 5 years of
operation. The FAP‑DOTC420 detector will then still
operate as a DOT detector and the FAP‑OTC 420
detector as an OT detector. The detectors should be
exchanged immediately in order to keep the higher
detection reliability of the DOTC/OTC versions.
Improved LSN features
The 420 Series Fire Detectors offer all the features of
the improved LSN technology:
• Flexible network structures, including "T‑tapping"
without additional elements
• Up to 254 LSN improved elements per loop or stub
line
• Automatic or manual detector addressing selectable
via rotary switch, in each case with or without auto-
detection
• Power supply for connected elements via LSN bus
• Unscreened fire detection cable can be used
• Cable length up to 3000 m (with LSN 1500 A)
• Downwards compatibility to existing LSN systems
and central units
LSN features
Operating data display
In addition, the FAP/FAH-420 detectors offer all the
established benefits of LSN technology. The RPS
programming software can be used to change the
detection characteristics of the respective room
utilization. In addition, each configured detector, with
the exception of the KKW, can provide the following
data:
• Serial number,
• Contamination level of the optical section,
• Operating hours,
• Current analog values.
Analog values:
• Optical system values: current measured value of the
scattered light sensor; the measuring range is linear
and covers from 170 (new) to 700 (dirty).
• Contamination: the contamination value shows how
much the current contamination value has increased
relative to the original condition.
• CO value: display of the current measured value
(max. 550).
Self-monitoring of sensor technology
The sensor is self-monitoring. The following errors are
indicated on the fire panel:
• Fault indication in the event of the failure of the
detector electronics
• Continuous display of contamination level during
service
• Fault indication if heavy contamination is detected (in
place of false alarms)