version 4.7.2 – July 10th, 2022 Firmware version V2.1.7 and higher
EXXFIRE Installation and Service Manual 91
Smoke detection and Alarm
The system continually monitors the status within the protected space by taking air samples and
testing it for smoke. Air is drawn into the EXXFIRE
®
750CNF/1500CNF/2250CNF using a centrifugal
fan.
The air is filtered through a high-grade filter, which allows the broad range of smoke particles to
pass freely through, while preventing harmful dust ingress. This minimizes the chance of false
alarms caused due to solid particulates and insects, while maintaining a high throughput.
The carefully filtered air is then passed into the detection chamber, where three high-sensitivity
optical smoke detectors are exposed to the same sample. Each of the three calibrated detectors
can build up a reliable histogram of smoke obscuration data, and thus provide a reliable output in
its own right. This temporal reliability is then fortified by redundancy, by using the three detectors to
vote simultaneously. This provides an exceptionally reliable means to detect a fire, which reduces
false alarms, and avoids dropping the gas unnecessarily.
The sensitivity level of the smoke detection system can be configured as described in section 5.1.
Factory settings are set at the lowest of four sensitivity level.
Each sensitivity level has 3 threshold values: for Pre-alarm 1, Pre-alarm 2 and Alarm.
When the threshold value for Pre-alarm 1 is exceeded the PRE-ALARM 1 LED on the UI panel will go
ON, the buzzer will go on (continuous sound) and the Pre-alarm relay will be activated, resulting in
the NO contacts to close. The buzzer can be muted by pressing the MUTE button on the UI panel.
In case the smoke concentration drops below the Pre-alarm 1 threshold value the PRE-ALARM 1
LED on the UI panel will be switched OFF, the buzzer will be switched off and the Pre-alarm relay will
be deactivated, resulting in the NO contacts to open.
When the threshold value for Pre-alarm 2 is exceeded the PRE-ALARM 2 LED on the UI panel will go
ON and the buzzer will go on (continuous sound). This is an extra indication on the UI panel that the
smoke concentration in the protected volume is increasing. The buzzer can be muted by pressing
the MUTE button on the UI panel.
In case the smoke concentration drops below the Pre-alarm 2 threshold value the PRE-ALARM 2
LED on the UI panel will be switched OFF.
When the threshold value for Alarm is exceeded the ALARM LED on the UI panel will go ON and the
Alarm relay will be activated, resulting in the NO contacts of this relay to close. The buzzer will go on
(continuous sound). This is a count down to the start of fire extinguishment. The duration of this
count down is dependent on the configuration setting for Extinguishing Gas Delay (see 5.2) and has
a minimum duration of 0 seconds and a maximum duration of 15 seconds.
At the end of the count down fire extinguishing will start, indicated by a continuous sound. This
process is described in section 7.7.
The Alarm state will remain active even when the smoke concentration drops below the threshold
value for Alarm. The Alarm state can only be reset by the RESET ALARM/GAS RELEASED procedure
described in section 0.
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