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Normal (15 sec.) or slow (35 sec.) detection time
Normal sensitivity (Default) Fire alarm offset is 3.0 % smoke obscuration per meter.
High sensitivity Fire alarm offset is 2.4% smoke obscuration per meter, i.e. less than for
normal sensitivity. This can be used when an "early" fire alarm is required.
Low sensitivity Fire alarm offset is 3.6 % smoke obscuration per meter, i.e. more than for
normal sensitivity. Can be used to reduce nuisance alarms but might not fulfil the AS7240.7
requirements.
Normal detection time - 15 sec. (Default) There will always be minimum 15 seconds alarm
120
delay
. This is a "normal filter" to reduce nuisance alarms.
Slow detection time - 35 sec. There will always be minimum 35 seconds alarm delay
This is an "extra filter" to reduce nuisance alarms but might not fulfil the AS7240.7
requirements.
Each Analogue smoke detector can have two alarm algorithms programmed (via EBLWin).
One Regular alarm algorithm that is normally used (N-15 is default) and one Alternative
alarm algorithm that is turned on/off via a time channel (internal or external) e.g. normal
sensitivity can be used during night-time and low sensitivity during daytime (i.e. the
alternative alarm algorithm is used to reduce nuisance alarms during working hours).
The alarm algorithm in use can be read in menu H4/U3.
17.4.2
Filtering algorithm
In order to secure a fast detection of real fire alarms and to reduce nuisance (false) alarms
to a minimum, a filtering algorithm is used.
The filtering algorithm uses the sensor values to calculate a decision value depending on
which alarm algorithm that is in use. The decision value starts at zero. Each time a new
sensor value is picked up (sampled) from an Analogue smoke detector 430x/440x, this new
sensor value is compared with the actual decision value which will be adjusted if required,
see below:
If the difference, between the new sensor value and the actual decision value is < "X", the
decision value is set equal to the new sensor value.
If the difference is > "X", the decision value is increased or reduced by "X".
"X" = the Step Value. It is different depending on the sensitivity and detection time, i.e. it
is dependent on the selected alarm algorithm, see Table 12 below.
The decision value will consequently not be increased / decreased with a value exceeding
the "X" value even if the sensor values are much higher / lower.
Table 12 Smoke Detector Alarm Algorithms
Analogue detector
121
122
4300
/ 4301
4400 / 4401
120
After the fire alarm level is reached / passed, it will take min. 15 alt. 35 seconds until fire alarm will be activated in th e C.I.E.
121
4300 is replaced by 4400.
122
4301 is replaced by 4401.
Normal detection time (15sec.)
H-15
N-15
2.4%,
3.0%,
High
Normal
sensitivity
sensitivity
X=8
X=10
104
Technical/Programming Manual
Slow detection time (35sec.)
L-15
H-35
3.6%,
2.4%,
Low
High
sensitivity
sensitivity
X=12
X=4
FT1020G3 Rev 2.2.1
120
N-35
L-35
3.0%,
3.6%,
Normal
Low
sensitivity
sensitivity
X=5
X=6
.
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