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Offset is a fixed value added to the week average sensor value to get the "alarm" level
respectively, e.g. week average sensor value 1 + offset 30 = 31 = the fire alarm level
(equivalent to 3.1 % obscuration per meter).
The step value gives the alarm delay time to the algorithm respectively, see chapter
"Functions / Services / Features", page 102.
The following example is for the N-15 algorithm for the 4301 detector. The values for other
algorithms and the 4300 detector are different.
Offset, smouldering: Offset value, default 15 (1.5%/m).
Offset, pre-warning: Offset value, default 22 (2.2%/m).
Offset, alarm: Offset value, default 30 (3.0%/m).
Level, heavy smoke: Heavy smoke level, default 150 (15%/m).
Step value: Default 10.
Note: Changing these parameters will affect the sensitivity and detection time and should
be done by authorised personnel only! In addition, a special password is required to
change the parameters for fire alarm.
22.3.3.2
Parameters for heat algorithms
Valid for detectors 3308/3309 and multi detectors 4300 / 4400. All in NORMAL mode.
The "alarm" levels are fixed, i.e. there are no offset values. The sensor values can be 0-
200, which is equivalent to 0-100° C. The rise time and step down gives a rate-of-rise
function (used in the A1 algorithm only). See also chapter "Algorithms for Analogue heat
detectors", page 107.
The following example is for the A1 algorithm for the 3308 detector. The values for other
algorithms are different.
Level, pre-warning: Level, default 92 (46° C).
Level, alarm: Level, default 112 (56° C).
Level, heavy alarm: Level, default 180 (90° C).
Rise time: Default 8.
Step down: Default 20
Note: Changing these parameters will affect the sensitivity and detection time and should
be done by authorised personnel only! In addition, a special password is required to
change the fire alarm parameters.
22.3.3.3
Parameters for combined decision algorithm
Valid for the detectors 4300 / 4400. All in NORMAL mode.
Offset, see "Parameters for smoke algorithms" above. Level, see "Parameters for heat
algorithms" above. See also "4300", page 56.
The following example is for the Dec algorithm for the 4300 detector.
Offset, pre-warning: Offset value, default 50 (5.0%/m).
Offset, alarm: Offset value, default 58 (5.8%/m).
Level, pre-warning: Level, default 50° C
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The week average value starts at "1" for a new (clean) detector. The very first average value will be calculated within two
minutes (after SSD download & restart) and thereafter every week. The fire alarm level will be adjusted or not adjusted ever y
week, depending on if the latest calculated week average value is the same as the previous, i.e. if it has increased or if it has
decreased. The week average value will normally increase very slowly in a long-time period, due to contamination.
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FT1020G3 Rev 2.2.1
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