VESDA VFT Product Guide
VESDA by Xtralis
6 www.xtralis.com
2.2 Alarms and Trace Mode
The default settings of the four alarm states (Alert, Action, Fire1 and Fire2) and Trace are shown in the
following table.
Table 2-1: Default Behavior of Alarm States and Trace Mode
Level Latched /
Unlatched
Threshold Delay Beacon Pulse
(On:Off)
Sounder
VFT-15 VFT-15-C
Trace Latched 0.03% obs/m
(0.009% obs/ft)
0.03% obs/m
(0.009% obs/ft)
3 secs - Continuous
Alert Latched 0.04% obs/m
(0.012% obs/ft)
0.5% obs/m
(0.15% obs/ft)
n/a 0.5 secs : 2 secs Continuous
Action Latched 0.06% obs/m
(0.018% obs/ft)
0.75% obs/m
(0.234% obs/ft)
n/a 0.5 secs : 1 sec Continuous
Fire1 Latched 0.08% obs/m
(0.024% obs/ft)
1.0% obs/m
(0.305% obs/ft)
n/a 0.5 secs : 0.5
secs
Continuous
Fire2 Latched 1.0% obs/m
(0.305% obs/ft)
2.0% obs/m
(0.625% obs/ft)
n/a Continuous Continuous
Trace parameters apply when the rotary valve is in the Overall position and all sectors are being monitored. If
latched, the Trace indicator will remain illuminated after the initiating event has ceased. It does NOT mean
that the unit will continue indefinitely in Trace (scan) mode. The system will only continue in Trace mode if the
detected smoke level is above the Trace threshold after scanning. The Alert relay may be programmed to be
activated by the Trace threshold. Its action will then follow that of the Trace indicator.
If any alarms are unlatched, all resultant actions (relay contacts, display panel indicators, sounder and
beacon) will clear if and when the triggering event ceases. If it is latched, all the warning mechanisms are
maintained until action is taken by the user (refer to Section 2.3). These alarm states are global and will be set
depending on the smoke density being measured, regardless of which sector is being sampled. Once in Trace
mode, each sector has an alarm indicator associated with it. These individual sector alarms pulse
progressively, depending on the degree of alarm status, in the same way as the Beacon (refer to Table 2-1).
2.2.1 Trace Relay
If Trace Relay is enabled, an all-sector Fire1 alarm will be generated if the all-sector smoke level is above the
All-Sector diluted Sector Fire1 threshold.
The All-Sector diluted Fire1 threshold is calculated by dividing the lowest of all the active Sector Fire1
thresholds by the number of active sectors.
l If the resultant threshold is less sensitive than Trace Threshold, then Trace Threshold will be used as
all sector Fire1 Threshold. This enables faster reporting of a Fire1 alarm without having to wait for
scanning to complete.
l If the resultant threshold is more sensitive than Trace Threshold, then the diluted Sector 1 Fire1
threshold is used.
If Trace Relay is disabled, the detector uses sector-based alarm reporting.
Example:
l Trace Relay = Enabled
l Trace Threshold = 0.100 %obs/m (0.03 %obs/ft)
l End Sector = 6
l Active Sectors = 1, 2, 3, 4, 5, 6
l Fire1 Thresholds for Active Sectors %obs/m = 1.5, 1.0, 2.0, 3.5, 1.5, 2.5
(%obs/ft = 0.458, 0.305, 0.610, 1.068, 0.458, 0.763)
l All-Sector diluted Fire 1 Threshold = 1.0/6 = 0.167 %obs/m (0.305/6 = 0.051% obs/ft)
l All-Sector diluted Fire 1 Threshold Fire1 Alarm will be reported when All-Sector smoke level reaches
0.167%obs/m (0.051%obs/ft)
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