Chapter 3: Operating instructions
64 EST3X Technical Reference Manual
Switching the smoke detector alarm
sensitivity threshold
Intelligent addressable smoke detectors are configured with two alarm sensitivity
thresholds: primary and alternate. The alarm sensitivity setting, determines how
easily automatic fire detectors can sense a fire alarm condition. This allows you
to increase or reduce an individual detector’s sensitivity at various times of the
day, dependent upon, environmental conditions, occupancy, manufacturing
processes, etc.
A time control is commonly used to automatically switch alarm sensitivity
thresholds. However, you can manually switch alarm sensitivity thresholds by
using command menus.
Primary alarm sensitivity threshold
Typically, the primary alarm sensitivity threshold is set to a lower threshold. This
threshold is commonly used for a daytime operation to reduce the occurrence of
nuisance alarms when a facility is occupied, or when environmental conditions
may create prealarm conditions.
Alternate alarm sensitivity threshold
The alternate alarm sensitivity threshold sets the secondary threshold at which
the smoke detector activates an alarm event. Typically, the alternate threshold is
set to a higher sensitivity threshold. This threshold is commonly used for a
nighttime or weekend operation, when the facility is unoccupied.
Alarm sensitivity setting levels
Alarm sensitivity settings are expressed in percent of smoke obscuration per foot.
The setting defines the threshold at which the detector will change to the alarm
state when the smoke in its sensing chamber exceeds the obscuration per foot
threshold. The alarm sensitivity levels for Signature devices are described below.
Note: When smoke detectors having both ionization and photoelectric elements
are used, the sensitivity setting applies to both elements.
• Most: Activates an alarm event when the smoke level reaches approximately
1.0 %/ft obscuration (0.7 %/ft for ionization detectors)
• More: Activates an alarm event when the smoke level reaches approximately
2.0 %/ft obscuration (1.0 %/ft for ionization detectors)
To Next Page
Loading...
