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takes the appropriate action to shut down fans and
blowers, change over air handling systems, notify the fire
alarm control panel, etc.
The sensor uses a process called differential sensing to
prevent gradual environmental changes from triggering
false alarms. A rapid change in environmental conditions,
such as smoke from a fire, causes the sensor to signal an
alarm state but dust and debris accumulated over time
does not.
For installations using two sensors, the duct smoke
detector does not differentiate which sensor signals an
alarm or trouble condition.
Duct smoke sensor
See
Detail A
Exhaust tube
Plug
Sampling tube
(ordered separately)
Intake
gasket
Cover gasket
(ordering option)
TSD-CO2
(ordering option)
Sensor housing
and electronics
Exhaust gasket
Coupling
Sensor cover
Detail A
Magnetic
test/reset
switch
Alarm
Trouble
Power
Dirty
C08209
Fig. 56 -- Smoke Detector Sensor
Smoke Detector Locations
Supply Air —
The Supply Air smoke detector sensor is located to the
left of the unit’s indoor (supply) fan. See Fig. 57. Access
is through the fan access panel. There is no sampling tube
used at this location. The sampling tube inlet extends
through the side plate of the fan housing (into a high
pressure area). The controller is located on a bracket to
the right of the return filter, accessed through the lift--off
filter panel.
Smoke Detector Sensor
C08245
Fig. 57 -- Typical Supply Air Smoke Detector Sensor
Location
Return Air without Economizer —
The sampling tube is located across the return air opening
on the unit basepan. See Fig. 58. The holes in the
sampling tube face downward, into the return air stream.
The sampling tube is connected via tubing to the return air
sensor that is mounted on a bracket high on the partition
between return filter and controller location. (This sensor
is shipped in a flat--mounting location. Installation
requires that this sensor be relocated to its operating
location and the tubing to the sampling tube be connected.
See “Completing Installation of Return Air Smoke
Sensor:” on page 36 for details.)
Return Air Detector Sampling Tube
Controller module
Return Air Detector module
(shipping position shown)*
*RA detector must be moved from shipping position to operating position by installer
C07307
Fig. 58 -- Typical Return Air Detector Location
Return Air with Economizer —
The sampling tube is inserted through the side plates of
the economizer housing, placing it across the return air
opening on the unit basepan. See Fig. 59. The holes in the
sampling tube face downward, into the return air stream.
The sampling tube is connected via tubing to the return air
sensor that is mounted on a bracket high on the partition
between return filter and controller location. (This sensor
is shipped in a flat--mounting location. Installation
requires that this sensor be relocated to its operating
location and the tubing to the sampling tube be connected.
See the following installation procedure.)
581J