Carrier 48LC Series Service And Maintenance Instructions page 16

Controller
The controller (see Fig. 19) includes a controller housing,
a printed circuit board, and a clear plastic cover. The
controller can be connected to one or two compatible duct
smoke sensors. The clear plastic cover is secured to the
housing with a single captive screw for easy access to the
wiring terminals. The controller has three LEDs (for
Power, Trouble and Alarm) and a manual test/reset button
(on the cover face).
Duct smoke sensor
controller
Controller housing
and electronics
Conduit couplings
(supplied by installer)
Fastener
(2X)
Alarm
Fig. 19 - - Controller Assembly
Sensor
The sensor (see Fig. 20) includes a plastic housing, a
printed circuit board, a clear plastic cover, a sampling
tube inlet and an exhaust tube. The sampling tube (when
used) and exhaust tube are attached during installation.
The sampling tube varies in length depending on the size
of the rooftop unit. The clear plastic cover permits visual
inspections without having to disassemble the sensor. The
cover attaches to the sensor housing using four captive
screws and forms an airtight chamber around the sensing
electronics. Each sensor includes a harness with an RJ45
terminal for connecting to the controller. Each sensor has
four LEDs (for Power, Trouble, Alarm and Dirty) and a
manual test/reset button (on the left- - side of the housing).
Air is introduced to the duct smoke detector sensor's
sensing chamber through a sampling tube that extends into
the HVAC duct and is directed back into the ventilation
system through a (shorter) exhaust tube.
Conduit nuts
(supplied by installer)
Conduit support plate
Terminal block cover
Cover gasket
(ordering option)
Controller cover
Trouble
Power
Test/reset
switch
C08208
The difference in air pressure between the two tubes pulls
the sampled air through the sensing chamber. When a
sufficient amount of smoke is detected in the sensing
chamber, the sensor signals an alarm state and the
controller automatically 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.
Duct smoke sensor
Exhaust tube
Exhaust gasket
See
Detail A
Intake
gasket
TSD-CO2
(ordering option)
Plug
Sampling tube
(ordered separately)
Coupling
Detail A
Magnetic
test/reset
switch
Alarm
Trouble
Fig. 20 - - Smoke Detector Sensor
For installations using two sensors, the duct smoke
detector does not differentiate which sensor signals an
alarm or trouble condition.
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. 21. 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.
16
Sensor housing
and electronics
Cover gasket
(ordering option)
Sensor cover
Power
Dirty
C08209