Smoke Detectors - Carrier 50HCQA05 Service And Maintenance Instructions

SMOKE DETECTORS

Smoke detectors are available as factory- - installed options
(FIOP) on 50HCQ models. Smoke detectors can be
specified for Supply Air only or for Return Air with or
without economizer or in combination of Supply Air and
Return Air. Return Air smoke detectors are arranged for
vertical return configurations only. All components
necessary for operation are
mounted. The unit is factory- - configured for immediate
smoke detector shutdown operation; additional wiring or
modifications to unit terminal board can be necessary to
complete the unit and smoke detector configuration to
meet project requirements.
System
The smoke detector system consists of a four- - wire
controller and one or two sensors. Its primary function is
to shut down the rooftop unit in order to prevent smoke
from circulating throughout the building. It is not to be
used as a life saving device.
Controller
The controller (see Fig. 44) 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 housing
and electronics
Conduit couplings
(supplied by installer)
Fastener
(2X)
Alarm
Fig. 44 - - Controller Assembly
factory- - provided and
controller
Conduit nuts
(supplied by installer)
Conduit support plate
Terminal block cover
Cover gasket
(ordering option)
Controller cover
Trouble
Power
Test/reset
switch
Sensor
The sensor (see Fig. 45) 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).
See Detail A
Intake
Gasket
TSD-CO2
(ordering option)
Plug
Sampling Tube
(ordered separately)
Detail A
Magnetic
Test/Reset
Fig. 45 - - Smoke Detector Sensor
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. 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
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false alarms. A rapid change in environmental conditions,
such as smoke from a fire, causes the sensor to signal an
29
Duct Smoke Sensor
Exhaust Tube
Exhaust Gasket
Sensor Housing
and Electronics
Coupling
Switch
Alarm
Power
Trouble
Dirty
Cover Gasket
(ordering option)
Sensor Cover
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