Smoke Detectors; System; Controller; Smoke Detector Sensor - Carrier 50FC 04 Series Service And Maintenance Instructions

SMOKE DETECTORS

Smoke detectors are available as factory-installed options on
50FC models. Smoke detectors may be specified for supply air
only, for return air without or with economizer, or in combination
of supply air and return air. Return air smoke detectors are ar-
ranged for vertical return configurations only. All components
necessary for operation are factory-provided and mounted. The
unit is factory-configured for immediate smoke detector shutdown
operation; additional wiring or modifications to unit terminal
board may 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 roof-
top 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. 43) includes a controller housing, a print-
ed 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 but-
ton (on the cover face).
Duct Smoke Sensor
Controller
Controller
Housing
and Electronics
Conduit Couplings
(Supplied by Installer)
Fastener (2X)
Alarm
Fig. 43 — Controller Assembly

Smoke Detector Sensor

The smoke detector sensor (see Fig. 44) 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).
Conduit Nuts
(Supplied by Installer)
Conduit Support Plate
Terminal Block Cover
Cover Gasket
(Ordering Option)
Controller
Cover
Trouble
Power
Test/Reset
Switch
Duct Smoke Sensor
See
Detail A
Intake
Gasket
TSD-CO2
(Ordering Option)
Plug
Sampling Tube
(Covered Separately)
Detail A
Magnetic
Test/Reset
Switch
Fig. 44 — 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 sam-
pled 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.
The difference in air pressure between the two tubes pulls the sam-
pled 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.
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 right of the
unit's indoor (supply) fan. See Fig. 45. Access is through the fan
access panel. The sampling tube inlet extends through the fan deck
(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.
24
Exhaust Tube
Exhaust Gasket
Sensor Housing and Electronics
Cover Gasket
(Ordering Option)
Coupling
Alarm Power
Trouble Dirty
Sensor
Cover