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Return Air Enthalpy Sensor —
Mount the return--air enthalpy sensor (33CSENTSEN) in
the return--air section of the economizer. The return air
sensor is wired to the enthalpy controller
(33CSENTHSW). See Fig. 54.
GRA
BLK
RED
– 4-20
Main
+ VDC
Out
– 4-20 Main
Out
+ 24-36
VDC In
LOW
GND
24V
7
CTB ECON
(RTU Open: to J2-6)
PL6-1 (24-V)
PL6-4 (COM)
Outside Air
Enthalpy Switch
Return Air
Enthalpy
Sensor
C11170
Fig. 54 -- Outside and Return Air Enthalpy Sensor
Wiring
To wire the return air enthalpy sensor, perform the
following:
1. Use a 2--conductor, 18 or 20 AWG, twisted pair cable
to connect the return air enthalpy sensor to the enthal-
py controller.
2. Connect the field--supplied RED wire to (+) spade
connector on the return air enthalpy sensor and the
(+) terminal on the enthalpy controller. Connect the
BLK wire to (--) spade connector on the return air en-
thalpy sensor and the (--) terminal on the enthalpy
controller.
Smoke Detectors
Smoke detectors are available as factory--installed options
on 581J models. Smoke detectors may be specified for
Supply Air only or for Return Air without or with
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 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.
Units equipped with factory--optional Return Air smoke
detectors require a relocation of the sensor module at unit
installation. See “Completing Installation of Return Air
Smoke Sensor:” on page 36 for details.
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. 55) 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
Fastener
(2X)
Controller cover
Conduit nuts
(supplied by installer)
Conduit support plate
Cover gasket
(ordering option)
Conduit couplings
(supplied by installer)
Terminal block cover
Controller housing
and electronics
Alarm
Power
Test/reset
switch
Trouble
C08208
Fig. 55 -- Controller Assembly
Sensor Module —
The sensor module (see Fig. 56) 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. 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
581J