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INTRODUCTION
The duct CO
2
device uses a highly accurate and reliable non-dispersive
infrared (NDIR) sensor in an attractive enclosure with a gasketed, hinged
cover for duct applications to monitor CO
2
levels. The sensor uses
dual channel optics and LTA (long term adjustment) signal processing
technology to deliver industry leading long term accuracy and reliability.
These technology features ensure optimum measurement stability for
both periodic and constant occupancy applications so the device is
equally suitable for return-air measurement from the classroom or the
hospital room.
Standard features include a field selectable output signal of either 4-20 mA, 0-5 Vdc or 0-10 Vdc for the
highest versatility, programmable CO
2
measurement span, a backlit alpha-numeric LCD and easy menu
operation for configuration.
Optional features include a resistive temperature sensor output (with LCD display of temperature in
either °C or °F), a control relay with programmable setpoint, hysteresis and time delay, and either a
conduit or cable gland connection point.
BEFORE INSTALLATION
Read these instructions carefully before installing and commissioning the device. Failure to follow these
instructions may result in product damage. Do not use in an explosive or hazardous environment, with
combustible or flammable gases, as a safety or emergency stop device or in any other application where
failure of the product could result in personal injury. Take electrostatic discharge precautions during
installation. De-energize the power supply prior to installation, this device is intended for indoor air
conditioned spaces, contact factory or other applications.
Do not exceed device ratings. This product
is not intended for life-safety applications.
NOTE:
This CO
2
sensor incorporates a Self Calibration feature to correct CO
2
sensor drift. This feature is
recommended for applications where the CO
2
will be exposed to fresh air (400 ppm) at least one hour
per day. If the monitored space is occupied 24 hours or consistently maintains higher or lower levels
of CO
2
, it is recommended that this feature be turned off, but yearly calibration will be required. If the
self calibration is disabled at installation time without allowing for 7 day auto calibration cycle, then a
manual calibration should be performed to ensure accuracy of the device.
MOUNTING
The duct type sensor installs on the outside of a return air duct with the sampling tube inserted into the
duct. Use the included foam plug to prevent air from entering the enclosure through the conduit and
causing an incorrect reading.
Mount the sensor in an easily accessible location in a straight section
of duct at least five feet from corners or other items that may cause
disturbances in the air flow. Avoid areas where the detector is exposed
to vibrations or rapid temperature changes.
The duct CO
2
detector principal of operation is based on the Venturi
effect of the probe that extends into the HVAC duct. Air flowing through
the duct is forced into the vent holes on one side of the probe, into
the enclosure, over the CO
2
sensor and then is drawn back out of the
enclosure via the probe vent holes on the opposite side.
NOTE
: To ensure proper temperature readings, if present, the
temperature inlet on the probe must be installed directly into the
airflow. See Figure 1.
EMT Connector
Thread adapter and
cable gland fitting
Figure 1
Airflow
Figure 3
Figure 2
IN-GE-CD2DTXXX-03
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Duct Carbon Dioxide Transmitter
CD2DT Series - Installation Instructions
