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The CO
2
sensors are all factory set for a range of 0 to
2000 ppm and a linear mA output of 4 to 20. Refer to the
instructions supplied with the CO
2
sensor for electrical
requirements and terminal locations. See Fig. 51 for
typical CO
2
sensor wiring schematic.
C07134
Fig. 51 -- Indoor/Outdoor Air Quality (CO
2
)Sensor
(33ZCSENCO2) -- Typical Wiring Diagram
To accurately monitor the quality of the air in the
conditioned air space, locate the sensor near a return--air
grille (if present) so it senses the concentration of CO
2
leaving the space. The sensor should be mounted in a
location to avoid direct breath contact.
Do not mount the IAQ sensor in drafty are as such as near
supply ducts, open windows, fans, or over heat sources.
Allow at least 3 ft (0.9 m) between the sensor and any
corner. Avoid mounting the sensor where it is influenced
by the supply air; the sensor gives inaccurate readings if
the supply air is blown directly onto the sensor or if the
supply air does not have a chance to mix with the room air
before i t is drawn into the return airstream.
Wiring the Indoor Air Quality Sensor —
For each sensor, use two 2--conductor 18 AWG (American
Wire Gage) twisted--pair cables (unshielde d) to connect
the separate isolated 24 vac power source to the sensor
and to connect the sensor to the control board terminal s.
To connect the sensor to the control, identify the positive
(4 to 20 mA) and ground (SIG COM) t erminals on the
sensor. See Fig. 51. Connect the 4--20 mA terminal to
terminal TB1 --9 and connect the SIG COM terminal to
terminal TB1--11. See Fig. 52.
C09155
Fig. 52 -- Indoor CO
2
Sensor (33ZCSENCO2)
Connections
Refer to the Rooftop PremierLink Installation, Start-Up,
and Configuration Instructions (Form 33CS--58SI),
PremierLink Installation, Start --up, and Configuration
Instructions, for detailed configuration information
Outdoor Air Quality Sensor (PNO 33ZCSENCO2 plus
weathe rproof enclosure) — The outdoor air CO
2
sensor is
designed to monitor carbon dioxide (CO
2
) levels in the
outside ventilation air and interface with the ventilation
damper in an HVAC system. The OAQ sensor is packaged
with an outdoor cover. See Fig. 53. The outdoor air CO
2
sensor must be located in the economizer outside air hood.
COVER REMOVED SIDE VIEW
C07135
Fig. 53 -- Outdoor Air Quality Sensor Cover
Wiring the Outdoor Air CO
2
Sensor — A dedicated power
supply is required for this sensor. A two--wire cable is
required to wire the dedicated power supply for the sensor.
The two wires should be connected to t he power supply
and terminals 1 and 2.
To connect the sensor to the control, identify the positive
(4 to 20 mA) and ground (SIG COM) t erminals on the
OAQ sensor. See Fig. 51. Connect the 4 to 20 mA
terminal to 48TC’s terminal TB1--13. Connect the SIG
COM terminal to 48TC’s terminal TB1--11. See Fig. 54.
SEN J5-2
J5-3
COM
13
11
TB1
TB1
PL
OAQ Sensor/RH Sensor
24 VAC
C08275
Fig. 54 -- Outdoor CO
2
Sensor Connections
48TC