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requirements and terminal locations. See Fig. 47 for
typical CO
2
sensor wiring schematic.
8
7
6
5
4
32
1
2
1
HG
24 VAC
OR
24 VDC
NC
ALARM
RELAY
CONTACTS
COM
NO
}
0-10VDC
SIG COM
4-20mA
+
+
-
+
-
J3 J4
C08635
Fig. 47 -- 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 areas 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 it 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 (unshielded) to connect
the separate isolated 24 vac power source to the sensor
and to connect the sensor to the control board terminals.
To connect the sensor to the control, identify the positive
(4 to 20 mA) and ground (SIG COM) terminals on the
sensor. See Fig. 47. Connect the 4--20 mA terminal to
RTU--MP J4--2 and connect the SIG COM terminal to
RTU--MP J4--3. See Fig. 48.
SEN
COM
J4-2
J4-3
IAQ Sensor
24 VAC
C08462
Fig. 48 -- RTU--MP / Indoor CO
2
Sensor
(33ZCSENCO2) Connections
Outdoor Air Quality Sensor (PNO 33ZCSENCO2 plus
weatherproof 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. 49. The outdoor air CO
2
sensor must be located in the economizer outside air hood.
COVER REMOVED SIDE VIEW
C07135
Fig. 49 -- 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 the 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) terminals on the
OAQ sensor. See Fig. 47. Connect the 4 to 20 mA
terminal to RTU--MP J4--5. Connect the SIG COM
terminal to RTU--MP J4--6. See Fig. 50.
SEN
COM
J4-5
J4-6
OAQ Sensor/RH Sensor
24 VAC
C08463
Fig. 50 -- RTU--MP / Outdoor CO
2
Sensor
(33ZCSENCO2) Connections
551J
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