12
Communicating sensors:
Any combination of sensors described in the “Rnet Communi-
cating Sensor Wiring” section can be used.
NOTE: Communicating CO
2
sensors and RH sensors can be aver-
aged if within the realm described.
CO
2
SENSOR(S) (IAQ AND OAQ)
The indoor air quality (IAQ) and outdoor air quality (OAQ)
sensors monitor carbon dioxide (CO
2
) levels. This information
is used to monitor the quality of air in terms of parts per million
(PPM). The same sensor is used for inside, outside, and duct
monitoring, except an aspirator box is required for outside and
duct mounting. The CO
2
sensor is preset for a range of 0 to
2000 ppm and a linear mA output of 4 to 20. The rooftop unit
may have a factory installed CO
2
sensor on the side of the
economizer assembly in the return air section of the unit and is
pre-wired and pre-configured at the factory. For field installed
sensors, a field supplied transformer must be used to power the
sensor. Refer to the instructions supplied with the CO
2
sensor
for electrical requirements and terminal locations. RTU Open
controller configurations must be changed after adding a CO
2
sensor. See below and Fig. 12 for typical CO
2
sensor wiring.
• J4-2 or J4-5 = 4-20mA signal input
• J4-3 or J4-6 = signal common
NOTE: The factory used J4-2 and 3 for CO
2
(IAQ) sensor inputs.
Combination Temperature and CO
2
Sensor:
If using a combination temperature and CO
2
sensor
(33ZCT55CO2-02 or 33ZCT56CO2-02), refer to the installa-
tion instructions provided with the sensor.
Fig. 10 — Space Temperature Averaging for Non-Communicating Sensors
RED
RED
BLK
BLK
J20
1
2
RED
BLK
BLK
RED
BLK
RED
SENSOR 2 SENSOR 3SENSOR 4SENSOR 1
SPACE TEMPERATURE AVERAGING — 4 SENSOR NON-COMMUNICATING APPLICATION
RED
BLK
RED
BLK
SENSOR 2
SENSOR 1
RED
RED
BLK
SENSOR 3
SENSOR 4
BLK
BLK
RED
RED
RED
BLK
BLK
SENSOR 8
SENSOR 9
SENSOR 5
RED
BLK
SENSOR 6
SENSOR 7
BLK
RED
SPACE TEMPERATURE AVERAGING — 9 SENSOR NON-COMMUNICATING APPLICATION
Factory Wiring
Field Wiring
J20
1
2
LEGEND
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