17
INDOOR-AIR QUALITY SENSOR INSTALLATION —
The indoor-air quality (IAQ) sensor accessory monitors carbon
dioxide levels. This information is used to increase the airflow
to the zone and may also modify the position of the outdoor-air
dampers to admit more outdoor air as required to provide the
desired ventilation rate. The wall sensor is used to monitor the
conditioned space. The sensor uses infrared technology to
measure the levels of CO
2
present in the air. The wall sensor is
available with or without an LCD readout to display the CO
2
level in ppm and is also available in a combination model
whichsensesbothtemperatureandCO
2
level.
The CO
2
sensors are factory set for a range of 0 to
2000 ppm and a linear voltage output of 0 to 10 vdc. Refer to
the instructions supplied with the CO
2
sensor for electrical re-
quirements and terminal locations. The sensor requires a sepa-
rate field-supplied 24 vac 25 va transformer to provide power
to the sensor. The transformer may be mounted in the control
box if space is provided (except electric heat units).
For factory configuration changes to some models of the
sensor, the User Interface Program (UIP) or Sensor Calibration
Service Kit is required.
To accurately monitor the quality of the air in the condi-
tioned air space, locate the sensor near the return air grille 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 space sensor in drafty areas such as near
supply diffusers, open window, fans, or over heat sources. Al-
low at least 3 ft 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.
To mount the sensor, refer to the installation instructions
shipped with the accessory kit.
INDOOR AIR QUALITY SENSOR WIRING — To wire the
sensor after it is mounted in the conditioned air space, see
Fig. 23-25 and the instructions shipped with the sensor. Use
two 2-conductor 20 American Wire Gage (AWG) twisted-pair
cables (see Table 7) to connect the field-supplied separate iso-
lated 24 vac power source to the sensor and to connect the sen-
sor to the control terminals. To connect the sensor to the
control, identify the positive (+) and ground (GND) terminals
on the sensor and connect the positive terminal to the RH/IAQ
terminal on the control and connect the ground terminal to
terminal GND.
HUMIDITY SENSOR (Wall-Mounted) INSTALLA-
TION — The accessory space humidity sensor is field sup-
plied and installed on an interior wall to measure the relative
humidity of the air within the occupied space. See Fig. 26.
Theuseofastandard2x4-in.electricalboxtoaccommo-
date the wiring is recommended for installation. The sensor can
be mounted directly on the wall, if acceptable by local codes.
If the sensor is installed directly on a wall surface, install the
humidity sensor using 2 screws and 2 hollow wall anchors
(field-supplied); do not overtighten screws.
The sensor must be mounted vertically on the wall. The
Carrier logo should be oriented correctly when the sensor is
properly mounted.
Do NOT clean or touch the sensing element with chemical
solvents; they can permanently damage the sensor.
Fig. 24 — Ventilation Rates Based on
CO
2
Set Point
Fig. 23 — Indoor Air Quality Sensor
(Wall-Mounted Version Shown) 33ZCSENCO2
Fig. 22 — Primary Air Temperature
Sensor Installation
(Air-Handling Unit Discharge Locations)
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