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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 re-
turn 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 con-
trol 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. 52. Connect the 4-20 mA terminal to the RTU Open con-
troller at J4-2 and connect the SIG COM terminal to the RTU
Open controller at J4-3. See Fig. 69.
IAQ Sensor
SEN
COM
24 VAC
Fig. 69 — RTU Open Controller/Indoor CO
(33ZCSPTCO2-01 or 33ZCSPTCO2LCD-01)
Connections
OUTDOOR AIR QUALITY SENSOR (P/N 33ZCSPTCO2
PLUS WEATHERPROOF ENCLOSURE) — The outdoor
air CO
sensor is designed to monitor carbon dioxide (CO
2
levels in the outside ventilation air and interface with the venti-
lation damper in an HVAC system. The OAQ sensor is pack-
aged with an outdoor cover. See Fig. 54. The outdoor air CO
sensor must be located in the economizer outside air hood.
Wiring the Outdoor Air CO
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 sen-
sor. See Fig. 52. Connect the 4 to 20 mA terminal to the RTU
Open controller at J4
5. Connect the SIG COM terminal to
—
the RTU Open controller at J4
OAQ Sensor
COM
24 VAC
Fig. 70 — RTU Open Controller/Outdoor CO
Sensor (33ZCSPTCO2-01 or 33ZCSPTCO2LCD-01)
Connections
J4-2
J4-3
Sensor
2
Sensor
A dedicated power
—
2
6. See Fig. 70.
—
SEN
J4-5
J4-6
SPACE RELATIVE HUMIDITY SENSOR OR HUMIDI-
STAT
Humidi-MiZer® System Control Wiring
equipped with the Humidi-MiZer option there are two pink
(PNK) wires loose in the control box used to control the dehu-
midification function of the unit. These pink wires are meant to
be tied to a space humidistat or thermidistat on an electrome-
chanical unit. On RTU Open equipped units these pink wires
must be connected to J11-7 and 8 to allow the Open board to
operate the dehumidification function for the unit. Disconnect
the J11 Phoenix style connector from the board and use the
plug screws to secure the pink wires in pins 7 and 8, reconnect
the plug to the board at J11.
Relative Humidity Sensors (Space or Duct Mounted)
accessory space humidity sensor (33ZCSENSRH-01) or duct
humidity sensor (33ZCSENDRH-01) is used to measure the
relative humidity of air within the space or return air duct. The
RH reading is used to control the Humidi-MiZer option of the
rooftop unit. For wiring distances up to 500 ft (152 m), use a 3-
conductor, 18 or 20 AWG shielded cable. The shield must be
removed from the sensor end of the cable and grounded at the
unit end. The current loop power for sensor is provided by the
RTU Open controller as 24 vdc. Refer to the instructions sup-
plied with the RH sensor for the electrical requirements and
terminal locations. RTU Open controller configurations must
be changed after adding an RH sensor. See Fig. 71 and 72 for
typical RH sensor wiring.
• J4
1 or J4
—
• J4
2 or J4
—
NOTE: The factory default for dehumidification control is nor-
mally open humidistat.
)
2
2
MOUNTING
HOLES
2
Fig. 71 — Space Relative Humidity Sensor Typical
49
4 = 24 vdc loop power
—
5 = 4-20 mA signal input
—
Io
Vin
Gnd
Vo
SW2
Vin - J4-1 or J4-4 24Vdc
Io - J4-2 or J4-5 -20mA output
Wiring
In
units
—
The
—
WIRING
OPENING
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