Carrier 48HC installation instructions Relative Humidity Sensors Space or Duct Mounted

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. 46. Connect the 4-20 mA terminal to RTU Open terminal J4-2 and connect the SIG COM terminal to RTU Open terminal J4-3. See Fig. 63.

IAQ Sensor

4-20mA J4-2

SIG COM J4-3 24 VAC

C10738

Fig. 63 - RTU Open / Indoor CO2 Sensor

(33ZCSENCO2) Connections

Outdoor Air Quality Sensor (PNO 33ZCSENCO2 plus weatherproof enclosure) —

The outdoor air CO2 sensor is designed to monitor carbon dioxide (CO2) 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. 48. The outdoor air CO2 sensor must be located in the economizer outside air hood.

Wiring the Outdoor Air CO2 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. 46. Connect the 4 to 20 mA terminal to RTU Open terminal J4-5. Connect the SIG COM terminal to RTU Open terminal J4-6. See Fig. 64.

OAQ Sensor/RH Sensor

4-20mA J4-5

SIG COM J4-6 24 VAC

C10739

Fig. 64 - RTU Open / Outdoor CO2 Sensor

(33ZCSENCO2) Connections

Space Relative Humidity Sensor or Humidistat —
Humidi-MiZerRControl Wiring: In units equipped
with the Humidi-MiZer option there are two pink (PNK)
wires loose in the control box used to control the
dehumidification function of the unit. These pink wires
are meant to be tied to a space humidistat or thermidistat
on an electromechanical unit. On RTU Open equipped
units these pink wires must be connected to J11-7 & 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):
The 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	48HC
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 24vdc. Refer to the instructions
supplied with the RH sensor for the electrical
requirements and terminal locations. RTU Open
configurations must be changed after adding an RH
sensor. See Fig. 65 and 66 for typical RH sensor wiring.
S J4-1 or J4-4 = 24vdc loop power
S J4-2 or J4-5 = 4-20mA signal input
NOTE: The factory default for dehumidification control
is normally open humidistat.

MOUNTING

HOLES

	WIRING
Io Vin Gnd Vo	OPENING

SW2

6	5	4	3	2	1
						ON

Vin -	J4-1 or J4-4	24Vdc
Io -	J4-2 or J4-5	-20mA output

C11087

Fig. 65 - Space Relative Humidity Sensor Typical Wiring

41