43
Connect T--59: The T--59 space sensor requires a
separat e, isolated power supply of 24 VAC. See Fig. 50
for internal connections at the T--59. Connect the SEN
terminal (BLU) to the RTU Open controll er at J20--1.
Connect the COM terminal (BRN) to J20--2. Connec t the
SET terminal (STO or BLK) to J20--3.
OR SET SEN
OPB COM- PWR+
BLU (SPT)
BLK (STO)
24 VAC
SENSOR
WIRING
POWER
WIRING
BRN (COM)
NOTE: Must use a separate isolated transformer.
J20-3
J20-2
J20-1
C10291
Fig. 50 -- Space Temperature Sensor Typical Wiring
(33ZCT59SPT)
Indoor Air Quality (CO
2)
Sensor —
The indoor air quality sensor accessory monitors space
carbon dioxide (CO
2
) levels. This information is used to
monitor IAQ levels. Several types of sensors are available,
for wall mounting in the space or in return duct, with and
without LCD display, and in combination with space
temperature sensors. Sensors use infrared technology to
mea sure the levels of CO
2
present in the space air.
The CO
2
sensors are all factory set for a range of 0 to
2000 ppm and a linear mA output of 4 to 20. Refer to the
instructions supplied with the CO
2
sensor for electrical
requirements and terminal locations. See Fig. 51 for
typical CO
2
sensor wiring schema tic.
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 cha nce to mix with the room air
before it is drawn i nto the return ai rstream.
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. 51 -- Indoor/Outdoor Air Quali ty (CO
2
)Sensor
(33ZCSENCO2) -- Typical Wiring Diagr am
Wiring the Indoor Air Quality Sensor: For each sensor,
use two 2--conduc tor 18 AWG (American Wire Gage)
twisted--pair cables (unshielded) to connect the separate
isolated 24 vac power source to the sensor and to connec t
the sensor to the cont rol 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. 51. Connect the 4--20 mA terminal to the
RTU Open controller at J4--2 and connect the SIG COM
terminal the RTU Open controller at J4--3. See Fig. 52.
SEN
COM
J4-2
J4-3
IAQ Sensor
24 VAC
C08462
Fig. 52 -- RTU Open Controller / Indoor CO
2
Sensor
(33ZCSENCO2) Connections
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