Space Temperature (SPT) Sensors —
There are two types of SPT sensors available from Carrier, resistive input
Connect
48TC**16
be also be written to from a building network or zoning system. However, it is still recommended that return air duct sensor be installed to allow
Field connections to
S 33ZCT55SPT, space temperature sensor with override button
S 33ZCT56SPT, space temperature sensor with override button and setpoint adjustment
S 33ZCT59SPT, space temperature sensor with LCD (liquid crystal display) screen, override button, and setpoint adjustment
BLK (STO)
BRN (COM)
BLU (SPT)
OR SET SEN
OPB COM- PWR+
24 VAC
POWER
WIRING
Use 20 gauge wire to connect the sensor to the controller. The wire is suitable for distances of up to 500 ft. Use a
Connect
SEN
SEN
C08460
Fig. 69 - RTU Open T-55 Sensor Connections
Connect
SEN
SEN
Jumper
SET
SET
C08461
Fig. 70 - RTU Open T-56 Sensor Connections
NOTE: Must use a separate isolated transformer.
C10291
Fig. 71 - Space Temperature Sensor Typical Wiring
(33ZCT59SPT)
Indoor Air Quality (CO2 sensor) —
The indoor air quality sensor accessory monitors space carbon dioxide (CO2) 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 measure the levels of CO2 present in the space air.
The CO2 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 CO2 sensor for electrical requirements and terminal locations. See Fig. 54 for typical CO2 sensor wiring schematic.
To accurately monitor the quality of the air in the conditioned air space, locate the sensor near a
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 chance to mix with the room air before it is drawn into the return airstream.
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