Carrier 48HC Space Temperature SPT Sensors, RTU Open T-55 Sensor Connections

to the RTU Open. Connect to the wires to the removable Phoenix connectors and then reconnect the connectors to the board.

Space Temperature (SPT) Sensors —

There are two types of SPT sensors available from Carrier, resistive input non-communicating (T55, T56, and T59)

Connect T-59:The T-59 space sensor requires a separate, isolated power supply of 24 VAC. See Fig. 62 for internal connections at the T-59. Connect the SEN terminal (BLU) to RTU Open J20-1. Connect the COM terminal (BRN) to J20-2. Connect the SET terminal (STO or BLK) to J20-3.

48HC

and Rnet communicating (SPS, SPPL, SPP, and SPPF) sensors. Each type has a variety of options consisting of: timed override button, set point adjustment, a LCD screen, and communication tie in. Space temperature can 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 stand-alone operation for back-up. Refer to the configuration section for details on controller configurations associated with space sensors.

S 33ZCT55SPT, space temperature sensor with override button (T-55)

S 33ZCT56SPT, space temperature sensor with override button and setpoint adjustment (T-56)

S 33ZCT59SPT, space temperature sensor with LCD (liquid crystal display) screen, override button, and

BLK (STO)

BRN (COM)

BLU (SPT)

OR SET SEN

OPB COM- PWR+

24 VAC

J20-3

J20-2SENSOR WIRING

J20-1

POWER

WIRING

setpoint adjustment (T-59)

Use 20 gauge wire to connect the sensor to the controller. The wire is suitable for distances of up to 500 ft. (152 m). Use a three-conductor shielded cable for the sensor and setpoint adjustment connections. If the setpoint adjustment (slidebar) is not required, then an unshielded, 18 or 20 gauge, two-conductor, twisted pair cable may be used.

Connect T-55:See Fig. 41 for typical T-55 internal connections. Connect the T-55 SEN terminals to RTU Open J20-1 and J20-2. See Fig. 60.

SEN J20-1

SEN J20-2

C08460

Fig. 60 - RTU Open T-55 Sensor Connections

Connect T-56:See Fig. 43 for T-56 internal connections. Install a jumper between SEN and SET terminals as illustrated. Connect T-56 terminals to RTU Open J20-1, J20-2 and J20-3 per Fig. 61.

SEN J20-1

SEN J20-2

Jumper

SET

SET J20-3

C08461

Fig. 61 - RTU Open T-56 Sensor Connections

NOTE: Must use a separate isolated transformer.

C10291

Fig. 62 - 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. 46 for typical CO2 sensor wiring schematic.

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 CO2 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 chance to mix with the room air before it is drawn into the return 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

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