Carrier 50TC Space Temperature SPT Sensors, RTU-MP T-55 Sensor Connections

50TC

Field Connections - Field connections for accessory sensors and input devices are made the RTU-MP, at plugs J1, J2, J4, J5, J11 and J20. All field control wiring that connects to the RTU-MP must be routed through the raceway built into the corner post as shown in Fig. 22. The raceway provides the UL required clearance between high- and low-voltage wiring. Pass the control wires through the hole provided in the corner post, then feed the wires thorough the raceway to the RTU-MP. Connect to the wires to the removable Phoenix connectors and then reconnect the connectors to the board.

Space Temperature (SPT) Sensors

Afield-supplied Carrier space temperature sensor is required with the RTU-MP to monitor space temperature. There are 3 sensors available for this application:

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

Use 20 gauge wire to connect the sensor to the controller. The wire is suitable for distances of up to 500 ft. 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. 30 for typical T-55 internal connections. Connect the T-55 SEN terminals to RTU-MP J20-1 and J20-2. See Fig. 48.

SEN J20-1

SEN J20-2

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Fig. 48 - RTU-MP T-55 Sensor Connections

Connect T-56 - See Fig. 32 for T-56 internal connections. Install a jumper between SEN and SET terminals as illustrated. Connect T-56 terminals to RTU-MP J20-1, J20-2 and J20-3 per Fig. 49.

SEN J20-1

SEN J20-2

Jumper

SET

SET J20-3

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Fig. 49 - RTU-MP T-56 Sensor Connections

Connect T-59 - The T-59 space sensor requires a separate, isolated power supply of 24 VAC. See Fig. 49 for internal connections at the T-59. Connect the SEN terminal (BLU) to RTU-MP J20-1. Connect the COM terminal (BRN) to J20-2. Connect the SET terminal (STO or BLK) to J20-3.

BRN (COM)
BLK (STO)	SENSOR
BLU (SPT)	WIRING

OR SET SEN

OPB COM- PWR+

	POWER
24 VAC	WIRING

NOTE: Must use a separate isolated transformer.

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Fig. 50 - Space Temperature Sensor Typical Wiring

(33ZCT59SPT)

Economizer controls —

Outdoor Air Enthalpy Control (PNO HH57AC077) -

The enthalpy control (HH57AC077) is available as a field-installed accessory to be used with the EconoMi$er2 damper system. The outdoor air enthalpy sensor is part of the enthalpy control. (The separate field-installed accessory return air enthalpy sensor (HH57AC078) is required for differential enthalpy control. See “Return Air Enthalpy Sensor” below.)

Locate the enthalpy control in the economizer hood. Locate two GRA leads in the factory harness and connect these leads to enthalpy control sensors 2 and 3. See Fig. 35. Connect the enthalpy control power input terminals to economizer actuator power leads RED (connect to TR) and BLK (connect to TR1).

The outdoor enthalpy changeover setpoint is set at the enthalpy controller.

Differential Enthalpy Control — Differential enthalpy control is provided by sensing and comparing the outside air and return air enthalpy conditions. Install the outdoor air enthalpy control as described above. Add and install a return air enthalpy sensor.

Return Air Enthalpy Sensor — Mount the return-air enthalpy sensor (HH57AC078) in the return-air duct. The return air sensor is wired to the enthalpy controller (HH57AC077). See Fig. 36.

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