Carrier 48TCA04---A12 appendix Space Temperature SPT Sensors, RTU-MP T-55 Sensor Connections

48TC

connects to the RTU-MP must be routed through the raceway built into the corner post as shown in Fig. 34. 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. 43 for typical T-55 internal connections. Connect the T-55 SEN terminals to RTU-MP J20-1 and J20-2. See Fig. 61.

SEN J20-1

SEN J20-2

C08460

Fig. 61 - RTU-MP T-55 Sensor Connections

Connect T-56 - See Fig. 45 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. 62.

SEN J20-1

SEN J20-2

Jumper

SET

SET J20-3

C08461

Fig. 62 - 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. 61 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.

C07132

Fig. 63 - 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 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.

48.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.

The enthalpy control receives the outdoor air enthalpy from the outdoor air enthalpy sensor and provides a dry contact switch input to the RTU-MP controller. A closed contact indicates that outside air is preferred to the return air. An open contact indicates that the economizer should remain at minimum position.

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

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