Carrier 50HCQA Economizer Controls, Configure the Unit for Thermostat Mode, Wiring

If the 50HCQ unit has an economizer system and free-cooling operation is required, a sensor representing Return Air Temperature must also be connected (field-supplied and installed). This sensor may be a T-55 Space Sensor (see Fig. 31) installed in the space or in the return duct, or it may be sensor PNO 33ZCSENSAT, installed in the return duct. Connect this sensor to TB1-1 and TB1-3 per Fig. 32.

Configure the Unit for Thermostat Mode —

Connect to the CCN bus using a CCN service tool and navigate to PremierLink Configuration screen for Operating Mode. Default setting is Sensor Mode (value 1). Change the value to 0 to reconfigure the controller for Thermostat Mode.

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 (33CSENTSEN) in the return-air section of the economizer. The return air sensor is wired to the enthalpy controller (33CSENTHSW). See Fig. 37.

50HCQA

When the PremierLink is configured for Thermostat Mode, these functions are not available: Fire Shutdown (FSD), Remote Occupied (RMTOCC), Compressor Safety (CMPSAFE), Supply Fan Status (SFS), and Filter Pressure Switch (FILTER).

Economizer Controls

Outdoor Air Enthalpy Control (PNO 33CSENTHSW) —

The enthalpy control (33CSENTHSW) is available as a field-installed accessory to be used with the EconoMi$er2

– 4-20	24V	RED
Main	GND	BLK
+ VDC
Out	LOW	GRA

+24-36 VDC In

–4-20 Main Out

ECONO

MOTOR

ESL

damper system. The outdoor air enthalpy sensor is part of the enthalpy control. (The separate field-installed accessory return air enthalpy sensor (33CSENTSEN) is required for differential enthalpy control. See Fig. 36.)

Locate the enthalpy control in the economizer next to the Actuator Motor. Locate two GRA leads in the factory harness and connect the gray lead labeled “ESL” to the terminal labeled “LOW”. See Fig. 36. Connect the enthalpy control power input terminals to economizer actuator power leads RED (connect to 24V) and BLK (connect to GND).

C09027

Fig. 37 - Outside and Return Air Enthalpy Sensor

Wiring

To wire the return air enthalpy sensor, perform the following:

1.	Use a 2-conductor, 18 or 20 AWG, twisted pair cable
	to connect the return air enthalpy sensor to the enthal-
	py controller.
2.	Connect the field-supplied RED wire to (+) spade
	connector on the return air enthalpy sensor and the
	(+) terminal on the enthalpy controller. Connect the

Enthalpy
Switch
24V	RED
GND	BLK
LOW	GRA	ESL

7

ECONO MOTOR

CTB

ECON

BLK wire to (-) spade connector on the return air en-

thalpy sensor and the (-) terminal on the enthalpy

controller.

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

Factory Wiring Harness

C09026

Fig. 36 - Enthalpy Switch (33CSENTHSW) Connections

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

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. 38 for typical CO2 sensor wiring schematic.

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