by the freeze condition. Unit reset is automatic when the contacts on the freeze protection switch close again. The contacts on the freeze protection switch open below 37 F.

TOWER SUMP TEMPERATURE SENSOR (50XJ PCB3) — This sensor is used for monitoring (only) the tower sump temperature.

LEAVING WATER TEMPERATURE SENSOR (50XJ PCB3) — This sensor is used for monitoring (only) the leav- ing water temperature.

BUILDING STATIC PRESSURE SENSOR (50XJ PCB3) — This sensor is used to control both the speed of the building exhaust fan and the building static pressure.

INDOOR AIR QUALITY (CO2) SENSOR (50XJ PCB3) — This sensor monitors CO2 levels.

INDOOR RELATIVE HUMIDITY SENSOR (50XJ PCB3) — This sensor monitors and controls the humidity control relay.

OUTDOOR AIR TEMPERATURE SENSOR (50XJ PCB3) — This sensor is used to monitor outdoor air and broadcast the value over the Carrier Comfort Network (CCN).

STAGE HEAT RELAYS (50XJ PCB3) — These relays con- trol up to four stages of electric heat, or other heating methods.

PUMP REQUEST RELAY (50XJ PCB3) — This relay turns on a tower pump when requested.

TOWER REQUEST/CONTROL RELAY (50XJ PCB3) — This relay is used to activate a tower fan.

BUILDING EXHAUST FAN SPEED CONTROL (50XJ PCB3) — This output controls building exhaust fan speed.

HUMIDITY CONTROL RELAY (50XJ PCB3) — This relay controls a humidifier or dehumidification device.

Wiring Control Devices — Standard controls for the 50XJ require no field-wiring. Standard 50XJ controls include: Supply Air Temperature (SAT), Duct Static Pressure (DSP), Duct High Static Limit Switch (DHS), Filter Status Switch (FLTS), Entering Water Temperature (EWT), Compressor Sta- tus (CSMUX), Supply Fan Start/Stop (SF), Supply Fan Speed (SPEED), and Mixed/Air Return/Air sensor (MA_RA).

NOTE: The MA_RA sensor will be located in the return air steam if the unit does not have a water economizer, and in the mixed airstream if the unit is equipped with a water economizer.

For the 50BV unit, standard controls include: Duct Static Pressure (DSP), Duct High Static Limit Switch (DHS), Com- pressor Status (CSMUX), Supply Fan Start/Stop (SF), and Supply Fan Speed (SPEED).

For the 50XJ unit, optional controls will be wired to the field terminal blocks (TB5 and TB6) provided. Refer to Fig. 2A and the descriptions below.

For the 50BV unit, optional controls are wired to field terminal block TB2 as shown in Fig. 2B.

EXTERNAL 0 TO 10 VOLT DC RESET SIGNAL (RESET) (50XJ PCB2) — This field-supplied 0 to 10 vdc signal is used to reset the 50XJ supply-air temperature. The controller will scale the signal to provide 0 reset at 0 volts and 20 degrees of reset at 10 volts. Wire the positive of the signal to the RESET terminal and the negative to the C or common terminal.

SUPPLY AIR RESET (50BV) — Use a 5k ohm sensor installed at the Entering Water Temperature sensor (EWT) location on PCB1. For space temperature averaging, two 10k ohm Space Temperature Sensors (SPT) can be wired in parallel.

SPACE TEMPERATURE SENSOR (50XJ PCB2) — The space temperature sensor (33ZCT55SPT) is used in the follow- ing cases:

When using the optional water economizer and not using Carrier’s ComfortID™ System.

Fig. 2A — Field Terminal Blocks for 50XJ Unit

Fig. 2B — Field Terminal Block for 50BV Unit

To determine the average temperature of the space being served.

To determine supply-air temperature reset, occupied heating, unoccupied heating and cooling (refer to Sequence of Operation in the Start-Up section.).

To wire the sensor, perform the following (see Fig. 3). Identify which cable is for the sensor wiring.

1. Strip back the jacket from the cable for at least

3 inches. Strip 1/4-in. of insulation from each conduc- tor. Cut the shield and drain wire from the sensor end of the cable.

2.Wire the sensor to the SPT and C terminals on the field terminal block (TB5). A typical 10K thermistor such as the 33ZCT55SPT sensor may be used. If the SPT sensor is not installed and the MA_RA (mixed air/ return air) sensor is configured for return air, the 50XJ unit will use this sensor to control supply air reset, occupied heat, and unoccupied heating and cooling

See Fig. 4 for space temperature sensor averaging.

HOT WATER OR STEAM VALVE (HWV) (50XJ PCB2) — The HWV terminal supplies the positive signal to control a 4 to 20 mA hot water or steam valve for occupied and unoccupied heat. Connect the common side of the valve to the C terminal or an equipment ground.

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Carrier 50XJ064-104 specifications Field Terminal Blocks for 50XJ Unit

50XJ064-104 specifications

The Carrier 50XJ064-104 is a high-efficiency rooftop air conditioning system designed to deliver exceptional cooling and heating capabilities for diverse commercial applications. One of the standout features of this model is its robust cooling capacity of 64,000 BTUs, making it suitable for mid to large-sized spaces. The 50XJ064-104 is engineered using advanced technologies to ensure energy efficiency and reliable performance, contributing to reduced operational costs and environmental sustainability.

One of the primary technologies employed in the Carrier 50XJ064-104 is the high-efficiency scroll compressor. This component plays a pivotal role in optimizing energy usage while delivering consistent cooling output. The system also incorporates an economizer that allows for enhanced energy savings by utilizing outdoor air for cooling when conditions are favorable. This not only decreases reliance on the compressor but also improves indoor air quality.

The microprocessor-based controls in the 50XJ064-104 provide precise temperature regulation, ensuring optimal comfort levels in various applications. These controls allow for easy programming and can be integrated into building management systems for centralized oversight. Additionally, the unit features a built-in fault detection and diagnostic system that aids in identifying potential issues before they escalate, minimizing downtime and maintenance costs.

The Carrier 50XJ064-104 is designed with durability in mind. It features a weather-resistant cabinet, designed to withstand harsh outdoor conditions and prolong service life. The high-quality insulation within the unit not only enhances energy efficiency but also minimizes noise levels, making it an ideal choice for urban environments where sound control is critical.

Another important characteristic is its environmentally friendly R-410A refrigerant, which has a lower impact on ozone depletion compared to older refrigerants. This aligns with Carrier's commitment to creating sustainable HVAC solutions that comply with current environmental regulations.

Overall, the Carrier 50XJ064-104 stands out for its combination of efficiency, advanced technologies, and durable construction. Whether for commercial buildings, retail spaces, or industrial applications, this rooftop air conditioning unit is designed to provide reliable performance and comfort year-round.