Carrier 48EZ-A Start-up Cooling and Make Adjust- ments, Checking Cooling Control Operation

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48EZ -- A

Step 4 — Start-up Cooling and Make Adjust- ments

Complete the required procedures given in the Pre-Start-Up section before starting the unit. Do not jumper any safety devices when operating the unit. Do not operate the compressor when the outdoor temperature is below 40°F (4.4°C) (unless accessory low-ambient kit is installed). Do not rapid-cycle the compressor. Allow 5 minutes between on cycles to prevent compressor damage.

Checking Cooling Control Operation

Start and check the unit for proper cooling control operation as follows:

1.Place room thermostat SYSTEM switch in OFF position. Observe that blower motor starts when FAN switch is placed in ON position and shuts down when FAN switch is placed in AUTO position.

2.Place SYSTEM switch in COOL position and FAN switch in AUTO position. Set cooling control below room temperature. Observe that compressor, condenser fan, and evaporator blower motors start. Observe that cooling cycle shuts down when control setting is satisfied. The evaporator fan will continue to run for 90 sec.

IMPORTANT: Three-phase, scroll compressors units are direction oriented. Unit must be checked to ensure proper compressor 3-phase power lead orientation. If not corrected within 5 minutes, the internal protector will shut off the compressor. The 3-phase power leads to the unit must be reversed to correct rotation. When turning backwards, the difference between compressor suction and discharge pressures will be near zero.

Checking and Adjusting Refrigerant Charge

The refrigerant system is fully charged with PuronR (R-410A) refrigerant and is tested and factory sealed. Allow system to operate a minimum of 15 minutes before checking or adjusting charge.

NOTE: Adjustment of the refrigerant charge is not required unless the unit is suspected of not having the proper PuronR (R-410A) charge.

The charging label and the tables shown refer to system temperatures and pressures in cooling mode only. A refrigerant charging label is attached to the inside of the compressor access panel (see Fig. 19). The chart includes the required liquid line temperature at given discharge line pressures and outdoor ambient temperatures.

An accurate thermocouple- or thermistor-type thermometer, and a gauge manifold are required when using the subcooling charging method for evaluating the unit charge. Do not use mercury or small dial-type thermometers because they are not adequate for this type of measurement.

!CAUTION

UNIT DAMAGE HAZARD

Failure to follow this caution may result in unit damage.

When evaluating the refrigerant charge, an indicated adjustment to the specified factory charge must always be very minimal. If a substantial adjustment is indicated, an abnormal condition exists somewhere in the cooling system, such as insufficient airflow across either coil or both coils.

Proceed as follows:

1.Remove caps from low- and high-pressure service fittings.

2.Using hoses with valve core depressors, attach low- and high-pressure gauge hoses to low- and high-pressure service fittings, respectively.

3.Start unit in Cooling Mode and let unit run until system pressures stabilize.

4.Measure and record the following:

a.Outdoor ambient-air temperature (°F [°C] db).

b.Liquid line temperature (°F [°C]).

c.Discharge (high-side) pressure (psig).

d.Suction (low-side) pressure (psig) (for reference only).

5.Using “Cooling Charging Charts,” compare outdoor-air temperature(°F [°C] db) with the discharge line pressure (psig) to determine desired system operating liquid line temperature (See Fig. 17).

6.Compare actual liquid line temperature with desired liquid line temperature. Using a tolerance of ± 2°F (±1.1°C), add refrigerant if actual temperature is more than 2°F (1.1°C) higher than proper liquid line temperature, or remove refrigerant if actual temperature is more than 2°F (1.1°C) lower than required liquid line temperature.

NOTE: If the problem causing the inaccurate readings is a refrigerant leak, refer to the Check for Refrigerant Leaks section.

Indoor Airflow and Airflow Adjustments

!CAUTION

UNIT OPERATION HAZARD

Failure to follow this caution may result in unit damage.

For cooling operation, the recommended airflow is 350 to 450 cfm for each 12,000 Btuh of rated cooling capacity. For heating operation, the airflow must produce a temperature rise that falls within the range stamped on the unit rating plate.

NOTE: Be sure that all supply-and return-air grilles are open, free from obstructions, and adjusted properly.

!WARNING

ELECTRICAL SHOCK AND EXPLOSION HAZARD

Failure to follow this warning could result in personal injury or death.

Before making any indoor wiring adjustments, shut off gas supply. Then disconnect electrical power to the unit and install lockout tag before changing blower speed.

This unit has independent fan speeds for gas heating and cooling. In addition, this unit has the field-selectable capability to run two different cooling fan speeds: A normal cooling fan speed (350~400 CFM/Ton) and an enhanced dehumidification fan speed (As low as 320 CFM/Ton) for use with either a dehumidistat or a thermostat that supports dehumidification.

This unit is factory-set up for use with a single cooling fan speed. The cooling speed is marked “LOW” on the interface fan board (IFB) (See Fig. 14) . The factory-shipped settings are noted in Table 10. There are 3 additional speed tap wires available for use in either gas heating or cooling (For color coding on the indoor fan motor leads, see Table 6). The additional 3 speed tap wires are shipped loose with vinyl caps and are located in the control box, near the interface fan board (IFB) (See Fig. 14).

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Contents Table of Contents Safety ConsiderationsCheck Equipment Receiving and InstallationIntroduction Provide Unit Support48EZ-A24-36 Unit Dimensions 48EZ-A42-60 Unit Dimensions Small Curb Personal Injury or Property Damage Rig and Place UnitProvide Clearances HazardConnect Condensate Drain Install Flue HoodInstall Gas Piping InspectionFire or Explosion Hazard Sediment TrapPhysical Data Unit 48EZ-A Unit Size 48EZPhysical Data Unit 48EZ-A Cont’d Maximum Gas Flow CapacityHeating Inputs Alternate Method Install Duct ConnectionsConfiguring Units for Downflow Vertical Discharge Unit Component Damage HazardSupply Duct Panels High-Voltage Connections Install Electrical ConnectionsSpecial Procedures for 208-V Operation Control Voltage ConnectionsTransformer Protection Balance Point Setting-Thermidistat or Hybrid ThermostatPRE-START-UP FIRE, EXPLOSION, Electrical Shock HazardCheck for Refrigerant Leaks Start-up Heating and Make Adjust- mentsSTART-UP Unit Sequence of OperationCheck Gas Input Adjust Gas InputCheck Heating Control Unit Damage HazardRollout Switch Airflow and Temperature RiseLimit Switches Check Burner FlameIndoor Airflow and Airflow Adjustments Start-up Cooling and Make Adjust- mentsChecking and Adjusting Refrigerant Charge Checking Cooling Control OperationContinuous Fan Operation Two Cooling Fan Speeds Set-up Dehumidification feature usedGas Heating Fan Speed Set-up Color Coding for Indoor Fan Motor LeadsFilter Pressure Drop Table IN. W.C 48EZ-A Wet Coil Pressure Drop IN. W.C741 638 547 415 Heating Low Blue 1234 1168 1093 1021 961 894 825 759 687 Heating Low Blue 1736 1695 1642 1601 1553 1512 1465 1427 1381 65oF Heating 1927 1893 1858 1824 1791 1759 1720 1689 1640 65oF Heating 48EZ a 208/230-3-60 Wiring Diagram, Unit 48EZ-A Cooling Charging Table-Subcooling Air Filter MaintenanceCleaning the Blower Motor and Wheel Indoor Blower and MotorBurner Ignition Limit SwitchInduced Draft combustion air Blower Assembly Main BurnersElectrical Controls and Wiring Outdoor FanRefrigerant Circuit Gas Input Pressure SwitchesLoss of Charge Switch Indoor AirflowHigh-Pressure Switch Copeland Scroll Compressor Puron RefrigerantExplosion Hazard Unit Operation and Safety Hazard Refrigerant SystemCompressor Oil Troubleshooting START-UP ChecklistPuronr R-410A Quick Reference Guide Troubleshooting Guide Cooling or Heat Pump Heating Mode Symptom Cause RemedyTroubleshooting Guide-Heating Troubleshooting Guide-LED Error CodesPreliminary Information Model no TemperaturesRemove and Store in Job Files III. START-UP Electrical Supply Voltage Compressor AmpsCatalog No 48EZ---06SI
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48EZ-A specifications

The Carrier 48EZ-A and 48VT-A are two advanced rooftop unit air conditioners that exemplify innovation and efficiency in HVAC technology. Designed for commercial applications, these units provide optimal comfort while ensuring energy conservation and reliability.

One of the standout features of the Carrier 48EZ-A is its high-efficiency cooling system. With SEER ratings reaching up to 16, this model uses advanced compressor technology to ensure that energy consumption stays low while maximizing cooling output. The 48EZ-A incorporates a two-stage scroll compressor that enhances performance during partial load conditions, making it ideal for varying temperature demands throughout the day.

Meanwhile, the Carrier 48VT-A is designed with variable speed technology that allows for precise modulation of airflow and cooling capacity, adapting seamlessly to real-time building conditions. This technology not only improves comfort but also significantly reduces energy usage by optimizing operational efficiency.

Both units are equipped with advanced microprocessor controls that facilitate superior management of the HVAC system. The controls offer programmable options allowing for enhanced control over system operation, scheduling, and diagnostics. This promotes easy maintenance and ensures long-term reliability.

In terms of construction, the Carrier 48EZ-A and 48VT-A units are built with corrosion-resistant materials, ensuring durability and longevity even in challenging environments. The cabinet is designed with insulated panels to minimize sound levels, making them suitable for installation in noise-sensitive locations.

Moreover, both models are equipped for easy installation and serviceability. The logical wiring design and access ports streamline maintenance, reducing downtime and optimizing overall performance. Additionally, they feature an energy-efficient fan design that maximizes airflow while minimizing energy use.

In summary, the Carrier 48EZ-A and 48VT-A rooftop units stand out in the HVAC market for their energy efficiency, advanced technology, and durable construction. These features make them ideal choices for various commercial applications where comfort, efficiency, and reliability are paramount. The combination of high-performance components and user-friendly features positions these models as leaders in modern HVAC solutions.