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

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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