Carrier 38AUZ appendix Pre-Start-Up, System Check

PRE-START-UP

IMPORTANT: Before beginning Pre-Start-Up or Start-Up, review Start-Up Checklist at the back of this book. The Checklist assures proper start-up of a unit and provides a record of unit condition, application requirements, system information, and operation at initial start-up.

UNIT DAMAGE HAZARD

Do not attempt to start the condensing unit, even momentarily, until the following steps have been completed. Compressor damage may result.

System Check

1.Check all air handler(s) and other equipment auxiliary components. Consult the manufacturer’s instructions regarding any other equipment connected to the con- densing unit. If the unit has field-installed accessories, be sure all are properly installed and correctly wired. If used, the airflow switch must be properly installed.

2.Be sure the unit is properly leak checked and dehydrated.

3.Check tightness of all electrical connections.

4.Open the liquid line and suction line service valves.

5.Be sure the unit is properly charged. See “Preliminary Charge”, on page 9.

6.The electrical power source must agree with the unit’s nameplate rating.

7.The crankcase heater must be firmly attached to the com- pressor crankcase. Be sure the crankcase is warm (heater must be on for 24 hours before starting compressor).

Turn On Crankcase Heater — Turn on the crankcase heater for 24 hours before starting the unit to be sure all the refrigerant is out of the oil. To energize the crankcase heater, proceed as follows:

1.Set the space thermostat set point above the space tem- perature so there is no demand for cooling.

2.Close the field disconnect.

Preliminary Charge — Before starting the unit, charge liquid refrigerant into the high side of the system through the liquid service valve. The amount of refrigerant added must be at least 80% of the operating charge listed in the Physical Data table (Tables 1A and 1B, pages 4 and 5). Allow high and low side pressures to equalize before starting compressor. If pressures do not equalize readily, charge vapor on low side of system to assure charge in the evaporator. Refer to GTAC II, Module 5, Charging, Recover, Recycling, and Reclamation for liquid charging procedures.

UNIT DAMAGE HAZARD

Prior to starting compressor, a preliminary charge of refrigerant must be added to avoid possible compressor damage.

START-UP

38AUZ Units — The compressor crankcase heater must be on for 24 hours before start-up. After the heater has been on for 24 hours, the unit can be started. If no time elapsed since the preliminary charge step was completed, it is unnecessary to wait the 24-hour period.

PRELIMINARY CHECKS

1.Check that electric power supply agrees with unit nameplate data.

2.Verify that the compressor crankcase heater is securely in place.

3.Check that the compressor crankcase heater has been on at least 24 hours.

4.Recheck for leaks using the procedure outlined in the Pre-Start-Up section, Leak Test and Dehydration. If any leaks are detected, repair as required. Evacuate and dehydrate as described in the Leak Test and Dehydration section.

5.Ensure that the preliminary charge has been added as described in the Pre-Start-Up section, Preliminary Charge.

6.All internal wiring connections must be tight, and all barriers and covers must be in place.

NOTE: The 38AUZ units are factory charged with the required amount of oil. If recharging in required, use Emka- rate RL 32-3MAF for the 38AUZ units.

COMPRESSOR ROTATION — On 3-phase units with scroll compressors, it is important to be certain that the compressor is rotating in the proper direction. To determine whether or not compressor is rotating in the proper direction:

1.Connect service gages to the suction and liquid pressure fittings.

2.Energize the compressor.

3.The suction pressure should drop and the liquid pressure should rise, as is normal on any start-up.

If the suction pressure does not drop and the liquid pressure does not rise to normal levels:

1.Turn off power to the unit, tag disconnect.

2.Reverse any two of the unit power leads.

3.Reapply power to the compressor, verify correct pressures.

The suction and liquid pressure levels should now move to their normal start-up levels.

COMPRESSOR OVERLOAD — This overload interrupts power to the compressor when either the current or internal motor winding temperature becomes excessive, and automati- cally resets when the internal temperature drops to a safe level. This overload may require up to 60 minutes (or longer) to reset. If the internal overload is suspected of being open, disconnect the electrical power to the unit and check the circuit through the overload with an ohmmeter or continuity tester.

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