Carrier 38AU - Manual (Page 19)

19
PRE-START-UP
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”, below.
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(s) through the liquid service valve(s). The
amount of refrigerant added must be at least 80% of the
operating charge listed in the Physical Data table (Tables 1A
through 2B, pages 4 through 7). Open the liquid line and
suction line service valves. 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.
START-UP
38AU Units
The compressor crankcase heater(s) 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 38AU units are factory charged with the
required amount of oil. If recharging in required, use
Emkarate RL 32-3MAF for the 38AU 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.
38AU units are equipped with a Comfort Alert Diagnostic
Module (CADM). Alert Code 7 indicates reverse power
phasing.
To correct phase order:
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 pres-
sures.
To verify the compressor is rotating in the proper direction:
1. Connect service gages to the suction and liquid pressure
fittings.
2. Energize the compressor.
The suction pressure should drop and the liquid pressure
should rise, as is normal on any start-up.
Compressor Overload
This overload interrupts power to the compressor when either
the current or internal motor winding temperature becomes ex-
cessive, and automatically resets when the internal temperature
drops to a safe level. This overload may require up to 60 min-
utes (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.
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.
UNIT DAMAGE HAZARD
Prior to starting compressor, a preliminary charge of
refrigerant must be added to avoid possible compressor
damage.