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Step 9 — Wind Baffles for Low Ambient Control
Models 38AZB and 38AUDB include the factory installed
32LT Motormaster Low Ambient Control. Model 38AUDC
(with hot gas bypass option) also includes the 32LT Motormaster
Low Ambient Control as a standard feature.
Units with 32LT Motormaster control require the addition of
wind baffles to ensure full range low ambient operation. Material
data and dimensions for wind baffles are included in the Appen-
dix C section, Low Ambient Control, starting on page 43. Fabri-
cate the wind baffles and mount per instructions.
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.
CAUTION
UNIT DAMAGE HAZARD
Failure to follow this caution may result in equipment
damage.
Do not attempt to start the condensing unit, even momentar-
ily, until the following steps have been completed. Compres-
sor damage may result.
System Check
1.
The electrical power source must agree with the unit's
nameplate rating.
2.
Check all air handler(s) and other equipment auxiliary
components. Consult the manufacturer's instructions
regarding any other equipment connected to the condens-
ing 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.
3.
Check tightness of all electrical connections.
4.
Be sure liquid line and low side of the system are prop-
erly leak checked and dehydrated.
5.
Be sure the unit is properly charged. See "Preliminary
Charge", below.
6.
Open the liquid line and suction line service valves.
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 (Table 6). Allow high and low
side pressures to equalize before starting compressor. If pressure
do not equalize readily, charge vapor on low side of system to as-
sure charge in the evaporator. Refer to GTAC II, Module 5,
Charging, Recover, Recycling, and Reclamation for liquid
charging procedures.
UNIT DAMAGE HAZARD
Failure to follow this caution may result in equipment
damage.
Prior to starting compressor, a preliminary charge of refriger-
ant must be added to avoid possible compressor damage.
The compressor crankcase heater must be on for 24 hours be-
fore 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 name-
plate 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 bar-
riers and covers must be in place.
NOTE: The 38AU units are factory charged with the required
amount of oil. If recharging is 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 Mod-
ule (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 pressures.
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.
3.
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 ei-
ther the current or internal motor winding temperature be-
comes excessive, and automatically 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 ohm-
meter or continuity tester.
23
CAUTION
START-UP
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