9
START-UPPreliminary Checks
1. Field electrical power source must agree with unit name-
plate rating.
2. Check that all internal wiring connections are tight and
that all barriers, covers, and panels are in place. Ensure no
electrical wires are in contact with refrigerant tubing.
3. Ensure all service valves are open. On 38AKS units, be
sure all compressor service valves are backseated.
4. Verify that compressor holddown bolts for units 38AKS
have been loosened and that flat/snubber washers can be
rotated by applying finger pressure (snug, but not tight).
5. Verify compressor crankcase heater is securely in place.
Crankcase heater must operate for at least 24 hours before
start-up. The 38AK unit size 007 does not require a
crankcase heater.
6. Note that compressor oil level is visible in the sight glass
(38AKS units only).
7. Check for leaks in refrigerant system by using soap bub-
bles and/or electronic leak detector.
8. Check that liquid line solenoid valve is located at evapo-
rator coil as shown in Filter Drier and Moisture Indicator
section, page 6.
9. Check voltage imbalance as shown in Table 5, Note 2.
10. Check that both outdoor and indoor units are properly
mounted in accordance with installation instructions and
applicable codes.
Compressor Rotation — On 3-phase units with scroll
compressors, it is important to be certain compresso r is rotating
in the proper direction. To determine whether or not compres-
sor is rotating in the proper direction:
1. Connect service gages to suction and discharge pressure
fittings.
2. Energize the compressor.
3. The suction pressure should drop and the discharge pres-
sure should rise, as is normal on any start-up.
If the suction pressure does not drop and the discharge
pressure does not rise to normal levels:
1. Note that the condenser fan is probably also rotating in
the wrong direction.
2. Turn off power to the unit, tag disconnect.
3. Reverse any two of the unit power leads.
4. Reapply power to the compressor, verify correct
pressures.
The suction and discharge pressure levels should now move
to their normal start-up levels.
Evacuate and Dehydrate — Evacuate and dehydrate
entire refrigerant system by use of the methods described in
Carrier GTAC II, Module 4, System Dehydration. Evacuate
system down to 500 microns and ensure vacuum hold for
15 minutes. If vacuum does not hold, pressurize system and
locate leak and repair.
Refrigerant Charge — Refer to Carrier GTAC II,
Module 5, Charging Recovery, Recycling, and Reclamation.
Unit panels must be in place when unit is operating during
charging procedure.
Unit is shipped with holding charge only. Weigh in 7 lb
(3 kg) of R-22 to start unit.
CHARGE COOLIN G — Use Cooling Charging Charts,
Fig. 8A or 8B and 9A or 9B. Unit must be charged in cooling
mode only. Vary refrigerant until the conditions of the chart are
met. Note that charging charts are different from type normally
used. Charts are based on charging the units to the correct sub-
cooling for the various operating conditions. Accurate pressure
gage and temperature sensing device are required. Connect the
pressure gage to the service port on the liquid line service
valve. Mount the temperature sensing device on the liquid line,
close to the liquid line service valve and insulate it so that out-
door ambient temperature does not affect the reading. Indoor
airflow must be within the normal operating range of the unit.
Operate unit a minimum of 15 minutes. Ensure pressure and
temperature readings have stabilized. Plot liquid pressure and
temperature on chart and add or reduce charge to meet curve.
Adjust charge to conform with charging chart, using liquid
pressure and temperature to read chart.
Fig. 8A — Cooling Charging Chart — 38AK007
(60 Hz)
Fig. 8B — Cooling Charging Chart — 38AK007
(50 Hz)