Carrier 38TUA, Installation And Start-Up Instructions Manual

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To prevent personal injury wear safety glasses, protective
clothing, and gloves when handling refrigerant and observe
the following:
• Back seating service valves are not equipped with Schrader
valves. Fully back seat (counter clockwise) valve stem before
removing gage port cap.
• Front seating service valves are equipped with Schrader
valves.
Do not vent refrigerant to atmosphere. Recover during system
repair or final unit disposal.
Follow these steps to properly pump down a system and avoid
negative suction.
1. Fully back seat (open) liquid and vapor tube service valves.
2. Unit is shipped with valve stem(s) front seated (closed) and
caps installed. Replace stem caps after system is opened to
refrigerant flow. Replace caps finger-tight and tighten with
wrench and additional 1/12 turn.
3. Close electrical disconnects to energize system.
4. Set room thermostat at desired temperature. Be sure set point
is below indoor ambient temperature.
5. Set room thermostat at COOL and fan control at ON or AUTO
mode, as desired. Operate unit for 15 minutes. Check system
refrigerant charge.
• 3-phase scroll compressors are rotation sensitive.
• A flashing LED on phase monitor indicates reverse rotation.
(See Fig. 6 and Table 3.)
• This will not allow contactor to be energized.
• Disconnect power to unit and interchange 2 field wiring
leads on unit contactor.
SEQUENCE OF OPERATION
Turn on power to indoor and outdoor units. Transformer is
energized.
On a call for cooling, thermostat makes circuits R-Y and R-G. On
three phase models with scroll compressors, the units are equipped
with a phase monitor to detect in the incoming power is correctly
phased for compressor operation. If the phasing is correct, circuit
R-Y energizes contactor, starting outdoor fan motor and compres-
sor circuit. R-G energizes indoor unit blower relay, starting indoor
blower motor on high speed.
NOTE:
If the phasing is incorrect, the contactor will not be
energized. To correct the phasing, interchange any two of the three
power connections on the field side.
When thermostat is satisfied, its contacts open, de-energizing
contactor and blower relay. Compressor and motors stop.
If indoor unit is equipped with a time-delay relay circuit, the
indoor blower runs an additional 90 sec to increase system
efficiency.
Step 11—Check Charge
UNIT CHARGE
Factory charge is shown on unit rating plate. Adjust charge by
following procedure shown on charging tables located on unit.
NOTE:
If superheat or subcooling charging conditions are not
favorable, charge must be weighed in accordance with unit rating
plate ± 0.6 oz/ft (56 g/m) of 3/8 in. (9.53mm) liquid line above or
below 15 ft (4.57m) respectively.
EXAMPLE:
25 ft - 15 ft = 10 ft X 0.6 oz/ft = 6 oz of additional charge
(7.62m - 4.57m = 3.05m X 56g/m = 171 g of additional charge)
COOLING ONLY PROCEDURE
The following procedure is valid when indoor airflow is within ±
21 percent of its rated CFM.
1. Operate unit a minimum of 10 minutes before checking
charge.
2. Measure suction pressure by attaching an accurate gage to
suction valve service port.
3. Measure suction temperature by attaching an accurate ther-
mistor type or electronic thermometer to suction line at service
valve.
4. Measure outdoor air dry-bulb temperature with thermometer.
5. Measure indoor air (entering indoor coil) wet-bulb tempera-
ture with a sling psychrometer.
6. Refer to Table 4 or 6. Find outdoor temperature and evapo-
rator entering air wet-bulb temperature. At this intersection,
note superheat.
7. Refer to Table 5 or 7. Find superheat temperature located in
item 6 and suction pressure. At this intersection, note suction
line temperature.
8. If unit has a lower suction line temperature than charted
temperature, add refrigerant until charted temperature is
reached.
9. If unit has a higher suction line temperature than cheated
temperature, reclaim refrigerant until cheated temperature is
reached.
10. If outdoor air temperature or pressure at suction valve
changes, charge to new suction line temperature indicated on
chart.
Fig. 6—Phase Monitor Control
A00010
Table 3—PHASE MONITOR LED INDICATORS
LED STATUS
OFF No call for compressor operation
FLASHING Reversed phase
ON Normal
7
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