Carrier 50ZH024-060 - Manual (Page 12)

START-UP
Use the Start-Up Checklist supplied at the end of this book,
and proceed as follows:
Check for Refrigerant Leaks — Locate and repair
refrigerant leaks and charge the unit as follows:
1. Using both high- and low-pressure ports, locate leaks and
reclaim remaining refrigerant to relieve system
pressure.
2. Repair leak following accepted practices.
NOTE: Install a filter drier whenever the system has been
opened for repair.
3. Check system for leaks using an approved method.
4. Evacuate refrigerant system and reclaim refrigerant if no
additional leaks are found.
5. Charge unit with R-22 refrigerant, using a volumetric-
charging cylinder or accurate scale. Refer to unit rating
plate for required charge. Be sure to add extra refrigerant
to compensate for internal volume of filter drier.
Start-Up Cooling Section and Make
Adjustments
Complete the required procedures given in the Pre-
Start-Up section page 11 before starting the unit.
Do not jumper any safety devices when operating the
unit.
Do not operate the compressor when the outdoor tem-
perature is below 40 F.
Do not rapid-cycle the compressor. Allow 5 minutes be-
tween ‘‘on’’ cycles to prevent compressor damage.
CHECKING COOLING AND HEATING CONTROL OP-
ERATION — Start and check the unit for proper control op-
eration as follows:
1. Place room thermostat SYSTEM switch in OFF position.
Observe that blower motor starts when FAN switch is placed
in ON position and shuts down within 30 seconds when
FAN switch is placed in AUTO. position.
2. Place SYSTEM switch in COOL position and FAN switch
in AUTO. position. Set control below room temperature.
Observe that compressor, outdoor fan, and indoor blower
motors start. Observe that cooling cycle shuts down when
control setting is satisfied.
3. Place system switch in HEAT position. Set control above
room temperature. Observe that heating cycle shuts down
when control setting is satisfied.
4. When using an automatic changeover room thermostat,
place both SYSTEM and FAN switches in AUTO. posi-
tions. Observe that unit operates in Cooling mode when
temperature control is set to ‘‘call for Cooling’’ (below
room temperature), and unit operates in Heating mode
when temperature control is set to ‘‘call for heating’’ (above
room temperature).
IMPORTANT: Three-phase, scroll compressors are
direction-oriented. Three-phase units must be checked
to ensure proper compressor 3-phase power lead ori-
entation. If not corrected within 5 minutes, the in-
ternal protector will shut off the compressor. The
3-phase power leads to the unit must be reversed to
correct rotation. When turning backwards, scroll com-
pressors emit elevated noise levels, and the differ-
ence between compressor suction and discharge
pressures may be dramatically lower than normal.
Refrigerant Charge — Amount of refrigerant charge
is listed on unit nameplate (also refer to Table 1). Refer to
Carrier Refrigerant Service Techniques Manual, Refriger-
ants section.
Unit panels must be in place when unit is operating dur-
ing charging procedure.
NO CHARGE — Use standard evacuating techniques. After
evacuating system, weigh in the specified amount of refrig-
erant (refer to Table 1).
LOW CHARGE COOLING — Use Cooling Charging Charts,
Fig. 15-20. Vary refrigerant until the conditions of the ap-
propriate chart are met. Note that charging charts are dif-
ferent from the type normally used. Charts are based on charging
the units to the correct superheat for the various operating
conditions. Accurate pressure gage and temperature sensing
device are required.
To measure suction pressure, perform the following:
1. Connect the pressure gage to the service port on the suc-
tion line.
2. Mount the temperature sensing device on the suction line
and insulate it so that outdoor ambient temperature does
not affect the reading. Indoor-air cfm must be within the
normal operating range of the unit.
TO USE COOLING CHARGING CHARTS
1. Take the outdoor ambient temperature and read the suc-
tion pressure gage.
2. Refer to appropriate chart to determine what the suction
temperature should be.
3. If suction temperature is high, add refrigerant. If suction
temperature is low, carefully recover some of the charge.
4. Recheck the suction pressure as charge is adjusted.
EXAMPLE: (Fig. 15)
Outdoor Temperature . . . . . . . . . . . . . . . . . . . . . . . 85
Suction Pressure . . . . . . . . . . . . . . . . . . . . . . . 76 psig
Suction Temperature should be . . . . . . . . . . . . . 64 F
(Suction Temperature may vary ±5° F.)
If Chargemaster
௡ charging device is used, temperature and
pressure readings must be accomplished using the charging
chart.
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