Carrier 48SX024-048 - Manual (Page 30)

Start Up Cooling Section and Make
Adjustments
A CAUTION
Complete the required procedures given in the Pre-
Start-Up section on page 21 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 (unless accessory low-ambient
kit is installed)
Do not rapid-cycle the compressor. Allow 5 minutes
between “on” cycles to prevent compressor damage.
CHECKING COOLING CONTROL OPERATION - Start
and check the unit for proper cooling control operation as
follows:
1. Place room thermostat SYSTEM switch in OFE posi­
tion. Observe that blower motor starts when FAN switch
is placed in ON position and shuts down when FAN switch
is placed in AUTO, position.
2. Place SYSTEM switch in COOL position and FAN switch
in AUTO, position. Set cooling control below room tem­
perature. Observe that compressor, condenser fan, and
evaporator blower motors start. Observe that cooling
cycle shuts down when control setting is satisfied. The
indoor fan will continue to run for 30 seconds.
3. When using an auto.-changeover room thermostat, place
both SYSTEM and FAN switches in AUTO, positions.
Observe that unit operates in heating mode when tem­
perature control is set to “call for heating” (above room
temperature) and operates in cooling mode when tem­
perature control is set to “call for cooling” (below room
temperature).
IMPORTANT: Scroll compressors in u n i t s
48SS048,060 and 48SX036-048 are direction-oriented.
Three-phase units must be checked to ensure proper
compressor 3-phase power lead orientation. If not cor­
rected within 5 minutes, the internal protector will shut
off the compressor. The 3-phase power leads to the
unit must be reversed to correct rotation. When turn­
ing backwards, scroll compressors emit elevated noise
levels, and the difference between compressor suc­
tion and discharge pressures may be dramatically lower
than normal.
CHECKING AND ADJUSTING REFRIGERANT CHARGE
— The refrigerant system is fully charged with R-22 refrig­
erant, tested, and factory-sealed.
NOTE: Adjustment of the refrigerant charge is not required
unless the unit is suspected of not having the proper R-22
charge.
A superheat charging label is attached to the inside of the
compressor access door. The label includes a “Superheat
Charging Table” and a “Required Suction-Tube (F)
Temperature” chart.
An accurate superheat, thermocouple-, or thermistor-
type thermometer, a sling psychrometer, and a gage mani­
fold are required when using the superheat charging method
for evaluating the unit charge. Do not use mercury or small
dial-type thermometers because they are not adequate for
this type of measurement.
A CAUTION
When evaluating the refrigerant charge, an indicated
adjustment to the specified factory charge must always
be very minimal. If a substantial adjustment is indi­
cated, an abnormal condition exists somewhere in the
cooling system, such as insufficient airflow across
either coil or both coils.
Proceed as follows:
1. Remove caps from low- and high-pressure service
fittings.
2. Using hoses with valve core depressors, attach low- and
high-pressure gage hoses to low- and high-pressure serv­
ice fittings, respectively.
3. Start unit in cooling mode and let unit run until system
pressures stabilize.
4. Measure and record the following:
a. Outdoor ambient-air temperature (F db).
b. Evaporator inlet-air temperature (F wb).
c. Suction-tube temperature (F) at low-side service
fitting.
d. Suction (low-side) pressure (psig).
5. Using “Superheat Charging Table,” compare outdoor-
air temperature (F db) with evaporator inlet-air temper­
ature (F wb) to determine desired system operating
superheat temperature. See Tables 7A-7G and 8A-8E.
6. Using “Required Suction-Tube (F) Temperature”
table, compare desired superheat temperature with suc­
tion (low-side) operating pressure (psig) to determine proper
suction-tube temperature. See Table 9.
7. Compare actual suction-tube temperature with proper
suction-tube temperature. Using a tolerance of ± 3° F,
add refrigerant if actual temperature is more than 3° F
higher than proper suction-tube temperature, or remove
refrigerant if actual temperature is more than 3° F lower
than required suction-tube temperature.
NOTE: If the problem causing the inaccurate readings is a
refrigerant leak, refer to Check for Refrigerant Leaks sec­
tion on page 21.
INDOOR AIRFLOW AND AIRFLOW ADJUSTMENTS
A CAUTION
For cooling operation, the recommended airflow is 350
to 450 cfm for each 12,000 Btuh of rated cooling ca­
pacity. For heating operation, the airflow must pro­
duce a temperature rise that falls within the range stamped
on the unit rating plate.
Table 6 shows the temperature rise at various airflow rates.
Tables 10-13 show both heating and cooling airflows at var­
ious external static pressures. Refer to these tables to de­
termine the airflow for the system being installed. See
Table 14 for wet coil pressure drop.
NOTE: Be sure that all supply- and return-air grilles are
open, free from obstructions, and adjusted properly.
A WARNING
Shut off gas supply then disconnect electrical power to
the unit before changing blower speed. Electrical shock
can cause personal injury or death.
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