Bryant 704A, Руководство по установке

Страница: 11 / 20

11
START--UP
CHECK FOR REFRIGERANT LEAKS
Proceed as follows to locate and repair a refrigerant leak and to
charge the unit:
1. Locate leak and make sure that refrigerant system pressure
has been relieved and reclaimed from both high-- and
low--pressure ports.
2. Repair leak following accepted practices.
NOTE
: Install a filter drier whenever the system has been opened
for repair.
3. Add a small charge of R--22 refrigerant vapor to system and
leak--test unit.
4. Recover refrigerant from system and evacuate to 500
microns 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 before starting the unit. Do not jumper any safety devices
when operating the unit. Do not operate the unit when the outdoor
temperature 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 OFF position.
Observe that blower motor starts when FAN switch is placed
in ON position and shuts down after 30 second fan time
delay expires 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
temperature. Observe that compressor, condenser fan, and
evaporator blower motors start. Observe that compressor
and outdoor fan shut down when control setting is satisfied
and that indoor blower shuts down after 30 second fan time
delay expires.
IMPORTANT : Three--phase, scroll compressors are direction
oriented. Unit must be checked to ensure proper compressor
3--phase power lead orientation. If not corrected 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
turning backwards, the difference between compressor suction and
discharge pressures may be dramatically lower than normal.
CHECKING AND ADJUSTING REFRIGERANT CHARGE
The refrigerant system is fully charged with R--22 refrigerant and
is 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 chart is attached to the outside of the service
access panel. The chart includes the required suction line
temperature at given suction line pressures and outdoor ambient
temperatures.
An accurate superheat, thermocouple-- or thermistor--type
thermometer, and a gauge manifold 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.
NOTE : Allow system to operate for a minimum of 10 minutes
before checking or adjusting refrigerant charge.
IMPORTANT : When evaluating the refrigerant charge, an
indicated adjustment to the specified factory charge must always be
very minimal. If a substantial adjustment is indicated, 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 gauge hoses to low-- and high--pressure
service fittings, respectively.
3. Start unit and let run until system pressures stabilize.
4. Measure and record the following:
a. Outdoor ambient--air temperature (
°
F db).
b. Suction--tube temperature (
°
F) at low--side service fitting.
c. Suction (low--side) pressure (psig).
5. Using Cooling Charging Charts compare outdoor--air
temperature (
°
F db) with the suction line pressure (psig) to
determine desired system operating suction line temperature
(See Fig. 16).
6. Compare actual suction--tube temperature with desired
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 section.
INDOOR AIRFLOW AND AIRFLOW ADJUSTMENTS
NOTE
: For cooling operation, the recommended airflow is 350 to
450 cfm for each 12,000 Btuh of rated cooling capacity.
Table 3 shows cooling airflows at various external static pressures.
Refer to this table to determine the airflow for the system being
installed.
NOTE
: Be sure that all supply-- and return--air grilles are open, free
from obstructions, and adjusted properly.
ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in personal injury
or death.
Disconnect electrical power to the unit and install lockout tag
before changing blower speed.
!
WARNING
704A