Bryant 701A - Manual (Page 13)

B. START-UP COOLING SECTION AND MAKE AD-
JUSTMENTS
CAUTION: 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 compressor 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.
C. 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 tem-
perature. 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.
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 tempera-
ture control is set to “call for heating” (above room
temperature) and operates in cooling mode when tempera-
ture control is set to “call for cooling” (below room
temperature).
IMPORTANT: Three-phase, scroll compressor units (701A048,
702A030-060) are direction-oriented. These units 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, scroll compressors
emit elevated noise levels, and the difference between compressor
suction and discharge pressures may be dramatically lower than
normal.
D. CHECKING AND ADJUSTING REFRIGERANT
CHARGE
The refrigerant system is fully charged with R-22 refrigerant,
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 tempera-
ture at given suction line pressures and outdoor ambient tempera-
tures (See Fig. 14–23).
An accurate superheat, thermocouple- or thermistor-type ther-
mometer, a sling psychrometer, 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 in the cooling mode for a
minimum of 10 minutes before checking or adjusting refrigerant
charge.
CAUTION: 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 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 “Cooling Charging Charts” compare outdoor-air
temperature (°F db) with the suction line pressure (psig) to
determine desired system operating suction line tempera-
ture. See Fig. 14-23.
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.
E.
INDOOR AIRFLOW AND AIRFLOW ADJUSTMENTS
CAUTION: For cooling operation, the recommended
airflow is 350 to 450 cfm for each 12,000 Btuh of rated
cooling capacity.
Tables 8 and 9 show cooling airflows at various external static
pressures. Refer to these tables 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.
WARNING: Disconnect electrical power to the unit and
install lockout tag before changing blower speed. Elec-
trical shock can cause serious injury or death.
Airflow can be changed by changing the lead connections of the
blower motor.
Unit 701A two- or three-speed motors (except size 030) are factory
wired for low speed operation. Unit 701A030 is factory wired for
medium speed.
All 702A units are factory wired for low speed and may need to be
wired for medium or high speed in the field.
F.
For 208/230V
For color coding on the 208/230V motor leads, see Table 6.
To change the speed of the indoor fan motor (IFM), remove the fan
motor speed leg lead from the time delay relay (TDR). This wire
is attached to terminal–3 of TDR for single-phase and 3-phase
units. To change the speed, remove and replace with lead for
desired blower motor speed. Insulate the removed lead to avoid
contact with chassis parts.
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