Indoor Airflow And Airflow Adjustments; Gas Heating Fan Speed Set-Up; Two Cooling Fan Speeds Set-Up - Carrier Performance 48VL-A Installation Instructions Manual

CAUTION
!
UNIT DAMAGE HAZARD
Failure to follow this caution may result in unit damage.
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 [°C] db).
b. Liquid line temperature (°F [°C]).
c. Discharge (high- -side) pressure (psig).
d. Suction (low- -side) pressure (psig) (for reference only).
5. Using "Cooling Charging Charts," compare outdoor- -air
temperature(°F [°C] db) with the discharge line pressure
(psig) to determine desired system operating liquid line
temperature (See Table 7).
6. Compare actual liquid line temperature with desired liquid
line temperature. Using a tolerance of ± 2°F (±1.1°C), add
refrigerant if actual temperature is more than 2°F (1.1°C)
higher than proper liquid line temperature, or remove
refrigerant if actual temperature is more than 2°F (1.1°C)
lower than required liquid line temperature.
NOTE:
If the problem causing the inaccurate readings is a
refrigerant leak, refer to the Check for Refrigerant Leaks section.

Indoor Airflow and Airflow Adjustments

CAUTION
!
UNIT OPERATION HAZARD
Failure to follow this caution may result in unit damage.
For cooling operation, the recommended airflow is 350 to
450 cfm for each 12,000 Btuh of rated cooling capacity. For
heating operation, the airflow must produce a temperature
rise that falls within the range stamped on the unit rating
plate.
NOTE: Be sure that all supply- -and return- -air grilles are open,
free from obstructions, and adjusted properly.
WARNING
!
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.
This unit has independent fan speeds for gas heating and cooling.
In addition, this unit has the field-selectable capability to run two
different cooling fan speeds: A normal cooling fan speed (350~450
CFM/Ton) and an enhanced dehumidification fan speed (As low as
320 CFM/Ton) for use with either a dehumidistat or a thermostat
that supports dehumidification.
This unit is factory-set up for use with a single cooling fan speed.
The cooling speed is marked "LOW" on the interface fan board
(IFB)(See Fig. 17) . The factory-shipped settings are noted in
Table 8. There are 3 additional speed tap wires available for use in
either gas heating or cooling (For color coding on the indoor fan
motor leads, see Table 6). The additional 3 speed tap wires are
shipped loose with vinyl caps and are located in the control box,
near the interface fan board (IFB) (See Fig. 17).

Gas Heating Fan Speed Set-up

To change the gas heating speed:
1. Remove the vinyl cap off of the desired speed tap wire
(Refer to Table 6 for color coding). Table 8 shows the
temperature rise associated with each fan speed for a given
static pressure. Make sure that the speed chosen delivers a
temperature rise within the rise range listed on the unit
rating plate.
2. Remove the current speed tap wire from the "GAS HEAT"
terminal on the interface fan board (IFB) (Fig.18) and place
vinyl cap over the connector on the wire.
3. Connect the desired speed tap wire to the "GAS HEAT"
terminal on the interface fan board (IFB).
Single Cooling Fan Speed Set-up (Dehumidification
feature not used)
To change cooling speed:
1. Remove the vinyl cap off of the desired speed tap wire
(Refer to Table 6 for color coding). Add the wet coil
pressure drop in Table 10 to the system static to determine
the correct cooling airflow speed in Table 8 that will deliver
the nominal cooling airflow as listed in Table 1 for each
size.
2. Remove the current speed tap wire from the "LOW"
terminal on the interface fan board (IFB) (See Fig. 17) and
place vinyl cap over the connector on the wire.
3. Connect the desired speed tap wire to the "LOW" terminal
on the interface fan board (IFB).
Two Cooling Fan Speeds Set-up (Dehumidification
feature used)
IMPORTANT: Dehumidification control must open control
circuit on humidity rise above set point.
Use of the dehumidification cooling fan speed requires use of
either a 24 VAC dehumidistat or a thermostat which includes
control of a 24 VAC dehumidistat connection. In either case, the
dehumidification control must open the control circuit on humidity
rise above the dehumidification set point.
1. Remove fan speed tap wire from the "LOW" terminal on
the interface fan board (IFB) (See Fig. 17).
2. Determine correct normal cooling fan speed for unit and
application. Add the wet coil pressure drop in Table 10 to
the system static to determine the correct cooling airflow
speed in Table 8 that will deliver the nominal cooling
airflow as listed in Table 1 for each size.
3. Remove the vinyl cap off of the desired speed tap wire
(Refer to Table 6 for color coding) for the normal cooling
fan speed and place desired speed tap wire on "HIGH" on
the interface board.
4. Refer to airflow tables (Table 8) to determine allowable
speeds for the dehumidification cooling fan speed. In Table
8, speeds that are not allowed for dehumidification cooling
are shaded.
5. Remove the vinyl cap off of the desired speed tap wire
(Refer to Table 6 for color coding) for the dehumidification
cooling fan speed and place desired speed tap wire on the
"LOW" connection on the interface board (IFB). Verify
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