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. Failure to adjust charge properly or
correct the abnormal conditions will cause damage to the
unit.
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. Indoor coil 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 Charts” compare outdoor-air
temperature (°F db) with the Indoor coil air inlet tempera-
ture (°F wb) to determine desired system operating super-
heat temperature. See Table 13A–H and Fig. 30.
6. Using ’’Required Suction-Tube Temperature (F)’’ table,
compare desired superheat temperature with suction (low-
side) operating pressure (psig) to determine proper suction-
tube temperature. See Fig. 30.
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 section.
F.
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 8 shows cooling airflows at various external static pressures.
Table 9 shows Fan Only and Cooling modes for ECM units
(048-060). 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 657A three-speed motors (024–042) are factory wired for low
speed operation.
G.
For 208/230v-PSC Blower Motor
For color coding on the 208/230V motor leads, see Table 4.
To change the speed of the indoor fan motor (IFM), remove the fan
motor speed leg lead from the indoor fan relay (IFR) and replace
with lead for desired blower motor speed. Insulate the removed
lead to avoid contact with chassis parts.
H.
For 208/230v-ECM Blower Motor
To configure the 657A 048-60 unit, move the 5 Easy Select board
wires to the terminals which control the airflow. Refer to the Easy
Select interface board (Fig. 29) located next to the terminal.
Perform the following steps for basic system configuration.
1. AUX HEAT RANGE (VIO) NOTE: If no heater is in-
stalled, this step can be omitted. The airflow for electric
heat is selected with the AUX HEAT RANGE terminals.
Refer to Table 2 and the installation instructions for electric
heaters for minimum airflow required for safe heater
operation. Refer to table below for the available airflows.
Each select pin is configured for a certain airflow. The
airflow will be supplied in the Heating mode on air
conditioners when electric heat is the primary heating
source. The preset factory default selection is the highest
airflow.
2. AC/HP SIZE (BLU) - The preset factory default selection
for AC/HP SIZE (air conditioner/heat pump) is set to 400
cfm/ton. The selection pins are configured for 350 cfm/ton
and 400 cfm/ton.
3. TYPE (ORN) - The TYPE is a preset factory default
selection. The preset factory default setting is AC for the
657A units. Default setting should not be altered.
4. AC/HP CFM ADJUST (BLK) - The preset factory default
selection is MED. Selections HI and LO will adjust the
airflow supplied for all operational modes (see table below).
The selection options allow installer to adjust airflow to
meet such individual needs as noise and static compensa-
tion, etc.
Fig. 28—Transformer Label
C95025
TRANSFORMER CONTAINS A MANUAL
RESET OVERCURRENT PROTECTOR
IT WILL NOT AUTOMATICALLY RESET
DISCONNECT POWER AND INSTALL
LOCKOUT TAG PRIOR TO SERVICING
THIS COMPARTMENT MUST BE CLOSED
EXCEPT WHEN SERVICING
TABLE 4—COLOR CODING FOR 208/230–V MOTOR
LEADS
3-SPEED
black = high speed
blue = medium speed
red = low speed
—21—
