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.
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.
Disconnect electrical power to the unit and install lockout tag
before changing blower speed. Electrical shock can cause
serious injury or death.
Airflow can be changed by changing the lead connections of the
blower motor.
Unit 50HX three-speed motors (024–042) are factory wired for
low speed operation.
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.
FOR 208/230V-ECM BLOWER MOTOR
To configure the 50HX 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 installed,
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 selec-
tion 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 50HX 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 compensation, etc.
5. AC/HP TIME DELAY (GRY) - Four motor operation delay
options are provided to customize system operation. See
listing below:
Unit Controls— All compressors have the following internal-
protection controls.
1. High-Pressure Relief Valve - This valve opens when the
pressure differential between the low and high side becomes
excessive.
2. Compressor Overload - This overload interrupts power to the
compressor when either the current or internal temperature
become excessive, and automatically resets when the internal
temperature drops to a safe level.
This overload may require up to 60 minutes (or longer) to
reset; therefore, if the internal overload is suspected of being
open, disconnect the electrical power to the unit and check the
circuit through the overload with an ohmmeter or continuity
tester.
COOLING SEQUENCE OF OPERATION
PSC Blower Motor Units (024–042)
NOTE: With the FAN switch in the ON position, 24-v is supplied
to the IFR through the G terminal on the thermostat. This voltage
energizes the coil of the contactor, closing the normally-open set of
contacts which provide continuous power to the indoor (evapora-
tor) fan motor (IFM). Moving the FAN switch back to the AUTO.
position, providing there is not a call for cooling, deenergizes the
IFR, opens the IFR contacts, and deenergizes the IFM. The FAN
switch in AUTO. position cycles upon a call for cooling.
On a call for cooling, 24 v is supplied to the compressor contactor
(C) and IFR simultaneously through the Y and G terminals of the
thermostat, respectively. On units with a compressor time delay
relay, there is a built-in, 5-minute (± 45 seconds) delay between
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
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