10
NOTE
:
24ANA7 series only, using non--communicating
(non--Infinity) Carrier electronic thermostats are equipped with a
15--minute staging timer. This timer prevents the two--stage
system from at high stage until unit has been operating in low
stage for 15 minutes unless there is at least a 5
_
F difference
between room temperature and thermostat set point. To force high
stage (after a minimum of 2 minutes in low stage), adjust the set
point at least 5
_
below room ambient.
6. Set room thermostat to COOL and fan control to AUTO
or ON as desired. Wait for appropriate time delay(s).
Operate unit for 15 minutes. Check refrigerant charge.
STEP 12
—
SYSTEM FUNCTIONS AND SEQUENCE OF
OPERATION
The outdoor unit control system has special functions. The
following is an overview of the two--stage control functions:
COOLING OPERATION
The 24ANA7 models utilize either a 2--stage cooling indoor
thermostat or an Infinity communicating User Interface. The
24ANA1 models utilize an Infinity communicating User Interface
only. With a call for first stage cooling, the outdoor fan and
low--stage compressor are energized. If low--stage cannot satisfy
cooling demand, high--stage is energized by the second stage of
indoor thermostat or User Interface. After second stage is
satisfied, the unit returns to low--stage operation until first stage is
satisfied or until second stage is required again. When both first
stage and second stage cooling are satisfied, the compressor will
shut off.
NOTE
: On 24ANA7 models, if unit has not operated within the
past 12 hrs, or following a unit power--up, upon the next
thermostat high-- or low--stage demand, unit operates for a
minimum of 5 minutes in high--stage.
NOTE
:
On 24ANA7 models with non--communicating
(non--Infinity) systems, with first stage of cooling, (Y1) is
powered on; and with second stage of cooling, (Y1 and Y2) are
on.
NOTE
: When two--stage unit is operating at low--stage, system
vapor (suction) pressure will be higher than a standard
single--stage system or high--stage operation.
NOTE
: Outdoor fan motor will continue to operate for one
minute after compressor shuts off, when outdoor ambient is
greater than or equal to 100
_
F.
COMMUNICATION AND STATUS FUNCTION LIGHTS
For Infinity Control Only, Green communications (COMM)
Light
A green LED
(COMM light)
on the outdoor board (see Fig. 10)
indicates successful communication with the other system
products. The green LED will remain OFF until communications
is established. Once a valid command is received, the green LED
will turn ON continuously. If no communication is received
within 2 minutes, the LED will be turned OFF until the next valid
communication.
Amber Status Light
An amber colored
STATUS light
is used to display the operation
mode and fault codes as specified in the troubleshooting section.
See Table 5 for codes and definitions.
NOTE
: Only one code will be displayed on the outdoor unit
control board (the most recent, with the highest priority).
UTILITY INTERFACE
With Infinity Control
The utility curtailment relay should be wired between R and Y2
connections on the control board for Infinity Communicating
Systems only (see Fig. 10.) This input allows a power utility
device to interrupt compressor operation during peak load
periods. When the utility sends a signal to shut the system down,
the User Interface will display, “Curtailment Active”.
ONE MINUTE STAGE CHANGE TIME DELAY ON
24ANA7 MODELS
When compressor changes stages from high to low or low to
high, there is a 1--minute time delay before compressor restarts.
The outdoor fan motor remains running.
COMPRESSOR OPERATION ON 24ANA7 MODELS
When the compressor operates in high stage operation, the motor
rotates clockwise. Both the lower and upper pistons are eccentric
with the rotating crankshaft and both compress refrigerant.
When the compressor operates in low stage operation the motor
reverses direction (rotates counterclockwise). The lower piston
becomes idle and the upper piston compresses refrigerant.
The
start and run windings are reversed.
COMPRESSOR OPERATION ON 24ANA1 MODELS
When the compressor is operating in low stage, the modulating
ring is de--activated, allowing two internal bypass ports to close
off 33% of the scroll compression area so the system operates at
part load capacity. The 24--volt solenoid coil is de--energized in
low stage operation.
When the compressor is operating at high stage, the modulating
ring is activated, sealing the bypass ports, which allows the
compressor to operate at full load capacity. The 24--volt solenoid
coil is energized in high stage operation. The 24ANA1 unit
contains a 230v to 24vac transformer to supply power to the
solenoid when it is energized. The compressor solenoid load
should not be included in the system (furnace or fan coil) control
power transformer sizing.
CRANKCASE HEATER OPERATION
The crankcase heater is energized during unit off cycle regardless
of OAT temperature on 24ANA7 models.
The crankcase heater is energized during off cycle below 65
_
F on
24ANA1 models.
OUTDOOR FAN MOTOR OPERATION
The outdoor unit control energizes the outdoor fan any time the
compressor is operating. The outdoor fan remains energized if a
pressure switch or compressor overload should open. Outdoor fan
motor will continue to operate for one minute after the
compressor shuts off when the outdoor ambient is greater than or
equal to 100
_
F.
On 24ANA7 models, the outdoor fan remains energized during
the 1--minute compressor staging time delay.
24AN
A