System Functions And Sequence Of Operation - Carrier Infinity 24ANB7 Installation Instructions Manual

Start- -Up
CAUTION
!
UNIT OPERATION AND SAFETY HAZARD
Failure to follow this caution may result in personal injury,
equipment damage or improper operation.
S Do not overcharge system with refrigerant.
S Do not operate unit in a vacuum or at negative pressure.
S Compressor dome temperatures may be hot.
CAUTION
!
PERSONAL INJURY HAZARD
Failure to follow this caution may result in personal injury.
Wear safety glasses, protective clothing, and gloves when
handling refrigerant and observe the following:
S Front seating service valves are equipped with Schrader
valves.
SYSTEM FUNCTIONS AND SEQUENCE
OF OPERATION
The 24ANB7 / 24ANB1 models utilize either an Infinity
Communicating User Interface or
thermostat. 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. 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. When a 2-stage unit is operating at
low-stage, system vapor (suction) pressure will be higher than a
standard single-stage system or high-stage operation.
When the outdoor ambient is more than 100_F (37.8_C), the
outdoor fan will continue to run for one minute after compressor
shuts off. this reduces pressure differential for easier starting in the
next cycle.
Communication and Status Function Lights
For Infinity Control Only, Green communications
(COMM)Light
Green LED (COMM Light)
A green LED (COMM light) on the outdoor board (see Fig. 7)
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 6 for codes and definitions.
NOTE: Only one code will be displayed on the outdoor unit
control board (the most recent, with the highest priority).
a 2-stage cooling indoor
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. 7). 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".
Compressor Operation
The basic scroll design has been modified with the addition of an
internal unloading mechanism that opens a by- -pass port in the first
compression pocket, effectively reducing the displacement of the
scroll.
The opening and closing of the by- -pass port is controlled by an
internal electrically operated solenoid. The modulated scroll uses a
single step of unloading to go from full capacity to approximately
67% capacity. A single speed, high efficiency motor continues to
run while the scroll modulates between the two capacity steps.
Modulation is achieved by venting a portion of the gas in the first
suction pocket back to the low side of the compressor, thereby
reducing the effective displacement of the compressor. Full
capacity is achieved by blocking these vents, thus increasing the
displacement to 100%.
A DC solenoid in the compressor controlled by a rectified 24 volt
AC signal in the external solenoid plug moves the slider ring that
covers and uncovers these vents. The vent covers are arranged in
such a manner that the compressor operates at approximately 67%
capacity when the solenoid is not energized and 100% capacity
when the solenoid is energized. The loading and unloading of the
two step scroll is done "on the fly" without shutting off the motor
between steps.
NOTE: 67% compressor capacity translates to approximately
75% cooling capacity at the indoor coil. The compressor will
always start unloaded and stay unloaded for five seconds even
when the thermostat is calling for high- -stage capacity.
Crankcase Heater Operation
The crankcase heater is de-energized when the compressor is
running. The crankcase heater is energized when the compressor is
off and the ambient is less than 42_F (5.55_C). When the ambient
temperature is between 65_F (18.33_C) and 42_F (5.55_C) the
crankcase heater is energized 30 minutes after the compressor is
turned off. When the ambient is above 65_F (18.33_C), the
crankcase heater remains de-energized after the compressor is
turned off.
Outdoor Fan Motor Operation
The outdoor unit control energizes the outdoor fan any time the
compressor is operating except for low- -ambient cooling operation.
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
(37.78_C) to allow for easier starting during next cooling cycle.
On 24ANB7 models - - The outdoor fan motor is a PSC type. A fan
relay on the control board turns the fan off and on by opening and
closing a high voltage circuit to the motor. It does not change
speeds between low and high stage operation.
On 24ANB1 models - - The outdoor fan is an ECM type. The
motor control is continuously powered with high voltage. The
motor speed is determined by electrical pulses provided by the
PWM outputs on the control board. The ECM motor RPM adjusts
to outdoor conditions as described in Table 3. The PWM output
can be measured between the PWM1 and PWM2 terminals on the
circuit board with a volt meter set to DC volts.
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