Troubleshooting - Carrier Performance 24APA Installation Instructions Manual

the coil temperature routine listed above for the remainder
of the cooling cycle. If the LPS does not close within 10
minutes, then the normal LPS trip response (shut down
cooling operation and generate LPS trip error) will occur.
Standard Thermostat low ambient cooling mode:
The following optional accessories must be installed for low
ambient operation in standard thermostat mode:
S Low Ambient Pressure Switch Kit
S Evaporator Freeze Thermostat
S Winter Start Control
S Crankcase Heater
The fan motor is a ball bearing type and does not need to be
changed. A crankcase heater must be installed. See Product Data
for accessory part numbers on appropriate unit size and series
units.

TROUBLESHOOTING

SYSTEMS COMMUNICATION FAILURE
If communication between outdoor unit, control board, and
indoor user interface control has failed, the control will flash the
appropriate fault code. (See table 3) Check the wiring to the UI,
indoor and outdoor units.
PRESSURE SWITCH PROTECTION
The outdoor unit is equipped with high- - and low- -pressure
switches. If the control senses the opening of a high or
low- -pressure switch, it will de- -energize the compressor
contactor, keep the outdoor fan operating for 15 minutes and
display the appropriate fault code. (See table 3)
After a 15 minute delay, if there is still a call for cooling, and the
LPS or HPS is reset, the compressor contactor is energized. If the
LPS or HPS has not closed after a 15 minute delay, the outdoor
fan is turned off. If the open switch closes anytime after the
15- -minute delay, then the unit will resume operation with a call
for cooling.
If the LPS or HPS trips for five consecutive cycles, then unit
operation is locked out for 4 hours and the appropriate fault code
(See table 3) is displayed.
In the event of a high- -pressure switch trip or high- -pressure
lockout, check the refrigerant charge, outdoor fan operation and
outdoor coil for airflow restrictions.
In the event of a low- -pressure switch trip or low- -pressure
lockout, check the refrigerant charge and indoor airflow.
CONTROL FAULT
If the outdoor unit control board has failed, the control will flash
the appropriate fault code. (See table 3) The control board should
be replaced.
24V BROWN OUT PROTECTION
If the control voltage is less than 15.5volts for at least 4 seconds,
the compressor contactor and fan relay are de- -energized.
Compressor and fan operation are not allowed until control
voltage is a minimum of 17.5volts. The control will flash the
appropriate fault code. (See table 3) Verify the control voltage is
in the allowable range of 18- -30volts.
COMPRESSOR VOLTAGE SENSING
The input terminals labeled VR and VS on the control board (see
Fig. 13) are used to detect compressor voltage status, and alert the
user of potential problems. The control continuously monitors the
high voltage on the run capacitor of the compressor motor.
Voltage should be present any time the compressor contactor is
energized, and voltage should not be present when the contactor
is de- -energized.
COMPRESSOR THERMAL CUTOUT OR LOSS OF 230V
POWER
If the control senses the compressor voltage after start- -up, and is
then absent for 10 consecutive seconds while cooling demand
exists, it will de- -energize the compressor contactor, keep the
outdoor fan operating for 15 minutes (if 230v power present) and
display the appropriate fault code. (See table 3) Possible causes
are compressor internal overload trip or loss of high voltage
(230V) to compressor without loss of control voltage.
After a 15 minute delay, if there is still a call for cooling, the
compressor contactor is energized. If the thermal protector has
not re- -set, the outdoor fan is turned off. If the call for cooling
continues, the control will energize the compressor contactor
every 15 minutes. If the thermal protector closes, (at the next 15
minute interval check), the unit will resume operation.
If the thermal cutout trips for three consecutive cycles, then unit
operation is locked out for 4 hours and the appropriate fault code
(See Table 3) is displayed.
CONTACTOR SHORTED DETECTION
If there is compressor voltage sensed when there is no demand for
compressor operation, the contactor may be stuck closed. The
control will flash the appropriate fault code. Check the contactor
and control box wiring.
NO 230V AT COMPRESSOR
If the compressor voltage is not sensed when the compressor
should be starting, the contactor may be stuck open or the unit
disconnect or circuit breaker may be open. The control will flash
the appropriate fault code. Check the contactor, unit disconnect
or circuit breaker and control box wiring.
TEMPERATURE THERMISTORS
Thermistors are electronic devices which sense temperature. As
the temperature increases, the resistance decreases. Thermistors
are used to sense outdoor air (OAT) and coil temperature (OCT).
If the outdoor air or coil thermistor should fail, the control will
flash the appropriate fault code. (See table 3)
IMPORTANT: The outdoor air thermistor and coil thermistor
are factory mounted in the correct locations. Do not re- -locate
thermistor sensors.
THERMISTOR SENSOR COMPARISON
The control continuously monitors and compares the outdoor air
temperature sensor and outdoor coil temperature sensor to ensure
proper operating conditions. The comparison is, if the outdoor air
sensor indicates ≥10 _F warmer than the coil sensor (or) the
outdoor air sensor indicates ≥20_F cooler than the coil sensor, the
sensors are out of range.
If the sensors are out of range, the control will flash the
appropriate fault code. (See Table 3)
The thermistor comparison is not performed during low ambient
cooling.
FAILED THERMISTOR DEFAULT OPERATION
Factory defaults have been provided in the event of failure of
outdoor air thermistor and/or coil thermistor.
If the OAT sensor should fail, low ambient cooling will not be
allowed, and the one minute outdoor fan off delay will not occur.
If the OCT sensor should fail, low ambient cooling will not be
allowed.
Thermistor Curve: The resistance vs. temperature chart shown in
Figure 12 enables the technician to check the outdoor air and
outdoor coil thermistors for proper resistance. Unplug the
thermistor assembly from the circuit board and measure resistance
across each thermistor. For example, if the outdoor temperature is
60ºF, the resistance reading across the outdoor air thermistor
should be around 16,000 Ohms.
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