Troubleshooting - Carrier 25VNA Service Manual

TROUBLESHOOTING

Systems Communication Failure
If communication with the Infinity control is lost with the User
Interface (UI), the control will flash the appropriate fault code (see
Table 5 and Table 6). Check the wiring to the User Interface and
the indoor and outdoor units and power.
Model Plug
Each control board contains a model plug. The correct model plug
must be installed for the system to operate properly (see Table 2).
Table 2—Model Plug Information
MODEL
MODEL PLUG
NUMBER
NUMBER
25VNA024 HK70EZ001
25VNA036 HK70EZ002
25VNA048 HK70EZ003
25VNA060 HK70EZ004
The model plug is used to identify the type and size of unit to the
control.
On new units, the model and serial numbers are input into the
board's memory at the factory. If a model plug is lost or missing at
initial installation, the unit will operate according to the
information input at the factory and the appropriate error code will
flash temporarily. An RCD replacement board contains no model
and serial information. If the factory control board fails, the model
plug must be transferred from the original board to the replacement
board for the unit to operate.
NOTE: The model plug takes priority over factory model
information input at the factory. If the model plug is removed after
initial power up, the unit will operate according to the last valid
model plug installed, and flash the appropriate fault code
temporarily.
Pressure Switch Protection
The outdoor unit is equipped with high pressure switch. If the
control senses the opening of a high pressure switch, it will
respond as follows:
1. De- -energize the contactor.
2. Keep the outdoor fan operating for 15 minutes.
3. Display the appropriate fault code (see Table 5 and Table 6).
4. After a 15 minute delay, if there is a call for cooling or heat-
ing and HPS is reset, the contactor is energized.
5. If 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 resume operation with a call for cool-
ing or heating at a temporary reduced capacity.
6. If HPS trips 3 consecutive cycles, the unit operation is
locked out for 4 hours.
7. In the event of a high- -pressure switch trip or high- -pressure
lockout, check the refrigerant charge, outdoor fan operation,
and outdoor coil (in cooling) for airflow restrictions, or in-
door airflow in heating.
8. In the event of a low- -pressure trip or low- -pressure lockout,
check the refrigerant charge and indoor airflow (cooling)
and outdoor fan operation and outdoor coil in heating.
PIN RESISTANCE
(K--- ohms)
Pins 1--- 4 Pins 2--- 3
5.1K 11K
5.1K 18K
5.1K 24K
5.1K 33K
Control Fault
If the outdoor unit control board has failed, the control will flash
the appropriate fault code. The control board should be replaced.
If the sensors are out of range, the control will flash the appropriate
fault code.
The thermistor comparisons are not performed during low ambient
cooling or defrost operation.
Failed Thermistor Default Operation
Factory defaults have been provided in the event of failure of
outdoor air thermistor (OAT) and/or outdoor coil thermistor
(OCT).
If the OAT sensor should fail, low ambient cooling will not be
allowed and the one- -minute outdoor fan off delay will not occur.
Defrost will be initiated based on coil temperature and time.
If the OCT sensor should fail, low ambient cooling will not be
allowed. Defrost will occur at each time interval during heating
operation, but will terminate after 5 minutes.
If there is a thermistor out- -of- -range error, defrost will occur at
each time interval during heating operation, but will terminate after
5 minutes.
Count the number of short and long flashes to determine the
appropriate flash code.
Outdoor Coil Thermistor
The outdoor coil thermistor is a 10Kohm resistor used for multiple
system operations. It provides the coil/liquid line temperature to
the heat pump board and user interface. Low ambient operation,
defrost initiation, defrost termination and assistance with OAT
temperature measurement of some of the functions. The sensor
must be securely mounted to the tube connecting the EXV and
distributor. See Fig.9 for proper placement.
OAT Thermistor must be
locked in place with
spherical nib end facing
towards the front of the
control box
Fig. 8 – OAT Thermistor Location (Bottom of Control Box)
Fig. 9 – Outdoor Coil Thermistor (OCT) Attachment
(On Distributor Tube)
10
A11142
OCT SENSOR
LOCATION
A11143