Troubleshooting; Systems Communication Failure; Model Plug; Pressure Switch Protection - Carrier Infinity 25VNA0 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 4 and Table 6 for 24VNA0 and Table 5 and Table 7 for
25VNA0.). 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 1).
Table 1—Model Plug Information
MODEL
MODEL PLUG
NUMBER NUMBER
24VNA024 HK70EZ011
24VNA036 HK70EZ012
24VNA048 HK70EZ013
24VNA060 HK70EZ014
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 4 and Table 6
for 24VNA0 and Table 5 and Table 7 for 25VNA0.).
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.
PIN RESISTANCE
(K--- ohms)
Pins 1--- 4 Pins 2--- 3
5.1K 150K
5.1K 180K
5.1K 220K
5.1K 270K
PIN RESISTANCE
(K--- ohms)
Pins 1--- 4 Pins 2--- 3
5.1K 11K
5.1K 18K
5.1K 24K
5.1K 33K
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.

Low Pressure Protection

The outdoor unit is equipped with low pressure transducer. If the
control senses a low pressure per the table below, it will respond as
follows:
S Cooling Low Pressure (3 minute operation) Cool mode
<= 55 psig
S Cooling and Heating Low Pressure (instantaneous) < 13
psig
S Heating Low Pressure (3 minute operation) Heat mode
< 23 psig.
1. Display the fault code 32 on the status LED and User
Interface.
2. If a demand persists after the 15- -minute delay and the
pressure has reached the operation level, then resume
operation. Reset the 15- -minute timer, clear the displayed
fault code and communicate cleared error to the Wall
Control. Status LED reverts to operation code display.
3. If a demand persists after the 15- -minute delay but the
pressure has not recovered, turn off the ODF. If the pressure
recovers any time after the 15- -minute delay, then resume
operation. Reset the 15- -minute timer, clear the displayed
error code and communicate cleared error to the Wall
Control. Status LED reverts to operation code display.
4. If a pressure drops below the instantaneous level three (3)
consecutive times, then lock out operation for 4 hours and
display the system malfunction code 83 and communicate
lockout status to the Wall Control. The trip counter will
reset to zero if 15 minutes of successful operation occurs
before the 3rd trip is recorded.
5. In the event of a low pressure trip or low pressure lockout,
check the refrigerant charge and indoor airflow.

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.
On the 25VNA0, defrost will be initiated based on coil temperature
and time.
If the OCT sensor should fail, low ambient cooling will not be
allowed. On the 25VNA0, 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 on the 25VNA0, but
will terminate after 5 minutes.
Count the number of short and long flashes to determine the
appropriate flash code.
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.
24VNA0 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 AC board and user interface. Low ambient operation, and
assistance with OAT temperature measurement are some of the
functions. The sensor must be securely mounted to the tube
connecting the coil and distributor.
placement. See Table 8 for proper resistances.
9
See Fig. 7 for proper