Major Components; Troubleshooting - Carrier 25HNA Infinity
Series Installation Instructions Manual

MAJOR COMPONENTS

2−Stage Control Board
The HP control board controls the following functions:
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High and low stage compressor contactor operation
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Outdoor fan motor operation
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Reversing valve operation
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Defrost operation
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Low ambient cooling
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Crankcase heater operation
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Compressor external protection
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Pressure switch monitoring
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Time Delays
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On 25HNA6 models, high− and low−stage start relay
and capacitor operation (Bristol compressor only)
Field Connections
On 25HNA6 models with non−communicating (non−Infinity)
system, the two−stage control receives 24vac low−voltage control
system inputs through the R, C, Y1, Y2 and O connections
located at the bottom of the control board (see Fig. 9.) On a
non−communicating system, output W1 is connected at the
bottom of the control board for auxiliary heat.
On 25HNA6 models with communicating system and all
25HNA9 models, use the ABCD Infinity connections.
Two Stage Compressor
The two stage compressor contains motor windings that provide
2−pole (3500 RPM) operation. For two−stage commpressor, refer
to Table 6 for correct winding resistance.
Compressor Internal Relief
The compressor is protected by an internal pressure relief (IPR)
which relieves discharge gas into the compressor shell when
differential between suction and discharge pressure exceeds
500−550 psi on 25HNA6 models and 550−625 psi on 25HNA9
models. The compressor is also protected by an internal overload
attached to motor windings.
Compressor Control Contactors
The contactor(s) have a 24volt coil. The electronic control board
controls the operation of the appropriate contactor.
Table 5—Model Plug Information
MODEL
MODEL
PLUG
NUMBER
NUMBER
25HNA624 HK70EZ002
25HNA636 HK70EZ004
25HNA648 HK70EZ006
25HNA660 HK70EZ008
25HNA924 HK70EZ010
25HNA936 HK70EZ012
25HNA948 HK70EZ014
25HNA960 HK70EZ016
PIN RESISTANCE
(K−ohms)
Pins 1−4 Pins 2−3
5.1 18
5.1 33
5.1 51
5.1 75
5.1 120
5.1 180
5.1 270
11 5.1

TROUBLESHOOTING

Systems Communication Failure
If communication with the Infinity control is lost with the User
Interface, the control will flash the appropriate fault code. (See
Table 7.) Check the wiring to the UI and the indoor and outdoor
units.
Model Plug
Each control board contains a model plug. The correct model
plug must be installed for or the system to operate properly. (See
Table 5.)
The model plug is used to identify the type and size of unit to the
control. On 25HNA6 models, the model plug is also used to
determine the start sequence timing for each individual model.
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− and low−pressure
switches. If the control senses the opening of a high− or
low−pressure switch, it will respond as follows:
1. De−energize the appropriate compressor contactor.
2. Keep the outdoor fan operating for 15 minutes.
3. Display the appropriate fault code (see Table 7).
4. After a 15 minute delay, if there is a call for cooling or
heating and LPS or HPS is reset, the appropriate
compressor contactor is energized.
5. If 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 resume operation with a
call for cooling or heating.
6. If LPS or 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 indoor airflow in heating.
8. In the event of a low−pressure switch trip or low−pressure
lockout, check the refrigerant charge and indoor airflow
(cooling) and outdoor fan operation and outdoor coil in
heating.
Control Fault
If the outdoor unit control board has failed, the control will flash
the appropriate fault code (see Table 7). The control board should
be replaced.
Brown−Out Protection
If the line voltage is less than 187v for at least 4 seconds, the
appropriate compressor contactor and fan relay are de−energized.
Compressor and fan operation are not allowed until voltage is a
minimum of 190v. The control will flash the appropriate fault
code (see Table 7).
230V Line (Power Disconnect) Detection
If there is no 230v at the compressor contactor(s) when the indoor
unit is powered and cooling or heating demand exists, the
appropriate fault code is displayed. Verify the disconnect is closed
and 230v wiring is connected to the unit.
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