Carrier 25VNA Installation Instructions Manual page 12

MAJOR COMPONENTS
Variable speed Control Board
The HP control board controls the following functions:
• Compressor speed
• Contactor operation
• Outdoor fan motor operation
• Reversing valve operation
• Defrost operation
• Low ambient cooling
• Crankcase heater operation
• Pressure switch monitoring
• Time Delays
• .Pressure Transducer
• .EXV operation control
• .Inverter communication and control
Inverter
The inverter is located inside the control box. This is an air-cooled
device that communicates with the control board and drives the
compressor to the demanded RPM. When the contactor closes, it
powers the inverter with line voltage. The inverter changes the line
voltage to 410 volts DC 3-phase, and varies the frequency to drive
the compressor at the desired RPM.
NOTE: Manually closing the contactor will not cause the unit to
operate. The unit must be operated with an Infinity Control. A
standard thermostat will allow operation only in the emergency
mode (high speed heating or cooling).
Variable Speed Compressor
This unit contains a variable speed compressor that has a wide
operating range. It operates on 410vdc provided by the inverter.
This compressor can only be operated by the specific inverter
supplied with the unit.
EQUIPMENT DAMAGE HAZARD
Failure to follow this caution may result in equipment damage
and/or improper operation.
Do not attempt to apply line voltage directly to the
compressor. This will destroy the compressor.
Electronic Expansion Valve (EXV)
This unit uses an electronic expansion valve for refrigerant
metering in the heating mode. The control board drives the EXV to
its proper position based on the operating mode and conditions.
The Infinity Control Service mode allows for manual opening and
closing of the EXV for troubleshooting and pump down.
Field control Connections
For normal operation use the ABCD Infinity connections only.
Only two wires, AB are required. See Fig. 18. Discrete inputs (Y,C,
O) are available for emergency operation if the Infinity Bus is not
in operation.
Pressure Transducer (SPT)
A 5 VDC output low pressure transducer that provides a 0-5 VDC
data for interpretation by the control board for a 0 to 200 psig
range of pressure at the suction tube. This interpreted pressure data
is then intelligently used by the control board for low pressure
cut-out, loss of charge management, compressor overall envelope
management, oil circulation management, lubrication management
and EXV control. (See Fig. 17.)
Compressor Control Contactor
The contactor has a 24 volt coil. The electronic control board
controls the operation of the contactor.
TROUBLESHOOTING
Systems
Communication Failure
If conmmnication with the Infinity control is lost with the User
Interface (UI), the control will flash the appropriate fault code (see
Table 7). Check the wiring to the User Interface and the indoor and
outdoor units and power.
Model Plu_
Each control board contains a model plug. The correct model plug
must be installed for the system to operate properly (see Table 3).
Table 3 - Model Plug Information
MODEL
NUMBER
MODEL PLUG
NUMBER
25VNA024 HK7OEZO01
25VNA036 HK7OEZO02
25VNA048 HK7OEZO03
25VNA060 HK7OEZO04
PIN RESISTANCE
(K-ohms)
Pins 1-4 Pins 2-3
5.1K 11K
5.1K 18K
5.1K 24K
5.1K 33K
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 nfissing 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 nfinutes.
3. Display the appropriate fault code (see Table 7).
4. After a 15 nfinute 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 nfinute delay, the outdoor
fan is turned off. If the open switch closes anytime after the
15 nfinute 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.
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.
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