24VNA6 / 25VNA4: Service Manual
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
10
Defrost Interval
The Defrost Interval is the amount of time that heating operation can
occur in frost-accumulating conditions before a defrost cycle is required
to clear the frost. Frost accumulating conditions are defined as operation
with a coil temperature below 35°F. The Defrost Interval can be set to a
fixed value, or it can be determined automatically by the control.
Automatic operation is recommended for most systems.
The Defrost Interval is set in the Infinity Control and communicated to
the outdoor equipment. In non-communicating systems, the Defrost
Interval is set with DIP switches on the PCM. Available Defrost Interval
settings are:
• 30 minutes
• 60 minutes
• 90 minutes
• 120 minutes (not available for non-communicating systems)
• Auto
Auto mode is recommended for all systems unless unusual application
conditions indicate a fixed setting should be used. Auto mode will
adjust the defrost interval dynamically and provide optimum system
performance.
Auto mode adjusts the defrost interval time based on the previous defrost
cycle time as shown in the following table.
Defrost Process
The defrost process begins when the defrost interval time is reached
under frost-accumulating conditions. The defrost process ends when the
coil reaches a temperature threshold - usually 60°F. Defrost may also
terminate as a result of a time limit - usually 10 minutes. If Defrost is
forced via the Forced Defrost input, defrost will be initiated regardless of
frost accumulation time or outdoor temperature. A forced defrost will
run at least 30 seconds, but may not run longer than 30 seconds if
ambient temperature is well above freezing.
The Defrost Process proceeds as follows:
1. The compressor ramps to RVS transition speed
2. RVS is switched to defrost position (fan stays on)
3. Compressor ramps to defrost speed
4. Fan turns off when coil temperature increases to ambient
temperature
5. Defrost completes when coil temperature reaches target or defrost
timeout is reached.
6. The compressor ramps to RVS transition speed
7. RVS is switched to heating position (fan stays off)
8. Compressor ramps to heating speed
9. Fan turns on when coil temperature falls to ambient temperature
PCM Indicators and Display Operation
Operation and interpretation of each indicator and display is described.
Status Light
The operation modes and meaning for each mode of the status light is
described in the table below for PCM SW versions 4.0 and above:
For PCM software versions older than 4.0, use the following table:
Comm Light
The Comm light indicates communication received from a
communicating control. If the Comm light is On, then communication
has been received within the last 2 minutes and the equipment is
operating in normal communication mode. If the Comm light is Off,
then communication has not been received within the last 2 minutes, and
the equipment is operating in emergency communicating mode.
VFD Comm Light
The VFD Comm light blinks every time there is a message received
from the VFD. If a message is received with no errors, the light will
flash green. If a message is received with an error, or if a message is
expected and not received, the light will flash red. When the equipment
is operating, communication is occurring very frequently. If
communication is operating properly, the light will continuously flash
while the equipment is operating.
Matrix Display
The matrix display will scroll a sequence of up to four active diagnostic
codes. If more than four diagnostic codes are active at one time, then
only the four highest priority codes are displayed. Codes are displayed
in decreasing order of priority beginning with the highest priority code
first. Scrolling repeats continuously with a brief pause between each
sequence. If there are no codes active, then the display will remain
blank. There are additional operating modes of the display associated
with troubleshooting procedures described in the Troubleshooting
section under Compressor Protection Delay Override and Diagnostic
Code Recall.
Reprogrammability
The software in both the PCM and the VFD can be reprogrammed.
Software updates are retrieved from the cloud by the Infinity Control and
downloaded to the equipment. The equipment can operate normally
during the download process. Once the homeowner or service tech
approves the update, the equipment will shut down (if operating), update
the software as necessary, and resume operation. The software update
process usually takes no more than a few minutes.
The software can also be updated from the Carrier Service Tech App via
the Bluetooth Module. This is the only software update method for
equipment using non-communicating control systems.
Previous Defrost Duration
Next Defrost Interval
Less than 3 minutes
120 minutes
Greater than 3 but less than 5 minutes
90 minutes
Greater than 5 but less than 7 minutes
60 minutes
Greater than 7 minutes
30 minutes
Mode
Meaning
Off
Power is removed from the PCM or there is a fundamental
PCM fault.
On
Equipment is in standby with no diagnostic conditions
preventing or limiting operation.
1 Slow Flash
Equipment is operating at low capacity (low stage in
emergency mode).
2 Slow Flashes
Equipment is operating at high capacity (high stage in
emergency mode).
Continuous Slow
Flash
Equipment operation has been interrupted or is being limited.
Continuous Fast
Flash
Equipment is in a lockout condition as a result of a diagnostic
condition or is in Diagnostic Code Recall mode.
Mode
Meaning
Off
Equipment is in standby with no diagnostic conditions
preventing or limiting operation.
On
N/A
1 Slow Flash
Equipment is operating at low capacity (low stage in
emergency mode).
2 Slow Flashes
Equipment is operating at high capacity (high stage in
emergency mode).
Flashing
A diagnostic code is present. The first digit of the fault base
code can be determined by the short flashes and the second
digit of the fault base code can be determined by the long
flashes.
Continuous Fast
Flash
N/A
