Panasonic U-4LE2E5 Service Manual & Test Run Service Manual page 136

3. Mini VRF Alarm Codes
F04 Alarm
Alarm code
Alarm meaning
Alarm conditions
Probable cause
Check
6
Correction
Example
Notes
F04
Compressor discharge temperature sensor has failure. (DISCH)
(1) Discharge temp. of 100°C or higher was detected 30 minutes or more after that compressor
stopped operating.
(2) Discharge temp. of 80°C or higher was detected after all compressors had been stopped for
60 minutes or longer.
(3) A/D step is 10 steps or less (short circuit).
(1) Sensor malfunction
• Sensor element malfunction
• Sensor wiring is partially disconnected, resulting in increased electrical resistance.
This alarm does not occur when the wiring is disconnected or when the connector is not
connected to the Outdoor Unit Control PCB.
(2) Outdoor Unit Control PCB failure
(3) The check valve on the discharge tube for that compressor is wet.
(4) An air short blockage in the area around the outdoor unit has increased the outdoor unit
ambient temperature, reducing the cooling effects after the compressor stops.
(5) There is a cause that results in P03 alarm.
(6) Electrical noise
(1) Sensor malfunction and Outdoor Unit Control PCB failure
Trouble: • Constantly indicates a high temperature.
• When monitoring software or other means are used for monitoring, the discharge
temperature at times fluctuates suddenly and wildly.
• In some cases, the precise temperature may not be known, even when monitoring
software is used.
Check: • Wiggle the sensor and check whether the trouble continues.
• Check whether the connector is partially disconnected from the Outdoor Unit Control
PCB.
An F04 alarm will not result if the connector is completely disconnected (circuit is
open).
• If the cause is still uncertain, check the following to determine whether a sensor or
Outdoor Unit Control PCB failure has occurred.
Step 1: Connect a discharge sensor where the F04 alarm has not occurred, to the
connector for this compressor on the Outdoor Unit Control PCB. Measure the
temperature at the same point (a location where temperature fluctuations are
small), and check whether there is a temperature difference.
Difference Õ
No difference Õ Outdoor Unit Control PCB and sensor are normal.
Step 2: If an abnormality was found at Step 1, connect the problem compressor
sensor to the Outdoor Unit Control PCB connector of a device where the F04
alarm has not occurred. Measure the temperature at the same point (a location
where temperature fluctuations are small), and check whether there is a
temperature difference.
Difference Õ
No difference Õ Outdoor Unit Control PCB failure.
It is convenient at this time to have a discharge temperature sensor on hand.
(2) The ambient temperature around the outdoor unit when it is stopped is 46 °C or higher.
(3) If the cause is still unknown after checking the above, then it is possible that electrical noise is
the cause of the trouble. It is necessary to provide a line filter or carry out other noise
countermeasures.
(1) Replace the sensor.
(2) Replace the Outdoor Unit Control PCB.
(3) Carry out noise countermeasures.
(4) Repair the refrigerant tubing.
(5) Adjust the amount of refrigerant.
(6) Correct the trouble.
(1) Sensor wiring is partially cut.
This alarm does not indicate that the sensor is disconnected.
In order to prevent overheating during operation, the outdoor units in this system will not allow a
compressor to start if the discharge temperature does not decrease while the compressor is
stopped. If a sensor malfunction results in continuous detection of a high discharge temperature,
then the compressor may stop for no apparent reason. The purpose of this alarm is to facilitate
identification of the problem in this case.
Outdoor Unit Control PCB or sensor failure is possible.
Sensor failure.
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Mini VRF SYSTEM
Trouble Diagnosis