Panasonic U-8ME1E8E Service Manual page 158

4. 2WAY Alarm Codes
F16 Alarm
Alarm code F16
Alarm meaning High-pressure sensor trouble (abnormal rise in high pressure) (In some cases this may not be
the result of a high-pressure sensor malfunction.)
Alarm conditions • High-pressure SW activated although the detected pressure was lower (3.03 MPa or below)
than the high-pressure SW activation pressure: Undershift
• High-pressure SW failed to activate although the detected pressure was higher (3.43 MPa or
above) than the high-pressure SW activation pressure: Overshift
• The saturation temperature at the detected pressure is 5°C or more below the highest indoor-
unit E1 temperature continuously for 30 minutes.
• High-pressure sensor disconnected or open circuit.
Probable cause (1) High-pressure sensor malfunction
(2) Failure to connect the connector to the outdoor unit PCB
(3) Failure to open the service valve
(4) Clogged tubing
(5) Valve leakage
(6) Over-charging
(7) Outdoor unit PCB failure
(8) Electrical noise
Check (1) High-pressure sensor failure
• Check the sensor resistance value. (Use a tester and measure the resistance between
sensor No. 1 and No. 3)
Resistance of less than 10kΩ indicates a short circuit or other trouble.
Resistance of 10kΩ - 200kΩ is normal. Resistance of more than 200kΩ indicates
an open circuit or other trouble.
Connect a gauge to the high-pressure outlet and check for changes in the value
•
dispalyed by the monitoring software, and for large deviation of the gauge pressure.
• During heating, check whether the temperature is lower than the highest indoor-unit E1
temperature.
* The pressure detected by the high-pressure sensor is the highest pressure in the system.
(2) Failure to open the service valve, clogged tubing, valve leakage, over-charging.
In all of these cases an alarm occurs when there are rapid pressure fl uctuations and tracking
of the detected pressure is poor.
• Check the open/closed status of the valve.
• Check for clogging of the tubing.
To check for clogging, disconnect the high-pressure sensor from the PCB and check
whether the high-pressure SW activates.
• Check for valve leakage and over-charging
When valve leakage or over-charging occurs, refrigerant is likely to accumulate in the
oudoor units or indoor units, resulting in a sudden rise in pressure at start that occurs
before the refrigerant in the heat exchanger is discharged.
* The representative valves to check are the liquid valves and mechanical valves.
(3) Outdoor unit PCB failure
• The check items are the same as for a high-pressure sensor malfunction.
A normal PCB is needed to determine whether the problem is a PCB failure or a pressure
sensor malfunction. If an abnormality was found at the check items for a high-pressure
sensor malfunction, fi rst try replacing the PCB and check again.
Therefore during heating the converted saturation temperature will never be lower than
any indoor-unit E1 temperature. During cooling this temperature will never be lower
than the outdoor unit liquid temperature.
Trouble is corrected: Outdoor unit PCB failure
Trouble is not corrected: High-pressure sensor malfunction
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2WAY SYSTEM
Trouble Diagnosis
6
Continued