Panasonic U-8MF2E8 Service Manual page 144

4. 3WAY Alarm Codes
P03, P17 Alarm
Alarm code
Alarm meaning
Alarm conditions
Probable cause
Check
5
Correction
Example
P03, P17
P03 : Compressor 1 discharge temperature trouble
P17 : Compressor 2 discharge temperature trouble
Compressor 1 : Pre-trip stops when the temperature exceeds 106°C.
Compressor 2 : Pre-trip stops when the temperature exceeds 106°C.
* The alarm occurs when pre-trip stop occurs more than once. However the pre-trip counter is cleared
if the compressor operates continuously for a specified length of time (more than 2.5 minuites).
(1) Malfunction of expansion valve (MOV4)
(2) Insufficient amount of refrigerant
(including trouble resulting from an insufficient initial charge and from gas leakage)
(3) Blocking of low-pressure parts caused by intrusion of foreign objects (moisture, scale, etc.)
(4) Crossing (tubing or PCB connectors) with the other compressor thermistor
(5) Malfunction of expansion valves (MOV1, MOV2)
(6) Refrigerant is accumulated into the stopped outdoor units.
(7) Compressor discharge sensor failure
(8) Outdoor unit PCB failure
(9) Failure to open the service valve of the outdoor unit
(10) Electrical noise
(1) Malfunction of expansion valve (MOV4)
Trouble: Although the expansion valve (MOV4) opens (MOV4 does not indicate "0" on the monitoring
software), the discharge temperature of the said compressor does not decrease.
Check: Check whether the MOV4 secondary side refrigerant tube is cold when the expansion valve
(MOV4) opens.
(2) Insufficient refrigerant
Trouble: Liquid effectiveness is poor.
Check: Check whether or not the superheating temperature is declining if the expansion valve is
opened to 300 pulses or more (after checking for foreign object intrusion).
(3) Foreign object intrusion
Trouble: Liquid valve effectiveness is poor.
Check: Check that there is no difference in the condensation or frost conditions between the
strainer primary-side and secondary-side tubing.
(4) Crossed thermistor
Trouble: The discharge temperature of the other compressor is high although only this compressor
is operating. When the liquid valve turns ON, the discharge temperature of the other
compressor decreases.
(5) Refrigerant is accumulated into the stopped outdoor units.
Trouble: System is OK when all outdoor units are operating, however symptoms of insufficient gas •
occur when a certain outdoor unit is stopped.
• Condensation or frost is visible up to the top of the accumulator of the stopped outdoor unit.
• After an outdoor unit stops, there is the sound of refrigerant flowing into an outdoor unit
that was stopped for a long time.
• When an outdoor unit starts after being stopped for a long time, the start is accompanied
by much vibration.
Check: • Check the following points limited to the stopped outdoor units (while the other outdoor
units are operating).
• Refrigerant leak on the expansion valves (MOV1, MOV2, MOV4)
• The expansion valve of the outdoor units stopped are all closed without any sound.
The sound of refrigerant flow can be heard when refrigerant leaks.
• Close the liquid service valve (normally "open") and check whether the sound of
refrigerant flow can be heard. When the sound stops, refrigerant leaks.
• If refrigerant leaks from the expansion valve (MOV4), the temperature of the secondary
refrigerant tube becomes lower than the outdoor temperature.
• Refrigerant leaks from the expansion valve (MOV2) and check valve connected in
apposition (check valves for 14 & 16HP only)
• When the outdoor units stoppped, there is no refrigerant flow normally. But once
refrigerant leaks, the sound of refrigerant flowing from the check valve can be heard.
• Close the liquid tube service valve (normally "open") and check whether the sound of
refrigerant flow from the check valve stops. When the sound stops, refrigerant leaks.
(6) Sensor failure
Check: • This alarm is likely to occur when wiring is partially cut. (It is difficult to identify, even
when continuity is checked.) The detected discharge temperature is high.
Although such conditions rarely occur, a P02 alarm is likely if the detected discharge
temperature is low.
• Replace the sensor with another discharge sensor and compare the temperature conditions.
(7) Failure to open the service valve of the outdoor unit
Check open/closed status of the outdoor unit service valve.
(8) If the cause is still unknown after checking the above, there is possibility that electrical noise is the
cause of the trouble.
(1) Replace the sensor.
(2) Replace the outdoor unit PCB.
(3) Correct the problem locations.
All of the probable causes
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3WAY SYSTEM
Trouble Diagnosis