Panasonic R410A Service Manual page 91

4. Mini VRF Alarm Codes
L18 alarm
Alarm code L18
Alarm meaning 4-way valve operation failure
Alarm conditions During heating, when 2 minutes and 30 seconds have elapsed after compressor operation started,
the temperature difference between the outdoor air temperature sensor and the heat exchanger
liquid temperature sensor (C1) is 40°F or higher.
Probable cause (1) The 4-way valve connector (20S CN005) has become disconnected from the control PCB.
(2) The 4-way valve circuit is locked (malfunctioning).
Check (1) Check the 4-way valve connector (20S CN005).
(2) If the connector is normal, check the 4-way valve wiring and the PCB circuit.
Correction If the connector is normal, correct or replace the problem locations.
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Example
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Notes
P03 alarm
Alarm code P03
Alarm meaning Compressor discharge temperature trouble
Alarm conditions Inverter compressor: Temperature is 222°F or higher and pre-trip stop has occurred.
Probable cause
(1) Insufficient amount of refrigerant (including trouble resulting from an insufficient initial charge
and from gas leakage)
Blocking of low-pressure parts caused by intrusion of foreign objects (moisture, scale, etc.)
(2) Expansion valve operation failure
(3) Compressor discharge sensor failure
(4) PCB failure (A/D conversion failure)
(5) Electrical noise
Check
(1) Insufficient refrigerant
Trouble:
Check:
(2) Sensor failure
Check:
(3) If the cause is still unknown after checking the above, then it is possible that electrical noise
is the cause of the trouble.
Correction (1) Replace the sensor.
(2) Replace the outdoor unit PCB.
(3) Correct the problem locations.
Example All of the probable causes
Operates continuously for a set length of time.
Notes
Indicates 2 minutes 30 seconds or longer for an inverter unit.
Liquid effectiveness is poor.
Check whether or not the superheating temperature is declining if the evaporator
mechanical valve is opened to 300 pulses or more (after checking for foreign
object intrusion).
• This alarm is likely to occur when wiring is partially cut. (It can be difficult to identify,
even when conductivity 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.
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Mini VRF SYSTEM
Trouble Diagnosis
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