Panasonic U-120ME2U9 Service Manual page 165

3. 2WAY Alarm Codes
H07 Alarm
Alarm code H07
Alarm meaning Low on oil or the oil recovery circuit has restriction.
Alarm conditions This alarm occurs when oil does not flow for a specified amount of time in tubing where oil
flow constantly. (The presence of oil is detected by a temperature sensor.)
Probable cause Insufficient amount of oil in the system
(1) The length of system tubing exceeds the allowable tubing length.
(2) The difference in height between system units exceeds the allowable value.
(3) A large amount of oil was drained when a compressor was replaced.
(4) Oil has accumulated in a stopped outdoor unit and has not returned, as a result of refrigerant
circuit clogging or valve leakage at the stopped outdoor unit.
(5) A valve (ORVR, ACV, BPV) in the oil circuit has malfunctioned, or there is clogging of the
circuit (capillaries) which returns oil from the oil separator to the compressor.
(6) If an excessive amount or liquid returns to the compressor, oil foaming may increase oil
discharge. The same occurs when the refrigerant proportion in the compressor is high at start,
due to an open circuit in the crank case heater.
(7) Oil sensor disconnected or open circuit
Check (1) Check the tubing length and height differences.
(2) Check the operation of system circuit valves.
(3) Check that there is not an excessive amount of liquid return. (Check that there is no
mechanical valve leakage.)
(4) Check the crank case heater (wintertime).
(5) Check that the oil sensor is not disconnected, and that the circuit is not open.
Correction (1) If insufficient oil is a possibility, then charge with additional oil.
(2) If it is clear that a valve failure has occurred, replace the valve.
Example —
Notes —
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2WAY VRF SYSTEM
Trouble Diagnosis
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