Panasonic Water Heaters Error Codes

H01

Panasonic tankless water heater will not start; display shows H01 and burner does not ignite.

Ignition Failure / No Flame Detected

H02

Panasonic water heater stops shortly after starting; display shows H02 and water remains cold.

Flame Loss During Operation

H03

Panasonic water heater shows H03 and shuts down; fan may not start or runs briefly then stops.

Combustion Fan Motor Failure

H04

Display shows H04 and heater will not ignite; unit may click repeatedly without starting.

Gas Valve Circuit Failure

H05

Panasonic water heater shows H05 and stops; water may briefly warm then go cold.

Water Flow Sensor / Turbine Failure

H06

Heater displays H06 and does not start; sometimes occurs intermittently when opening taps.

Inlet Water Temperature Sensor (Thermistor) Failure

H07

Display shows H07; heater may overheat quickly or shut down soon after ignition.

Outlet Water Temperature Sensor (Thermistor) Failure

H08

Panasonic water heater shows H08 and shuts down; may be associated with very hot outlet water.

Heat Exchanger Overheat / Safety Thermostat Trip

H09

Heater displays H09 and will not operate; may occur after power fluctuations or lightning.

Main Control PCB Failure / Internal Error

H10

Panasonic water heater shows H10; unit may start but then shut down with unstable temperature.

Mixing / Outlet Temperature Control Error

H11

Remote controller cannot communicate with the heater; display shows H11 or communication error.

Remote Controller Communication Failure

H12

Heater shows H12; may be associated with incorrect gas type or combustion adjustment issues.

Gas Type / Combustion Setting Error

H13

Panasonic water heater shows H13 and shuts down; often related to flue or ventilation problems.

Exhaust / Flue Blockage or Draft Error

H14

Heater displays H14; unit may not start or may shut down unexpectedly.

Fan Speed / Airflow Sensor Error

H15

Panasonic water heater shows H15; may be associated with power supply issues or internal low‑voltage faults.

Power Supply / Low Voltage Error

H16

Heater shows H16 and stops; may be related to abnormal water temperature readings.

Heat Exchanger Temperature Sensor Error

H17

Panasonic water heater displays H17; unit may not ignite or may shut down quickly.

Gas Pressure Sensor Error

H18

Heater shows H18; may be associated with circulation or internal pump issues on models with built‑in pump.

Circulation Pump Failure (if equipped)

H19

Panasonic water heater shows H19; unit may not respond correctly to remote commands.

Remote Controller Address / Configuration Error

H20

Heater displays H20; water may be too hot or unit may shut down on high temperature.

Outlet Over‑Temperature Protection

H21

Panasonic water heater shows H21; unit may not ignite or may shut down with gas‑related issues.

Gas Solenoid Valve Error

H22

Heater displays H22; may be associated with abnormal combustion or flame detection.

Abnormal Flame Detection / Flame Rod Error

H23

Panasonic water heater shows H23; unit may not start or may shut down with sensor‑related issues.

Ambient / Internal Temperature Sensor Error

H24

Heater displays H24; may be associated with freeze protection or low ambient temperature issues.

Freeze Protection Sensor / Heater Error

H25

Panasonic water heater shows H25; unit may not start in very cold conditions.

Freeze Protection Activation / Low Temperature Lockout

H26

Heater displays H26; may be associated with abnormal combustion or CO sensor on some models.

Combustion Safety / CO Sensor Error (model‑dependent)

H27

Panasonic water heater shows H27; may be related to internal communication between PCBs on multi‑board models.

Internal PCB Communication Error

H28

Heater displays H28; may be associated with sensor calibration or internal reference errors.

Sensor Calibration / Reference Error

H29

Panasonic water heater shows H29; may be related to abnormal water flow or bypass valve issues.

Bypass Valve / Flow Control Error

H30

Heater displays H30; may be associated with abnormal inlet water pressure or pressure sensor issues.

Water Pressure Sensor Error

Symptom

Water heater displays normal operation but hot water smells metallic or has discoloration.

Water Quality / Corrosion Contamination

Symptom

Water heater does not turn on at all; no lights or display on Panasonic unit.

No Power / Dead Unit

Symptom

Water heater emits a burning smell or plastic odor during operation.

Overheating Components / Electrical Overload

Symptom

Water heater emits a clicking sound but fails to ignite; no error code displayed.

Intermittent Ignition Failure

Symptom

Water heater frequently shuts off when other taps or appliances are used, causing temperature drops.

Water Supply Interaction / Pressure Drop

Symptom

Water heater is leaking from the pressure relief valve discharge pipe.

Overpressure / Relief Valve Discharge

Symptom

Water heater is leaking water from the bottom or inside the casing.

Internal Water Leak

Symptom

Water heater is very noisy; fan noise or vibration is excessive during operation.

Excessive Vibration / Fan Imbalance

Symptom

Water heater makes loud banging or popping noises during operation.

Scale Buildup / Boiling in Heat Exchanger

Symptom

Water heater output is lukewarm only; cannot reach set temperature even at maximum setting.

Insufficient Heating Capacity

Symptom

Water heater powers on but produces no hot water; water remains cold even with taps fully open.

No Heating / No Ignition Without Error Code

Symptom

Water heater produces hot water but then shuts off after a few minutes, requiring tap to be closed and reopened.

Short Cycling / Flow Detection Dropout

Symptom

Water heater takes a very long time to deliver hot water to taps.

Long Hot Water Delivery Time

Symptom

Water heater trips the circuit breaker or RCD when starting or during operation.

Electrical Short / Ground Fault

Symptom

Water temperature fluctuates between hot and cold during a shower on Panasonic water heater.

Temperature Fluctuation / Hunting