Immergas
Immergas Boilers Error Codes
Complete list of fault codes and troubleshooting guides. Use the search below to find your specific error.
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01
Boiler locks out with error code 01; the burner does not ignite, the red lockout LED is on, and the fan may start briefly then stop.
Ignition Failure / No Flame Detection
02
Boiler displays error code 02 and locks out shortly after an ignition attempt; the flame appears briefly then extinguishes.
Flame Loss During Operation
03
Boiler displays error code 03; the fan does not start or starts then stops, and there is no ignition sequence.
Flue Fan / Air Pressure Switch Fault
04
Boiler displays error code 04; there is no ignition, sometimes accompanied by a humming sound from the gas valve area.
Gas Valve Control / Internal Gas Valve Fault
05
Boiler displays error code 05; it will not start, and the display may indicate a fan or flue fault depending on the model.
Flue System / Fan Speed Control Fault
06
Boiler displays error code 06; there is no ignition, often occurring after a power surge or wiring disturbance.
Control Board / Internal Electronics Fault
10
Boiler displays error code 10; there is no heating or hot water, and the pump may run briefly then stop.
Flow Sensor / Circulation Fault
11
Boiler displays error code 11; domestic hot water does not start when a tap is opened, though heating may still work.
DHW Flow Detection Fault
20
Boiler displays error code 20; it will not operate, often occurring after overheating or dry firing.
Primary Overheat / Safety Thermostat Tripped
21
Boiler displays error 21; temperature reading is erratic or fixed at an extreme value; the boiler may short cycle.
Flow Temperature Sensor (NTC) Fault
22
Boiler shows error 22; the return temperature reading is incorrect, and the boiler may shut down prematurely.
Return Temperature Sensor (NTC) Fault
23
Boiler displays error 23; domestic hot water temperature is not regulated correctly and may be too hot or too cold.
DHW Temperature Sensor (NTC) Fault
24
Boiler shows error 24, often associated with low system pressure or air in the system.
Low Water Pressure / Pressure Sensor Fault
27
Boiler displays error 27, often related to flue gas recirculation or combustion issues.
Flue Gas / Combustion Fault
28
Boiler shows error 28; ignition attempts are noisy or delayed, sometimes with small explosions (misfires).
Delayed Ignition / Combustion Instability
29
Boiler displays error 29, often associated with condensate drainage problems in condensing models.
Condensate Drain / Siphon Fault
31
Boiler shows error 31, a communication error with the remote control or external interface.
Communication / Bus Fault
37
Boiler displays error 37, often related to fan speed or air pressure anomalies.
Fan Speed / Air Pressure Regulation Fault
40
Boiler shows error 40, often indicating a generic sensor or configuration fault.
Generic Sensor / Configuration Error
A01
Boiler displays A01, ignition lockout, burner does not light; user must reset.
Ignition Lockout (No Flame)
A02
Boiler displays A02, safety thermostat intervention; boiler overheated and shut down.
Overheat Lockout
A03
Boiler displays A03, water pressure too low; boiler will not start.
Low System Pressure Lockout
A04
Boiler displays A04, flue gas safety device intervention; boiler shuts down.
Flue Gas Safety / Overtemperature Fault
A05
Boiler displays A05, fan or air pressure fault; boiler does not ignite.
Fan / Air Pressure Lockout
A06
Boiler displays A06, flame detected when there should be none (false flame).
False Flame Detection
A07
Boiler displays A07, domestic hot water NTC fault; DHW temperature control lost.
DHW NTC Sensor Error
A08
Boiler displays A08, flow NTC fault; boiler may not regulate heating temperature.
Flow NTC Sensor Error
A09
Boiler displays A09, return NTC fault; may cause incorrect modulation or lockout.
Return NTC Sensor Error
E01
Boiler displays E01, ignition failure, similar to A01 on some models.
Ignition Failure
E02
Boiler displays E02, indicating an overheat or safety thermostat intervention.
Overheat Protection
E03
Boiler displays E03, indicating a flue or fan fault, resulting in no ignition.
Flue/Fan Safety Lockout
E10
Boiler displays E10, indicating low water pressure or a pressure sensor fault.
Low Pressure / Sensor Error
E20
Boiler displays E20, indicating a circulation or pump fault, causing the boiler to overheat quickly.
Pump / Circulation Fault
Symptom
Boiler cycles on and off rapidly (short cycling) without maintaining stable temperature.
Short Cycling / Control Instability
Symptom
Boiler display is on but unresponsive to buttons, or settings change randomly.
User Interface / Control Panel Fault
Symptom
Boiler does not start at all, no display or lights, completely dead.
No Power / Electrical Supply Fault
Symptom
Boiler frequently loses pressure and needs topping up every few days.
Chronic Pressure Loss
Symptom
Boiler frequently trips the household electrical circuit breaker or RCD when starting or during operation.
Electrical Short / Earth Leakage
Symptom
Boiler heats radiators even when there is no call for heating (overheating house).
Unwanted Heating / Control Fault
Symptom
Boiler is leaking water from underneath the casing or from internal components.
Internal Water Leak
Symptom
Boiler is very noisy during operation (whining, grinding, or rattling sounds).
Mechanical Noise / Vibration
Symptom
Boiler locks out intermittently, especially in windy conditions, with no consistent error code.
Intermittent Flue / Combustion Disturbance
Symptom
Boiler makes loud banging or knocking noises (kettling) during operation, especially at high temperatures.
Kettling / Localized Boiling in Heat Exchanger
Symptom
Boiler or flue emits unusual smells (burning, plastic, or flue gas odour) during operation.
Overheating / Flue Gas Leakage
Symptom
Boiler provides central heating but no domestic hot water, or hot water is only lukewarm.
DHW Production / Plate Heat Exchanger Fault
Symptom
Boiler provides hot water but central heating does not come on, even when the room thermostat calls for heat.
Heating Demand / Diverter Valve Fault
Symptom
Boiler runs but radiators do not get hot or only partially heat up.
Poor Heating Performance / Circulation Issue
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| 01 |
Boiler locks out with error code 01; the burner does not ignite, the red lockout LED is on, and the fan may start briefly then stop.
|
Ignition Failure / No Flame Detection | View Details |
| 02 |
Boiler displays error code 02 and locks out shortly after an ignition attempt; the flame appears briefly then extinguishes.
|
Flame Loss During Operation | View Details |
| 03 |
Boiler displays error code 03; the fan does not start or starts then stops, and there is no ignition sequence.
|
Flue Fan / Air Pressure Switch Fault | View Details |
| 04 |
Boiler displays error code 04; there is no ignition, sometimes accompanied by a humming sound from the gas valve area.
|
Gas Valve Control / Internal Gas Valve Fault | View Details |
| 05 |
Boiler displays error code 05; it will not start, and the display may indicate a fan or flue fault depending on the model.
|
Flue System / Fan Speed Control Fault | View Details |
| 06 |
Boiler displays error code 06; there is no ignition, often occurring after a power surge or wiring disturbance.
|
Control Board / Internal Electronics Fault | View Details |
| 10 |
Boiler displays error code 10; there is no heating or hot water, and the pump may run briefly then stop.
|
Flow Sensor / Circulation Fault | View Details |
| 11 |
Boiler displays error code 11; domestic hot water does not start when a tap is opened, though heating may still work.
|
DHW Flow Detection Fault | View Details |
| 20 |
Boiler displays error code 20; it will not operate, often occurring after overheating or dry firing.
|
Primary Overheat / Safety Thermostat Tripped | View Details |
| 21 |
Boiler displays error 21; temperature reading is erratic or fixed at an extreme value; the boiler may short cycle.
|
Flow Temperature Sensor (NTC) Fault | View Details |
| 22 |
Boiler shows error 22; the return temperature reading is incorrect, and the boiler may shut down prematurely.
|
Return Temperature Sensor (NTC) Fault | View Details |
| 23 |
Boiler displays error 23; domestic hot water temperature is not regulated correctly and may be too hot or too cold.
|
DHW Temperature Sensor (NTC) Fault | View Details |
| 24 |
Boiler shows error 24, often associated with low system pressure or air in the system.
|
Low Water Pressure / Pressure Sensor Fault | View Details |
| 27 |
Boiler displays error 27, often related to flue gas recirculation or combustion issues.
|
Flue Gas / Combustion Fault | View Details |
| 28 |
Boiler shows error 28; ignition attempts are noisy or delayed, sometimes with small explosions (misfires).
|
Delayed Ignition / Combustion Instability | View Details |
| 29 |
Boiler displays error 29, often associated with condensate drainage problems in condensing models.
|
Condensate Drain / Siphon Fault | View Details |
| 31 |
Boiler shows error 31, a communication error with the remote control or external interface.
|
Communication / Bus Fault | View Details |
| 37 |
Boiler displays error 37, often related to fan speed or air pressure anomalies.
|
Fan Speed / Air Pressure Regulation Fault | View Details |
| 40 |
Boiler shows error 40, often indicating a generic sensor or configuration fault.
|
Generic Sensor / Configuration Error | View Details |
| A01 |
Boiler displays A01, ignition lockout, burner does not light; user must reset.
|
Ignition Lockout (No Flame) | View Details |
| A02 |
Boiler displays A02, safety thermostat intervention; boiler overheated and shut down.
|
Overheat Lockout | View Details |
| A03 |
Boiler displays A03, water pressure too low; boiler will not start.
|
Low System Pressure Lockout | View Details |
| A04 |
Boiler displays A04, flue gas safety device intervention; boiler shuts down.
|
Flue Gas Safety / Overtemperature Fault | View Details |
| A05 |
Boiler displays A05, fan or air pressure fault; boiler does not ignite.
|
Fan / Air Pressure Lockout | View Details |
| A06 |
Boiler displays A06, flame detected when there should be none (false flame).
|
False Flame Detection | View Details |
| A07 |
Boiler displays A07, domestic hot water NTC fault; DHW temperature control lost.
|
DHW NTC Sensor Error | View Details |
| A08 |
Boiler displays A08, flow NTC fault; boiler may not regulate heating temperature.
|
Flow NTC Sensor Error | View Details |
| A09 |
Boiler displays A09, return NTC fault; may cause incorrect modulation or lockout.
|
Return NTC Sensor Error | View Details |
| E01 |
Boiler displays E01, ignition failure, similar to A01 on some models.
|
Ignition Failure | View Details |
| E02 |
Boiler displays E02, indicating an overheat or safety thermostat intervention.
|
Overheat Protection | View Details |
| E03 |
Boiler displays E03, indicating a flue or fan fault, resulting in no ignition.
|
Flue/Fan Safety Lockout | View Details |
| E10 |
Boiler displays E10, indicating low water pressure or a pressure sensor fault.
|
Low Pressure / Sensor Error | View Details |
| E20 |
Boiler displays E20, indicating a circulation or pump fault, causing the boiler to overheat quickly.
|
Pump / Circulation Fault | View Details |
| – |
Boiler cycles on and off rapidly (short cycling) without maintaining stable temperature.
|
Short Cycling / Control Instability | View Details |
| – |
Boiler display is on but unresponsive to buttons, or settings change randomly.
|
User Interface / Control Panel Fault | View Details |
| – |
Boiler does not start at all, no display or lights, completely dead.
|
No Power / Electrical Supply Fault | View Details |
| – |
Boiler frequently loses pressure and needs topping up every few days.
|
Chronic Pressure Loss | View Details |
| – |
Boiler frequently trips the household electrical circuit breaker or RCD when starting or during operation.
|
Electrical Short / Earth Leakage | View Details |
| – |
Boiler heats radiators even when there is no call for heating (overheating house).
|
Unwanted Heating / Control Fault | View Details |
| – |
Boiler is leaking water from underneath the casing or from internal components.
|
Internal Water Leak | View Details |
| – |
Boiler is very noisy during operation (whining, grinding, or rattling sounds).
|
Mechanical Noise / Vibration | View Details |
| – |
Boiler locks out intermittently, especially in windy conditions, with no consistent error code.
|
Intermittent Flue / Combustion Disturbance | View Details |
| – |
Boiler makes loud banging or knocking noises (kettling) during operation, especially at high temperatures.
|
Kettling / Localized Boiling in Heat Exchanger | View Details |
| – |
Boiler or flue emits unusual smells (burning, plastic, or flue gas odour) during operation.
|
Overheating / Flue Gas Leakage | View Details |
| – |
Boiler provides central heating but no domestic hot water, or hot water is only lukewarm.
|
DHW Production / Plate Heat Exchanger Fault | View Details |
| – |
Boiler provides hot water but central heating does not come on, even when the room thermostat calls for heat.
|
Heating Demand / Diverter Valve Fault | View Details |
| – |
Boiler runs but radiators do not get hot or only partially heat up.
|
Poor Heating Performance / Circulation Issue | View Details |
No matching codes found
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