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Main Boilers Error Codes
Complete list of fault codes and troubleshooting guides. Use the search below to find your specific error.
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E01
Boiler will not ignite, display shows E01 and burner does not light
Ignition Lockout
E02
Boiler locks out with E02, no heating or hot water, fan may start briefly then stop
Flame Detection Failure
E03
Boiler shows E03 and shuts down, fan may run but burner does not light
Flue Fan or Air Pressure Switch Fault
E04
Boiler displays E04 and will not run, overheat light may be on
Primary Overheat Thermostat Trip
E05
Boiler shows E05, heating and hot water unavailable, temperature reading may be erratic
Flow Temperature Sensor (NTC) Fault
E06
Boiler displays E06, hot water temperature unstable or boiler shuts down during DHW demand
DHW Temperature Sensor (NTC) Fault
E07
Boiler shows E07 and will not fire, often after power interruption or wiring work
Low Water Pressure or Pressure Sensor Fault
E08
Boiler intermittently shuts down with E08, especially when heating demand is high
Pump Circulation Fault
E09
Boiler displays E09 and shuts down, often accompanied by gurgling noises
Condensate Drain Blockage
E10
Boiler shows E10, fan may not start, no ignition attempt
Fan Speed or Feedback Fault
E11
Boiler locks out with E11, often after overheating or circulation issues
Return Temperature Sensor (NTC) Fault
E12
Boiler shows E12, no response to thermostat demand, display may be blank or frozen
Control PCB Communication or Internal Fault
E13
Boiler displays E13, particularly when using weather compensation or advanced controls
Communication Fault with External Control or Sensor
E14
Boiler shows E14 and shuts down, often after a loud noise or electrical event
Flame Loss During Operation
E15
Boiler displays E15, often with rapid temperature rise and shutdown
Flow/Return Temperature Differential Too High
E16
Boiler shows E16, no heating or hot water, may occur after wiring changes
External Thermostat or Control Fault
E17
Boiler intermittently shows E17, especially during hot water use with combi models
Flow Switch or Turbine Fault (DHW Flow Detection)
E18
Boiler shows E18, pressure gauge may read very high or very low
Water Pressure Sensor Range/Calibration Fault
E19
Boiler displays E19 and will not start, often after a power surge
Internal PCB Power Supply Fault
E20
Boiler shows E20, fan may run but ignition does not occur
Air Pressure Switch Stuck or Out of Range
Symptom
Boiler cycles on and off with loud clicking from the gas valve but no sustained flame
Failed Ignition Sequence / Gas Valve or Ignition Issue
Symptom
Boiler display is blank but fused spur is on
No Power to Boiler Electronics
Symptom
Boiler does not fire for hot water unless heating is also on (combi models)
Diverter Valve Stuck in Heating Position
Symptom
Boiler does not respond to room thermostat or programmer, but has power and pressure
Control Signal Not Reaching Boiler
Symptom
Boiler emits a burning smell or plastic smell when running
Overheating Electrical or Plastic Component
Symptom
Boiler fan runs continuously even when there is no demand for heating or hot water
Fan Overrun or Stuck Relay
Symptom
Boiler frequently loses pressure and needs topping up every few days
Chronic Pressure Loss
Symptom
Boiler frequently short cycles (turns on and off rapidly) during heating
Short Cycling / Oversized Boiler or Poor Control
Symptom
Boiler is very noisy with whistling or howling sounds from the flue
Flue Resonance or Combustion Noise
Symptom
Boiler leaking water from underneath the casing or pipe connections
Internal Water Leak
Symptom
Boiler makes loud banging or kettling noises during operation
Kettling Due to Scale or Sludge in Primary Heat Exchanger
Symptom
Boiler pressure rises to the red zone when heating is on and may discharge water outside
Expansion Vessel Failure or PRV Operation
Symptom
Boiler repeatedly locks out and needs frequent manual resets
Intermittent Lockout (Underlying Fault Not Resolved)
Symptom
Boiler runs but flue terminal drips heavily or stains the wall
Condensate Management / Flue Drainage Issue
Symptom
Boiler runs but some radiators stay cold or only warm at the bottom
Poor Heat Distribution / Sludged Radiators
Symptom
Hot water temperature fluctuates or runs hot then cold on a combi boiler
Unstable DHW Temperature Control
Symptom
Radiators do not heat up even though the boiler appears to run
No Central Heating Circulation
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| E01 |
Boiler will not ignite, display shows E01 and burner does not light
|
Ignition Lockout | View Details |
| E02 |
Boiler locks out with E02, no heating or hot water, fan may start briefly then stop
|
Flame Detection Failure | View Details |
| E03 |
Boiler shows E03 and shuts down, fan may run but burner does not light
|
Flue Fan or Air Pressure Switch Fault | View Details |
| E04 |
Boiler displays E04 and will not run, overheat light may be on
|
Primary Overheat Thermostat Trip | View Details |
| E05 |
Boiler shows E05, heating and hot water unavailable, temperature reading may be erratic
|
Flow Temperature Sensor (NTC) Fault | View Details |
| E06 |
Boiler displays E06, hot water temperature unstable or boiler shuts down during DHW demand
|
DHW Temperature Sensor (NTC) Fault | View Details |
| E07 |
Boiler shows E07 and will not fire, often after power interruption or wiring work
|
Low Water Pressure or Pressure Sensor Fault | View Details |
| E08 |
Boiler intermittently shuts down with E08, especially when heating demand is high
|
Pump Circulation Fault | View Details |
| E09 |
Boiler displays E09 and shuts down, often accompanied by gurgling noises
|
Condensate Drain Blockage | View Details |
| E10 |
Boiler shows E10, fan may not start, no ignition attempt
|
Fan Speed or Feedback Fault | View Details |
| E11 |
Boiler locks out with E11, often after overheating or circulation issues
|
Return Temperature Sensor (NTC) Fault | View Details |
| E12 |
Boiler shows E12, no response to thermostat demand, display may be blank or frozen
|
Control PCB Communication or Internal Fault | View Details |
| E13 |
Boiler displays E13, particularly when using weather compensation or advanced controls
|
Communication Fault with External Control or Sensor | View Details |
| E14 |
Boiler shows E14 and shuts down, often after a loud noise or electrical event
|
Flame Loss During Operation | View Details |
| E15 |
Boiler displays E15, often with rapid temperature rise and shutdown
|
Flow/Return Temperature Differential Too High | View Details |
| E16 |
Boiler shows E16, no heating or hot water, may occur after wiring changes
|
External Thermostat or Control Fault | View Details |
| E17 |
Boiler intermittently shows E17, especially during hot water use with combi models
|
Flow Switch or Turbine Fault (DHW Flow Detection) | View Details |
| E18 |
Boiler shows E18, pressure gauge may read very high or very low
|
Water Pressure Sensor Range/Calibration Fault | View Details |
| E19 |
Boiler displays E19 and will not start, often after a power surge
|
Internal PCB Power Supply Fault | View Details |
| E20 |
Boiler shows E20, fan may run but ignition does not occur
|
Air Pressure Switch Stuck or Out of Range | View Details |
| – |
Boiler cycles on and off with loud clicking from the gas valve but no sustained flame
|
Failed Ignition Sequence / Gas Valve or Ignition Issue | View Details |
| – |
Boiler display is blank but fused spur is on
|
No Power to Boiler Electronics | View Details |
| – |
Boiler does not fire for hot water unless heating is also on (combi models)
|
Diverter Valve Stuck in Heating Position | View Details |
| – |
Boiler does not respond to room thermostat or programmer, but has power and pressure
|
Control Signal Not Reaching Boiler | View Details |
| – |
Boiler emits a burning smell or plastic smell when running
|
Overheating Electrical or Plastic Component | View Details |
| – |
Boiler fan runs continuously even when there is no demand for heating or hot water
|
Fan Overrun or Stuck Relay | View Details |
| – |
Boiler frequently loses pressure and needs topping up every few days
|
Chronic Pressure Loss | View Details |
| – |
Boiler frequently short cycles (turns on and off rapidly) during heating
|
Short Cycling / Oversized Boiler or Poor Control | View Details |
| – |
Boiler is very noisy with whistling or howling sounds from the flue
|
Flue Resonance or Combustion Noise | View Details |
| – |
Boiler leaking water from underneath the casing or pipe connections
|
Internal Water Leak | View Details |
| – |
Boiler makes loud banging or kettling noises during operation
|
Kettling Due to Scale or Sludge in Primary Heat Exchanger | View Details |
| – |
Boiler pressure rises to the red zone when heating is on and may discharge water outside
|
Expansion Vessel Failure or PRV Operation | View Details |
| – |
Boiler repeatedly locks out and needs frequent manual resets
|
Intermittent Lockout (Underlying Fault Not Resolved) | View Details |
| – |
Boiler runs but flue terminal drips heavily or stains the wall
|
Condensate Management / Flue Drainage Issue | View Details |
| – |
Boiler runs but some radiators stay cold or only warm at the bottom
|
Poor Heat Distribution / Sludged Radiators | View Details |
| – |
Hot water temperature fluctuates or runs hot then cold on a combi boiler
|
Unstable DHW Temperature Control | View Details |
| – |
Radiators do not heat up even though the boiler appears to run
|
No Central Heating Circulation | View Details |
No matching codes found
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