Keston
Keston 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 the burner does not light
Ignition Lockout
E02
Boiler locks out with E02; the fan runs briefly then stops, and there is no flame
Flame Detection Failure
E03
Boiler shows E03 and shuts down shortly after starting; the primary flow temperature rises rapidly
Primary Overheat / High Limit Trip
E04
Boiler displays E04 and will not fire; the fan may not start
Flue Fan / Air Pressure Fault
E05
Boiler shows E05, no heating or hot water; the display may show a low pressure symbol
Low Water Pressure / Water Pressure Switch Open
E06
Boiler locks out with E06; temperature readings appear incorrect or fluctuate rapidly
Flow Temperature Sensor Fault
E07
Boiler displays E07, may run briefly then shut down, and shows an abnormal return temperature reading.
Return Temperature Sensor Fault
E08
Boiler displays E08 and will not start, fan may not run.
Air Pressure Switch / Flue Differential Fault
E09
Boiler displays E09, with no heating or hot water, and the pump may run briefly.
Circulation Pump Fault
E10
Boiler displays E10, system pressure rises rapidly when heating, safety valve may discharge.
Expansion Vessel / System Overpressure Fault
E11
Boiler displays E11, and the domestic hot water temperature is unstable or excessively hot.
DHW NTC Sensor Fault
E12
Boiler displays E12, no response to thermostat or programmer, boiler may stay off.
External Control / Thermostat Circuit Fault
E13
Boiler displays E13; the fan runs, but the ignition sequence does not start.
Gas Valve Control Fault
E14
Boiler intermittently locks out with E14, especially in windy conditions.
Flame Loss During Operation
E15
Boiler displays E15, with no display backlight or intermittent power loss.
Mains Supply / PCB Power Fault
E16
Boiler displays E16, condensate may be visible around the base of the boiler.
Condensate Drain / Trap Fault
E17
Boiler displays E17; fan speed appears abnormal or noisy.
Fan Speed / Tachometer Fault
E18
Boiler intermittently displays E18, particularly when switching between heating and hot water.
Diverter Valve Position Fault
E19
Boiler displays E19; DHW flow is detected, but the burner does not fire.
DHW Flow Detection Fault
E20
Boiler displays E20; burner shuts down shortly after lighting, and primary temperature rises too quickly.
Primary Flow Restriction / Heat Exchanger Blockage
E21
Boiler displays E21; the display may indicate a sensor mismatch or an internal communication error.
Internal Communication / PCB Sensor Bus Fault
E22
Boiler intermittently displays E22, particularly after power cuts or brownouts.
Supply Voltage / Brownout Fault
E23
Boiler displays E23; the safety thermostat has tripped and must be manually reset.
Manual Reset Overheat Thermostat Trip
E24
Boiler displays E24; an internal leak or low insulation resistance is detected.
Internal Water Leak / Earth Fault
E25
Boiler displays E25; CH flow temperature rises too quickly at low load.
Low Flow / Minimum Flow Rate Fault
E26
Boiler intermittently displays E26, particularly when DHW demand is low.
DHW Overheat / Flow Restriction
E27
Boiler shows E27, external sensor or weather compensation not detected or faulty.
Outdoor Sensor / Weather Compensation Fault
Symptom
Boiler casing feels excessively hot or there is a smell of hot dust or plastic
Overheating Casing / Poor Ventilation
Symptom
Boiler fires but hot water temperature at taps is poor or fluctuates.
Inadequate or Unstable Domestic Hot Water
Symptom
Boiler flue terminal shows white staining or water dripping excessively
Condensate / Flue Condensation Issue
Symptom
Boiler frequently loses pressure and needs topping up every few days.
Chronic Pressure Loss
Symptom
Boiler is very noisy during operation, with whistling, droning, or vibration.
Excessive Operational Noise
Symptom
Boiler leaking water from underneath the casing or from pipe connections.
Internal Water Leak
Symptom
Boiler locks out more often in very cold weather, with visible condensate issues
Frozen or Restricted Condensate Discharge
Symptom
Boiler makes loud banging or kettling noises during operation.
Kettling / Localised Boiling in Heat Exchanger
Symptom
Boiler runs but radiators do not get hot or only partially heat up.
Poor Central Heating Circulation
Symptom
Boiler short cycles, frequently turning on and off with little heat delivered.
Short Cycling / Oversized Boiler or Control Issue
Symptom
Boiler starts then shuts down after a few seconds without showing a specific error code.
Flame Establishment Instability
Symptom
Boiler will not start at all, no lights or display.
No Power / Dead Boiler
Symptom
Radiators get hot when only hot water is demanded, or hot water is poor when heating is on
Diverter Valve Cross-Leak or Stuck Position
Symptom
Strong smell of gas near the boiler, whether running or off
Gas Leak at Boiler
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| E01 |
Boiler will not ignite, display shows E01, and the burner does not light
|
Ignition Lockout | View Details |
| E02 |
Boiler locks out with E02; the fan runs briefly then stops, and there is no flame
|
Flame Detection Failure | View Details |
| E03 |
Boiler shows E03 and shuts down shortly after starting; the primary flow temperature rises rapidly
|
Primary Overheat / High Limit Trip | View Details |
| E04 |
Boiler displays E04 and will not fire; the fan may not start
|
Flue Fan / Air Pressure Fault | View Details |
| E05 |
Boiler shows E05, no heating or hot water; the display may show a low pressure symbol
|
Low Water Pressure / Water Pressure Switch Open | View Details |
| E06 |
Boiler locks out with E06; temperature readings appear incorrect or fluctuate rapidly
|
Flow Temperature Sensor Fault | View Details |
| E07 |
Boiler displays E07, may run briefly then shut down, and shows an abnormal return temperature reading.
|
Return Temperature Sensor Fault | View Details |
| E08 |
Boiler displays E08 and will not start, fan may not run.
|
Air Pressure Switch / Flue Differential Fault | View Details |
| E09 |
Boiler displays E09, with no heating or hot water, and the pump may run briefly.
|
Circulation Pump Fault | View Details |
| E10 |
Boiler displays E10, system pressure rises rapidly when heating, safety valve may discharge.
|
Expansion Vessel / System Overpressure Fault | View Details |
| E11 |
Boiler displays E11, and the domestic hot water temperature is unstable or excessively hot.
|
DHW NTC Sensor Fault | View Details |
| E12 |
Boiler displays E12, no response to thermostat or programmer, boiler may stay off.
|
External Control / Thermostat Circuit Fault | View Details |
| E13 |
Boiler displays E13; the fan runs, but the ignition sequence does not start.
|
Gas Valve Control Fault | View Details |
| E14 |
Boiler intermittently locks out with E14, especially in windy conditions.
|
Flame Loss During Operation | View Details |
| E15 |
Boiler displays E15, with no display backlight or intermittent power loss.
|
Mains Supply / PCB Power Fault | View Details |
| E16 |
Boiler displays E16, condensate may be visible around the base of the boiler.
|
Condensate Drain / Trap Fault | View Details |
| E17 |
Boiler displays E17; fan speed appears abnormal or noisy.
|
Fan Speed / Tachometer Fault | View Details |
| E18 |
Boiler intermittently displays E18, particularly when switching between heating and hot water.
|
Diverter Valve Position Fault | View Details |
| E19 |
Boiler displays E19; DHW flow is detected, but the burner does not fire.
|
DHW Flow Detection Fault | View Details |
| E20 |
Boiler displays E20; burner shuts down shortly after lighting, and primary temperature rises too quickly.
|
Primary Flow Restriction / Heat Exchanger Blockage | View Details |
| E21 |
Boiler displays E21; the display may indicate a sensor mismatch or an internal communication error.
|
Internal Communication / PCB Sensor Bus Fault | View Details |
| E22 |
Boiler intermittently displays E22, particularly after power cuts or brownouts.
|
Supply Voltage / Brownout Fault | View Details |
| E23 |
Boiler displays E23; the safety thermostat has tripped and must be manually reset.
|
Manual Reset Overheat Thermostat Trip | View Details |
| E24 |
Boiler displays E24; an internal leak or low insulation resistance is detected.
|
Internal Water Leak / Earth Fault | View Details |
| E25 |
Boiler displays E25; CH flow temperature rises too quickly at low load.
|
Low Flow / Minimum Flow Rate Fault | View Details |
| E26 |
Boiler intermittently displays E26, particularly when DHW demand is low.
|
DHW Overheat / Flow Restriction | View Details |
| E27 |
Boiler shows E27, external sensor or weather compensation not detected or faulty.
|
Outdoor Sensor / Weather Compensation Fault | View Details |
| – |
Boiler casing feels excessively hot or there is a smell of hot dust or plastic
|
Overheating Casing / Poor Ventilation | View Details |
| – |
Boiler fires but hot water temperature at taps is poor or fluctuates.
|
Inadequate or Unstable Domestic Hot Water | View Details |
| – |
Boiler flue terminal shows white staining or water dripping excessively
|
Condensate / Flue Condensation Issue | View Details |
| – |
Boiler frequently loses pressure and needs topping up every few days.
|
Chronic Pressure Loss | View Details |
| – |
Boiler is very noisy during operation, with whistling, droning, or vibration.
|
Excessive Operational Noise | View Details |
| – |
Boiler leaking water from underneath the casing or from pipe connections.
|
Internal Water Leak | View Details |
| – |
Boiler locks out more often in very cold weather, with visible condensate issues
|
Frozen or Restricted Condensate Discharge | View Details |
| – |
Boiler makes loud banging or kettling noises during operation.
|
Kettling / Localised Boiling in Heat Exchanger | View Details |
| – |
Boiler runs but radiators do not get hot or only partially heat up.
|
Poor Central Heating Circulation | View Details |
| – |
Boiler short cycles, frequently turning on and off with little heat delivered.
|
Short Cycling / Oversized Boiler or Control Issue | View Details |
| – |
Boiler starts then shuts down after a few seconds without showing a specific error code.
|
Flame Establishment Instability | View Details |
| – |
Boiler will not start at all, no lights or display.
|
No Power / Dead Boiler | View Details |
| – |
Radiators get hot when only hot water is demanded, or hot water is poor when heating is on
|
Diverter Valve Cross-Leak or Stuck Position | View Details |
| – |
Strong smell of gas near the boiler, whether running or off
|
Gas Leak at Boiler | View Details |
No matching codes found
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