52 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
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The GC number on your boiler's data badge identifies the exact appliance and production years, as recorded in the UK Product Characteristics Database.
| GC number | Appliance (register name) | Produced |
|---|---|---|
| 47-709-02 | NCB-28LDWE | 2014–present |
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Your boiler has detected an internal communication error and has safely shut itself down as a precaution.
Your boiler has failed to light the flame properly and has stopped attempting to heat your home or water for safety reasons.
Your boiler has detected an issue related to the flow of water inside the unit, which has caused it to stop working to protect itself from potential overheating.
Your boiler has failed to ignite or has lost the flame during operation because it is not receiving a consistent supply of gas.
Your boiler has detected an issue with the sensors that monitor the water flow, which is preventing it from firing up correctly.
Your boiler has detected an issue with the airflow or exhaust system, meaning it cannot operate safely and has shut itself down.
Your boiler has detected that it is not effectively removing waste gases produced during the heating process, causing it to shut down for safety.
Your boiler has detected an issue with the air flowing through the flue system, causing it to shut down for safety.
Your boiler has detected an issue with the air flowing through the system, preventing it from starting safely.
Your boiler's external temperature sensor is reporting an issue, which may cause it to run inefficiently or struggle to heat your home correctly.
Your boiler has detected that the flue pipe responsible for safely venting exhaust gases outside has become loose or disconnected.
Your boiler's main control unit and the display panel are having trouble 'talking' to each other, which prevents the system from operating correctly.
Your boiler has detected that the water temperature inside is getting dangerously high and has shut itself down to prevent damage or overheating.
Your boiler has failed to light the flame needed to heat your water and home.
Your boiler has detected a flame when it shouldn't be burning, suggesting a sensor error or a gas valve issue that prevents the unit from starting safely.
Your boiler is failing to stay lit, so it has shut down to keep you safe.
Your boiler has detected that it is getting too hot and has automatically shut itself down to prevent any damage to its internal parts.
Your boiler has detected that the gases leaving the unit are hotter than they should be, causing it to shut down to prevent overheating.
Your boiler has detected that it is running much hotter than it should be and has switched itself off to prevent damage.
Your boiler has detected that it is running too hot and has automatically shut itself down to prevent damage.
Your boiler has detected that the temperature in the exhaust flue is too high, causing it to shut down for safety reasons.
Your boiler is having trouble managing the air and gas mixture needed to burn fuel safely and effectively.
Your boiler's fan is struggling to spin correctly, which prevents it from safely venting gases and means the boiler has shut down to keep you safe.
Your boiler is having trouble breathing, which prevents it from safely venting exhaust gases and starting your heating.
Your boiler has lost the ability to accurately measure the temperature of the water being sent to your radiators, so it has safely shut itself down to prevent overheating.
Your boiler has lost the ability to read the temperature of the water returning to it, so it has shut down as a precaution to prevent overheating.
Your boiler is having trouble measuring its own internal temperature, so it has shut down to prevent it from getting too hot or cold.
Your boiler is struggling to accurately measure the temperature of the water returning to it, which prevents it from heating your home or water correctly.
Your boiler has been trying to refill its internal water supply for too long but has failed to reach the required level.
Your boiler has detected that the water pressure inside the heating system is too high for it to operate safely.
Your boiler is struggling to accurately read the water pressure inside the system, which is preventing it from firing up safely.
Your boiler is struggling to detect the temperature of the water for your taps and shower because a sensor has stopped communicating correctly.
Your boiler is having trouble measuring incoming water temperature due to a faulty sensor, which is currently preventing it from heating your water correctly.
Your boiler is struggling to correctly manage the flow of water because an internal component responsible for adjusting water volume has detected an error.
Your boiler is struggling to detect the flow of water through the system, which means it cannot safely heat your home or provide hot water.
Your boiler is having trouble sensing the temperature of your hot water supply, which will likely prevent it from heating your water correctly.
Your boiler is having trouble managing the flow of water between your heating system and your hot water taps, which may cause your heating or hot water to stop working properly.
Your boiler's main computer is having trouble processing information and needs to be looked at by a professional.
Your boiler's internal configuration settings are currently mismatched, which is preventing it from starting up correctly.
Your boiler's computer memory has encountered a data error, which is preventing it from starting up correctly.
Your boiler's computer has detected an internal error with its data storage, meaning it cannot reliably operate its settings or programs.
Your boiler is struggling to talk to other linked heating units in your system, meaning it cannot coordinate its operation properly.
Your boiler is struggling to read the temperature outside, which means it cannot automatically adjust your heating to match the weather conditions.
Your boiler is having trouble detecting the temperature of the water reserved for your hot water system, which may prevent it from heating your taps correctly.
Your boiler is struggling to detect the exhaust vent, likely because the flue pipe is not fitted securely or is the wrong size for your home.
Your boiler has detected that the type of gas being supplied does not match what the boiler is set up to use, meaning it cannot operate safely.
Your boiler has detected that a safety device installed outside the main unit is reporting a dangerously low water level, preventing the boiler from starting to protect it from damage.
Your boiler's main control panel is failing to communicate with the internal system, which will prevent your heating and hot water from working properly.
Your boiler is having trouble communicating with the external controls or zoning system that tells it when to heat each area of your home.
Your boiler's front cover is not properly attached or secured, which acts as a safety disconnect to prevent the unit from running while it is open.
Your boiler has detected an issue with the amount of gas it is receiving or the settings used to burn it, which prevents it from operating safely.
Your boiler is failing to light the internal flame, which means it cannot produce any hot water or heating for your home.
Not faults — these are normal operating states. Tap to expand.
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BoilerFaultCodes