26 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 |
|---|---|---|
| 33-010-44 | CLAS ONE 30 | 2017–present |
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Your boiler has detected that parts of its internal system are getting too hot and has automatically shut down to prevent damage.
Your boiler has detected that it is getting too hot and has automatically shut down to prevent damage or dangerous overheating.
Your boiler has detected that it is running much hotter than it should be and has switched itself off to prevent internal damage.
Your boiler is struggling to push water around your heating system because the flow is too restricted or the pressure is too low.
Your boiler is struggling to move water around your heating system correctly, which is preventing it from working as it should.
Your boiler is struggling to move enough water through your heating system, usually because there is trapped air, a blockage, or the system pressure is too low.
Your boiler has detected that the water pressure inside the system is too low to operate safely.
Your boiler has detected that the water pressure inside your heating system is too high, which can put unnecessary strain on the internal components.
Your boiler has lost the ability to read the temperature of the water circulating through your radiators, so it has safely shut down to prevent overheating.
Your boiler has lost the ability to read the temperature of the water returning to it, so it has safely shut down to prevent overheating.
Your boiler is having trouble communicating with the outdoor weather sensor, which means it cannot automatically adjust your heating based on the temperature outside.
Your boiler is struggling to accurately detect the temperature of the water being sent to your radiators, so it has stopped working as a safety precaution.
Your boiler has detected that water is not moving around your heating system fast enough, triggering a safety shut-off to prevent overheating.
Your boiler is struggling to move enough water through your heating system, which usually means there is a blockage, air trapped in the pipes, or a pump struggling to work.
Your boiler is struggling to move water around your heating system effectively, usually due to low pressure or trapped air.
Your boiler is struggling to read the temperature correctly because it has lost its connection to the room thermostat or internal sensor.
Your boiler has stopped working because it cannot detect a flame, meaning it is currently unable to safely ignite or stay lit to provide heating and hot water.
Your boiler has failed to light the flame on the first attempt, which usually happens because there is an issue with the gas supply or the ignition system.
Your boiler has failed to fire up twice and has now locked itself out as a safety precaution while trying to light the flame.
Your boiler is struggling to clear exhaust gases properly, so it has safely shut itself down to prevent any risk.
Your boiler has detected a break in an internal safety circuit, which is preventing it from firing up to ensure the system remains safe.
Your boiler has detected that a safety switch associated with your underfloor heating system has tripped or disconnected, causing the system to pause to prevent overheating.
Your boiler has detected that it is running too hot and has automatically switched itself off to prevent any damage or safety issues.
Your boiler's internal computer is experiencing a software glitch that is preventing it from starting up correctly.
Your boiler has stopped working because it cannot light the internal flame needed to heat your water.
Your boiler's computer memory has encountered a data corruption error, meaning it can no longer remember its settings or operating instructions.
Not faults — these are normal operating states. Tap to expand.
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BoilerFaultCodes