BoilerFaultCodesThe 6 most common faults
Your boiler has detected that there is not enough water in the central heating system to operate safely.
Locate the filling loop (the silver braided hose) underneath the boiler.Slowly open the blue or black taps on the filling loop until you hear water flowing.Monitor the pressure gauge until it reaches between 1.0 and 1.5 bar, then close the taps fully.
Your boiler is repeatedly struggling to keep the flame lit while it is running, causing it to shut down for safety after multiple failures.
Check that your gas pre-payment meter has creditEnsure other gas appliances in your home, like a hob, are working correctlyReset the boiler by pressing the 'R' or 'Reset' button
Your boiler has sensed that the water returning from your radiators is hotter than the water leaving the boiler, which usually means there is a circulation problem or a sensor fault.
Ensure all radiator valves (TRVs) are fully openCheck that the boiler pressure is between 1.0 and 1.5 barPress the Reset button for five seconds
Your boiler has detected that water is not moving through the system properly, which has caused it to shut down to prevent overheating.
Check the pressure gauge and top it up to 1.5 bar using the filling loop if it is too lowEnsure all radiator valves are fully openCheck for any visible leaks around your pipeworkRestart the boiler using the reset button
Your boiler has shut down because it thinks it is getting too hot or it has detected a technical fault with its internal temperature sensor.
Check that all radiator valves are fully openEnsure the boiler pressure is between 1 and 1.5 bar on the gaugeTurn the boiler off and back on again to attempt a reset
Your boiler has shut down because the water inside has become far too hot, likely due to a circulation problem.
Check that your radiator valves are fully openEnsure there is enough water pressure in the system (usually between 1.0 and 1.5 bar on the gauge)Try resetting the boiler by turning the selector knob to 'R' for five seconds
on the Baxi 800 System 2
Based on parts cited in our fault code database. Your engineer will confirm what's actually needed after diagnosis.
Call a Gas Safe engineer if…
- You can smell gas or see signs of a leak
- The Baxi shows an Emergency or High severity code
- The boiler keeps locking out after repeated resets
- You've tried the DIY checks and the fault hasn't cleared
- There's visible water leaking from the boiler
- The flame is yellow or orange instead of blue
Avoid the next call-out bill
Monthly cover means no unexpected bills when your boiler breaks down.
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