BoilerFaultCodesThe 6 most common faults
Your boiler has detected that the water returning from your radiators is dangerously hot, causing it to shut down to prevent damage.
Why it happens: This fault occurs when water cannot move through your heating system quickly enough to carry heat away from the boiler, causing the temperature to spike. The most common reasons are a failed internal pump that has stopped spinning or a physical blockage in the pipework that is restricting the flow of water.
Check that all radiator valves are fully openEnsure there are no obstructions to the air ventsReset the boiler using the control knob once the system has cooled down
Your boiler is overheating because it cannot circulate heat away from the burner fast enough, so it has safely shut itself down to prevent damage.
Why it happens: This fault occurs when the water inside the boiler heats up at an unnaturally fast rate, causing the sensors to trigger a safety shutdown before the unit overheats. The most common reason is a lack of water flow, often caused by a failing internal pump or a blockage in the system that prevents heat from being moved away from the burner quickly enough.
Check that all radiator valves are fully openEnsure the central heating system pressure is between 1.0 and 1.5 barPress the reset button once the boiler has cooled down
Your boiler is unable to drain the water it produces during normal operation, which is causing it to shut down to prevent internal damage.
Why it happens: This fault occurs when the internal trap or the external drainage pipe becomes obstructed, preventing the boiler from safely disposing of the wastewater it produces during operation. The most common reason is a buildup of sludge and debris within the trap itself, or an ice blockage in the external pipework following a cold spell.
Check the white plastic pipe leading outside to see if it is frozen or blocked.If frozen, gently pour warm (not boiling) water over the external pipe to melt the ice.Carefully check the plastic trap underneath the boiler for visible blockages if accessible without opening the boiler casing.Restart the boiler once the blockage is cleared.
Your boiler has detected that the water is not circulating properly, meaning it is getting too hot inside the unit compared to the temperature of the water being sent out to your radiators.
Why it happens: This fault occurs when the boiler's internal sensors detect that the water temperature is rising too fast or there is too much of a difference between the flow and return pipes. The most common reason is a blockage in the system or a failing pump that prevents the hot water from moving away from the heat exchanger quickly enough. It can also be caused by air trapped in the boiler or sensors that have become faulty and are giving incorrect readings.
Check that your radiator valves are open to allow water flowCheck the boiler pressure gauge and top up to 1.5 bar if it is lowBleed your radiators to remove any trapped air pocketsReset the boiler using the control dial
Your boiler is failing to light the fuel inside, so it has safely shut down to prevent gas from building up.
Why it happens: This fault occurs when the boiler attempts to ignite but its internal sensors cannot detect a flame. The most common reasons include a lack of gas supply to the unit, a build-up of carbon on the ignition probes, or an electrical failure preventing the spark from jumping.
Check if other gas appliances, like a gas hob, are working to ensure gas is reaching the propertyCheck that your gas meter has credit if you use a pre-payment meterPress the Reset button or turn the dial to 'Reset' for a few seconds to see if the boiler restarts
Your boiler has stopped working because it has detected a major internal error that has forced it to shut down for safety reasons.
Why it happens: This fault occurs when the boiler's control system detects a complete interruption in electrical supply or a critical communication failure between internal components. It often happens because a fuse has blown on the main circuit board or because the board itself can no longer process power correctly. In some cases, loose wiring or a sudden power surge can trigger this emergency shutdown to protect the appliance from electrical damage.
Check if your main electrical consumer unit (fuse box) has any tripped switches.Ensure the boiler's power isolation switch is turned on.If power is present, try to reset the boiler using the control knob or reset button.
on the Vokera Hydra
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 Vokera 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