BoilerFaultCodesThe 6 most common faults
Your boiler is unable to light the flame needed to heat your water and radiators, often due to a temporary interruption in the gas supply.
Why it happens: This fault occurs when the boiler tries to start up but cannot successfully create or see a flame at the burner. The most common reasons are a temporary interruption in your gas supply, a build-up of dirt on the ignition probes, or a component failure that prevents the gas from flowing correctly. Essentially, the safety system has stepped in because it cannot confirm that the fuel is burning safely.
Check if other gas appliances, like a cooker, are working to confirm gas is reaching the property.Ensure your gas meter has credit if you use a pre-payment meter.Press the reset button on the boiler control panel and hold for a few seconds to try and restart the ignition sequence.
Your boiler has reached an unsafe temperature because the water is not circulating correctly through the system.
Why it happens: This fault occurs when the water inside the boiler gets too hot because it cannot flow away from the heat source quickly enough. The most common reasons are a pump that has seized up or internal valves being accidentally left closed, which traps the heat and triggers a safety shutdown.
Check that the isolation valves under the boiler are in the open positionEnsure all radiator valves (TRVs) are turned up to fullTry resetting the boiler using the control knob to see if the pump clears the blockage
Your boiler has detected that the water pressure is too low to operate safely, which is usually caused by a leak or air trapped in the system.
Why it happens: This fault occurs when the internal sensors detect that the water level inside your central heating system has dropped below a safe threshold. The most common reason is a slow leak from a pipe or radiator, though sometimes the pressure drops simply because air has escaped through the system's vent.
Locate the filling loop (a flexible silver hose) underneath the boiler.Slowly open the one or two taps on the hose until you hear water flowing.Watch the pressure gauge and close the taps once the needle reaches between 1.0 and 1.5 bar.
Your boiler has tried to start up but cannot light the gas to produce heat or hot water.
Why it happens: This fault occurs when the boiler has tried to ignite several times but cannot establish a stable flame to start the heating process. The most common reasons are a lack of gas reaching the burner, worn-out spark electrodes that can no longer create a light, or a faulty sensor that fails to 'see' the flame once it has started.
Check if other gas appliances like a hob are working to ensure gas is reaching the propertyCheck if your gas meter has credit or if the emergency control valve is openPress the 'Reset' button on the boiler control panel to attempt a restart
Your boiler has stopped working because it thinks the waste water pipe is full or there is an issue with the sensor that detects blockages.
Why it happens: This fault occurs when the boiler's internal safety sensor detects that the waste water, known as condensate, is not draining away properly. It is usually caused by a physical blockage in the external pipework or a build-up of debris within the boiler's collector trap. In some cases, the sensor itself may have failed or become corroded, wrongly telling the boiler that it is full of water.
Check the external plastic condensate pipe for signs of freezing if the weather is very cold.Thaw a frozen external pipe using a hot water bottle or warm (not boiling) water.Check that the condensate discharge pipe is not blocked by debris or leaves.
Your boiler has detected that the water pressure is too low to operate safely and has shut down to prevent damage.
Why it happens: This fault occurs when the water level inside your central heating system drops below the minimum level required for the boiler to pump heat around your home. The most common reasons for this are a leak somewhere in the pipework or radiators, or the air pressure in your expansion vessel needing to be recharged.
Locate the filling loop (usually a silver flexible hose) underneath the boiler.Slowly open the one or two taps on the hose until you hear water flowing.Watch the pressure gauge until it reaches between 1.0 and 1.5 bar, then close the taps fully.
on the Vokera Syntesi 29
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